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Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2016 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 03/31/2016  
Task Last Updated: 08/01/2016 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Werneth, Charles  NASA Langley Research Center 
Norman, Ryan  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor: Simonsen, Lisa  
Center Contact:  
lisa.c.simonsen@nasa.gov 
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Flight Assignment/Project Notes: NOTE: Extended to 3/31/2016 per S. Monk/LaRC (Ed., 9/14/15)

NOTE: Extended to 12/31/2015 per S. Monk/LaRC (Ed., 6/17/15)

Task Description: Currently, the deterministic space radiation transport code HZETRN (High charge (Z) and Energy TRaNsport), is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO (radiation health officer), and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physics improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer - 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (International Space Station-ISS, Lunar, or Mars)? Pion production models are also being worked on.

Research Impact/Earth Benefits: The radiation transport codes developed at NASA Langley Research Center can potentially be used in other applications such as proton and heavy ion therapy treatments for cancer.

Task Progress & Bibliography Information FY2016 
Task Progress: Galactic cosmic ray (GCR) simulation has been studied for development at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) on Long Island, New York. The space radiation environment consists of a wide variety of ion species with a continuous range of energies. However, most accelerator-based space radiation experiments have been performed with single ion beams at fixed energies. Thanks to recent developments in beam switching technology implemented at NSRL, it is now possible to rapidly switch ion species and energies, allowing for the possibility to more realistically simulate the actual radiation environment found in space. A variety of issues related to implementation of GCR simulation at NSRL, especially for experiments in radiobiology, have been studied. Reference field specification and beam selection strategies at NSRL have been examined and a recommended GCR simulation strategy at NSRL has been outlined. Comparisons have been made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It was found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e., shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Also, variation in the induced tissue field associated with shielding configuration and solar activity has been addressed. It was found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. An approach for selecting beams at NSRL to simulate the designated reference field has been worked out. This represents the first important step in the full development of GCR simulation at NSRL.

The effects of relativistic kinematics have been studied for general nuclear collisions between a projectile and target nucleus. Relativistic effects are seen to come into play at high energies for non-equal mass nuclei. However, a very surprising result was found. When the mass of the projectile and target are the same, then relativistic kinematic effects disappear! The Lippman-Schwinger equation with the first order optical potential was analysed and the resulting differential cross sections calculated with and without relativistic effects become indistinguishable because the relativistic and non-relativistic elastic scattering amplitudes are essentially indistinguishable.

The 3-Dimensional High charge (Z) and Energy TRaNsport (3DHZETRN) formalism was developed as an extension to HZETRN with an emphasis on 3D corrections for neutrons and light ions. Comparisons to Monte Carlo (MC) simulations were used to verify the 3DHZETRN methodology in slab and spherical geometry, and it was shown that 3DHZETRN agrees with MC codes to the degree that various MC codes agree among themselves. One limitation of such comparisons is that all of the codes (3DHZETRN and three MC codes) utilize different nuclear models/databases; additionally, using a common nuclear model is impractical due to the complexity of the software. It was therefore difficult to ascertain if observed discrepancies are caused by transport code approximations or nuclear model differences. Previous transport model results in specific geometries have now been combined with additional results in related geometries to study neutron leakage using the Webber 1956 solar particle event as a source boundary condition. It has been found that although the current version of 3DHZETRN is reasonably accurate compared to MC simulations, improved leakage estimates can be obtained by replacing the isotropic/straight-ahead approximation with more detailed descriptions.

This report was compiled from abstracts of papers listed in the bibliography.

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Norbury JW, Schimmerling W, Slaba TC, Azzam E, Badavi FF, Baiocco G, Benton E, Bindi V, Blakely EA, Blattnig SR, Boothman DA, Borak TB, Britten RA, Curtis S, Dingfelder M, Durante M, Dynan W, Eisch AJ, Robin Elgart S, Goodhead DT, Guida PM, Heilbronn LH, Hellweg CE, Huff JL, Kronenberg A, La Tessa C, Lowenstein D, Miller J, Morita T, Narici L, Nelson GA, Norman RB, Ottolenghi A, Patel ZS, Reitz G, Rusek A, Schreurs A-S, Scott-Carnell LA, Semones E, Shay JW, Shurshakov VA, Sihver L, Simonsen LC, Story M, Turker MS, Uchihori Y, Williams J, Zeitlin CJ. "Galactic cosmic ray simulation at the NASA Space Radiation Laboratory." Life Science in Space Research. 2016 Feb;8:38-51. http://dx.doi.org/10.1016/j.lssr.2016.02.001 ; PMID: 26948012 , Feb-2016
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Norbury JW, Rusek A, La Tessa C. "Reference field specification and preliminary beam selection strategy for accelerator-based GCR simulation." Life Sciences in Space Research. 2016 Feb;8:52-67. http://dx.doi.org/10.1016/j.lssr.2016.01.001 ; PubMed PMID: 26948013 , Feb-2016
Articles in Peer-reviewed Journals Werneth CM, Maung KM, Ford WP. "Relativistic elastic differential cross sections for equal mass nuclei." Physics Letters B. 2015 Oct 7;749:331-6. http://dx.doi.org/10.1016/j.physletb.2015.08.002 , Oct-2015
Articles in Peer-reviewed Journals Wilson JW, Slaba TC, Badavi FF, Reddell BD, Bahadori AA. "3DHZETRN: Neutron leakage in finite objects." Life Sciences in Space Research. 2015 Nov;7:27-38. http://dx.doi.org/10.1016/j.lssr.2015.09.003 , Nov-2015
Articles in Peer-reviewed Journals Wilson JW, Slaba TC, Badavi FF, Reddell BD, Bahadori AA. "Solar proton exposure of an ICRU sphere within a complex structure Part I: Combinatorial geometry." Life Sciences and Space Research. 2016 Jun;9:69-76. http://dx.doi.org/10.1016/j.lssr.2016.05.002 ; PubMed PMID: 27345203 , Jun-2016
Articles in Peer-reviewed Journals Slaba TC, Wilson JW, Badavi FF, Reddell BD, Bahadori AA. "Solar proton exposure of an ICRU sphere within a complex structure part II: Ray-trace geometry." Life Sciences and Space Research. 2016 Jun;9:77-83. http://dx.doi.org/10.1016/j.lssr.2016.05.001 ; PubMed PMID: 27345204 , Jun-2016
Articles in Peer-reviewed Journals Heilbronn LH, Borak TB, Townsend LW, Tsai PE, Burnham CA, McBeth RA. "Neutron yields and effective doses produced by Galactic Cosmic Ray interactions in shielded environments in space." Life Sciences and Space Research. 2015 Nov;7:90-9. http://dx.doi.org/10.1016/j.lssr.2015.10.005 ; PubMed PMID: 26553642 , Nov-2015
Articles in Peer-reviewed Journals Gronoff G, Norman RB, Mertens CJ. "Computation of cosmic ray ionization and dose at Mars. I: A comparison of HZETRN and Planetocosmics for proton and alpha particles." Advances in Space Research. 2015 Apr;55:1799-805. http://dx.doi.org/10.1016/j.asr.2015.01.028 , Apr-2015
Articles in Peer-reviewed Journals Straume T, Slaba TC, Bhattacharya S, Braby LA. "Cosmic-ray interaction data for designing biological experiments in space." Life Sci Space Res (Amst). 2017 May;13:51-59. https://doi.org/10.1016/j.lssr.2017.04.002 ; PubMed PMID: 28554510 , May-2017
Articles in Peer-reviewed Journals Norbury JW, Slaba TC, Sobolevsky N, Reddell B. "Comparing HZETRN, SHIELD, FLUKA and GEANT transport codes." Life Sci Space Res (Amst). 2017 Aug;14:64-73. Epub 2017 Apr 20. https://doi.org/10.1016/j.lssr.2017.04.001 ; PubMed PMID: 28887946 , Aug-2017
Articles in Peer-reviewed Journals Slaba TC, Stoffle NN. "Evaluation of HZETRN on the Martian surface: Sensitivity tests and model results." Life Sci Space Res. 2017 Aug;14:29-35. https://doi.org/10.1016/j.lssr.2017.03.001 ; PubMed PMID: 28887940 , Aug-2017
Articles in Peer-reviewed Journals Warner JE, Norman RB, Blattnig SR. "HZETRN radiation transport validation using balloon-based experimental data." Life Sci Space Res. 2018 May;17:23-31. https://doi.org/10.1016/j.lssr.2018.02.003 ; PMID: 29753410 , May-2018
Articles in Peer-reviewed Journals Norbury JW, Slaba TC, Aghara S, Badavi FF, Blattnig SR, Clowdsley MS, Heilbronn LH, Lee K, Maung KM, Mertens CJ, Miller J, Norman RB, Sandridge CA, Singleterry R, Sobolevsky N, Spangler JL, Townsend LW, Werneth CM, Whitman K, Wilson JW, Xu SX, Zeitlin C. "Advances in space radiation physics and transport at NASA." Life Sci Space Res (Amst). 2019 Aug;22:98-124. https://doi.org/10.1016/j.lssr.2019.07.003 ; PMID: 31421854. , Aug-2019
NASA Technical Documents Wilson JW, Slaba TC, Badavi FF, Reddell BD, Bahadori AA. "Solar Proton Transport within an ICRU Sphere Surrounded by a Complex Shield: Combinatorial Geometry." Hampton, VA: NASA Langley Research Center, 2015. NASA Technical Publication 218980. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160001628.pdf , Nov-2015
NASA Technical Documents Slaba TC, Wilson JW, Badavi FF, Reddell BD, Bahadori AA. "Solar Proton Transport within an ICRU Sphere Surrounded by a Complex Shield: Ray-Trace Geometry." Hampton, VA: NASA Langley Research Center, 2015. NASA Technical Publication 218994. http://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2015-218994.pdf , Dec-2015
Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2015 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 03/31/2016  
Task Last Updated: 07/08/2015 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Simonsen, Lisa  NASA Langley Research Center 
Werneth, Charles  NASA Langley Research Center 
Norman, Ryan  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor: Simonsen, Lisa  
Center Contact:  
lisa.c.simonsen@nasa.gov 
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Flight Assignment/Project Notes: NOTE: Extended to 3/31/2016 per S. Monk/LaRC (Ed., 9/14/15)

NOTE: Extended to 12/31/2015 per S. Monk/LaRC (Ed., 6/17/15)

Task Description: Currently, the deterministic space radiation transport code HZETRN (High charge (Z) and Energy TRaNsport), is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO (radiation health officer), and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physics improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer - 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (International Space Station-ISS, Lunar, or Mars)? Pion production models are also being worked on.

Research Impact/Earth Benefits: The radiation transport codes developed at NASA Langley Research Center can potentially be used in other applications such as proton and heavy ion therapy treatments for cancer.

Task Progress & Bibliography Information FY2015 
Task Progress: Active magnetic radiation shielding was re-evaluated. Many active magnetic shielding designs have been proposed in order to reduce the radiation exposure received by astronauts on long duration, deep space missions. While these designs are promising, they pose significant engineering challenges. This work presents a survey of the major systems required for such unconfined magnetic field design, allowing the identification of key technologies for future development. Basic mass calculations are developed for each system and are used to determine the resulting galactic cosmic radiation exposure for a generic solenoid design, using a range of magnetic field strength and thickness values, allowing some of the basic characteristics of such a design to be observed. The study focused on a solenoid shaped, active magnetic shield design; however, many of the principles discussed are applicable regardless of the exact design configuration, particularly the key technologies cited.

Shielding evaluation for solar particle events was studied and detailed analyses of Solar Particle Events (SPE) were performed to calculate primary and secondary particle spectra behind aluminum, at various thicknesses in water. The simulations were based on Monte Carlo (MC) radiation transport codes, MCNPX and PHITS, and the space radiation analysis website called OLTARIS (On-Line Tool for the Assessment of Radiation in Space) version 3.4 (uses deterministic code, HZETRN, for transport). The study investigated the impact of SPEs spectra transporting through 10 or 20 g/cm^2 Al shield followed by 30 g/cm2 of water slab. Four historical SPE events were selected and used as input source spectra and particle differential spectra for protons, neutrons, and photons are presented. The total particle fluence as a function of depth is presented. In addition to particle flux, the dose and dose equivalent values are calculated and compared between the codes and with the other published results. Overall, the particle fluence spectra from all three codes show good agreement with the MC codes showing closer agreement compared to the OLTARIS results. The neutron particle fluence from OLTARIS is lower than the results from MC codes at lower energies (E<100MeV). Based on mean square difference analysis the results from MCNPX and PHITS agree better for fluence, dose, and dose equivalent when compared to OLTARIS results.

Elastic differential cross sections for space radiation applications were evaluated. The eikonal, partial wave (PW) Lippmann-Schwinger, and three-dimensional Lippmann-Schwinger (LS3D) methods are compared for nuclear reactions that are relevant for space radiation applications. Numerical convergence of the eikonal method is readily achieved when exact formulas of the optical potential are used for light nuclei, and the momentum-space representation of the optical potential is used for heavier nuclei. The PW solution method is known to be numerically unstable for systems that require a large number of partial waves, and, as a result, the LS3D method is employed. The effect of relativistic kinematics is studied with the PWand LS3D methods and is compared to eikonal results. It is recommended that the LS3D method be used for high-energy nucleon-nucleus reactions and nucleus-nucleus reactions at all energies because of its rapid numerical convergence and stability.

The new trapped environment AE9/AP9/SPM at low Earth orbit was evaluated. The completion of the International Space Station (ISS) in 2011 has provided the space research community an ideal proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the validation of radiation environmental models, nuclear transport codes, and nuclear reaction cross sections. Indeed, prior measurements on the space transportation system (STS; shuttle) provided vital information impacting both the environmental models and the nuclear transport code developments by indicating the need for an improved dynamic model of the low Earth orbit (LEO) trapped environment. Additional studies using thermo-luminescent detector (TLD), tissue equivalent proportional counter (TEPC) area monitors, and computer aided design (CAD) model of earlier ISS configurations, confirmed STS observations that, as input, computational dosimetry requires an environmental model with dynamic and directional (anisotropic) behavior, as well as an accurate six degree of freedom (DOF) definition of the vehicle attitude and orientation along the orbit of ISS.

A new three dimensional (3D) version of the NASA transport code HZETRN was developed. The computationally efficient HZETRN code has been used in recent trade studies for lunar and Martian exploration and is currently being used in the engineering development of the next generation of space vehicles, habitats, and extra vehicular activity equipment. Code development has been based on a progression of approximations first assuming all particles are produced in the initiator direction of incidence (straight-ahead) later improved by treating neutrons produced in the backward hemisphere as moving straight-back (bi-directional). A new version (3DHZETRN) capable of transporting High charge (Z) and Energy (HZE) and light ions (including neutrons) under space-like boundary conditions with enhanced neutron and light ion propagation in transverse directions is developed. New algorithms for light ion and neutron propagation with well defined convergence criteria in 3D objects were developed and tested against Monte Carlo simulations of 3D effects.

A deterministic (non-statistical) two dimensional (2D) computational model describing the transport of electron and photon typical of space radiation environment in various shield media was developed. The 2D formalism is cast into a code which is an extension of a previously developed one dimensional (1D) deterministic electron and photon transport code. For candidate shielding materials, using the trapped electron radiation environments at low Earth orbit (LEO), geosynchronous orbit (GEO), and Jupiter moon Europa, verification of the 2D formalism vs. 1D and an existing Monte Carlo code was studied.

A Galactic Cosmic Ray (GCR) simulator was developed and is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at the NASA Space Radiation Lab (NSRL) are the main focus, but the analysis presented herein may be modified for other facilities. First, comparisons were made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It was found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly. Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It was found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, an approach for selecting beams at NSRL to simulate the designated reference field was developed. Drawbacks of the proposed methodology have been investigated and weighed against alternative simulation strategies.

A new Galactic Cosmic Ray Flux Model was developed. The Badhwar-O'Neill (BON) Galactic Cosmic Ray (GCR) model is based on GCR measurements from particle detectors. The model has mainly been used by NASA to certify microelectronic systems and the analysis of radiation health risks to astronauts in space missions. The BON14 model numerically solves the Fokker-Planck equation to account for particle transport in the heliosphere due to diffusion, convection, and adiabatic deceleration under the assumption of a spherically symmetric heliosphere. The model also incorporates an empirical time delay function to account for the lag of the solar activity to reach the boundary of the heliosphere. Using a comprehensive measurement database, it was shown that BON14 is significantly improved over the previous version, BON11.

The importance of neutrons and light ions was considered when astronauts spend considerable time in thickly shielded regions of a spacecraft. This may be relevant for space missions both in and beyond low Earth orbit. In addition to heavy ion experiments at accelerators, it is suggested that an increased emphasis on experiments with lighter ions may be useful in reducing biological uncertainties.

Estimates of extreme solar particle event radiation exposures on Mars were made. Estimates of effective doses and organ doses for male and female crewmembers are made for solar particle event proton environments comparable to several of the most significant solar particle events, which occurred in the second half of the 19th century. The incident proton energy distributions for these solar particle events are assumed to be similar to that of the November 1960 event, one of the most energetic of the modern space era. The crewmembers are assumed to be located at the mean surface elevation on Mars, at the lowest elevation on Mars in the Hellas Impact Basin, and on the summit of Olympus Mons, the highest surface elevation on Mars. The crewmembers were assumed to be shielded by the overlying carbon dioxide atmosphere of Mars, and locally shielded by a space suit, a surface landing spacecraft, or a surface habitat. These estimates are compared with current NASA Permissible Exposure Limits.

This report was compiled from abstracts of papers listed in the bibliography.

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Norbury J, Slaba T. "Space radiation accelerator experiments – The role of neutrons and light ions." Life Sciences in Space Research. 2014 Oct;3:90-4. http://dx.doi.org/10.1016/j.lssr.2014.09.006 , Oct-2014
Articles in Peer-reviewed Journals Badavi FF. "Validation of the new trapped environment AE9/AP9/SPM at low Earth orbit." Advances in Space Research. 2014 Sep 15;54(6):917-28. http://dx.doi.org/10.1016/j.asr.2014.05.010 , Sep-2014
Articles in Peer-reviewed Journals Washburn SA, Blattnig SR, Singleterry RC, Westover SC. "Active magnetic radiation shielding system analysis and key technologies" Life Sciences in Space Research. 2015 Jan;4:22-34. http://dx.doi.org/10.1016/j.lssr.2014.12.004 , Jan-2015
Articles in Peer-reviewed Journals Wilson JW, Slaba TC, Badavi FF, Reddell BD, Bahadori AA. "Advances in NASA radiation transport research: 3DHZETRN." Life Sciences in Space Research. 2014 Jul;2:6-22. http://dx.doi.org/10.1016/j.lssr.2014.05.003 , Jul-2014
Articles in Peer-reviewed Journals Wilson JW, Slaba TC, Badavi FF, Reddell BD, Bahadori AA. "3DHZETRN: Shielded ICRU spherical phantom." Life Sciences in Space Research. 2015 Jan;4:46-61. http://dx.doi.org/10.1016/j.lssr.2015.01.002 , Jan-2015
Articles in Peer-reviewed Journals Werneth CM, Maung KM, Ford WP, Norbury JW, Vera MD. "Elastic differential cross sections for space radiation applications." Physical Review C. 2014 Dec 9;90(6):064905. http://dx.doi.org/10.1103/PhysRevC.90.064905 , Dec-2014
Articles in Peer-reviewed Journals Townsend LW, Adamczyk AM, Werneth CM, Moussa HM, Townsend JP. "Estimates of extreme solar particle event radiation exposures on Mars." Progress in Nuclear Science and Technology. 2014;4:793-7. http://dx.doi.org/10.15669/pnst.4.793 , Jan-2014
Articles in Peer-reviewed Journals Badavi FF, Nealy JE. "A deterministic computational model for the two dimensional electron and photon transport." Acta Astronautica. 2014 Dec;105(2):476-86. http://dx.doi.org/10.1016/j.actaastro.2014.10.030 , Dec-2014
Articles in Peer-reviewed Journals Badavi FF, Walker SA, Santos Koos LM. "Low Earth orbit assessment of proton anisotropy using AP8 and AP9 trapped proton models." Life Sci Space Res. 2015 Apr;5:21-30. http://dx.doi.org/10.1016/j.lssr.2015.04.001 , Apr-2015
Articles in Peer-reviewed Journals Aghara SK, Sriprisan SI, Singleterry RC, Sato T. "Shielding evaluation for solar particle events using MCNPX, PHITS and OLTARIS codes." Life Sciences in Space Research. 2015 Jan;4:79-91. http://dx.doi.org/10.1016/j.lssr.2014.12.003 , Jan-2015
NASA Technical Documents O'Neill PM, Golge S, Slaba TC. "Badhwar-O'Neill 2014 galactic cosmic ray flux model description." Houston, TX: NASA Johnson Space Center, 2015 Mar. 32 p. NASA/TP-2015-218569. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150003026.pdf ; accessed 11/13/19. , Mar-2015
NASA Technical Documents Wilson J, Slaba T, Badavi F, Reddell B, Bahadori A. "A 3DHZETRN Code in a Spherical Uniform Sphere with Monte Carlo Verification." Hampton, VA: NASA Langley Research Center, 2014 May. 40 p. NASA Technical Paper 2014-218271. http://spaceradiation.larc.nasa.gov/nasapapers/NASA-TP-2014-218271.pdf , May-2014
NASA Technical Documents Slaba TC, Blattnig SR, Norbury JW, Rusek A, La Tessa C, Walker SA. "GCR Simulator Reference Field and a Spectral Approach for Laboratory Simulation." Hampton, VA: NASA Langley Research Center, 2015 Mar. 31 p. NASA Technical Paper 2015-218698 NASA/TP-2015-218698. http://ntrs.nasa.gov/search.jsp?R=20150003791&hterms=gcr+simulator&qs=Ntx%3Dmode%2Bmatchallany%26Ntk%3DAll%26N%3D0%26Ntt%3Dgcr%2Bsimulator , Mar-2015
Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2014 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 12/31/2015  
Task Last Updated: 07/14/2014 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Simonsen, Lisa  NASA Langley Research Center 
Werneth, Charles  NASA Langley Research Center 
Norman, Ryan  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor: Simonsen, Lisa  
Center Contact:  
lisa.c.simonsen@nasa.gov 
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Flight Assignment/Project Notes: NOTE: Extended to 12/31/2015 per S. Monk/LaRC (Ed., 6/17/15)

Task Description: Currently, the deterministic space radiation transport code HZETRN (High charge (Z) and Energy TRaNsport), is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO, and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physic improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer - 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (ISS, Lunar, or Mars)? Pion production models are also being worked on.

Research Impact/Earth Benefits: The radiation transport codes developed at NASA Langley Research Center can potentially be used in other applications such as proton and heavy ion therapy treatments for cancer.

Task Progress & Bibliography Information FY2014 
Task Progress: Improvements to photonuclear cross sections were made. The Weisskopf-Ewing (WE) and Hauser-Feshbach (HF) theory are statistical methods, which are often used to calculate photonuclear cross sections for compound nucleus reactions. In our past work, WE methodology was presented and photonuclear reaction cross sections for nucleon emission were calculated using WE theory. Now, the previous results, which neglect pre-equilibrium emissions and do not include multiple particle emission, were compared to those calculated with HF theory and experimental data. For the reactions we considered, it was found that the WE theory and HF method are in reasonable agreement below the two neutron separation energy assuming an energy dependent branching ratio for intermediate and heavy nuclei.

The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) has been developed. It makes integral use of the HZETRN code, which has been developed under the Human Research Program. NAIRAS is a real-time, global, physics-based model used to assess radiation exposure to commercial aircrews and passengers. The model is a free-running physics-based model in the sense that there are no adjustment factors applied to nudge the model into agreement with measurements. The model predicts dosimetric quantities in the atmosphere from both galactic cosmic rays (GCR) and solar energetic particles, including the response of the geomagnetic field to interplanetary dynamical processes and its subsequent influence on atmospheric dose. The focus of the work is on atmospheric GCR exposure during geomagnetically quiet conditions, with three main objectives. First, provide detailed descriptions of the NAIRAS GCR transport and dosimetry methodologies. Second, present a climatology of effective dose and ambient dose equivalent rates at typical commercial airline altitudes representative of solar cycle maximum and solar cycle minimum conditions and spanning the full range of geomagnetic cutoff rigidities. Third, conduct an initial validation of the NAIRAS model by comparing predictions of ambient dose equivalent rates with tabulated reference measurement data and recent aircraft radiation measurements taken in 2008 during the minimum between solar cycle 23 and solar cycle 24. By applying the criterion of the International Commission on Radiation Units and Measurements (ICRU) on acceptable levels of aircraft radiation dose uncertainty for ambient dose equivalent greater than or equal to an annual dose of 1 mSv, the NAIRAS model is within 25% of the measured data, which fall within the ICRU acceptable uncertainty limit of 30%. The NAIRAS model predictions of ambient dose equivalent rate are generally within 50% of the measured data for any single-point comparison. The largest differences occur at low latitudes and high cutoffs, where the radiation dose level is low. Nevertheless, analysis suggests that these single-point differences will be within 30% when a new deterministic pion-initiated electromagnetic cascade code is integrated into NAIRAS, an effort which is currently underway.

Estimates of Carrington class solar particle even radiation exposures were made as a function of altitude in the atmosphere of Mars. Radiation exposure estimates for crew members on the surface of Mars may vary widely because of the large variations in terrain altitude. The maximum altitude difference between the highest (top of Olympus Mons) and the lowest (bottom of the Hellas impact basin) points on Mars is about 32 km. In this work estimates of radiation exposures as a function of altitude, from the Hellas impact basin to Olympus Mons, are made for a solar particle event proton radiation environment comparable to the Carrington event of 1859. We assume that the proton energy distribution for this Carrington-type event is similar to that of the Band Function fit of the February 1956 event. In this work we use the HZETRN 2010 radiation transport code, originally developed at NASA Langley Research Center, and the Computerized Anatomical Male and Female human geometry models to estimate exposures for aluminum shield areal densities similar to those provided by a spacesuit, surface lander, and permanent habitat as a function of altitude in the Mars atmosphere. Comparisons of the predicted organ exposures with current NASA Permissible Exposure Limits (PELs) are made.

A comparative study of space radiation organ doses and associated cancer risks using Particle and Heavy Ion Transport Code System (PHITS) and HZETRN was performed. NASA currently uses one dimensional deterministic transport to generate values of the organ dose equivalent needed to calculate stochastic radiation risk following crew space exposures. In this study, organ absorbed doses and dose equivalents were calculated for 50th percentile male and female astronaut phantoms using both the NASA High Charge and Energy Transport Code to perform one-dimensional deterministic transport and the Particle and Heavy Ion Transport Code System to perform three-dimensional Monte Carlo transport. Two measures of radiation risk, effective dose and risk of exposure-induced death (REID) are calculated using the organ dose equivalents resulting from the two methods of radiation transport. For the space radiation environments and simplified shielding configurations considered, small differences (<8%) in the effective dose and REID are found. However, for the galactic cosmic ray (GCR) boundary condition, compensating errors are observed, indicating that comparisons between the integral measurements of complex radiation environments and code calculations can be misleading. Code-to-code benchmarks allow for the comparison of differential quantities, such as secondary particle differential fluence, to provide insight into differences observed in integral quantities for particular components of the GCR spectrum.

The new radiation belt AE9/AP9/SPM model for a cislunar mission was evaluated. Space mission planners continue to experience challenges associated with human space flight. Concerned with the omnipresence of harmful ionizing radiation in space, at the mission design stage, mission planners must evaluate the amount of exposure the crew of a spacecraft is subjected to during the transit trajectory from low Earth orbit (LEO) to geosynchronous orbit (GEO) and beyond (free space). The Earth’s geomagnetic field is located within the domain of LEO-GEO and, depending on latitude, extends out some 40,000 - 60,000 km. This field contains the Van Allen trapped electrons, protons, and low-energy plasmas, such as the nuclei of hydrogen, helium, oxygen, and to a lesser degree other atoms. In addition, there exist the geomagnetically attenuated energetic galactic cosmic rays (GCR). These particles are potentially harmful to improperly shielded crew members and onboard subsystems. Mitigation strategies to limit the exposure due to free space GCR and sporadic solar energetic particles (SEP) such as flare and coronal mass ejection (CME) must also be exercised beyond the trapped field. Presented in this work is the exposure analysis for a multi-vehicle mission planned for the epoch of February 2020 from LEO to the Earth-moon Lagrange-point two (L2), located approximately 63,000 km beyond the orbit of the Earth-moon binary system. Space operation at L2 provides a gravitationally stable orbit for a vehicle and partially eliminates the need for periodic thrust-vectoring to maintain orbital stability. In the cislunar (Earth-moon) space of L2, the mission trajectory and timeline in this work call for a cargo vehicle to rendezvous with a crew vehicle. This is followed by 15 days of space activities at L2 while the cargo and crew vehicles are docked after which the crew returns to Earth. The mission epoch of 2020 is specifically chosen as it is anticipated that the next solar minimum (i.e. end of cycle 24) in the Sun’s approximate 11 years cycle will take place around this time. From a mission planning point of view, this date is ideal as the predictable GCR exposure will be at a maximum, while the sporadic SEP will be at a minimum. In addition, it is anticipated that by 2020 a vehicle capable of launching a crew of four will be operationally ready. During the LEO–GEO transit, the crew and cargo vehicles will encounter exposure from trapped particles and attenuated GCR, followed by free space exposure due to GCR and SEP during solar active times. Within the trapped field, a challenge arises from properly calculating the amount of exposure acquired. Within this field, in the absence of SEP (i.e. solar quiet times), the vehicles will have to transit through an inner proton belt, an inner and outer electron belts, and an attenuated GCR field. There exist a number of models to define the intensities of the trapped particles during the quiet and active SEP. Among the more established trapped models are the historic and popular electron/proton AE8/AP8 model dating back to the 1980s, the historic and less popular electron/proton Combined Release and Radiation Effects Satellite (CRRES) model dating back to 1990s, and the recently released electron/proton/space plasma AE9/AP9/SPM model.

Radiation shielding effectiveness with correlated uncertainties was evaluated. The space radiation environment is composed of energetic particles which can deliver harmful doses of radiation that may lead to acute radiation sickness, cancer, and even death for insufficiently shielded crew members. Spacecraft shielding must provide structural integrity and minimize the risk associated with radiation exposure. The risk of radiation exposure induced death (REID) is a measure of the risk of dying from cancer induced by radiation exposure. Uncertainties in the risk projection model, quality factor, and spectral fluence are folded into the calculation of the REID by sampling from probability distribution functions. Consequently, determining optimal shielding materials that reduce the REID in a statistically significant manner has been found to be difficult. In this work, the difference of the REID distributions for different materials is used to study the effect of composition on shielding effectiveness. It is shown that the use of correlated uncertainties allows for the determination of statistically significant differences between materials despite the large uncertainties in the quality factor. This is in contrast to previous methods where uncertainties have been generally treated as uncorrelated. It is concluded that the use of correlated quality factor uncertainties greatly reduces the uncertainty in the assessment of shielding effectiveness for the mitigation of radiation exposure.

Nucleus-nucleus relativistic multiple scattering theory with delta degrees of freedom was studied. It is well known that multiple scattering theories are very useful in the study of nucleon-nucleus and nucleus-nucleus scattering processes. The derivation of a nonrelativistic multiple scattering theory (NRMST) is well established and clear. A key component to the formulation of an NRMST is the ability to separate the unperturbed Hamiltonian from the residual interaction. For the relativistic problem, it is not clear how to perform this separation starting from a field theoretical Lagrangian. Instead, one starts from an infinite set of Feynman diagrams, which play the role of the kernel in the Bethe-Salpeter equation for nucleus-nucleus scattering. Once the kernel is defined, it is straightforward to develop a relativistic multiple scattering theory (RMST). To be more complete than previous studies, delta degrees of freedom are included, which is a minimum requirement to explain pion production. It is demonstrated that an RMST can be formulated by expressing the kernel in a form that is similar to the residual interaction in the NRMST.

Finite sum expressions for elastic and reaction cross section were derived. Nuclear cross section calculations are often performed by using the partial wave method or the Eikonal method through Glauber theory. The expressions for the total cross section, total elastic cross section, and total reaction cross section in the partial wave method involve infinite sums and do not utilize simplifying approximations. Conversely, the Eikonal method gives these expressions in terms of integrals but utilizes the high energy and small angle approximations. In this paper, by using the fact that the lth partial wave component of the T-matrix can be very accurately approximated by its Born term, the infinite sums in each of the expressions for the differential cross section, total elastic cross section, total cross section, and total reaction cross section are re-written in terms of finite sums plus closed form expressions. The differential cross sections are compared to the Eikonal results for elastic scattering. Total cross sections, total reaction cross sections, and total elastic cross sections are compared to the Eikonal results.

Influence of dust loading on atmospheric ionizing radiation on Mars was studied. Measuring the radiation environment at the surface of Mars is the primary goal of the Radiation Assessment Detector on the NASA Mars Science Laboratory’s Curiosity rover. One of the conditions that Curiosity will likely encounter is a dust storm. The objective of this paper is to compute the cosmic ray ionization in different conditions, including dust storms, as these various conditions are likely to be encountered by Curiosity at some point. In the present work, the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety model, recently modified for Mars, was used along with the Badhwar & O’Neill 2010 galactic cosmic ray model. In addition to galactic cosmic rays, five different solar energetic particle event spectra were considered. For all input radiation environments, radiation dose throughout the atmosphere and at the surface was investigated as a function of atmospheric dust loading. It is demonstrated that for galactic cosmic rays, the ionization depends strongly on the atmosphere profile. Moreover, it is shown that solar energetic particle events strongly increase the ionization throughout the atmosphere, including ground level, and can account for the radio blackout conditions observed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on the Mars Express spacecraft. These results demonstrate that the cosmic rays’ influence on the Martian surface chemistry is strongly dependent on solar and atmospheric conditions that should be taken into account for future studies.

An analytical-HZETRN model for rapid assessment of active magnetic radiation shielding was developed. The use of active radiation shielding designs has the potential to reduce the radiation exposure received by astronauts on deep space missions at a significantly lower mass penalty than designs utilizing only passive shielding. Unfortunately, the determination of the radiation exposure inside these shielded environments often involves lengthy and computationally intensive Monte Carlo analysis. In order to evaluate the large trade space of design parameters associated with a magnetic radiation shield design, an analytical model was developed for the determination of flux inside a solenoid magnetic field due to the Galactic Cosmic Radiation (GCR) radiation environment. This analytical model was then coupled with NASA’s radiation transport code, HZETRN, to account for the effects of passive/structural shielding mass. The resulting model can rapidly obtain results for a given configuration and can therefore be used to analyze an entire trade space of potential variables in less time than is required for even a single Monte Carlo run. Analyzing this trade space for a solenoid magnetic shield design indicates that active shield bending powers greater than about 15 Tm and passive/structural shielding thicknesses greater than 40 g/cm2 have a limited impact on reducing dose equivalent values. Also, it is shown that higher magnetic field strengths are more effective than thicker magnetic fields at reducing dose equivalent.

A sensitivity analysis for galactic cosmic ray environments was performed. Accurate galactic cosmic ray (GCR) models are required to assess crew exposure during long-duration missions to the Moon or Mars. Many of these models have been developed and compared to available measurements, with uncertainty estimates usually stated to be less than 15%. However, when the models are evaluated over a common epoch and propagated through to effective dose, relative differences exceeding 50% are observed. This indicates that the metrics used to communicate GCR model uncertainty can be better tied to exposure quantities of interest for shielding applications. This is the first of three papers focused on addressing this need. In this work, the focus is on quantifying the extent to which each GCR ion and energy group, prior to entering any shielding material or body tissue, contributes to effective dose behind shielding. Results can be used to more accurately calibrate model-free parameters and provide a mechanism for refocusing validation efforts on measurements taken over important energy regions. Results can also be used as references to guide future nuclear cross-section measurements and radiobiology experiments. It is found that GCR with Z > 2 and boundary energies below 500 MeV/n induce less than 5% of the total effective dose behind shielding. This finding is important given that most of the GCR models are developed and validated against Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer (ACE/CRIS) measurements taken below 500 MeV/n. It is therefore possible for two models to very accurately reproduce the ACE/CRIS data while inducing very different effective dose values behind shielding.

This report was compiled from abstract of papers listed in the bibliography.

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Badavi FF, Walker SA, Santos Koos LM. "Evaluation of the new radiation belt AE9/AP9/SPM model for a cislunar mission." Acta Astronautica. 2014 Sep-Oct;102:156-68. http://dx.doi.org/10.1016/j.actaastro.2014.06.008 , Sep-2014
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR. "GCR environmental models II: Uncertainty propagation methods for GCR environments." Space Weather. 2014 Apr;12(4):225-32. http://dx.doi.org/10.1002/2013SW001026 , Apr-2014
Articles in Peer-reviewed Journals Slaba TC, Xu X, Blattnig SR, Norman RB. "GCR environmental models III: GCR model validation and propagated uncertainties in effective dose." Space Weather. 2014 Apr;12(4):233-45. http://dx.doi.org/10.1002/2013SW001027 , Apr-2014
Articles in Peer-reviewed Journals Mertens CJ, Meier MM. "Reply to comment by Socol et al. on 'NAIRAS aircraft radiation model development, dose climatology, and initial validation.' " Space Weather. 2014 Feb;12(2):122. http://dx.doi.org/10.1002/2014SW001034 , Feb-2014
Articles in Peer-reviewed Journals Tobiska W, Gersey B, Wilkins R, Mertens C, Atwell W, Bailey J. "Reply to comment by Rainer Facius et al. on 'U.S. Government shutdown degrades aviation radiation monitoring during solar radiation storm.' " Space Weather. 2014 Jan;12(1):1-2. , Jan-2014
Articles in Peer-reviewed Journals Washburn SA, Blattnig SR, Singleterry RC, Westover SC. "Analytical-HZETRN model for rapid assessment of active magnetic radiation shielding." Advances in Space Research. 2014 Jan;53(1):8-17. http://dx.doi.org/10.1016/j.asr.2013.09.038 , Jan-2014
Articles in Peer-reviewed Journals Norman RB, Gronoff G, Mertens CJ. "Influence of dust loading on atmospheric ionizing radiation on Mars." Journal of Geophysical Research: Space Physics. 2014 Jan;119(1):452-61. http://dx.doi.org/10.1002/2013JA019351 , Jan-2014
Articles in Peer-reviewed Journals Werneth CM, Maung KM, Blattnig SR, Clowdsley MS, Townsend LW. "Radiation shielding effectiveness with correlated uncertainties." Radiation Measurements. 2014 Jan;60:23-34. http://dx.doi.org/10.1016/j.radmeas.2013.11.008 , Jan-2014
Articles in Peer-reviewed Journals Townsend LW, Anderson JA, Adamczyk AM, Werneth CM. "Estimates of Carrington-class solar particle event radiation exposures as a function of altitude in the atmosphere of Mars." Acta Astronautica. 2013 Aug-Sep;89:189-94. http://dx.doi.org/10.1016/j.actaastro.2013.04.010 , Aug-2013
Articles in Peer-reviewed Journals Bahadori AA, Sato T, Slaba TC, Shavers MR, Semones EJ, Van Baalen M, Bolch WE. "A comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN." Physics in Medicine and Biology. 2013 Oct 21;58(20):7183-207. http://dx.doi.org/10.1088/0031-9155/58/20/7183 ; PubMed PMID: 24061091 , Oct-2013
Articles in Peer-reviewed Journals Mertens CJ, Meier MM, Brown S, Norman RB, Xu X. "NAIRAS aircraft radiation model development, dose climatology, and initial validation." Space Weather. 2013 Oct;11(10):603-35. http://dx.doi.org/10.1002/swe.20100 , Oct-2013
Articles in Peer-reviewed Journals Singleterry RC. "Radiation engineering analysis of shielding materials to assess their ability to protect astronauts in deep space from energetic particle radiation." Acta Astronautica. 2013 Oct-Nov;91:49-54. http://dx.doi.org/10.1016/j.actaastro.2013.04.013 , Oct-2013
Articles in Peer-reviewed Journals Werneth CM, Maung KM, Mead LR, Blattnig SR. "Finite sum expressions for elastic and reaction cross sections." Nuclear Instruments and Methods in Physics Research B. 2013 Aug;308:40-5. http://dx.doi.org/10.1016/j.nimb.2013.05.003 , Aug-2013
Articles in Peer-reviewed Journals Werneth CM, Maung KM. "Nucleus–nucleus relativistic multiple scattering theory with delta degrees of freedom." Canadian Journal of Physics. 2013 May;91(5):424-32. http://dx.doi.org/10.1139/cjp-2012-0519 , May-2013
Articles in Peer-reviewed Journals Adamczyk AM, Norbury JW, Townsend LW. "Weisskopf-Ewing and Hauser-Feshbach calculations of photonuclear cross sections used for electromagnetic dissociation." Radiation Physics and Chemistry. 2013 Sep;90:21-5. http://dx.doi.org/10.1016/j.radphyschem.2013.04.027 , Sep-2013
Articles in Peer-reviewed Journals Joshi RP, Qiu H, Tripathi RK. "Evaluation of a combined electrostatic and magnetostatic configuration for active space-radiation shielding." Advances in Space Research. 2013 May;51(9):1784–91. http://dx.doi.org/10.1016/j.asr.2012.12.016 , May-2013
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR. "GCR environmental models I: Sensitivity analysis for GCR environments." Space Weather. 2014 Apr;12(4):217-24. http://dx.doi.org/10.1002/2013SW001025 , Apr-2014
Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2013 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 09/30/2015  
Task Last Updated: 07/10/2013 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Simonsen, Lisa  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor: Simonsen, Lisa  
Center Contact:  
lisa.c.simonsen@nasa.gov 
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Task Description: Currently, the deterministic space radiation transport code HZETRN (High charge (Z) and Energy TRaNsport), is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO, and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physic improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer - 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (ISS, Lunar, or Mars)? Pion production models are also being worked on.

Research Impact/Earth Benefits: The radiation transport codes developed at NASA Langley Research Center can potentially be used in other applications such as proton and heavy ion therapy treatments for cancer.

Task Progress & Bibliography Information FY2013 
Task Progress: Exposure estimates have been made for repair satellites at geosynchronous orbit. Communications and weather satellites in geosynchronous (GEO) and geostationary orbits (GSO) are revolutionizing our ability to almost instantly communicate with each other, capture high resolution global imagery for weather forecasting and obtain a multitude of other geophysical data for environmental protection purposes. The rapid increase in the number of satellites at GEO is partly due to the exponential expansion of the internet, its commercial potential, and the need to deliver a large amount of digital information in near real time. With the large number of satellites operating at GEO and particularly at GSO, there is a need to think of viable approaches to retrieve, rejuvenate, and perhaps repair these satellites. The first step in this process is a detailed understanding of the ionizing radiation environment at GEO. Currently, the most widely used trapped particle radiation environment definition near Earth is based on NASA’s static AP8/AE8 models which define the trapped proton and electron intensities. These models are based on a large number of satellite measurements carried out in the 1960s and 1970s. The AP8/AE8 models as well as a heavy ion galactic cosmic ray (GCR) model were used to define the radiation environments for protons, electrons and heavy ions at low Earth orbit (LEO), medium Earth orbit (MEO), and GEO. LEO and MEO dosimetric calculations are included in the analysis since any launch platform capable of delivering a payload to GEO will accumulate exposure during its transit through LEO and MEO. The computational approach (particle transport) taken was to use the static LEO, MEO, GEO, and geomagnetically attenuated GCR environments as input to the two deterministic particle transport codes called HZETRN and CEPTRN. This was done through exposure prediction within a spherical shell, a legacy Apollo era command service module configuration, and a large modular structure represented by a specific configuration of the International Space Station. Conclusions were drawn on the exposure levels accumulated by these geometries throughout a mission to GEO.

Light ion and multiple nucleon removal cross sections due to electromagnetic dissociation were calculated. Light ion (H and He isotopes) and neutron production in galactic cosmic ray interactions are important for space radiation analyses. They occur via strong or electromagnetic dissociation (EMD) interactions. A parameterization for single nucleon, multiple nucleon and light ion production in EMD was developed which supersedes previous work in the following ways. The calculations were compared to a more extensive set of experimental data. EMD calculations for alpha particle production were in better agreement with experiment. Finally, a parameterization of multiple nucleon removal was developed and compared to data. Overall, the new work includes more reactions and compares better to experimental data than previous calculations.

An extension of the radiation transport code HZETRN, for cosmic ray initiated electromagnetic cascades, was developed. Safe and efficient mission operations in space require an accurate understanding of the physical interactions of space radiation. As the primary space radiation interacts with intervening materials, the composition and spectrum of the radiation environment changes. The production of secondary particles can make a significant contribution to radiation exposure. HZETRN was extended to include the transport of electrons, positrons, and photons. The production of these particles is coupled to the initial cosmic ray radiation environment through the decay of neutral pions, which produce high energy photons, and through the decay of muons, which produce electrons and positrons. The photons, electrons, and positrons interact with materials producing more photons, electrons and positrons generating an electromagnetic cascade. Electron and positron production in Earth’s atmosphere was investigated and compared to experimental balloon-flight measurements. Reasonable agreement was seen between HZETRN and data.

Validation of nuclear models used in space radiation shielding applications was undertaken. Validation metrics applicable to testing both model accuracy and consistency with experimental data were developed. The developed metrics treat experimental measurement uncertainty as an interval and are therefore applicable to cases in which epistemic uncertainty dominates the experimental data. To demonstrate the applicability of the metrics, nuclear physics models used by NASA for space radiation shielding applications were compared to an experimental database consisting of over 3600 experimental cross sections. A cumulative uncertainty metric was applied to the question of overall model accuracy, while a metric based on the median uncertainty was used to analyze the models from the perspective of model development by examining subsets of the model parameter space.

Pion and electromagnetic contribution to dose and comparisons of HZETRN to Monte Carlo results and ISS data was studied. Recent work has indicated that pion production and the associated electromagnetic (EM) cascade may be an important contribution to the total astronaut exposure in space. Recent extensions to HZETRN allow the production and transport of pions, muons, electrons, positrons, and photons. The extended code was compared to the Monte Carlo codes, Geant4, PHITS, and FLUKA, in slab geometries exposed to galactic cosmic ray (GCR) boundary conditions. While improvements in the HZETRN transport formalism for the new particles are needed, it was shown that reasonable agreement on dose is found at larger shielding thicknesses commonly found on the International Space Station (ISS). The extended code was compared to ISS data on a minute-by-minute basis over a seven day period in 2001. The impact of pion/EM production on exposure estimates and validation results wa clearly shown. The Badhwar–O’Neill (BO) 2004 and 2010 models were used to generate the GCR boundary condition at each time-step allowing the impact of environmental model improvements on validation results to be quantified as well. It was found that the updated BO2010 model noticeably reduces overall exposure estimates from the BO2004 model, and the additional production mechanisms in HZETRN provide some compensation. It was shown that the overestimates provided by the BO2004 GCR model in previous validation studies led to deflated uncertainty estimates for environmental, physics, and transport models, and allowed an important physical interaction (pion/EM) to be overlooked in model development. Despite the additional pion/EM production mechanisms in HZETRN, a systematic under-prediction of total dose was observed in comparison to Monte Carlo results and measured data.

Reduced discretization error was achieved with HZETRN. In a previous work, numerical methods in the code were reviewed, and new methods were developed that further improved efficiency and reduced overall discretization error. It was also shown that the remaining discretization error could be attributed to low energy light ions (A < 4) with residual ranges smaller than the physical step-size taken by the code. Accurately resolving the spectrum of low energy light particles is important in assessing risk associated with astronaut radiation exposure. Modifications to the light particle transport formalism were presented that accurately resolve the spectrum of low energy light ion target fragments. The modified formalism was shown to significantly reduce overall discretization error and allowed a physical approximation to be removed. For typical step-sizes and energy grids used in HZETRN, discretization errors for the revised light particle transport algorithms are shown to be less than 4% for aluminum and water shielding thicknesses as large as 100 g/cm2 exposed to both solar particle event and galactic cosmic ray environments.

Heavy ion contributions to organ dose equivalent for the 1977 galactic cosmic ray spectrum was investigated. Estimates of organ dose equivalents for the skin, eye lens, blood forming organs, central nervous system, and heart of female astronauts from exposures to the 1977 solar minimum galactic cosmic radiation spectrum for various shielding geometries involving simple spheres and locations within the Space Transportation System (space shuttle) and the International Space Station (ISS) were made using the HZETRN 2010 space radiation transport code. The dose equivalent contributions were broken down by charge groups in order to better understand the sources of the exposures to these organs. For thin shields, contributions from ions heavier than alpha particles comprise at least half of the organ dose equivalent. For thick shields, such as the ISS locations, heavy ions contribute less than 30% and in some cases less than 10% of the organ dose equivalent. Secondary neutron production contributions in thick shields also tend to be as large, or larger, than the heavy ion contributions to the organ dose equivalents.

Pion cross section parameterizations were developed for use in space radiation codes. The space radiation environment consists of energetic particles that originate from the Sun and from sources outside the solar system. It is necessary to understand how these particles interact with materials to design effective radiation shielding. The transport of radiation through materials can be described by the Boltzmann equation. Efficient space radiation transport codes often require parameterized energy-dependent spectral distributions. A recent study showed that pions may contribute considerably to the total dose in galactic cosmic ray environments. Consequently, accurate parameterized pion spectral distributions are needed. In other studies, the Badhwar parameterization has been used for inclusive pion production in high energy nucleon-nucleon and nucleon-nucleus collisions, whereas a thermal model has been used to describe pion production in low energy nuclear collisions. The thermal model was parameterized in terms of projectile energy, projectile nucleon number, and target nucleon number. Thermal and Badhwar model predictions of pion spectra from nucleon-nucleus and nucleus-nucleus collisions were compared for projectile energies ranging from 0.3 to 158 A GeV. It is recommended that the thermal model be used for projectile energies between 0.4 and 5 A GeV and the Badhwar model be used for higher projectile energies.

This report was compiled from abstracts of papers listed in the bibliography.

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Norbury JW, Miller J. "Review of nuclear physics experimental data for space radiation." Health Physics. 2012 Nov;103(5):640-2. http://dx.doi.org/10.1097/HP.0b013e318261fb7f ; PubMed PMID: 23032893 , Nov-2012
Articles in Peer-reviewed Journals Norbury J. "Nuclear physics and space radiation." Journal of Physics: Conference Series. 2012 Sep;381:012117. http://dx.doi.org/10.1088/1742-6596/381/1/012117 , Sep-2012
Articles in Peer-reviewed Journals Slaba T, Blattnig S, Tweed J. "Reduced discretization error in HZETRN." Journal of Computational Physics. 2013 Feb;234:217-29. http://dx.doi.org/10.1016/j.jcp.2012.09.042 , Feb-2013
Articles in Peer-reviewed Journals Norbury J. "Light ion and multiple nucleon removal due to electromagnetic dissociation." Nuclear Instruments and Methods in Physics Research A. 2013 Mar;703:220-43. http://dx.doi.org/10.1016/j.nima.2012.10.027 , Mar-2013
Articles in Peer-reviewed Journals Werneth C, Norbury J, Blattnig S. "Pion cross section parameterizations for space radiation codes." Nuclear Instruments and Methods in Physics Research B. 2013 Mar;298:86-95. http://dx.doi.org/10.1016/j.nimb.2012.12.121 , Mar-2013
Articles in Peer-reviewed Journals Walker SA, Townsend LW, Norbury JW. "Heavy ion contributions to organ dose equivalent for the 1977 galactic cosmic ray spectrum." Advances in Space Research. 2013 May 1;51(9):1792-9. http://dx.doi.org/10.1016/j.asr.2012.12.011 , May-2013
Articles in Peer-reviewed Journals Norman RB, Slaba TC, Blattnig SR. "An extension of HZETRN for cosmic ray initiated electromagnetic cascades." Advances in Space Research. 2013 Jun 15;51(12):2251-60. http://dx.doi.org/10.1016/j.asr.2013.01.021 , Jun-2013
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Reddell B, Bahadori A, Norman RB, Badavi FF. "Pion and electromagnetic contribution to dose: Comparisons of HZETRN to Monte Carlo results and ISS data." Advances in Space Research. 2013 Jul 1;52(1):62-78. http://dx.doi.org/10.1016/j.asr.2013.02.015 , Jul-2013
Articles in Peer-reviewed Journals Blattnig SR, Luckring JM, Morrison JH, Sylvester AJ, Tripathi RK, Zang TA. "NASA Standard for Models and Simulations: Philosophy and requirements overview." Journal of Aircraft. 2013 Jan;50(1):20-8. http://dx.doi.org/10.2514/1.C000303 , Jan-2013
Articles in Peer-reviewed Journals Badavi F. "Exposure estimates for repair satellites at geosynchronous orbit." Acta Astronautica. 2013 Feb-Mar;83:18–26. http://dx.doi.org/10.1016/j.actaastro.2012.09.021 , Feb-2013
Articles in Peer-reviewed Journals Norman RB, Blattnig SR. "Validation of nuclear models used in space radiation shielding applications." Journal of Computational Physics. 2013 Jan 15;233:464-79. http://dx.doi.org/10.1016/j.jcp.2012.09.006 , Jan-2013
NASA Technical Documents Slaba TC. "Faster Heavy Ion Transport for HZETRN." Hampton, VA : NASA Langley Research Center, 2013. NASA technical publication 2013-217803. (NASA/TP–2013-217803) http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130009742_2013009193.pdf , Feb-2013
NASA Technical Documents Werneth CM, Maung KM, Blattnig SR, Clowdsley MS, Townsend LW. "Correlated Uncertainties in Radiation Shielding Effectiveness." Hampton, VA : NASA Langley Research Center, 2013. NASA technical publication 2013-217965. (NASA/TP–2013-217965) http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130010711_2013010164.pdf , Feb-2013
NASA Technical Documents Slaba TC, Mertens CJ, Blattnig SR. "Radiation Shielding Optimization on Mars." Hampton, VA : NASA Langley Research Center, 2013. NASA technical publication 2013-217983. (NASA/TP–NASA/TP–2013-217983) http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130012456_2013011531.pdf , Apr-2013
Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2012 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 09/30/2015  
Task Last Updated: 06/25/2012 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Simonsen, Lisa  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor:  
Center Contact:   
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Task Description: Currently, the deterministic space radiation transport code HZETRN (High charge (Z) and Energy TRaNsport), is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO, and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physic improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer - 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (ISS, Lunar, or Mars)? Pion production models are also being worked on.

Research Impact/Earth Benefits: The radiation transport codes developed at NASA Langley Research Center can potentially be used in other applications such as proton and heavy ion therapy treatments for cancer.

Task Progress & Bibliography Information FY2012 
Task Progress: Nuclear data for space radiation has been studied. Human space flight requires protecting astronauts from the harmful effects of space radiation. The availability of measured nuclear cross section data needed for space radiation has been reviewed. The energy range of interest for radiation protection is approximately 100 MeV/n - 10 GeV/n. Most data are for projectile fragmentation partial and total cross sections, including both charge changing and isotopic cross sections. The cross section data are organized into categories which include charge changing, elemental, isotopic for total, single and double differential with respect to momentum, energy and angle. Gaps in the data relevant to space radiation protection were studied and recommendations for future experiments have been made.

Deterministic pion and muon transport in Earth’s atmosphere has been studied. Secondary particles produced by primary space radiation particle interactions with materials are an important contribution to radiation risk. Many pions are produced in the nuclear interactions typical of space radiations and can be an important contribution to radiation exposure. Charged pions decay to muons, which must also be considered in space radiation exposure studies. The NASA space radiation transport code HZETRN (High charge (Z) and Energy TRaNsport) has been extended to include the transport of charged pions and muons. Muon production in the Earth’s upper atmosphere was investigated, and comparisons with recent balloon flight measurements of differential muon flux were presented. Muon production from an updated version of HZETRN is found to agree well with experiment.

Light ion improvements to the NUCFRG (NUClear FRaGmentation) model has been studied. The simple light ion production model has been replaced with a light ion coalescence model and an improved electromagnetic dissociation (EMD) model has been added. Prior versions of the model provide reasonable overall agreement with measured data; however, those versions lacked a physics-based description for coalescence and EMD. The new version, NUCFRG3, has improved the theoretical descriptions of these mechanisms and offers additional benefits, such as the capability to calculate EMD cross sections for single deuteron, triton, helion, and alpha particle emission. NUCFRG3 model evaluation and validation show that the predictive capability has been improved and strengthened by the light ion physics-based changes.

Variation in lunar neutron dose estimates has been studied. The transport code, HZETRN2010 was used to calculate the albedo neutron contribution to effective dose as a function of shielding thickness for different space radiation environments and to determine to what extent various factors affect such estimates. Albedo neutron spectra computed with HZETRN2010 were compared to Monte Carlo result. The impact of lunar regolith composition on the albedo neutron spectrum was examined, and the variation on effective dose caused by neutron fluence to effective dose conversion coefficients was studied. The combined variation caused by environmental models, shielding materials, shielding thickness, regolith composition, and conversion coefficients on the albedo neutron contribution to effective dose was determined. It was shown that a single percentage number for characterizing the albedo neutron contribution to effective dose can be misleading. In general, the albedo neutron contribution to effective dose was found to vary between 1 - 32%, with the environmental model, shielding material, and shielding thickness being the most important factors.

A low Earth orbit (LEO) dynamic model for proton anisotropy validation has been studied. Previous ionizing radiation measurements on the space transportation system have provided information impacting both the environmental models and the nuclear transport code development by requiring dynamic models of the LEO environment. Previous studies using computer aided design models of the International Space Station (ISS) have demonstrated that the dosimetric prediction for a spacecraft at LEO requires the description of an environmental model with accurate anisotropic as well as dynamic behavior. The developed model is a component of a suite of codes collectively named GEORAD (GEOmagnetic RADiation) which computes cutoff rigidity, trapped proton and trapped electron environments. Within SAA (South Atlantic Anomaly), the EW anisotropy results in different levels of exposure to different sections of a spacecraft such as ISS. The study draws quantitative conclusions on the combined effect of proton pitch angle and the EW anomaly.

Low Earth orbit validation of a dynamic and anisotropic trapped radiation model through ISS measurements has been studied, and applies to trapped electrons at various Earth orbits. The trapped electron capabilities of GEORAD are accessible through OLTARIS web interface. GEORAD and OLTARIS interests are in the study of long term effects (i.e. a meaningful portion of solar cycle). Therefore, GEORAD does not incorporate any short term external field contribution due to solar activity. These environmental models were applied to selected target points within ISS 6A (circa early 2001), 7A (circa late 2001), and 11A during its passage through the SAA to assess the validity of the environmental models at ISS altitudes.

A dynamic model for the validation of cosmic ray anisotropy at low Earth orbit has been studied. Within the framework of GEORAD, we described the dynamic and anisotropic capabilities of GEORAD as applied to the interaction of GCR with the geomagnetic field at low Earth orbit (LEO). While the magnitude of the GCR anisotropy at LEO depends on a multitude of factors such as the ions rigidity, transmission, attitude and orientation of the spacecraft along the velocity vector, the study draws quantitative conclusions on the effect of GCR anisotropy at LEO.

Estimates of Carrington - class solar particle event radiation exposures on Mars has been studied. Radiation exposure estimates for astronauts on the surface of Mars were made for solar particle event proton radiation environments comparable to the Carrington event of 1859. It was assumed that the proton energy distributions for these Carrington - type events were similar to those measured for other, more recent large events. The fluence levels of these hypothetical events were normalized to the value for the Carrington event, as reported from measurements in ice core data. Comparisons of the predicted organ exposures with current NASA permissible exposure limits were made.

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Norbury JW, Miller J, Adamczyk AM, Heilbronn LH, Townsend LW, Blattnig SR, Norman RB, Guetersloh SB, Zeitlin CJ. "Nuclear data for space radiation." Radiation Measurements. 2012 May;47(5):315-63. http://dx.doi.org/10.1016/j.radmeas.2012.03.004 , May-2012
Articles in Peer-reviewed Journals Badavi FF, Nealy JE, Wilson JW. "The Low Earth Orbit validation of a dynamic and anisotropic trapped radiation model through ISS measurements." Advances in Space Research. 2011 Oct 15;48(8):1441-58. http://dx.doi.org/10.1016/j.asr.2011.06.009 , Oct-2011
Articles in Peer-reviewed Journals Townsend LW, PourArsalan M, Hall MI, Anderson JA, Bhatt S, DeLauder N, Adamczyk AM. "Estimates of Carrington-class solar particle event radiation exposures on Mars." Acta Astronautica. 2011 Sep-Oct;69(7-8):397-405. http://dx.doi.org/10.1016/j.actaastro.2011.05.020 , Sep-2011
Articles in Peer-reviewed Journals Badavi FF. "A low earth orbit dynamic model for the proton anisotropy validation." Nuclear Instruments & Methods in Physics Research B, 2011 Nov 1;269(21):2614-22. http://dx.doi.org/10.1016/j.nimb.2011.08.002 , Nov-2011
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Clowdsley MS. "Variation in lunar neutron dose estimates." Radiat Res. 2011 Dec;176(6):827-41. Epub 2011 Aug 22. PubMed PMID: 21859325 , Dec-2011
Articles in Peer-reviewed Journals Badavi FF. "A dynamic model for the validation of cosmic rays anisotropy at low Earth orbit." IEEE Transactions on Nuclear Science, 2012 Apr;59(2):447-55. http://dx.doi.org/10.1109/TNS.2012.2186981 , Apr-2012
Articles in Peer-reviewed Journals Norman RB, Blattnig SR, De Angelis G, Badavi FF, Norbury JW. "Deterministic pion and muon transport in Earth’s atmosphere." Advances in Space Research, 2012 Jul;50(1):146-55. http://dx.doi.org/10.1016/j.asr.2012.03.023 , Jul-2012
Articles in Peer-reviewed Journals Adamczyk AM, Norman RB, Sriprisan SI, Townsend LW, Norbury JW, Blattnig SR, Slaba TC. "NUCFRG3: Light ion improvements to the nuclear fragmentation model." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012 Jun 21;678:21-32. http://dx.doi.org/10.1016/j.nima.2012.02.021 , Jun-2012
NASA Technical Documents Norbury J, Miller J, Adamczyk A, Heilbronn L, Townsend L, Blattnig S, Norman R, Guetersloh S, Zeitlin C. "Review of nuclear physics experiments for space radiation." Hampton, VA : NASA Langley Research Center, 2011. NASA technical publication 2011-217179 (NASA/TP–2011-217179). http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110016415_2011017506.pdf , Sep-2011
Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2011 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 09/30/2015  
Task Last Updated: 07/15/2011 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Simonsen, Lisa  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor: Cucinott1a, Francis  
Center Contact: 281-483-0968 
noaccess@nasa.gov 
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:
No. of PhD Candidates:
No. of Master's Candidates:
No. of Bachelor's Candidates:
No. of PhD Degrees:
No. of Master's Degrees:
No. of Bachelor's Degrees:
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Task Description: Currently, the deterministic space radiation transport code HZETRN, is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO, and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physic improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer – 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (ISS, Lunar, or Mars)?

with improved models and transport to improve estimates/reduce uncertainty of light ion and neutron production and transport through spacecraft materials and secondary environments on the lunar and Mars surface.

Research Impact/Earth Benefits: The radiation transport codes developed at NASA Langley Research Center can potentially be used in other applications such as proton and heavy ion therapy treatments for cancer.

Task Progress & Bibliography Information FY2011 
Task Progress: One of the most important products that the NASA Langley Space Radiation Group delivers are space radiation transport codes capable of predicting the radiation environment in a spacecraft or habitat, given the external environment. The NASA Langley Space Radiation Group develops the transport code HZETRN, which is the NASA standard code for space radiation. The HZETRN acronym stands for High charge (Z) and Energy TRaNsport. The Physics and Transport activities have been divided up into Phase 1 and Phase 2, with the dividing point being the year 2007. The present report will mainly describe Phase 2 activities. The focus of Phase 1 activities was on further development of the 1-dimensional version of HZETRN together with emphasis on heavy ion transport. The focus of Phase 2 activities is concerned with 3-dimensional transport. This involves the development of 3-dimensional transport models and the associated 3-dimensional nuclear reaction cross sections required as input. It also shifts the focus concerning the particles being transported. Heavy nuclear fragments tend to travel with the same speed and direction as the initial high energy nuclear beam, and therefore are well described with 1-dimensional methods. However, neutrons, light ions and mesons suffer significant deflections from straight line motion and require 3-dimensional methods. Therefore, the 3-dimensional focus of Phase 2 Physics and Transport automatically includes special consideration of neutrons, light ions and mesons.

The last major update of HZETRN was with the release of the 2005 version. A new version was released at the end of the year 2010. The 2010 version contains improved transport methods and a new nuclear model, both of which are described below.

The NUClear FRaGmentation (NUCFRG) model used in HZETRN calculates total cross sections for the production of nuclear fragments in high energy nucleus - nucleus collisions. The current third version of the code (NUCFRG3) now includes the following a new coalescence model for the formation of light ions and a new Coulomb dissociation model for the formation of light ions.

HZETRN2010 is the most recent update to a series of space radiation transport codes developed at NASA Langley Research Center (LaRC). Since the last official release in 2005 (HZETRN2005), several modifications, improvements, and corrections have been made to the numerical methods, transport methodologies, and nuclear physics models. A large portion of the source code has been updated from Fortran 77 to Fortran 90 to allow dynamic memory allocation and increased user flexibility, and code documentation has been greatly improved. The following sections summarize these efforts and summarize the capabilities of HZETRN2010. The deterministic codes developed at NASA LaRC, referred to generally as HZETRN, are all based on the straight-ahead approximation where all particles and reaction products are assumed to propagate along a common axis. Numerical marching algorithms are derived by inverting the one-dimensional Boltzmann transport equation, and employing perturbative methods to allow rapid evaluation of the resulting integrals. As with any differential equation solver, continuous variables must be discretized to allow numerical evaluation. Convergence tests are often used to quantify the error associated with this discretization. A comprehensive convergence test for HZETRN has been completed. In that work, the need for double precision calculations was clearly identified along with a new convergence criterion related to low energy charged target fragments that had never been addressed in the literature. New numerical methods were also developed and shown to be nearly 10 - 100 times faster than their predecessors. Detailed convergence tests were then used to show that the new methods are also more accurate, and total discretization errors were quantified for several scenarios in which HZETRN is commonly used. The new methods have been implemented in HZETRN2010. Along with improved numerical methods, a low energy transport model was also developed for neutrons and light ions (Z < 3). The low energy model is an improvement on the straight-ahead approximation and allows the separation of neutron flux into forward and backward components. The elastic interactions that dominate low energy neutron transport are fully accounted for through a Neumann series solution allowing the multiple reflections (from forward to backward, and vice versa) to be included. The neutron transport model is also fully coupled into the HZETRN solution through a source term representing the production of low energy light target fragments from the low energy neutrons. The low energy model has been compared to various Monte Carlo codes and it was shown that HZETRN agrees with the Monte Carlo codes to the extent that they agree with each other. The low energy transport model has been implemented in HZETRN2010. The heavy ion (Z > 2) nuclear fragmentation model used in HZETRN was recently updated. In particular, a coalescence model for light ion formation and light ion production via electromagnetic dissociation has been included. The updated fragmentation model, NUCFRG3, has been implemented in HZETRN2010. Along with the improvements in the numerical methods, transport models, and nuclear physics models, the overall code architecture of HZETRN2010 has also been improved. The new code has been updated from Fortran 77 to Fortran 90 as much as possible, allowing a more efficient use of CPU power and memory. Dynamically allocated arrays have also been introduced to allow more user flexibility. There is no limit on the atomic complexity of the target (previous limit was 10 atomic elements). In multi-layer mode, there is no limit on the number of spatial grid points or total transport depth (previous limit was 20 points in each layer with maximum thickness of 100 g/cm^2). The multi-layer transport mode can be used with user-defined materials (previous materials were fixed to aluminum, polyethylene, and water). Users can select from a database of pre-defined environments, including free space SPE, free-space GCR, trapped protons in Low Earth Orbit (LEO), and GCR in LEO (previous code could do free-space SPE and free space GCR). User-defined environments can also be added through a database file, as discussed in the HZETRN2010 User Guide. Users can also select from a variety of response functions, including dose, dose equivalent using ICRP 60 quality factors, differential and integral LET spectra, and differential and integral flux spectra. HZETRN2010 also contains a new slab-geometry mode where users can specify a slab with no limit on the number of layers, layer thickness, or material complexity. The low energy transport model discussed previously is utilized in this mode. In general, the HZETRN2010 architecture is very simple - three source codes and a database of static data files. The first source code generates the nuclear and atomic cross sections for a user-defined material. The second source code transports a space radiation environment through a multilayer configuration or a slab geometry. The third source code computes the various dosimetric quantities discussed above. The 2010 version of HZETRN will be upgraded again in 2015. The new nuclear physics models, transport methods and validation methods being developed for the 2015 version will now be described.

Work is also continuing on pion transport and the associated electromagnetic cascade. One of the most interesting developments in space radiation recently has been the discovery that pions can contribute a substantial fraction of the radiation dose. One therefore needs to also take account of the associated electromagnetic cascade and transport methods have been developed that are capable of dealing with this. Work is also continuing on developing a nuclear database. With the Phase 1 activity in Physics & Transport described previously, there was both a theoretical and experimental program, with both focusing on heavy ion production. As previously mentioned, the focus of Phase 2 is on neutrons and light ions. An extensive survey of all nuclear physics experiments that are relevant to space radiation has recently been completed. This shows the gaps in measurements and this will be used to recommend future experiments.

The web site at http://spaceradiation.larc.nasa.gov/ has a list of all publications contained in this task throughout its history.

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Norbury JW. "Perspective on space radiation for space flights in 2020-2040." Advances in Space Research. 2011 Feb 15;47(4):611-21. http://dx.doi.org/10.1016/j.asr.2010.10.012 , Feb-2011
Articles in Peer-reviewed Journals Heinbockel JH, Slaba TC, Blattnig SR, Tripathi RK, Townsend LW, Handler T, Gabriel TA, Pinsky LS, Reddell B, Clowdsley MS, Singleterry RC, Norbury JW, Badavi FF, Aghara SK. "Comparison of the transport codes HZETRN, HETC and FLUKA for a solar particle event." Advances in Space Research. 2011 Mar 15;47(6):1079-88. http://dx.doi.org/10.1016/j.asr.2010.11.012 , Mar-2011
Articles in Peer-reviewed Journals Heinbockel JH, Slaba TC, Tripathi RK, Blattnig SR, Norbury JW, Badavi FF, Townsend LW, Handler T, Gabriel TA, Pinsky LS, Reddell B, Aumann AR. "Comparison of the transport codes HZETRN, HETC and FLUKA for galactic cosmic rays." Advances in Space Research. 2011 Mar 15;47(6):1089-105. http://dx.doi.org/10.1016/j.asr.2010.11.013 , Mar-2011
Articles in Peer-reviewed Journals Zeitlin C, Miller J, Guetersloh S, Heilbronn L, Fukumura A, Iwata Y, Murakami T, Blattnig SR, Norman R, Mashnik S. "Fragmentation of 14N, 16O, 20Ne, and 24Mg nuclei at 290 to 1000 MeV/nucleon." Physical Review C. 2011 Mar;83(3):034909. http://dx.doi.org/10.1103/PhysRevC.83.034909 , Mar-2011
Articles in Peer-reviewed Journals Walker SA, Slaba TC, Clowdsley MS, Blattnig SR. "Investigating material approximations in spacecraft radiation analysis." Acta Astronautica. 2011 Jul-Aug;69(1-2):6-17. http://dx.doi.org/10.1016/j.actaastro.2011.02.013 , Jul-2011
Articles in Peer-reviewed Journals Badavi FF, Wilson JW, Hunter A. "Numerical study of the generation of linear energy transfer spectra for space radiation applications." Advances in Space Research. 2011 May 3;47(9):1608-15. http://dx.doi.org/10.1016/j.asr.2010.12.023 , May-2011
Articles in Peer-reviewed Journals Badavi F, Blattnig S, Atwell W, Nealy J, Norman R. "A deterministic electron, photon, proton and heavy ion transport suite for the study of the Jovian moon Europa." Nuclear Instruments and Methods in Physics Research Section B. 2011 Feb;269(3):232-8. http://dx.doi.org/10.1016/j.nimb.2010.12.022 , Feb-2011
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Badavi FF, Stoffle NN, Rutledge RD, Lee KT, Zapp EN, Dachev TP, Tomov BT. "Statistical validation of HZETRN as a function of vertical cutoff rigidity using ISS measurements." Advances in Space Research. 2011 Feb 15;47(4):600-10. http://dx.doi.org/10.1016/j.asr.2010.10.021 , Feb-2011
Articles in Peer-reviewed Journals Adamczyk AM, Norbury JW. "Electromagnetic dissociation cross sections using Weisskopf-Ewing theory." Nuclear Technology. 2011 Jul;175(1):216-27. http://www.new.ans.org/pubs/journals/nt/a_12293 , Jul-2011
Articles in Peer-reviewed Journals Walker SA, Tweed J, Tripathi RK, Badavi FF, Miller J, Zeitlin C, Heilbronn LH. "Validation of a multi-layer Green's function code for ion beam transport." Advances in Space Research. 2011 Feb 1;47(3):533-44. http://dx.doi.org/10.1016/j.asr.2010.09.012 , Feb-2011
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Clowdsley MS, Walker SA, Badavi FF. "An improved neutron transport algorithm for HZETRN." Advances in Space Research. 2010 Sep 15;46(6):800-10. http://dx.doi.org/10.1016/j.asr.2010.03.005 , Sep-2010
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Badavi FF. "Faster and more accurate transport procedures for HZETRN." Journal of Computational Physics. 2010 Dec 10;229(24):9397-417. http://dx.doi.org/10.1016/j.jcp.2010.09.010 , Dec-2010
Articles in Peer-reviewed Journals Zeitlin C, Guetersloh S, Heilbronn L, Miller J, Fukumura A, Iwata Y, Murakami T, Sihver L. "Nuclear fragmentation database for GCR transport code development." Advances in Space Research. 2010 Sep 15;46(6):728-34. http://dx.doi.org/10.1016/j.asr.2010.04.035 , Sep-2010
Articles in Peer-reviewed Journals Straume T, Blattnig S, Zeitlin C. "Radiation hazards and the colonization of Mars: Brain, body, pregnancy, in-utero development, cardio, cancer, degeneration." Journal of Cosmology. 2010 Oct- Nov;12:3992-4033. http://journalofcosmology.com/Mars124.html , Oct-2010
Articles in Peer-reviewed Journals Nealy JE, Chang CK, Norman RB, Blattnig SR, Badavi FF, Adamczyk AM. "A deterministic computational procedure for space environment electron transport." Nuclear Instruments and Methods in Physics Research Section B. 2010 Aug;268(15):2415-25. http://dx.doi.org/10.1016/j.nimb.2010.04.014 , Aug-2010
Articles in Peer-reviewed Journals Badavi FF, Adams DO, Wilson JW. "On the validity of the aluminum equivalent approximation in space radiation shielding applications." Advances in Space Research. 2010 Sep 15;46(6):719-27. http://dx.doi.org/10.1016/j.asr.2010.04.006 , Sep-2010
Articles in Peer-reviewed Journals Kim MH, Qualls GD, Slaba TC, Cucinotta FA. "Comparison of organ dose and dose equivalent for human phantoms of CAM vs. MAX." Advances in Space Research. 2010 Apr 1;45(7):850-7. http://dx.doi.org/10.1016/j.asr.2009.09.027 , Apr-2010
Articles in Peer-reviewed Journals Norbury, JW, Dick F, Norman RB, Maung KM. "Cross-sections from scalar field theory." Canadian Journal of Physics 2010 Mar;88(3):149-56. http://dx.doi.org/10.1139/P10-002 , Mar-2010
Articles in Peer-reviewed Journals Slaba TC, Blattnig SR, Aghara SK, Townsend LW, Handler T, Gabriel TA, Pinsky LS, Reddell B. "Coupled neutron transport for HZETRN." Radiation Measurements. 2010 Feb;45(2):173-82. http://dx.doi.org/10.1016/j.radmeas.2010.01.005 , Feb-2010
Articles in Peer-reviewed Journals Slaba TC, Qualls GD, Clowdsley MS, Blattnig SR, Walker SA, Simonsen LC. "Utilization of CAM, CAF, MAX, and FAX for space radiation analyses using HZETRN." Advances in Space Research. 2010 Apr 1;45(7):866-83. http://dx.doi.org/10.1016/j.asr.2009.08.017 , Apr-2010
Articles in Peer-reviewed Journals Mertens CJ, Moyers MF, Walker SA, Tweed J. "Proton lateral broadening distribution comparisons between GRNTRN, MCNPX, and laboratory beam measurements." Advances in Space Research. 2010 Apr 1;45(7):884-91. http://dx.doi.org/10.1016/j.asr.2009.08.013 , Apr-2010
Articles in Peer-reviewed Journals Mansur LK, Charara YM, Guetersloh SB, Remec I, Townsend LW. "Fragmentation calculations for energetic ions in candidate space radiation shielding materials." Nuclear Technology 2009 Jun;166(3):263-72. http://www.new.ans.org/pubs/journals/nt/a_8840 , Jun-2009
Articles in Peer-reviewed Journals Badavi FF, Xapsos MA, Wilson JW. "An analytical model for the prediction of a micro-dosimeter response function." Advances in Space Research. 2009 Jul 15;44(2):190-201. http://dx.doi.org/10.1016/j.asr.2009.03.010 , Jul-2009
Articles in Peer-reviewed Journals Norbury J. "Parameterizations of inclusive cross sections for kaon, proton and antiproton production in proton-proton collisions." Astrophysical Journal Supplement Series 2009 May;182(1):120-6. http://dx.doi.org/10.1088/0067-0049/182/1/120 , May-2009
Articles in Peer-reviewed Journals Norbury JW. "Total cross section parameterizations for pion production in nucleon–nucleon collisions." Nuclear Instruments and Methods in Physics Research Section B. 2009 Apr;267(7):1209-12. http://dx.doi.org/10.1016/j.nimb.2009.02.067 , Apr-2009
Articles in Peer-reviewed Journals Aghara SK, Blattnig SR, Norbury JW, Singleterry RC. "Monte Carlo analysis of pion contribution to absorbed dose from Galactic cosmic rays." Nuclear Instruments and Methods in Physics Research Section B. 2009 Apr;267(7):1115-24. http://dx.doi.org/10.1016/j.nimb.2009.01.136 , Apr-2009
Articles in Peer-reviewed Journals Norbury JW. "Pion cross section parametrizations for intermediate energy, nucleus-nucleus collisions." Physical Review C. 2009 Mar;79(3):037901. http://dx.doi.org/10.1103/PhysRevC.79.037901 , Mar-2009
Articles in Peer-reviewed Journals Dick F, Norbury JW. "Singularity in the laboratory frame angular distribution derived in two-body scattering theory." European Journal of Physics 2009 Mar;30(2):403-16. http://dx.doi.org/10.1088/0143-0807/30/2/019 , Mar-2009
Articles in Peer-reviewed Journals Tripathi RK, Wilson JW, Youngquist RC. "Electrostatic space radiation shielding." Advances in Space Research. 2008 Sep 15;42(6):1043-9. http://dx.doi.org/10.1016/j.asr.2007.09.015 , Sep-2008
Articles in Peer-reviewed Journals Zeitlin C, Sihver L, La Tessa C, Mancusi D, Heilbronn L, Miller J, Guetersloh SB. "Comparisons of fragmentation spectra using 1 GeV/amu 56Fe data and the PHITS model." Radiation Measurements. 2008 Aug;43(7):1242-53. http://dx.doi.org/10.1016/j.radmeas.2008.02.013 , Aug-2008
Articles in Peer-reviewed Journals Slaba TC, Heinbockel JH, Blattnig SR. "Neutron transport models and methods for HZETRN and coupling to low energy light ion transport." SAE International Journal of Aerospace 2009 Apr;1(1):510-21. http://saeaero.saejournals.org/content/1/1/510.abstract , Apr-2009
Articles in Peer-reviewed Journals Zeitlin C, Guetersloh S, Heilbronn L, Miller J, Fukumura A, Iwata Y, Murakami T, Sihver L, Mancusi D. "Fragmentation cross sections of medium-energy 35Cl, 40Ar, and 48Ti beams on elemental targets." Physical Review C. 2008 Mar;77(3):034605. http://dx.doi.org/10.1103/PhysRevC.77.034605 , Mar-2008
Articles in Peer-reviewed Journals Sihver L, Mancusi D, Niita K, Sato T, Townsent L, Farmer C, Pinsky L, Ferrari A, Cerutti F, Gomes I. "Benchmarking of calculated projectile fragmentation cross-sections using the 3-D, MC codes PHITS, FLUKA, HETC-HEDS, MCNPX_HI, and NUCFRG2." Acta Astronautica 2008 Oct-Nov;63(7-10):865-77. http://dx.doi.org/10.1016/j.actaastro.2008.02.012 , Oct-2008
Articles in Peer-reviewed Journals Charara YM, Townsend LW, Gabriel TA, Zeitlin CJ, Heilbronn LH, Miller J. "HETC-HEDS code validation using laboratory beam energy loss spectra data." IEEE Transactions on Nuclear Science 2008 Dec;55(6):3164-8. http://dx.doi.org/10.1109/TNS.2008.2006607 , Dec-2008
Articles in Peer-reviewed Journals Singleterry RC Jr, Blattnig SR, Clowdsley MS, Qualls GD, Sandridge CA, Simonsen LC, Slaba TC, Walker SA, Badavi FF, Spangler JL, Aumann AR, Zapp EN, Rutledge RD, Lee KT, Norman RB, Norbury JW. "OLTARIS: On-line tool for the assessment of radiation in space." Acta Astronautica. 2011 Apr-May;68(7-8):1086-97. http://dx.doi.org/10.1016/j.actaastro.2010.09.022 , Apr-2011
Project Title:  Measurements and Transport Phase 2 Physics Project Reduce
Fiscal Year: FY 2008 
Division: Human Research 
Research Discipline/Element:
HRP SR:Space Radiation
Start Date: 10/01/2007  
End Date: 09/30/2015  
Task Last Updated: 05/03/2011 
Download report in PDF pdf
Principal Investigator/Affiliation:   Norbury, John  Ph.D. / NASA Langley Research Center 
Address:  Mail Stop 188E 
LaRC-D309 
Hampton , VA  23681-2199 
Email: John.w.norbury@nasa.gov 
Phone: 757-864-1480  
Congressional District:
Web:  
Organization Type: NASA CENTER 
Organization Name: NASA Langley Research Center 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Blattnig, Steve  NASA Langley Research Center 
Clowdsley, Martha  NASA Langley Research Center 
Slaba, Tony  NASA Langley Research Center 
Simonsen, Lisa  NASA Langley Research Center 
Singleterry, Robert  NASA Langley Research Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA LaRC 
Grant Monitor: Cucinott1a, Francis  
Center Contact: 281-483-0968 
noaccess@nasa.gov 
Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: GROUND 
Flight Program:  
TechPort: No 
No. of Post Docs:  
No. of PhD Candidates:  
No. of Master's Candidates:  
No. of Bachelor's Candidates:  
No. of PhD Degrees:  
No. of Master's Degrees:  
No. of Bachelor's Degrees:  
Human Research Program Elements: (1) SR:Space Radiation
Human Research Program Risks: (1) Cancer:Risk of Radiation Carcinogenesis
Human Research Program Gaps: (1) Cancer11:What are the most effective shielding approaches to mitigate cancer risks?
(2) Cancer12:What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)? (IRP Rev F)
Task Description: Currently, the deterministic space radiation transport code HZETRN, is the major tool used by NASA to evaluate radiation environments inside spacecraft. Deterministic codes have been shown to be superior to Monte Carlo transport for engineering studies. However HZETRN is a one dimensional transport code. The transport of heavy ions (Z > 2) has been shown to be valid in the one dimensional approximation because the relativistic heavy ions found in the space radiation spectrum pass through materials relatively un-deflected from their initial trajectories. The cross sections required for one dimensional transport are total absorption and spectral distributions. Meson production and the associated electromagnetic cascade have not yet been incorporated into HZETRN. Phase 1 studies have shown the importance of these processes, which must be included in Phase 2. This project implements the recommendations of several workshops by emphasizing the development of a more accurate description of neutron and light ion transport. Neutrons and light ions scatter at large angles and the one dimensional approximation is no longer valid. Therefore, the one dimensional code HZETRN must begin to include the three dimensional transport of light ions and neutrons to more accurately quantify secondary radiation environments in tissue while maintaining computational speed and efficiency. Such a three dimensional transport code in turn requires fully double differential cross sections as input.

Phase II Measurements and Physics Project focuses on light ion production and transport to develop space radiation transport codes capable of predicting primary and secondary spectra of space radiation environment interaction behind typical spacecraft shielding, planetary surfaces, and atmospheres with increased accuracy. Configuration managed V&V'ed source codes are released to the radiation user community including Exploration, RHO, and Operations as well as industry partners or commercial entities. Current exploration vehicle requirements specify that HZETRN shall be utilized by the government for radiation requirement verification. Transport codes directly support verification of NASA STD 3001 Vol. 2 requirements.

Phase 2 focus:

• Current focus is on light ion and neutron transport and production including 3-D effects of neutron backscattered and inclusion of dose received from pion production

• Future nuclear physic improvements will focus on improved models needed for definition of Mars Surface Environment

Implementation of Phase 2 Physics supports closing the following gaps,

• Cancer - 11: What are the most effective shielding approaches to mitigate cancer risks?

• Cancer – 12: What level of accuracy do NASA’s space environment, transport code and cross sections describe radiation environments in space (ISS, Lunar, or Mars)? with improved models and transport to improve estimates/reduce uncertainty of light ion and neutron production and transport through spacecraft materials and secondary environments on the lunar and Mars surface.

Research Impact/Earth Benefits: 0

Task Progress & Bibliography Information FY2008 
Task Progress: New project for FY2008.

[Ed. note: added to Task Book 5/3/2011 when received project information]

Bibliography Type: Description: (Last Updated: 01/11/2021)  Show Cumulative Bibliography Listing
 
 None in FY 2008