Aim 1: Characterize and quantify changes in operationally-relevant sensorimotor and vestibular performance as a function of gravitational load.

Aim 2: Characterize and quantify changes in physiology—particularly in brain function and autonomic activation during behavioral performance—as a function of gravitational load.

Aim 3: Develop a model to predict behavioral performance and neurophysiological responses under different gravitational loads based on preflight ground testing data.

Hypotheses: (Hyp1) We predict a monotonic but non-linear relationship between Robotics On-Board Trainer-r (ROBoT-r) performance and gravitational load, with larger departures from 1g leading to more impaired performance. (Hyp2) Behavioral alterations will be paralleled by physiological changes at different gravity loads, including activation of prefrontal and vestibular cortex, and autonomic nervous system activation. (Hyp3) Ground-based challenges to the vestibular system will induce detectable neurophysiological responses, and the amplitude of these responses (i.e., an indicator of individual “sensitivity” to these provocations) will help (3a) predict neurophysiological responses in-flight, and (3b) predict behavioral performance in flight.

Deliverables: Overall, our project will characterize (1) operationally-relevant performance and (2) neurophysiological responses as a function of gravity load, as well as (3) providing models to predict performance and neurophysiological impacts of partial gravity based on preflight-data. This work has the potential to identify individuals who are particularly resilient to altered gravity, and will be key for planning future exploration-class missions where survival will depend on the operational capabilities of astronauts in partial-gravity environments.

Aim 1: Characterize and quantify changes in operationally relevant sensorimotor and vestibular performance as a function of gravitational load. Aim 2: Characterize and quantify changes in physiology—particularly in brain function and autonomic activation during behavioral performance—as a function of gravitational load. Aim 3: Develop a model to predict behavioral performance and neurophysiological responses under different gravitational loads based on preflight ground testing data.

Hypotheses: (Hyp1) We predict a monotonic but non-linear relationship between Robotics On-Board Trainer-r (ROBoT-r) performance and gravitational load, with larger departures from 1g leading to more impaired performance. (Hyp2) Behavioral alterations will be paralleled by physiological changes at different gravity loads, including activation of prefrontal and vestibular cortex, and autonomic nervous system activation. (Hyp3) Ground-based challenges to the vestibular system will induce detectable neurophysiological responses, and the amplitude of these responses (i.e., an indicator of individual “sensitivity” to these provocations) will help (3a) predict neurophysiological responses in-flight, and (3b) predict behavioral performance in flight.

Deliverables: Overall, our project will characterize (1) operationally relevant performance and (2) neurophysiological responses as a function of gravity load, as well as (3) providing models to predict performance and neurophysiological impacts of partial gravity based on preflight data. This work has the potential to identify individuals who are particularly resilient to altered gravity and will be key for planning future exploration-class missions where survival will depend on the operational capabilities of astronauts in partial-gravity environments.

RESEARCH IMPACT The proposed parabolic flights will help fill critical knowledge gaps regarding human exposure to fractional-gravity conditions. Specifically, our project will address gaps regarding operational performance, neurophysiological status, individual sensitivity to different gravitational loads between 0-1g, as well as prediction of behavioral performance and physiological responses to partial gravity. In addition to filling key gaps surrounding the human performance of operationally relevant tasks in partial gravity, this work may provide a method to help identify crewmembers who are particularly resilient for performing particular tasks under novel gravity loadings. The results have the further benefit of providing a better understanding of the role of disorientation in Earth-based operational performance. This is relevant not only to fighter pilots but to task performance by individuals with neurological or medical conditions that adversely affect the vestibular system (e.g., stroke, infections).

TASK PROGRESS Over the past year, we finished all preparations for the planned experiments, and all parabolic flight data collection was conducted over a 2-week period from June 3-16, 2023. Achievements include the following: • Completion of Novespace paperwork: All paperwork (in particular the Experiment Safety Data Package, ESDP), and related forms were completed as required to fly, in collaboration with Novespace. • New Hand Controllers: Dr. Strangman worked closely with NASA Human Research Program (HRP) and the NASA Dynamic Skills Trainer (DST) lab to finalize the design and performance characteristics of the new hand controllers. Four sets of controllers were fabricated to be used in this study, and Dr. Strangman worked with NASA Human Factors and Behavioral Performance (HFBP) and DST to optimize the controllers prior to final delivery. • New ROBoT-r Workstations: A set of 4 workstations (8 HP Zbook computers plus cabling) were assembled by the DST lab for use aboard the parabolic flights. These were delivered to Novespace in Bordeaux along with the other hardware coming directly from NASA (see Shipping, below). • ROBoT-r Task Truncation – Revised Initial Conditions: Dr. Strangman developed new initial conditions for the ROBoT-r task to accommodate the short (~20 sec) periods of altered gravity available during each parabola for task performance. • ROBoT-r Racks: Novespace required specialized racks to support the ROBoT workstations in flight, which ultimately needed to be fabricated from scratch. Since all ROBoT-r workstation hardware was being developed and finalized at the DST Lab, the DST Lab was engaged to fabricate these support racks. The racks were primarily an adjustable (sliding) “stand-up desk” to which computers, trackballs, and cabling could be attached. These were completed mid-May 2023 for shipment to France. • Shipping: ROBoT-r workstations and racks were shipped directly from NASA, whereas all remaining hardware was hand-carried to Novespace in June 2023. • Data Collection: Ground-based data collection was conducted over 4 days (totaling 45 hours of testing time, plus setup/cleaning/breakdown). Ground tests included (1) familiarization with ROBoT-r and Zibrio, donning/doffing of NINscan, (2) two training sessions, and (3) baseline data collection on ROBoT-r and balance tasks with vection, head-tilt, and GVS challenges. On Flight Day 1 (0g parabolas), flight data collection involved all 12 subjects, where each subject participated in 10 parabolas. They performed the abbreviated ROBoT-r task for the first 7 parabolas and the balance task for the last 3 parabolas. After every 10 parabolas, subjects were swapped in/out of stations. On Flight Days 2-4 (involving 10 parabolas at each partial-g value), we only had 4 subjects per flight, so no equipment swaps were necessary. 99% of the data inflight was collected as expected. • Data Quality Control: Data was downloaded and assessed on each day of experimental data collection, to confirm that all equipment was still operating nominally.

Aim 1: Characterize and quantify changes in operationally-relevant sensorimotor and vestibular performance as a function of gravitational load.

Aim 2: Characterize and quantify changes in physiology—particularly in brain function and autonomic activation during behavioral performance—as a function of gravitational load.

Aim 3: Develop a model to predict behavioral performance and neurophysiological responses under different gravitational loads based on preflight ground testing data.

Hypotheses: (Hyp1) We predict a monotonic but non-linear relationship between Robotics On-Board Trainer-r (ROBoT-r) performance and gravitational load, with larger departures from 1g leading to more impaired performance. (Hyp2) Behavioral alterations will be paralleled by physiological changes at different gravity loads, including activation of prefrontal and vestibular cortex, and autonomic nervous system activation. (Hyp3) Ground-based challenges to the vestibular system will induce detectable neurophysiological responses, and the amplitude of these responses (i.e., an indicator of individual “sensitivity” to these provocations) will help (3a) predict neurophysiological responses in-flight, and (3b) predict behavioral performance in flight.

Deliverables: Overall, our project will characterize (1) operationally-relevant performance and (2) neurophysiological responses as a function of gravity load, as well as (3) providing models to predict performance and neurophysiological impacts of partial gravity based on preflight-data. This work has the potential to identify individuals who are particularly resilient to altered gravity, and will be key for planning future exploration-class missions where survival will depend on the operational capabilities of astronauts in partial-gravity environments.

Aim 1: Characterize and quantify changes in operationally-relevant sensorimotor and vestibular performance as a function of gravitational load.

Aim 2: Characterize and quantify changes in physiology—particularly in brain function and autonomic activation during behavioral performance—as a function of gravitational load.

Aim 3: Develop a model to predict behavioral performance and neurophysiological responses under different gravitational loads based on preflight ground testing data.

Hypotheses: (Hyp1) We predict a monotonic but non-linear relationship between Robotics On-Board Trainer-r (ROBoT-r) performance and gravitational load, with larger departures from 1g leading to more impaired performance. (Hyp2) Behavioral alterations will be paralleled by physiological changes at different gravity loads, including activation of prefrontal and vestibular cortex, and autonomic nervous system activation. (Hyp3) Ground-based challenges to the vestibular system will induce detectable neurophysiological responses, and the amplitude of these responses (i.e., an indicator of individual “sensitivity” to these provocations) will help (3a) predict neurophysiological responses in-flight, and (3b) predict behavioral performance in flight.

Deliverables: Overall, our project will characterize (1) operationally-relevant performance and (2) neurophysiological responses as a function of gravity load, as well as (3) providing models to predict performance and neurophysiological impacts of partial gravity based on preflight-data. This work has the potential to identify individuals who are particularly resilient to altered gravity, and will be key for planning future exploration-class missions where survival will depend on the operational capabilities of astronauts in partial-gravity environments.

• Flight campaign: The date of the parabolic flight campaign was tentatively set to the last half of 2022, and there will most likely be a single flight campaign of 3-4 days instead of two flight campaigns.

• Experimental re-design: Due to the reduction in flight campaigns from our proposal’s original plan, the experimental plan was re-designed to maximize statistical power. Changes included the following:

o Flights & Parabolas: We had assumed 2 campaigns of 4-flights each (8 flights total), with 40 parabolas in each flight, or a total of 320 parabolas. This would have provided 10 parabolas at each of 0, ¼, ½, and ¾ g loadings (with blocks of 10 g loads pseudorandomly interleaved for counterbalancing). An amount of time equal to 10 parabolas would also be spent on the ground or in level flight to conduct 1g testing. To date, negotiations have indicated 4 flights of 30 parabolas each, or 120 parabolas total. This spurred various other changes (below).

o ROBoT-r (Robotic On-Board Trainer (ROBoT)): To help recover statistical power, it was decided that ROBoT-r would be used exclusively, instead of half of the data from ROBoT-r and half from SpaceDock. This required the fabrication and assembly of multiple additional ROBoT-r workstations, including multiple sets of new hand controllers. The delivery time for these pushed the flight to sometime past the middle of 2022.

o New Hand Controllers; Dr. Strangman worked closely with HRP and the DST Lab to finalize the design and performance characteristics of the new hand controllers, to be fabricated by DST lab personnel.

o Ratio of Operational Performance Measures: Originally, due to the ROBoT-r recycle-time, we anticipated only being able to use every other parabola for ROBoT-r because the computers would be re-initializing for the next run during the intervening parabolas. However, Novespace pauses longer between parabolas—more so than other NASA/Zero-G flights—giving ROBoT-r just enough time to reset for every parabola. We therefore were able to re-assign the 10 parabolas such that ROBoT-r is used for 7 of them, and the balance force-plate is used for the remaining 3. This improves power on ROBoT-r, without having a significant negative impact on the postural stability assessments.

o Ground Testing: Various plans for ground-based pretesting have been considered, given the constraints on availability of test subjects for training and assessment prior to flight. This issue is still under discussion, with a target of at least 4 days (ideally consecutive) for training/testing on the ground prior to the first flight-day.

• Institutional Review Board (IRB) Protocols are well underway. These will be completed and submitted once the experimental design/logistics details above are finalized.

Hypotheses: (Hyp1) We predict a monotonic but non-linear relationship between Robotics On-Board Trainer-r (ROBoT-r) performance and gravitational load, with larger departures from 1g leading to more impaired performance. (Hyp2) Behavioral alterations will be paralleled by physiological changes at different gravity loads, including activation of prefrontal and vestibular cortex, and autonomic nervous system activation. (Hyp3) Ground-based challenges to the vestibular system will induce detectable neurophysiological responses, and the amplitude of these responses (i.e., an indicator of individual “sensitivity” to these provocations) will help (3a) predict neurophysiological responses in-flight, and (3b) predict behavioral performance in flight. Our project involves three closely interrelated specific aims:

Aim 1: Characterize and quantify changes in operationally-relevant sensorimotor and vestibular performance as a function of gravitational load.

Aim 2: Characterize and quantify changes in physiology—particularly in brain function and autonomic activation during behavioral performance—as a function of gravitational load.

Aim 3: Develop a model to predict behavioral performance and neurophysiological responses under different gravitational loads based on preflight ground testing data.

Deliverables: Overall, our project will characterize (1) operationally-relevant performance and (2) neurophysiological responses as a function of gravity load, as well as (3) providing models to predict performance and neurophysiological impacts of partial gravity based on preflight-data. This work has the potential to identify individuals who are particularly resilient to altered gravity, and will be key for planning future exploration-class missions where survival will depend on the operational capabilities of astronauts in partial-gravity environments.

Significance: The proposed parabolic flights are an excellent platform to help fill critical knowledge gaps regarding human exposure to fractional-gravity conditions. Our project will specifically address gaps regarding operational performance, neurophysiological status, individual sensitivity to gravitational loading, as well as prediction of behavioral performance and physiological responses to partial gravity. In addition to filling key gaps surrounding human performance of operationally-relevant tasks in partial gravity, this work may provide a method to help identify crewmembers who are particularly resilient for performing particular tasks under novel gravity loadings.