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Habitable spacecraft designs are critical to achieve mission success in human spaceflight. As NASA’s priorities shift toward longer duration flights in deep space microgravity or on the surface of the Moon or Mars, the impact of insufficient spacecraft habitat design is exacerbated. Longer duration missions farther from the Earth reduce the total amount of volume available, thus leading to smaller crew sizes and increasing the level of isolation and confinement. In recent years, alternative reality technologies (e.g., virtual reality, augmented reality) have experienced rapid development and adoption as design tools in other industries. For spacecraft design and evaluation, though, many of these tools have yet to be adopted. This may be due to the long design cycles associated with building spacecraft and the unknown risks to improper designs associated with performing evaluations using these tools. The objective of this work is to evaluate the spectrum of alternative reality tools and their ability to facilitate the evaluation of spacecraft habitat designs.
The specific aims of this study are:
Specific Aim 1: We characterized and defined the four categories of design tools (physical, augmented, hybrid and virtual realities) and established a set of high-level guidelines from the literature for how each approach is typically used. This was documented as a table of advantages, disadvantages, and comments. This characterization included specific definitions of these categories, metrics by which to evaluate them, and system requirements. We also project into future technology development on the horizon from interaction with experts in academia, government, and industry, such that this benchmark assessment is not limited to current state-of-the-art.
Specific Aim 2: We conducted experimental evaluations to investigate volumetric perception and task performance in volumetric assessment of a spacecraft habitat environment. These tasks were determined in conjunction with NASA personnel to be the highest utility to achieve NASA objectives. The experiments investigated the advantages and limitations of each aforementioned environment for the application of spacecraft habitat design evaluation.
Aim 1 was delivered to NASA as a technical report, and is currently under revision as a journal publication in Virtual Reality. The findings from Aim 2 have been written into one journal publication on the environment development, which is under review in Virtual Reality, and a second publication on the experimental findings is currently in preparation.
We present a framework for using alternative reality technologies in spacecraft habitat design. From a literature review of existing taxonomies, we identified the characteristics of alternative reality technologies and their most relevant Spectrums for use in spacecraft habitat design and evaluation. The spectrums identified are: 1. Superposition – the extent to which knowledge of the environment is virtualized; 2. Causality – the degree of interaction the user experiences with the environment; 3. Presence – the extent to which the user feels he or she is occupying the environment; 4. Augmentation – the method by which information about the user and environment is captured and transmitted; and 5. Fidelity – the degree of accuracy with which the environment captures a true desired representation. Within each Spectrum, there are anchor points that define the degree to which the environment is altered by changing its features.
From our framework, four specific XR Classifications were identified as a defined set of terms that could be used in common vernacular. The identified classifications lie along Milgram and Kishino’s Continuum of Virtuality and are defined as: 1. Physical Reality (PR), 2. Augmented Reality (AR), 3. Hybrid Reality (HR), and 4. Virtual Reality (VR). PR is defined as an environment with objective existence, perceived in a traditional manner. It may contain digital content, but only if that content is reflective of true implementation. AR has an increased amount of virtualized and simulated content in an otherwise real environment. That content is integrated into the environment but does not dominate it. HR is a nearly virtual environment, but it incorporates elements with objective physical existence. Finally, VR is a fully virtualized environment simulating relevant aspects across sensing modalities.
Alternative realities are achieved by influencing human sensing Modalities. Three Modalities were investigated: Visual, Auditory, and Tactile. In this context, we include an individual’s perception of motion, orientation, and proprioception within the Tactile modality. Within each sensing Modality, sub-dimensions were identified comprising the technical elements by which the Modality is altered within XR environments. Some sub-dimensions lie along a continuum, while others are discrete technology choices the user may make. The technical requirements of a sub-dimension can be linked to the Spectrums outlined above. In this way, the framework provides a mapping between different sensing Modalities and the environmental aspects influenced by a given technology choice. The objective of this framework is to allow users to transition between Spectrums and Modalities more easily and to identify areas in which to focus development based on their specific needs.
From the detailed framework, high-level guidelines were provided to assist stakeholders within spacecraft habitat design (SHD) in choosing an XR category to suit their evaluation objectives. The stakeholders identified were evaluators in Program Management, Human Systems Integration, Operations and Training, Engineering, and Manufacturing and Assembly. Information for the stakeholder groups on their evaluation needs was acquired by reviewing the evaluation criteria against which stakeholders perform SHD evaluations, from documentation provided by NASA personnel, and interviews with subject matter experts. These data were then aggregated into a series of tables incorporating the anticipated advantages, disadvantages, and applicable phases in the design process. A list of tools that can be used by evaluators within an XR classification was also compiled. These guidelines and tool lists should continue to be expanded and adapted as hardware and technology development continues, in order to ensure it remains contemporary. This research provides a functional set of practices that can be used to help SHD evaluators achieve their mission to reduce the risk of incompatible spacecraft habitat design.
We defined a framework that links theoretical Spectrums to technical requirements within a sensing Modality and define four XR Classification groups. We converted the detailed framework developed into a functional set of guidelines and potential practice cases for stakeholders in spacecraft habitat and design, with a focus on design evaluation.
From these findings, we experimentally investigated the ability of subjects to perceive volume in spacecraft habitats across the XR spectrum. One of the most important aspects of SHD evaluation is to understand the spacecraft’s volume, layout, and its impact on the crew. It was noted across the literature, interviews, and NASA documents that virtual representations of interiors, while instructive, are not realistic enough to provide a true evaluation of volume considerations. This mismatch may be due to the 2D projection of a 3D space, the capacity of the human eye and brain to integrate information, or the lack of personal sense within a virtual volume when not visualized. To investigate this, we experimentally evaluated what scaling difference across volume representations were present in VR, HR, and AR as compared to PR.
Further, we performed a side-by-side comparison of the four XR environments for volumetric evaluation purposes. Across the literature, comparisons of PR and VR are widely documented, particularly at early stages of design. The comparison of PR and VR with AR and HR, though, are less well documented. This was also reflected in the reduced familiarity our subject matter experts had with these technologies and how they could best be implemented in their SHD evaluations. We performed direct performance comparisons across all four XR Classifications, in a manner similar to that has been done previously.
Equal-fidelity mockups were made in each XR environment, depicting a single, common interior vehicle layout. We detailed the steps taken to construct all four environments and highlighted the various advantages and limitations of each alternative reality approach. Moreover, a novel hybrid reality setup that includes intuitive interactions, realistic haptics, and a fully virtual audiovisual scene was implemented. Our experimental results indicate that VR is the most likely to produce results consistent with a real physical mock-up. Each of our metrics was internally consistent and many results were consistent even across experiments. There remain challenges merging physical and virtualized content, perhaps contributing to the poorer overall performance of HR and AR. These environments show promise, though, particularly as the state-of-the-art in XR technology advances.
This research contributes to the understanding of alternative reality technologies and their application in all stages of spacecraft habitat design and evaluation. This research will assist in evaluating requirements and can be used to improve habitability, ergonomics and space allocation, and to meet engineering constraints. This work addresses Gap HAB – 05: We need to identify technologies, tools, and methods for data collection, modeling, and analysis that are appropriate for design and assessment of vehicles/habitats… for predetermined mission attributes, and for refinement and validation of level of acceptable risk. This research identifies how emerging and existing alternative reality technologies can be incorporated by SHD stakeholders across various phases of design evaluation to reduce the risk of incompatible spacecraft habitat environments.
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