Evaluating Extravehicular Activity Access Options for a Lunar Surface Habitat

One major factor for operational safety and planning of human extravehicular activities (EVAs) is the topography of the landing region. During planning for EVAs for future crewed missions, digital elevation models (DEMs) and derived slope maps are often used to place constraints on proposed EVA paths to minimize the slopes and vertical meters traveled. However, the specification of these constraints has not yet been studied in detail and has to date relied on generalized assumptions. The Apollo program was the subject of meticulous planning and execution over an extended period. Our study concentrated on the pivotal aspect of mission planning, namely the topographic conditions of all Apollo landing sites. Furthermore, there are numerous conditions of lunar exploration whose "ground truth" can only be fully comprehended by astronauts who have personally visited the Moon. Certainly, there are technical constraints for the use and operation of equipment and tools, such as suits and instrument carts. However, astronaut observational physiological and psychological experiences and constraints are need to be considered for the planning of successful EVAs. In this study, we examined a variety of data sources, including topographic data, Apollo astronaut reports, audio and video recordings, in order to assess their experience and performance in relation to the topography and slopes along each Apollo extra vehicular activity (EVA). The ability of the astronauts to accurately perceive distances, slopes, and to move with confidence is contingent upon topographic and illumination conditions, as well as the specific equipment that they are required to carry. Future mission planning must take realistic traverse speeds into account, as well as the perception of both real and perceived hazards on challenging traverses.

Modeling a 15-min extravehicular activity prebreathe protocol using NASA׳s exploration atmosphere (56.5 kPa/34% O2)

Extravehicular activity (EVA) is a highly hazardous phase of human spaceflight, yet one of the most scientifically rewarding. Ensuring the safety, efficiency, and autonomy of astronauts is essential for the success of Artemis mission EVAs. Prior work has developed automated EVA planning tools, but none incorporate monitoring of physiological data. The Navigational Ground Assessment & Trajectory Optimization Router (NaviGATOR) is designed to process surface environment data, physiological data, consumables levels, and preselected scientific regions of interest (ROI) to determine the EVA path that minimizes astronaut energy expenditure and maximizes scientific return. First, a grid-based representation of the lunar surface is constructed from slope data. Metabolic rate (MR) is predicted for each grid cell using slope data, locomotion speed, and mass of the astronaut-suit system. Grid cells with slopes that exceed allowable ranges as defined in Exploration EVA System's Concept of Operations are constrained as unusable. All other grid cells are assigned a normalized cost based on MR predictions. Once the coordinates of start points, end points, and ROIs are provided, the tool uses mixed integer linear programming to determine the optimal ordering of ROI visits. Optimal Rapidly-exploring Random Trees planpaths between ROIs to minimize energy expenditure while satisfying constraints. The tool can plan paths both before an EVA and adjust paths during EVA based on astronaut vital signs and suit consumable levels, thus facilitating better-informed mission planning and improving crew autonomy. The tool's performance was validated through comparison to Apollo EVAs, which showed that the tool orders ROIs identically to visitation order by Apollo astronauts, plans paths between ROIs similar to those the Apollo astronauts traversed, and predicts MRs comparable to Apollo mission-recorded data. Overall, this tool may be able to improve safety, efficiency, and autonomy of astronauts on surface EVAs. NaviGATOR is maintained on a public GitHub repository.

<div class="htmlview paragraph">An extravehicular activity (EVA) path-planning and navigation tool, called the Mission Planner, has been developed to assist with pre-mission planning, scenario simulation, real-time navigation, and contingency replanning during astronaut EVAs, The Mission Planner calculates the most efficient path between user-specified waypoints. Efficiency is based on an exploration cost algorithm, which is a function of the estimated astronaut metabolic rate. Selection of waypoints and visualization of the generated path are realized within a 3D mapping interface through terrain elevation models. The Mission Planner is also capable of computing the most efficient path back home from any point along the path.</div>

DIANA: An underwater analog space mission

A successful transition to global clean energy hinges on meeting the world’s growing demand for power, while at the same time reducing greenhouse gas emissions. Achieving this will require significant growth in electricity generation from clean and carbon-free energy sources. Several energy providers (Acar and Dincer, 2019, “Review and Evaluation of Hydrogen Production Options for Better Environment,” J. Cleaner Prod., 218, pp. 835–849 and Nagashima, M., 2024, “Japan’s Hydrogen Strategy and Its Economic and Geopolitical Implications,” Afficher la page d’accueil du site) have already begun the transition from traditional carbon-based fuels to cleaner alternatives, such as hydrogen (H2) and hydrogen-enriched natural gas (HENG). However, there are still many technical questions/challenges that must be addressed when applying these fuels in gas turbines. The application of H2 or H2/natural gas (NG) blends to advanced-class gas turbines, which have higher operating pressures and temperatures, has raised concerns about the potential for leakages or fuel sequencing operations where flammable mixtures of fuel and air could auto-ignite. Public information on the auto-ignition of H2 in the air at atmospheric pressure shows an auto-ignition temperature (AIT) between 520 and 585 °C (U.S. Department of Energy, 2024, “U.S. Department of Energy Hydrogen Program Plan,” U.S. Department of Energy, Washington, DC; Georgia Power, 2022, “Georgia Power, Mitsubishi Power, EPRI Complete World’s Largest Hydrogen Fuel Blending at Plant McDonough-Atkinson,” Georgia Power, Atlanta, GA; and gepower-v2, 2024, “New York Power Authority: GE Vernova,” gepower-v2, Cambridge, MA). Such data show AIT of H2 is ∼100 °C lower than that of methane (CH4) which has a minimum AIT of around 600 °C (Huth, M., and Heilos, A., 2013, “Fuel Flexibility in Gas Turbine Systems: Impact on Burner Design and Performance,” Modern Gas Turbine Systems, Sawston, UK, pp. 635–684). Studies also show that as pressure increases, methane’s AIT decreases significantly to around 390 °C (Loving, C., Mastantuono, G., Terracciano, A. C., Vasu, S. S., Pigon, T., Hernandez, A., and Cloyd, S., 2023, “Auto-Ignition Test Results of Hydrogen and Natural Gas Fuels at Atmospheric and Elevated Pressures for Gas Turbine Safety,” ASME Paper No. GT2023-102674). However, there was insufficient information in the published literature to characterize the influence of pressure on the AIT of H2 and HENG fuels. At atmospheric conditions, H2 has a wider flammability range of equivalence ratios that ignition can occur compared to methane. H2’s flammability ranges from 4% to 75% molar (volume) fuel concentration, which is an equivalence ratio range of 0.137–2.57. Methane’s flammability limit ranges from 5% to 15% molar (volume) or an equivalence ratio between 0.53 and 1.58 (National Aeronautics and Space Administration, 1997, Safety Standard for Hydrogen and Hydrogen Systems: Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and Transportation, National Aeronautics and Space Administration, Office of Safety and Mission Assurance; National Technical Information Service, Distributor, Washington, DC, Springfield, VA). Previous research has also been done to determine the effect of longer hydrocarbons present in natural gas mixtures. The presence of ethane (C2H6) and propane (C3H8) has been shown to reduce the AIT of natural gas, especially at elevated pressures (The Association, 1994, NFPA 49: Hazardous Chemicals Data, The Association, Quincy, MA). These longer hydrocarbons also tend to promote ignition in richer conditions, whereas methane tends to ignite easier in slightly lean conditions (National Aeronautics and Space Administration, 1997, Safety Standard for Hydrogen and Hydrogen Systems: Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and Transportation, National Aeronautics and Space Administration, Office of Safety and Mission Assurance; National Technical Information Service, Distributor, Washington, DC, Springfield, VA). Numerous variables besides the pressure, fuel, and equivalence ratio can affect the AIT including chamber volume size, chamber materials, presence of diluents, and other factors (Standards Australia International, 2000, Electrical Apparatus for Explosive Gas Atmospheres. Part 20, Data for Flammable Gases and Vapours, Relating to the Use of Electrical Apparatus, Standards Australia International; Standards New Zealand, Strathfield, NSW, Wellington, NZ). This study describes the test methodology used to evaluate conditions where auto-ignition occurs for various fuel–air mixtures operating at different pressures (1–30 atm) and temperatures. Testing was completed with 100% H2 and multiple H2/NG blends at various equivalence ratios (ER) between 0.2 and 2.5. Testing was similarly performed for 100% NG to validate the test and data collection methods cited in prior published literature. Results indicate that, at atmospheric pressures, an increase in H2 concentration results in a reduced AIT. However, at 30 atm, the increased presence of H2 increased the AIT. At elevated pressures above 10 atm, increased equivalence ratio resulted in reduced AIT for all mixtures with NG having the greatest sensitivity to equivalence ratio. Variations of auto-ignition delay times (AIDT) were also observed during the testing and are compared to modeling predictions, providing insight into auto-ignition characteristics.

In 2014, in response to a large volume of feedback from industry, the science community, and internal to Goddard Space Flight Center (GSFC), GSFC’s Safety and Mission Assurance (SMA) Directorate began a transition to a risk-based implementation of SMA, departing from its longstanding practice of being primarily driven by a mostly static set of Mission Assurance Requirements. The transition started out with a pilot project involving risk-based acceptance of bare-printed circuit boards that was enormously successful, continued through a complete organizational transformation in 2015, and culminated with the baselining of formal Risk-Based SMA policy in 2016. This article highlights five major examples of successful implementation of Risk-Based SMA that have demonstrated not only substantial savings in project resources, but also the ability to achieve the lowest level of risk in developing and operating inherently risky systems.

This paper describes the Safety and Mission Assurance (SMA) processes and the role of the NASA-delegated Safety and Mission Assurance Technical Authority (SMATA) that together contributed to the Mars 2020 Project development through launch. The M2020 flight system development included many high heritage designs and new developments. Inheritance reviews at the subsystem level fully document and confirmed the level of inheritance. New developments for subsystems, assemblies, and instruments followed a standard phased development cycle per standards at the Jet Propulsion Laboratory (JPL) through delivery to JPL Assembly, Test, and Launch Operations (ATLO). SMA processes exercised oversight and insight through all phases including ATLO. SMA processes were adapted for oversight and insight of contributed instruments. SMA Disciplines at JPL managed approval of EEE Parts and design analyses, specification of mission environments and required testing and analyses as well as accepted completion of the required testing and analysis. Software Quality Assurance (SQA) oversaw all flight software development. All hardware processing and testing was completed under the watchful eye and approval of Hardware Quality Assurance (HQA). Finally, System Safety continually assured safe execution of all hazardous processes. Throughout development, SMA assessed risk resulting from anomalies, requirement waiver requests, and other technical risks. SMATA independently reported risk to the Project Manager, JPL Management, and NASA culminating in a Safety and Mission Success Review (SMSR) prior to launch.

Safety and mission assurance in a better, faster, cheaper environment

The NASA Office of Safety and Mission Assurance (OSMA) has pursued the development of an implementable objectives based strategy approach to managing several aspects of the assurance disciplines. Reliability and Maintainability (R&M) engineering and Software Assurance are among the initial disciplines tackled. The objectives based approach involves creating a hierarchy of interwoven objectives and strategies designed to effectively meet the top-level objective of being “as safe as reasonably possible” or to “perform as required over the life cycle.” The logical constructs emerge as tools to enhance management of the assurance functions for flight projects. This paper presents some clear examples of how an objectives based strategy can be effectively employed to promote: •flexible and tailorable standardization for a range of risk levels •rapid self-assessment for Verification & Validation (V&V) •risk acceptance through safety and assurance cases that aggregate the necessary evidence to demonstrate the desired project outcomes. Techniques developed to apply the hierarchy concept to management of assurance are presented, along with examples used to support the new OSMA policy framework. This clearly demonstrates the efficacy of the objectives based approach. This is based on research and practice within the assurance and systems engineering communities, and reflects a high degree of utility for the objectives based strategy among the assurance communities.

Integrated system health management (ISHM) technologies have been developed to address safety, replace time-based maintenance with condition-based maintenance, and to reduce life cycle costs. Traditional space system designs have focused on safety to minimize the risk to crew and to protect the public, astronauts and pilots, the NASA workforce, and high-value equipment and property. Systems have relied on high reliability components to provide the necessary safety margins and avoid operational mission failures. The current vision for future manned and unmanned space missions to the International Space Station, the Moon, Mars, and beyond, will require longer duration missions and will rely on complex assemblages of components. Increased mission duration and complexity increase the probability of operational mission failures that must be mitigated without jeopardizing safety or the objectives of the current or future missions that might reuse critical mission components. ISHM technology will be essential for providing near-real-time assessments of system capability, safety margins, and maintenance and sustainment requirements. The Applied Research Lab has conducted a series of workshops for NASA which focused on defining requirements for integrated system health monitoring and for the integration of health monitoring and control to provide intelligent self situational awareness (ISSA). The results of these workshops indicate that the benefits of ISHM and greater integration between ISHM and control include increased safety and mission assurance, the ability to rapidly respond to system failures, and decreased operator workload. Emerging open system standards such as OSA-EAI provide a framework for integrating system health monitoring with control functionality in spacecraft avionics systems. The purpose of this paper is to describe areas where system health monitoring can impact safety, reliability and sustainment in space applications and present the results of workshops conducted for NASA to identify requirements for the integration of health monitoring and control in future space systems

Issues arising from the NASA safety standard to control orbital debris

Soil Moisture Active Passive (SMAP) is a NASA-developed Earth science satellite currently mapping the soil moisture content and freeze/thaw state of Earth's land mass from a 685km, near-polar, sun-synchronous orbit. It was launched on January 31, 2015 from Vandenberg AFB upon a Delta II 7320 launch vehicle. Due to external considerations, SMAP's launch vehicle selection remained an open item until Project Critical Design Review (CDR). Thus, certain key aspects of the spacecraft design had to accommodate a diverse range of candidate launch vehicle environments, performance envelopes, interfaces and operational scenarios. Engineering challenges stemmed from two distinct scenarios: decisions that had to be made prior to launch vehicle selection to accommodate all possible outcomes, and post-selection changes constrained by schedule and the existing spacecraft configuration. The effects of the timing of launch vehicle selection reached virtually every aspect of the Observatory's design and development. Physical environments, mass allocations, material selections, propulsion system performance, dynamic response, launch phase and mission planning, overall size and configuration, and of course all interfaces to the launch vehicle were heavily dependent on this outcome. This paper will discuss the resolution of these technical challenges.

The National Aeronautics and Space Administration has conducted a comprehensive study to identify the most appropriate and efficient modulation, coding, multiple access and link protocol options for future space communication links supported by NASA's Ground Network, space network, deep space network, and earth-based ground terminals and in-situ relay satellites envisioned for Constellation Program mission support at the Moon and Mars. This paper briefly describes the study process and summarizes the multiple access recommendations for future NASA space communications.

After giving a short overview about the published instrumentation and control standards worldwide with regard to the separation measures, as released by the different safety authorities, this paper provides a first assessment of the different needs and requirements to be considered in the frame of separation measures which are to be implemented in the instrumentation and control design. According to this analysis the corresponding design aspects and features are derived and analyzed. The experience gained both in nuclear power plant modernization projects and new builds show that there are margins both for interpretation possibilities and for possible technical solutions, which can be proposed to the customer in order to fulfill the concerned standards. A conclusion about the design approach and solutions as well as possible future scenarios is given.