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NASA׳s plans for future human exploration missions utilize a new atmosphere of 56.5 kPa (8.2 psia), 34% O 2 , 66% N 2 to enable rapid extravehicular activity (EVA) capability with minimal gas losses; however, existing EVA prebreathe protocols to mitigate risk of decompression sickness (DCS) are not applicable to the new exploration atmosphere. We provide preliminary analysis of a 15-min prebreathe protocol and examine the potential benefits of intermittent recompression (IR) and an abbreviated N 2 purge on crew time and gas consumables usage. A probabilistic model of decompression stress based on an established biophysical model of DCS risk was developed, providing significant ( p 2 is located, are reduced to about the levels (30.0 vs. 27.6 kPa) achieved during a standard Shuttle prebreathe protocol. IR reduced estimated DCS risk from 9.7% to 7.9% (1.8% reduction) and from 8.4% to 6.1% (2.3% reduction) for the scenarios modeled; the penalty of N 2 reuptake during IR may be outweighed by the benefit of decreased bubble size. Savings of 75% of purge gas and time (0.22 kg gas and 6 min of crew time per person per EVA) are achievable by abbreviating the EVA suit purge to 20% N 2 vs. 5% N 2 at the expense of an increase in estimated DCS risk from 9.7% to 12.1% (2.4% increase). A 15-min prebreathe protocol appears feasible using the new exploration atmosphere. IR between EVAs may enable reductions in suit purge and prebreathe requirements, decompression stress, and/or suit operating pressures. Ground trial validation is required before operational implementation.

The Mars Ascent Vehicle (MAV) is the largest indivisible payload and has the largest “gear ratio” in NASA's Evolvable Mars Campaign (EMC) architecture. For this reason, the mass and related volume of the MAV cabin drives requirements for Mars Surface In-Situ Resource Utilization generators to manufacture propellants, which: drives the surface power needs, sets the Lander payload size, drives the in-space transportation architecture, and drives the number of launches and time required to land humans on Mars' surface. Some of the architectures currently under consideration in the EMC use a chemical/solar electric propulsion hybrid that inserts into a 5 sol orbit and may require that the crew spend several days in the MAV before a rendezvous with the Mars transit vehicle. There have been no human-in-the-loop (HITL) evaluations to generate the data necessary to inform decisions on the required size of the MAV. These data are critical to begin to close the various EMC architectures. The common cabin concept consists of a core cabin with ECLSS, power, thermal and GNC systems that can be coupled to various mobility systems resulting in use of the core cabin design within a lander cabin, MAV — an in-space taxi between locations in the Mars system, as a Mars moons exploration vehicle, and a Mars surface rover. The common cabin approach could be facilitated through a standard interface design that allows for attachment of the different mobility systems. The interior of the cabin would also be outfitted differently based on the mission of the particular vehicle. The focus of the project summarized here is to determine the size of the smallest viable MAV from a sizing and habitability perspective. Multiple options were considered, two of which were studied in greater depth; one that provides maximum commonality with other cabins needed across the EMC and the other being a unique minimalist cabin. To enable the sizing and habitability assessments, the project completed analysis tasks including generation of functional requirements, development of mission timelines for all phases of MAV operations (from launch to berthing with a transit habitat), definition of required subsystems, computer aided design modeling of potential cabin layouts, and development of preliminary mass equipment lists. A maximum commonality cabin was evaluated with a 4-person crew executing all phases of the mission timeline. Additionally a minimalist cabin design was subjectively evaluated using computer generated models of vehicle layout and design. The results of the test findings and analysis are described in this paper. The results suggested that the volume and mass of the common cabin and the minimalist cabins were nearly identical. The benefits of the common cabin also include the potential use as a habitable airlock/node as part of a Cislunar habitat system, buying down risk and gaining flight experience with this Mars-forward habitation element.

NASA Extreme Environment Mission Operations (NEEMO) is an underwater spaceflight analog that provides a true mission-like operational environment for aquanauts living in the Aquarius undersea habitat for up to several weeks at a time. During these analog missions, aquanauts go out on multi-hour extravehicular activities (EVAs) and use buoyancy effects and added weight to simulate different gravity levels. The NEEMO 21 mission was undertaken in July of 2016. During this mission, the effects of several operations concepts (ConOps, defined as operational design elements that guide the organization and flow of hardware, personnel, communications, and data products through the course of a mission implementation) and a communication latency of 15 min oneway light time (OWLT) were studied in six aquanaut test subjects. These “Mars” aquanaut crewmembers conducted scientific exploration of the reef surrounding the Aquarius habitat while interacting with an “Earth-based” science team (ST) that was located topside. The ST provided guidance to the aquanauts throughout the EVAs across the 15 min communication latency. Exploration EVA traverses and timelines were planned in advance based on precursor data. During these 4-hr EVAs, the aquanauts completed science-related tasks, including pre-sampling surveys and marine-science-based sampling. Objective data included task completion times, total EVA time, crew idle time, translation time, ST-assimilation time (defined as time available for the ST to discuss, review, and act upon incoming data from the aquanauts). Subjective data included acceptability, simulation quality, and capability assessment ratings and associated comments. Additionally, feedback from both the crew and the ST were captured during the post-mission debrief. Each ConOps tested was found to provide advantages and disadvantages and it is likely that each will be used during the exploration of Mars. The choice of ConOps for Mars' EVAs will likely be dependent on the science objectives of that EVA balanced with the associated operational costs (such as human and rover transport cost).

This paper describes low-latency teleoperations (LLT) analyses performed by the NASA Human Spaceflight Architecture Team (HAT), as part of the Evolvable Mars Campaign (EMC). We will cover a variety of mission operations concepts and activities, including task details such as assumptions, sequences, timelines, and potential work systems. We will also present a preliminary task prioritization and potential implications for the Evolvable Mars Campaign and associated technology development.

The Desert Research and Technology Studies (D-RATS) 2011 field test involved the planning and execution of a series of exploration scenarios under operational conditions similar to those expected during a human exploration mission to a near-Earth asteroid (NEA). The focus was on understanding the operations tempo during simulated NEA exploration and the implications of communications latency and limited data bandwidth. Anchoring technologies and sampling techniques were not evaluated due to the immaturity of those technologies and the inability to meaningfully test them at D-RATS. Reduced gravity analogs and simulations are being used to fully evaluate Space Exploration Vehicle (SEV) and extravehicular (EVA) operations and interactions in near-weightlessness at a NEA as part of NASA's integrated analogs program. Hypotheses were tested by planning and performing a series of 1-day simulated exploration excursions comparing test conditions all of which involved a single Deep Space Habitat (DSH) and either 0, 1, or 2 SEVs; 3 or 4 crewmembers; 1 of 2 different communications bandwidths; and a 50-second each-way communications latency between the field site and Houston. Excursions were executed at the Black Point Lava Flow test site with a remote Mission Control Center and Science Support Room at Johnson Space Center (JSC) being operated with 50-second each-way communication latency to the field. Crews were composed of astronauts and professional field geologists. Teams of Mission Operations and Science experts also supported the mission simulations each day. Data were collected separately from the Crew, Mission Operations, and Science teams to assess the test conditions from multiple perspectives. For the operations tested, data indicates practically significant benefits may be realized by including at least one SEV and by including 4 versus 3 crewmembers in the NEA exploration architecture as measured by increased scientific data quality, EVA exploration time, capability assessment ratings, and consensus acceptability ratings provided by Crew, Mission Operations, and Science teams. A combination of text and voice was used to effectively communicate over the communications latency, and increased communication bandwidth yielded a small but practically significant improvement in overall acceptability as rated by the Science team, although the impact of bandwidth on scientific strategic planning and public outreach was not assessed. No effect of increased bandwidth was observed with respect to Crew or Mission Operations team ratings of overall acceptability.

Introduction A pair of small pressurized rovers (multi-mission space exploration vehicles, or MMSEVs) is at the center of the Global Point-of-Departure architecture for future human lunar exploration. Simultaneous operation of multiple crewed surface assets should maximize productive crew time, minimize overhead, and preserve contingency return paths. Methods A 14-day mission simulation was conducted in the Arizona desert as part of NASA's 2010 Desert Research and Technology Studies (DRATS) field test. The simulation involved two MMSEV earth-gravity prototypes performing geological exploration under varied operational modes affecting both the extent to which the MMSEVs must maintain real-time communications with the mission control center (Continuous [CC] versus Twice-a-Day [2/D]) and their proximity to each other (Lead-and-Follow [LF metrics showed a marginal increase while qualitative assessments suggested a practically significant difference. For the communications architecture evaluated, significantly more crew time (14% per day) was required to maintain communications during D&C than during L&F (5%) or 2/D (2%), increasing the time required to complete all traverse objectives. Situational awareness of the other vehicle's location, activities, and contingency return constraints were qualitatively enhanced during L&F and 2/D modes due to line-of-sight and direct MMSEV-to-MMSEV communication. Future testing will evaluate approaches to operating without real-time space-to-earth communications and will include quantitative evaluation and comparison of the efficacy of mission operations, science operations, and public outreach operations.

The NASA Extreme Environment Mission Operations (NEEMO) 15 mission was focused on evaluating techniques for exploring near-Earth asteroids (NEAs). It began with a University of Delaware autonomous underwater vehicle (AUV) systematically mapping the coral reef for hundreds of meters surrounding the Aquarius habitat. This activity is akin to the type of “far-field survey” approach that may be used by a robotic precursor in advance of a human mission to a NEA. Data from the far-field survey were then examined by the NEEMO science team and follow-up exploration traverses were planned, which used Deepworker single-person submersibles. Science traverses at NEEMO 15 were planned according to a prioritized list of objectives developed by the science team. These objectives were based on review and discussion of previous related marine science research, including previous marine science saturation missions conducted at the Aquarius habitat. AUV data were used to select several areas of scientific interest. The Deepworker science traverses were then executed at these areas of interest during 4 days of the NEEMO 15 mission and provided higher resolution data such as coral species distribution and mortality. These traverses are analogous to the “near-field survey” approach that is expected to be performed by a Multi-Mission Space Exploration Vehicle (MMSEV) during a human mission to a NEA before extravehicular activities (EVAs) are conducted. In addition to the science objectives that were pursued, the NEEMO 15 traverses provided an opportunity to test newly developed software and techniques. Sample collection and instrument deployment on the NEA surface by EVA crew would follow the “near-field survey” in a human NEA mission. Sample collection was not necessary for the purposes of the NEEMO science objectives; however, the engineering and operations objectives during NEEMO 15 were to evaluate different combinations of vehicles, crew members, tools, and equipment that could be used to perform these science objectives on a NEA. Specifically, the productivity and acceptability of simulated NEA exploration activities were systematically quantified and compared when operating with different combinations of crew sizes and exploration systems including MMSEVs, EVA jet packs, and EVA translation devices. Data from NEEMO 15 will be used in conjunction with data from software simulations, parametric analysis, other analog field tests, anchoring models, and integrated testing at Johnson Space Center to inform the evolving architectures and exploration systems being developed by the Human Spaceflight Architecture Team.

NASA Extreme Environment Mission Operations (NEEMO) is an underwater spaceflight analog that allows a true mission-like operational environment and uses buoyancy effects and added weight to simulate different gravity levels. Three missions were undertaken from 2014–2015, NEEMO 18–20. All missions were performed at the Florida International University's Aquarius Reef Base, an undersea research habitat. During each mission, the effects of communication latencies on operations concepts, timelines, and tasks were studied METHODS: Twelve subjects (4 per mission) were weighed out to simulate near-zero or partial gravity extravehicular activity (EVA) and evaluated different operations concepts for intergration and management of a simulated Earth-based science team (ST) to provide input and direction during exploration activities. Exploration traverses were preplanned based on precursor data. Subjects completed science-related tasks including presampling surveys, geologic-based sampling, and marine-based sampling as a portion of their tasks on saturation dives up to 4 hours in duration that were designed to simulate EVA on Mars or the moons of Mars. One-way communication latencies, 5 and 10 minutes between space and mission control, were simulated throughout the missions. Objective data included task completion times, total EVA times, crew idle time, translation time, ST assimilation time (defined as time available for ST to discuss data/imagery after data acquisition). Subjective data included acceptability, simulation quality, capability assessment ratings, and comments. RESULTS: Precursor data can be used effectively to plan and execute exploration traverse EVAs (plans included detailed location of science sites, high-fidelity imagery of the sites, and directions to landmarks of interest within a site). Operations concepts that allow for presampling surveys enable efficient traverse execution and meaningful Mission Control Center (MCC) interaction across communication latencies and can be done with minimal crew idle time. Imagery and contextual information from the EVA crew that is transmitted real-time to the intravehicular activity (IVA) crewmember(s) can be used to verify that exploration traverse plans are being executed correctly. That same data can be effectively used by MCC (across comm latency) to provide meaningful feedback and instruction to the crew regarding sampling priorities, additional tasks, and changes to the EVA timeline. Text / data capabilities are preferred over voice capabilities between MCC and IVA when executing exploration traverse plans over communication latency.

A propellant-saving hopper mobility system was studied that could help facilitate the exploration of small bodies such as Phobos for long-duration human missions. The NASA Evolvable Mars Campaign (EMC) has proposed a mission to the moons of Mars as a transitional step for eventual Mars surface exploration. While a Mars transit habitat would be parked in High-Mars Orbit (HMO), crew members would visit the surface of Phobos multiple times for up to 14 days duration (up to 50 days at a time with logistics support). This paper describes a small body surface mobility concept that is capable of transporting a small, two-person Pressurized Exploration Vehicle (PEV) cabin to various sites of interest in the low-gravity environment. Using stored kinetic energy between bounces, a propellant-saving hopper mobility system can release the energy to vector the vehicle away from the surface in a specified direction. Alternatively, the stored energy can be retained for later use while the vehicle is stationary in respect to the surface. The hopper actuation was modeled using a variety of launch velocities, and the hopper mobility was evaluated using NASA Exploration Systems Simulations (NExSyS) for transit between surface sites of interest. A hopper system with linear electromagnetic motors and mechanical spring actuators coupled with Control Moment Gyroscope (CMG) for attitude control will use renewable electrical power, resulting in a significant propellant savings.

A TBDM DCS probability model based on an existing biophysical model of inert gas bubble growth provides significant prediction and goodness-of-fit with 84 cases of DCS in 668 human altitude exposures. 2. Model predictions suggest that 15-minute O2 prebreathe protocols used in conjunction with suit ports and an 8.2 psi, 34% O2, 66% N2 atmosphere may enable rapid EVA capability for future exploration missions with the risk of DCS ≤ 12%.  EVA could begin immediately at 6.0 psi, with crewmembers decreasing suit pressure to 4.3 psi after completing the 15-minute in-suit prebreathe. 3. Model predictions suggest that intermittent recompression during exploration EVA may reduce decompression stress by 1.8% to 2.3% for 6 hours of total EVA time. Savings in gas consumables and crew time may be accumulated by abbreviating the EVA suit N2 purge to 2 minutes (20% N2) compared with 8 minutes (5% N2) at the expense of an increase in estimated decompression risk of up to 2.4% for an 8-hour EVA.  Increased DCS risk could be offset by IR or by spending additional time at 6 psi at the beginning of the EVA.  Savings of 0.48 lb of gas and 6 minutes per person per EVA corresponds to more than 31 hours of crew time and 1800 lb of gas and tankage under the Constellation lunar architecture. 6. Further research is needed to characterize and optimize breathing mixtures and intermittent recompression across the range of environments and operational conditions in which astronauts will live and work during future exploration missions. 7. Development of exploration prebreathe protocols will begin with definition of acceptable risk, followed by development of protocols based on models such as ours, and, ultimately, validation of protocols through ground trials before operational implementation.

The NASA Research and Technology Studies (RATS) 2012 test focused on optimizing utilization of a four-person crew, deep space habitat (DSH), multi-mission space exploration vehicle (MMSEV), extravehicular activity (EVA) jetpacks, and Mission Control Center operating with 50-seconds each-way communication latency during exploration within an immersive virtual-reality simulation of the near-Earth asteroid (NEA) Itokawa. Test subjects operated the MMSEV and interacted with the simulation environment from inside an MMSEV prototype while viewing the simulation on video walls through the MMSEV windows. Head-mounted displays, instrumented gloves, and an EVA jetpack control module were used during simulated free-flying EVAs while a gravity offloading system was used during simulated anchored EVAs. Simulation telemetry and consensus subjective ratings were used to assess, evaluate, and compare exploration traverses incorporating different combinations of extravehicular and intravehicular crewmembers; anchored versus freeflying operations; EVA jetpacks versus astronaut positioning system (APS) attached to the MMSEV; and NEA size and spin rates. Human factors of the Generation 2A MMSEV prototype were evaluated by two separate two-person crews, each inhabiting the MMSEV for 3 days and 2 nights. For the operations tested, the recommended distribution of crewmembers is two in the DSH, one in the MMSEV, and one EVA. Crewmembers rated this condition as “Acceptable” and experienced lower workload and greater situational awareness versus conditions involving two EVA crewmembers. Free-flying modes were preferred versus anchoring the MMSEV to the NEA because of decreased overhead and increased situational awareness, although propellant savings of 31% were estimated with anchoring. Alternating between APS and jetpack (versus APS only) did not improve acceptability but may reduce propellant usage. MMSEV Delta-V usage during manual station-keeping  ω 2 x r, where ω = NEA angular velocity and r = distance from spin axis. Human factors of the Generation 2A MMSEV were rated “Acceptable” overall.

During the last two weeks of October 2008, the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) Advanced Extravehicular Activity (AEVA) team led the field test portion of the 2008 Desert Research and Technology Studies (D-RATS) near Flagstaff, AZ. The Desert RATS field test activity is the year-long culmination of various individual science and advanced engineering discipline areas technology and operations development efforts into a coordinated field test demonstration under representative (analog) planetary surface terrain conditions. The 2008 Desert RATS was the eleventh RATS field test and was the most focused and successful test to date with participants from six NASA field centers, three research organizations, one university, and one other government agency. The main test objective was to collect Unpressurized Rover (UPR) and Lunar Electric Rover (LER) engineering performance and human factors metrics while under extended periods of representative mission-based scenario test operations involving long drive distances, night-time driving, Extravehicular Activity (EVA) operations, and overnight campover periods. The test was extremely successful with all teams meeting the primary test objective. This paper summarizes Desert RATS 2008 test hardware, detailed test objectives, test operations, and test results.

In an effort to design the next generation Lunar suit, NASA has initiated a series of tests aimed at understanding the human physiological and biomechanical affects of space suits under a variety of conditions. The first of these tests was the EVA Walkback Test (ICES 2007-01-3133). NASA-JSC assembled a multi-disciplinary team to conduct the second test of the series, titled Integrated Suit Test 1 (IST-1), from March 6 through July 24, 2007. Similar to the Walkback Test, this study was performed with the Mark III (MKIII) EVA Technology Demonstrator suit, a treadmill, and the Partial Gravity Simulator in the Space Vehicle Mock-Up Facility at Johnson Space Center. The data collected for IST-1 included metabolic rates, ground reaction forces, biomechanics, and subjective workload and controllability feedback on both suited and unsuited (shirt-sleeve) astronaut subjects. For IST-1 the center of gravity was controlled to a nearly perfect position while the weight, pressure and biomechanics (waist locked vs. unlocked) were varied individually to evaluate the effects of each on the ability to perform level (0 degree incline) ambulation in simulated Lunar gravity. The detailed test methodology and preliminary key findings of IST-1 are summarized in this report.

As planetary suit and planetary life support systems develop, specific design inputs for each system relate to a presently unanswered question concerning operational concepts: What distance can be considered a safe walking distance for a suited EVA crew member exploring the surface of the Moon to "walk-back" to the habitat in the event of a rover breakdown, taking into consideration the planned EVA tasks as well as the possible traverse back to the habitat? It has been assumed, based on Apollo program experience, that 10 kilometers (6.2 mi) will be the maximum EVA excursion distance from the lander or habitat to ensure the crew member s safe return to the habitat in the event of a rover failure. To investigate the feasibility of performing a suited 10 km Walkback, NASA-JSC assembled a multi-disciplinary team to design and implement the Lunar Walkback Test . The test was designed not only to determine the feasibility of a 10 km excursion, but also to collect human performance, biomedical, and biomechanical data relevant to optimizing space suit design and life support system sizing. These data will also be used to develop follow-on studies to understand interrelationships of such key parameters as suit mass, inertia, suit pressure, and center of gravity (CG), and the respective influences of each on human performance.