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In preparation for testing five Broad Agency Announcement (BAA) commercial cislunar habitat designs, the National Aeronautics and Space Administration (NASA) embarked on a yearlong in-house training program. This consisted of in-house testing for subject matter experts (SMEs) and crew to informed and ensure evaluation data collection techniques for each of the contractor options. Many evaluation techniques were tested with some continuing forward. Two-test conditions were employed - 1) habitat centric functions with one space element and 2) distributed functions across two or more space elements. This paper will look at one of these techniques—human circulation patterns—to assess a spacecraft habitat’s internal configuration while the crew is working a three day simulated cislunar mission. Real time tracking of the crew was accomplished using the AllTraq© system of ultra- wideband frequency (UWB) receivers and radio frequency identification tags (RFID). Heat maps, Zone Time Histograms, Zone Time Utilizations Tables and Task/Time Density Tables were constructed from the collected data. Results indicated distributing functions across elements decreased crew interference and task wait times. Additionally, areas of underutilization were located, which lead to interior layout design changes.

The NASA Next Space Technologies for Exploration Partnerships (NextSTEP) program is a public-private partnership model that seeks commercial development of deep space exploration capabilities to support human spaceflight missions around and beyond cislunar space. NASA research engineers and subject matter experts have been tasked with developing the ground test protocol that will serve as the primary means by which these Phase 2 prototypes will be systematically evaluated. The purpose of a common ground test protocol for the Phase 2 Habitation Concepts is to consistently evaluate different commercial partner ground prototypes to provide data-driven, actionable recommendations for Phase 3. This paper describes the process by which the ground test protocol was developed and the objectives, methods, and metrics by which the NextSTEP Phase 2 Habitation Concepts will be assessed. Ground test evaluations will include human-in-the-loop (HITL) habitation tests, subsystem standalone tests, analyses, and inspections. HITL testing will involve crews of four astronauts conducting multiday mission timelines that integrate all habitation operations (e.g., eating, sleeping, waste collection system operations, exercise), representative science and robotics tasks (e.g., low-latency teleoperations rover operations, sample return, life science, medical evaluations), and extravehicular activity (EVA), (e.g., airlock configuration, pre/post operations). Established subjective and objective metrics will be collected and analyzed to provide the data and actionable recommendations for Phase 3 of the NextSTEP program. This paper begins with a summary of NASA's deep space habitation plans, the goals of the NASA NextSTEP activity, and the process by which the ground test objectives were derived. It then details the strategic questions and hypotheses, and describes the inspections, analyses, subsystem standalone tests, and HITL integrated tests that will be used to address the functional requirements and ground test objectives. Data collected from these assessments will be analyzed to determine the acceptability of habitation element configurations and the combinations of capabilities that will result in the best habitation platform to be recommended by the test team for Phase 3.

Introduction The Hypobaric Decompression Sickness (DCS) Treatment Model links a decrease in computed bubble volume from increased pressure (ΔP), increased oxygen (O2) partial pressure, and passage of time during treatment to the probability of symptom resolution [P(SR)]. The decrease in offending volume is realized in two stages: 1) during compression via Boyles law; and 2) during subsequent dissolution of the gas phase via the oxygen window. Methods We established an empirical model for the P(SR) while accounting for multiple symptoms within subjects. The data consisted of 154 cases of hypobaric DCS symptoms with ancillary information from tests on 56 men and 18 women. Results Our best estimated model is P(SR)=1/(1+exp(-(ln(ΔP)-1.510+0.795×AMB-0.00308×Ts)/0.478)), where ΔP is pressure difference (psid); AMB=1 if ambulation took place during part of the altitude exposure, otherwise AMB=0; and Ts is the elapsed time in minutes from the start of altitude exposure to recognition of a DCS symptom. Discussion Values of ΔP as inputs to the model would be calculated from the Tissue Bubble Dynamics Model based on the effective treatment pressure: ΔP=P2-P1|=P1×V1/V2-P1, where V1 is the computed volume of a bubble at low pressure P1 and V2 is computed volume after a change to a higher pressure P2. If 100% ground-level oxygen was breathed in place of air, then V2 continues to decrease through time at P2 at a faster rate.

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.

Introduction Ambulation during extravehicular activity on Mars may increase the risk of decompression sickness through enhanced bubble formation in the lower body. Hypotheses walking effort (ambulation) before an exercise-enhanced denitrogenation (prebreathe) protocol at 14.7 psia does not increase the incidence of venous gas emboli (VGE) at 4.3 psia, but does increase incidence if performed after tissues become supersaturated with nitrogen at 4.3 psia. Methods VGE results from 45 control subjects who performed exercise prebreathe without ambulation before or during a 4-h exposure to 4.3 psia were compared to 21 subjects who performed the same prebreathe but ambulated before and during the hypobaric exposure (Group I) and to 41 subjects who only ambulated before the hypobaric exposure (Group II). Monitoring for VGE in the pulmonary artery was for 4 min at about 12-min intervals using precordial Doppler ultrasound (2.5 mHz). Detected VGE were assigned a categorical grade from I to IV. The detection of Grade III or IV was classified as "high VGE grade." Results The incidence of high VGE grade for Group I (57%) was greater than the control (17%) and Group II (15%). The incidence of pain-only decompression sickness was greater for Group I (20%) than the control (0%) and Group II (5%). Conclusions High-grade VGE are increased by mild ambulation conducted under a supersaturated state (Group I vs. II); however, no increase was observed with mild ambulation during the saturated state alone (control vs. Group II).Conkin J, Pollock NW, Natoli MJ, Martina SD, Wessell JH III, Gernhardt ML. Venous gas emboli and ambulation at 4.3 psia. Aerosp Med Hum Perform. 2017; 88(4):370-376.

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.

BACKGROUND To reduce bubble formation and growth during hypobaric exposures, a denitrogenation or nitrogen "washout" procedure is performed. This procedure consists of prebreathing oxygen fractions as close to one as possible (oxygen prebreathe) prior to depressurization before ascending to the working altitude or low spacesuit pressures. During the NASA prebreathe reduction program (PRP), it was determined that the addition of a light arm exercise to short, individually designed, performance-based heavy exercise (dual cycle ergometry) during an abbreviated 2-h prebreathe (F1O2 - 1.0) reduced the occurrence of decompression sickness (DCS). Heavy-exercise-induced DCS reduction is likely to be related to the enhancement of the tissue nitrogen washout during the oxygen prebreathe. In addition to the heavy-exercise-induced microcirculatory adaptation, we hypothesized that the light exercise would not cause sufficient microcirculatory changes in the limbs to explain alone this further DCS protection. We evaluated microcirculatory changes as minimal by replicating the exercise characteristics of the PRP trials in 13 healthy subjects. METHODS Noninvasive near infrared spectroscopy (NIRS) allowed observation of instantaneous variations of total, oxygenated, and deoxygenated hemoglobin/myoglobin concentrations in the microcirculatory networks (probes facing the vastus lateralis and deltoid muscles) of active limbs during dynamic exercise. RESULTS The high-intensity leg exercise alone produced the changes in NIRS parameters; the light arm exercise induced minimal microcirculatory volume changes. However, this coupling appeared to be critical in previous altitude PRP chamber studies by reducing DCS. DISCUSSION With only minimal microcirculatory blood volume changes, it is unlikely that light exercise alone causes significant nitrogen tissue washout. Therefore, our results suggest that in addition to nitrogen tissue washout, another unknown exercise-induced effect may have further enhanced the DCS protection, possibly mediated via the anti-inflammatory effect of exercise, gas micronuclei reduction, NO pathways, or other molecular mechanisms.

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.

Phobos is a scientifically interesting destination which offers engineering, operational and public outreach activities that could enhance subsequent Mars surface missions. A Phobos mission would serve to facilitate the development of the human-based Mars transportation infrastructure, unmanned cargo delivery systems, as well as habitation and exploration assets that would be directly relevant to subsequent Mars surface missions. It would also potentially provide for low latency teleoperations (LLT) of Mars surface robots performing a range of tasks from landing site validation to infrastructure development to support future crewed Mars surface Missions. A human mission to Phobos would be preceded by a cargo predeploy of a Phobos surface habitat and a pressurized excursion vehicle (PEV) to Mars orbit. Once in Mars orbit, the habitat and PEV would spiral to Phobos using solar electric propulsion (SEP)-based systems. When a crewed mission is launched to Phobos, it would include the remaining systems to support the crew during the Earth-to-Mars orbit transit and to reach Phobos after insertion into a high Mars orbit (HMO). The crew would taxi from HMO to Phobos in a spacecraft that is based on a MAV to rendezvous with the predeployed systems. A predominantly static Phobos surface habitat was chosen as a baseline architecture. The habitat would have limited capability to relocate on the surface to shorten excursion distances required by the PEV during exploration and to provide rescue capability should the PEV become disabled. PEVs would contain closed-loop guidance and provide life support and consumables for two crewmembers for two weeks plus reserves. The PEV has a cabin that uses the exploration atmosphere of 8.2psi with 34% oxygen. This atmosphere enables EVA to occur with minimal oxygen prebreathe before crewmembers enter their EVA suits through suit ports, and provides dust control to occur by keeping the suits outside the pressurized volume. When equipped with outriggers, the PEV enables EVA tasks without the need to anchor. Tasks with higher force requirements can be performed with PEV propulsion providing the necessary thrust to counteract forces. This paper overviews the mission operational concepts, and timelines, along with analysis of the power, lighting, habitat stability, and EVA forces. Exploration of Phobos builds heavily on the development of the cis-lunar proving ground and significantly reduces Mars surface risk by facilitating the design, development and testing of habitats, MAVs, and pressurized rover cabins that are all investments in Mars surface assets.

Introduction: To limit the risk of fire and reduce denitrogenation time to prevent decompression sickness to support frequent extravehicular activities on the Moon, a hypobaric ( P B = 414 mmHg ) and mildly hypoxic ( ppO 2 = 132 mmHg , 32% O 2 – 68 % N 2 ) living environment is considered for the Crew Exploration Vehicle (CEV) and Lunar Surface Access Module (LSAM). With acute change in ppO 2 from 145 – 178 mmHg at standard vehicular operating pressure to less than 125 mmHg at desired lunar surface vehicular operating pressures, there is the possibility that some crewmembers may develop symptoms of Acute Mountain Sickness (AMS). The signs and symptoms of AMS (headache plus nausea, dizziness, fatigue, or sleeplessness) could impact crew health and performance on lunar surface missions. Methods: We performed a literature review on the topic of the physiological effects of reduced ppO 2 and absolute pressure. The results of nine studies were evaluated. Results: There is evidence for an absolute pressure effect per se on AMS, so the higher the altitude for a given hypoxic alveolar oxygen ( O 2 ) partial pressure ( P A O 2 ) , the greater the AMS response is. Between 7% and 25% of adults may experience mild AMS near 2000 m altitude following a rapid ascent from sea level while breathing air (6500 ft, acute P A O 2 = 75 mmHg ) . The operational experience with the Shuttle staged denitrogenation protocol at 528 mmHg (3048 m) while breathing 26.5% O 2 (acute P A O 2 = 85 mmHg ) in astronauts adapting to microgravity suggests a similar likely experience in the proposed CEV environment. Conclusions: We believe the risk of mild AMS is greater given a P A O 2 of 77 mmHg at 4876 m altitude while breathing 32% O 2 than at 1828 m altitude while breathing 21% O 2 . Only susceptible astronauts would develop mild and transient AMS with prolonged exposure to 414 mmHg (4876 m) while breathing 32% O 2 (acute P A O 2 = 77 mmHg ). So the following may be employed for operational risk reduction: (1) develop procedures to increase P B as needed in the CEV, and use a gradual or staged reduction in cabin pressure during lunar outbound; (2) train crews for symptoms of hypoxia, to allow early recognition and consider pre-adaptation of crews to a hypoxic environment prior to launch; (3) consider prophylactic acetazolamide for acute pressure changes and be prepared to treat any AMS associated symptoms early with both carbonic anhydrase inhibitors and supplemental oxygen.

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.

This study developed, analyzed, and compared mission architectures for human exploration of Mars' moons within the context of an Evolvable Mars Campaign. METHODS: All trades assumed conjunction class missions to Phobos (approximately 500 days in Mars system) as it was considered the driving case for the transportation architecture. All architectures assumed that the Mars transit habitat would remain in a high-Mars orbit (HMO) with crewmembers transferring between HMO and Phobos in a small crew taxi vehicle. A reference science/exploration program was developed including performance of a standard set of tasks at 55 locations on the Phobos surface. Detailed EVA timelines were developed using realistic flight rules to accomplish the reference science tasks using exploration systems ranging from jetpacks to multi-person pressurized excursion vehicles combined with Phobos surface and orbital (L1, L4/L5, 20 km distant-retrograde-orbit [DRO]) habitat options. Detailed models of propellant mass, crew time, science productivity, radiation exposure, systems and consumables masses, and other figures of merit were integrated to enable quantitative comparison of different architectural options. Options for prestaging assets using solar electric propulsion versus delivering all systems with the crew were also evaluated. Seven discrete mission architectures were evaluated. RESULTS: The driving consideration for habitat location (Phobos surface versus orbital) was radiation exposure, with an estimated reduction in cumulative mission radiation exposure of up to 34% (versus a Mars orbital mission) when the habitat is located on the Phobos surface, compared with only 3% to 6% reduction for a habitat in a 20-km DRO. The exploration utility of lightweight unpressurized excursion vehicles was limited by the need to remain within 20 minutes of solar particle event radiation protection combined with complex guidance, navigation, and control systems required by the nonintuitive and highly-variable gravitational environment. Two-person pressurized excursion vehicles as well as mobile surface habitats offer significant exploration capability and operational benefits compared with unpressurized extravehicular activity (EVA) mobility systems at the cost of increased system and propellant mass. Mechanical surface translation modes (ie, hopping) were modeled and offered potentially significant propellant savings and the possibility of extended exploration operations between crewed missions. Options for extending the use of the crew taxi vehicle were examined, including use as an exploration asset for Phobos surface exploration (when combined with an alternate mobility system) and as an EVA platform, both on Phobos and for contingency EVA on the Mars transit habitat. CONCLUSIONS: Human exploration of Phobos offers a scientifically meaningful first step towards human Mars surface missions that develops and validates transportation, habitation, and exploration systems and operations in advance of the Mars landing systems.

Quantifying the preferred transition speed (PTS) from walking to running has provided insight into the underlying mechanics of locomotion. The dynamic similarity hypothesis suggests that the PTS should occur at the same Froude number across gravitational environments. In normal Earth gravity, the PTS occurs at a Froude number of 0.5 in adult humans, but previous reports found the PTS occurred at Froude numbers greater than 0.5 in simulated lunar gravity. Our purpose was to (1) determine the Froude number at the PTS in actual lunar gravity during parabolic flight and (2) compare it with the Froude number at the PTS in simulated lunar gravity during overhead suspension. We observed that Froude numbers at the PTS in actual lunar gravity (1.39±0.45) and simulated lunar gravity (1.11±0.26) were much greater than 0.5. Froude numbers at the PTS above 1.0 suggest that the use of the inverted pendulum model may not necessarily be valid in actual lunar gravity and that earlier findings in simulated reduced gravity are more accurate than previously thought.

INTRODUCTION The fitting of probabilistic decompression sickness (DCS) models is more effective when data encompass a wide range of DCS incidence. We obtained such data from the Air Force Research Laboratory Altitude Decompression Sickness Research Database. The data are results from 29 tests comprising 708 human altitude chamber exposures (536 men and 172 women). There were 340 DCS outcomes with per-test DCS incidence ranging from 0 to 88%. The tests were characterized by direct ascent at a rate of 5000 ft x min(-1) (1524 m x min(-1)) to a range of altitudes (226 to 378 mmHg) for 4 h after prebreathe times of varying length and with varying degrees of physical activity while at altitude. METHODS Logistic regression was used to develop an expression for the probability of DCS [P(DCS)] using the Hill equation with decompression dose as the main predictor. Here, decompression dose is defined in terms of either the tissue ratio (TR) or a bubble growth index (BGI). Other predictors in the model were gender and peak exercise intensity at altitude. RESULTS All three predictors (decompression dose, gender, and exercise intensity) were important contributions to the model for P(DCS). DISCUSSION Higher TR or BGI, male gender, and higher exercise intensity at altitude all increased the modeled decompression dose. Using either TR or BGI to define decompression dose provided comparable results, suggesting that a simple TR is adequate for simple altitude exposures as an abstraction of the true decompression dose. The model is primarily heuristic and limits estimates of P(DCS) to only a 4-h exposure.

OBJECTIVES: 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. The 13-day NEEMO 16 mission was performed at the Aquarius undersea research habitat. It was focused on near-Earth asteroid (NEA) exploration techniques evaluation, including evaluation of different combinations of vehicles, crewmembers, tools, and equipment that could be used to perform exploration tasks on a NEA surface. The effects of representative communication latencies associated with NEA missions were also studied during the mission. METHODS: Four subjects were weighed out using buoyancy control techniques to simulate zero gravity and evaluated different techniques and tools to perform a NEA exploration circuit on the sea floor outside Aquarius. Subjects completed tasks including float sampling, rock chip sampling, core sampling, soil sampling, geophysical array deployment, and large instrument deployment. The core tasks were completed using translation lines, a rotational/translational boom, extravehicular activity (EVA) jetpack, and a foot restraint on a Deep Worker submersible representative of the Multi-Mission Space Exploration Vehicle (MMSEV). A one-way communication latency of 50 seconds between a NEA and mission control was simulated throughout the mission. Subjective data included acceptability, simulation quality, capability assessment ratings, and comments. Photo and video were also collected. RESULTS: The only completely acceptable method for performing all the NEA exploration tasks was determined to be from a foot restraint on an MMSEV. EVA jetpacks and methods that used anchoring to the NEA surface (boom and translation lines) were found to be acceptable for a limited set of tasks. Technology development should include a vehicle with EVA foot restraints, EVA jetpacks, and possibly an EVA boom that could be anchored to an MMSEV or the surface. Tool and just-in-time training improvements were identified to better handle nominal and contingency operations with NEA-like communication latency.

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.

(1996). Earth observations during space shuttle mission sts‐69 Endeavour's Images of Earth (September 7–18, 1995) Geocarto International: Vol. 11, No. 1, pp. 91-104.

As humans venture back to the Moon, or onward to near-Earth objects and Mars, it is expected that the rigors of this exploration will far exceed those of Apollo. Terrestrial analogs can play a key role in our preparations for these complex voyages, since in addition to their scientifi c value, analogs afford the exploration community a means to safely prepare and test exploration strategies for future robotic and human planetary missions. Many relevant analog studies exist, and each is focused on a particular aspect of strategic development. Some analog programs such as the Pavilion Lake Research Project (PLRP) present the opportunity to investigate both real scientifi c and real exploration scenarios in tandem. The activities of this research program demand the use of techniques, tools, and strategies for underwater scientifi c exploration, and the challenges associated with the scientifi c exploration of Pavilion Lake are analogous to those human explorers will encounter on other planetary and small solar system bodies. The goal of this paper is to provide a historical synopsis of the PLRP’s objectives, milestones, and contributions to both the scientifi c and exploration community. Here, we focus on detailing the development and deployment of an integrated science and exploration program with analog application to our understanding of early Earth systems and the preparation for future human space exploration. Over a decade of exploration and discovery is chronicled herein. Spec483_CH07_p085-116.indd 86 29/09/11 7:13 PM A historical overview of the Pavilion Lake Research Project 87 spe 483-01 page 87 THE SCIENTIFIC DISCOVERY OF PAVILION LAKE

Introduction: The existence of a general influence of exercise on the incidence of decompression sickness (DCS) has been known for more than a half-century. However, quantification of the effect has not been done for several reasons, including isolation of exercise as the only variable.The DCS database at Brooks City-Base, TX, contains detailed physiologic information on over 3000 altitude exposures. The purpose of this study was to measure Vo 2 during the activities performed during those exposures to retrospectively determine if Vo 2 , a quantifiable index of exercise intensity, was related to the level of reported DCS. Methods: Ground-level activity was designed to duplicate the standardized activity during the altitude exposures. Breath-by-breath Vo 2 was determined for each activity using a COSMED® metabolic measurement system. Comparison of the Vo 2 during four levels of activity performed under otherwise comparable conditions allowed a determination of correlation between Vo 2 and DCS risk observed during the altitude exposures. Results and Discussion: Four previous altitude exposure profiles at 8992 m to 9144 m (29,500 to 30,000 ft; 231 to 226 mmHg) for 4 h following a 1-h prebreathe resulted in 38-86% DCS. This study provided the Vo 2 of activities during those studies. The correlation between DCS incidence and the highest 1-min Vo 2 of activity was 0.89. Conclusion: The highest 1-min Vo 2 showed a high correlation with level of DCS risk. Future exposures involving lower levels of activity could provide data that would allow improvement in modeling of DCS risk.

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.

A patent foramen ovale (PFO) has been reported to be an important risk factor for cardioembolic cerebrovascular accidents through paradoxical systemic embolization, and it provides one potential mechanism for the paradoxical systemic embolization of venous gas bubbles produced after altitude or hyperbaric decompressions. Here, we present in a single document a summary of the original findings and views from authors in this field. It is a comprehensive review of 145 peer-reviewed journal articles related to PFO that is intended to encourage reflection on PFO detection methods and on the possible association between PFO and stroke. There is a heightened debate on whether aviators, astronauts, and scuba divers should go through screening for PFO. Because it is a source of an important controversy, we prefer to present the findings in the format of a neutral bibliographic review independent of our own opinions. Each cited peer-reviewed article includes a short summary in which we attempt to present potential parallels with the pathophysiology of decompression bubbles. Two types of articles are summarized, as follows. First, we report the original clinical and physiological findings which focus on PFO. The consistent reporting sequence begins by describing the method of detection of PFO and goal of the study, followed by bulleted results, and finally the discussion and conclusion. Second, we summarize from review papers the issues related only to PFO. At the end of each section, an abstract with concluding remarks based on the cited articles provides guidelines.

Physical effort, compensation, and controllability in a spacesuit can be affected by suit mass and gravity level. Because of limitations in certain reduced-gravity simulators and the finite selection of lunar prototype suits, it is difficult to ascertain how a change in suit mass affects suited human performance. One method of simulating a change in mass is to vary the total gravity-adjusted weight (TGAW), which is defined as the sum of the suit mass and subject mass, multiplied by the gravity level. PURPOSE: To determine if two methods of changing TGAW during parabolic flight - changing suit mass or gravity level - affect subjective ratings of suited human performance equally.METHODS: A custom weight support structure was connected to a lunar prototype spacesuit, allowing the addition of mass to the suit while maintaining a near-constant center of mass. In the varied-weight (VW) series, suit mass (120 kg) was constant at 0.1-g, 0.17-g, and 0.3-g, yielding TGAWs of 196, 333, and 588 N, assuming an 80-kg subject. In the varied-mass (VM) series, gravity level was constant at 0.17-g and suit mass was 89, 120, and 181 kg, yielding TGAWs of 282, 333, and 435 N. The 333 N condition was common to both series. Direct comparison was not possible due to limited adjustability of suit mass and limited options for parabolic profiles. Five astronaut subjects (80.311.8 kg) completed 4 different tasks (walk, bag pickup, lunge, and shoveling) in all conditions and provided ratings of perceived exertion (RPE) and the gravity compensation and performance scale (GCPS) upon completion of each task. RESULTS: Where VM and VW series overlapped, RPE and GCPS trend lines were similar. Mean RPE and GCPS at 333 N was 8.4 and 3.7. Mean RPE and GCPS for VM was 7.8 and 3.8 for 282 N and 9.8 and 4.1 for 435 N. Extrapolation of the VM trend to match VW TGAWs 196 and 588 N predicts an RPE of 6.5 and 12.3 and GCPS of 4.4 and 5.9, whereas the measured VW values for RPE were 8.1 and 9.8 and GCPS were 4.4 and 3.7. CONCLUSION: Modeling a change in suit mass by altering weight alone may be an adequate simulation through a limited range when looking at gross metrics of subjective suited human performance. Whether altering weight alone will be sufficient for more precise metrics of human performance, and across a wider range of activities, still needs further study