Andrew F. J. Abercromby

NASA Research and Technology Studies (RATS) 2012: Virtual Simulation and Evaluation of Human and Robotic Systems for Exploration of Near-Earth Asteroids

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.

NEEMO 16: Evaluation of Systems for Human Exploration of Near-Earth Asteroids

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.

Human exploration missions to phobos prior to crewed mars surface missions

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 crew members 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.

NEEMO 18–20: Analog testing for mitigation of communication latency during human space exploration

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 Universitys 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.

NASA's Analog Missions: Driving Exploration Through Innovative Testing

Human exploration beyond low-Earth orbit (LEO) will require a unique collection of advanced, innovative technologies and the precise execution of complex and challenging operational concepts. One tool we in the Analog Missions Project at the National Aeronautics and Space Administration (NASA) utilize to validate exploration system architecture concepts and conduct technology demonstrations, while gaining a deeper understanding of system-wide technical and operational challenges, is our analog missions. Analog missions are multi-disciplinary activities that test multiple features of future spaceflight missions in an integrated fashion to gain a deeper understanding of system-level interactions and integrated operations. These missions frequently occur in remote and extreme environments that are representative in one or more ways to that of future spaceflight destinations. They allow us to test robotics, vehicle prototypes, habitats, communications systems, in-situ resource utilization, and human performance as it relates to these technologies. And they allow us to validate architectural concepts, conduct technology demonstrations, and gain a deeper understanding of system-wide technical and operational challenges needed to support crewed missions beyond LEO. As NASA develops a capability driven architecture for transporting crew to a variety of space environments, including the moon, near-Earth asteroids (NEA), Mars, and other destinations, it will use its analog missions to gather requirements and develop the technologies that are necessary to ensure successful human exploration beyond LEO. Currently, there are four analog mission platforms: Research and Technology Studies (RATS), NASA s Extreme Environment Mission Operations (NEEMO), In-Situ Resource Utilization (ISRU), and International Space Station (ISS) Test bed for Analog Research (ISTAR).

Hypobaric Decompression Sickness Treatment Model.

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.

Fifteen-minute Extravehicular Activity Prebreathe Protocol Using NASA's Exploration Atmosphere (8.2 psia/ 34% 02)

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.

Small Body Hopper Mobility Concepts

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 misson 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 propellantsaving 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.

Extravehicular activity operations concepts under communication latency and bandwidth constraints

The Biologic Analog Science Associated with Lava Terrains (BASALT) project is a multi-year program dedicated to iteratively develop, implement, and evaluate concepts of operations (ConOps) and supporting capabilities intended to enable and enhance human scientific exploration of Mars. This paper describes the planning, execution, and initial results from the first field deployment, referred to as BASALT-1, which consisted of a series of ten simulated extravehicular activities on volcanic flows in Idahos Craters of the Moon National Monument and Preserve. The ConOps and capabilities deployed and tested during BASALT-1 were based on previous NASA trade studies and analog testing. Our primary research question was whether those ConOps and capabilities work acceptably when performing real (non-simulated) biological and geological scientific exploration under four different Mars-to-Earth communication conditions: 5 and 15 min one-way light time communication latencies and low (0.512 Mb/s uplink, 1.54 Mb/s downlink) and high (5.0 Mb/s uplink, 10.0 Mb/s downlink) bandwidth conditions, which represent two alternative technical communication capabilities currently proposed for future human exploration missions. The synthesized results, based on objective and subjective measures, from BASALT-1 established preliminary findings that the baseline ConOp, software systems, and communication protocols were scientifically and operationally acceptable with minor improvements desired by the “Mars” extravehicular and intravehicular crewmembers. However, unacceptable components of the ConOps and required improvements were identified by the “Earth” Mission Support Center. These data provide a basis for guiding and prioritizing capability development for future BASALT deployments and, ultimately, future human exploration missions.

Characterization of variability sources associated with measuring inspired CO 2 in spacesuits

NASA seeks a validated, standardized methodology for measuring the inspired carbon dioxide gas (CO2) in spacesuits to verify that ventilation designs maintain safe levels of CO2 during suited operations. To date, several studies have been performed to assess the CO2 washout capability of different spacesuits using a variety of in-suit sampling techniques and devices, while different approaches are used to test breathing masks for applications such as firefighting and diving. This study reviews existing methodologies for measuring CO2 washout and then describes a series of systematic evaluations conducted to characterize sources of variability associated with spacesuit CO2 washout measurement equipment and methods so that calculations of inspired CO2 may be appropriately adjusted or interpreted to account for the known measurement errors. To systematically isolate and identify the contributions of variability associated with each component of measurement equipment and methods, a technique was developed using 4% CO2 calibration gas and 1% CO2 calibration gas to simulate perfect washout with respiratory traces of exactly known expired CO2 levels. Using this technique, sample line length, line inner diameter, effect of fittings, and placement of flow controllers such as rotameters were tested sequentially to quantify their effects on the resulting simulated respiratory trace. The results of this testing indicate that unsuited, ambient sampling for CO2 should be performed with small diameter, short length tubing, at high flow rates with minimal flow interrupters (e.g., fittings, valves) in order to minimize errors associated with loss of data integrity. Of the conditions tested, data integrity was best maintained when sampling at 1000 mL/min, using a practical sample tube of 3.0 m (10 ft) length and 1.6 mm (0.063 in) inner diameter, with no flow interrupters between the CO2 source and the CO2 sensor. In the near-term, the results of this study will inform a follow-up study, the objectives of which are to define a validated, standardized methodology for measuring inspired CO2 in pressurized spacesuits, and to characterize intra-subject and inter-subject variability during human-in-the-loop (HITL) testing of CO2 washout in the extravehicular mobility unit (EMU) spacesuit.