Mars One Surface Exploration Suit (SES) Conceptual Design Assessment
Document Number: 807300008 Revision: B
Controlled By: Programs
Prepared and Approved By: Title Signature & Date Norman Hahn Senior Aerospace Engineer Electronic Approval and Date on File Barry W. Finger Chief Engineer Electronic Approval and Date on File
Approved By: Title Signature & Date Grant Anderson President/CEO Electronic Approval and Date on File Justin Cook Export Control Compliance Electronic Approval and Date on File
3481 East Michigan Street Tucson, Arizona 85714 Tel: 520-903-1000/Fax: 520-903-2000 1-800-TO ORBIT (866-7248) www.ParagonSDC.com 807300008B Revisions Rev Description Date NC Original DRAFT Release to initiate discussions with customer for Sections 1 through 4. 05/06/13 A Export controlled release for delivery to customer only 09/11/15 B Revisions throughout document to comply with Export Control requirements for public 09/12/16 release.
Page i of iii
807300008B Table of Contents REVISIONS ...... I TABLE OF CONTENTS ...... II List of Figures ...... iii List of Tables ...... iii 1 INTRODUCTION ...... 1 1.1 Background ...... 1 1.2 Scope ...... 1 1.3 Purpose ...... 2 1.4 Methods ...... 2 1.5 Mission Concept of Operations ...... 2 1.5.1 Phase 1: 1st Rover Delivery ...... 2 1.5.2 Phase 2: Cargo Missions ...... 2 1.5.3 Phase 3: System Checkout and Crew Launch Verification ...... 3 1.5.4 Phase 4: First Crew Arrival ...... 3 1.5.5 Phase 5: Crew Expansion ...... 3 1.6 Reference Documents ...... 4 2 SYSTEM-LEVEL DESIGN DRIVERS ...... 5 2.1 Overview ...... 5 2.2 Atmospheric and Martian Surface Conditions ...... 5 2.3 Other Considerations ...... 6 3 LEVEL I SES REQUIREMENTS ...... 8 3.1 Functional Requirements ...... 8 3.1.1 Atmosphere Management ...... 8 3.1.2 Water Management ...... 9 3.1.3 Food Management ...... 9 3.1.4 Crew Waste Management ...... 9 3.1.5 Thermal Management ...... 9 3.1.6 Communications & Tracking ...... 9 3.1.7 Electrical Power ...... 10 3.1.8 Command & Data Handling ...... 10 3.1.9 BioMedical ...... 11 3.2 Performance Requirements ...... 11 3.3 Design & Construction ...... 14 3.4 Interfaces ...... 15 3.4.1 Human Interfaces ...... 15 3.4.2 System Interfaces ...... 15 3.4.3 Natural and Induced Environments ...... 16 3.5 Safety, Quality, and Mission Assurance ...... 18 4 FUNCTIONAL BASELINE DEFINITION ...... 21 4.1 Pressure Suit ...... 21 4.1.1 Helmet ...... 21 4.1.2 In-Suit Communication System ...... 22 4.1.3 Upper Torso ...... 22 4.1.4 Arms ...... 22 4.1.5 Gloves ...... 22 4.1.6 Waist ...... 23 4.1.7 Brief/Hip/Thigh ...... 23 4.1.8 Legs ...... 23 4.1.9 Boots ...... 24 4.1.10 Liquid Thermal Garment ...... 24 4.1.11 Thermal Micrometeoroid Garment (TMG) ...... 24 4.2 Portable Life Support System ...... 24 4.2.1 Overview ...... 24 4.2.2 Communications ...... 25 4.2.3 Power Storage, Distribution, and Generation ...... 25
Page ii of iii
807300008B
4.2.4 Environmental Control and Life Support ...... 25 4.2.5 Command and Data Handling ...... 27 4.2.6 Health Monitor ...... 28 4.3 Master Equipment List (MEL) ...... 29 5 RISK AND OPPORTUNITY MANAGEMENT ...... 30 5.1 Cost and Schedule Risk Drivers ...... 30 5.1.1 Robustness of Design ...... 30 5.1.2 Safety and Crew Productivity ...... 31 5.1.3 Environmental ...... 32 5.2 Opportunities to Reduce Risk ...... 35 5.2.1 Future Studies ...... 35 5.2.2 Precursor Tests (Mars Rover 2020) ...... 35 5.2.3 Minimize Suit Pressure ...... 35 5.2.4 Additive Manufacturing ...... 35 5.2.5 Common Parts ...... 36 5.2.6 Establish Common Interfaces Early ...... 36
List of Figures Figure 1: External view of the Mars One Habitat Concept after the first crew landing (inflatable habitat modules are out of view behind the landers)...... 1 Figure 2: Internal view of the Mars One Habitat Housing Concept ...... 2 Figure 3: Surface SEA Suit System ...... 8 Figure 4: Surface Exploration Pressure Suit Functional Flow Block Diagram ...... 8 Figure 5: Surface SEA PLSS Functional Breakdown ...... 8 Figure 6. Typical Spacesuit Configuration...... 21 Figure 7: Mars One Helmet Architecture ...... 21 Figure 8: Advanced Helmet Lighting System – Waist Entry I-Suit ...... 21 Figure 9: Heads-Free Communication System ...... 22 Figure 10: Waist Entry I-Suit Soft Upper Torso (SUT) ...... 22 Figure 11: I-Suit Arm Architecture ...... 22 Figure 12: Current Phase VI ISS EMU ...... 22 Figure 13: Rear Entry I-Suit Mobility Evaluation on an ATV ...... 23 Figure 14: Critical Surface EVA Operations Evaluated during NASA D-RATS Testing in Arizona ...... 23 Figure 15: ILC Dover EMU LCVG ...... 24 Figure 16: Power Subsystem Schematic...... 25 Figure 17: MTSA Pressure, Temperature and Air Revitalization System...... 26 Figure 18: Command and Data Handling Subsystem Schematic ...... 27 Figure 19: Radiation Climate on Mars (source: Scientific American December 9, 2013) ...... 34
List of Tables Table 1: Paragon Documents ...... 4 Table 2: Other Reference Documents ...... 4 Table 3: SES MEL and On-back Mass Estimates ...... 29
Page iii of iii
807300008B
1 Introduction
1.1 Background Paragon Space Development Corporation (Paragon) has been contracted by Mars One to conduct a conceptual design of the Mars One Surface Exploration Suit (SES) to be used by the crew while exploring and working in the external Martian environmeent and an Environmental Control and Life Support System (ECLSS) module for the Mars One Habitat. This document serves to compile for transmittal to the customer the emerging assessment of the SES conceptual design and has been internally reviewed and approved for release in the public domain.
Additional technical specifications may be available for the systems detailed in this emerging assessment, but may be export controlled under Department of Commerce, Bureau of Industry and Security’s Export Administration Regulations (EAR), specifically under Export Control Classification Number (ECCN) 9E515.f. Mars One may not release any additional technical specifications to any outside person or organization without the receipt of written authorization from Paragon.
For the equivalent work on the Habitat ECLSS Module, please refer to Mars One Habitat ECLSS Conceptual Design Assessment (807300009).
1.2 Scope The scope of this conceptual design assessment is limited to the Mars One Surface Exploration Suit (SES). The SES includes the soft-goods and hardware associated with the pressure suit and the Portable Life Support System (PLSS) that provides the necessary functions to surrvive in the pressure suit during surface exploration. The PLSS functions include communication, power, atmosphere management, water management, food management and waste management, as well as the active thermal control of the person and electrical components. It is noted that the SES does not include other essential subsystems and components required to conduct surface operations. Those other essential elements include but are not limited to: the habitat airlockk, mobility vehicles, external recharge ports, the refurbishment station required to perform planned and unplanned maintenance, and recharge station(s). Figure 1 illustrates the arrangement of two ECLSS modules, two rovers, and two supply landers after arrival of the first crew. Figure 2 provides a cut-away view of one of the two inflatable habitat module concepts.
Figure 1: External view of the Mars One Habitat Concept after the first crew landing (inflatable habitat modules are out of view behind thee landers).
Page 1 of 36
807300008B
Figure 2: Internal view of the Mars One Habitat Housiing Concept
1.3 Purpose The purpose of this Design and Development book is to document the evolution of the SES architecture prior to formal definition of the Development Component Baseline. As such, this document will serve as the Design Requirements Baseline, Functional Baselinee, and Level II Allocated Baseline as defined by Section 5.0 of Paragon’s Configuration Management Plan (E999019).
1.4 Methods Design, development, documentation and data management will be in accordance with Paragon’s established processes.
1.5 Mission Concept of Operations
1.5.1 Phase 1: 1st Rover Delivery In 2022 the first settlement rover will land on Mars. While the general location of the outpost will be known, the rover's task is to find the ideal spot within the area. As with the Curiosity Mars Rover, the 6 to 40 minute round-trip delay in communication (depending upon the positions of the Earth and Mars in their orbits) requires that the rover has some autonomy while much of its functions will be controlled by instruction from Earth. A video stream will be broadcast on Earth 24/7/365.
1.5.2 Phase 2: Cargo Missions (courtesy mars-one.org) In 2025 all initial cargo components of the settlement have reached their destination in six separate landers. Two living units (each containing two complete SES), twwo life support units, a supply unit containing additional SES spares, and another rover arrive on Mars. The two rovers take all components to the settlement location, deploy external structures such as solar panels and radiators, and prepare for the later arrival of Mars Team One, the first humans on Mars. A second video stream will be broadcast to Earth 24/7/365. (courtesy mars-one.org)
Operations will be conducted autonomously with robotic assistance and the ECLSS initiates pressurization of the habitat with a breathable atmosphere (10.2 psia, 3.1 psi O2, balance N2 and Ar), and storage of oxygen and potable water.
Page 2 of 36
807300008B
1.5.3 Phase 3: System Checkout and Crew Launch Verification All water, oxygen and atmosphere production will be ready by early 2026, which is when the Earth crew is granted the go-for-launch of Mars Team One. Each component of the Mars transit vehicle is launched into a low Earth orbit and linked. In September history is made as the first four astronauts along with a contingent of four surface suits are launched on their journey to the Red Planet.
Prior to the crew’s departure, the two Habitat ECLSS (courtesy mars-one.org) modules will have achieved full operational capability for water and atmosphere production. Other essential systems such as Electrical power and Communications must be fully operational as well.
1.5.4 Phase 4: First Crew Arrivala The Mars Team One astronauts land in 2027 – the first humans to set foot on Mars! Once settled in, their first surface operations tasks include installing the connecting passageways between the individual capsules and assembling the remaining solar photovoltaic panels. All of these activities require the crew to utilize the SES. The exploration of Mars, their new home planet, begins with everyone on Earth engaged in the 24/7/365 broadcast. A few weeks later, (courtesy mars-one.org) five cargo missions arrive, bringing additional living units, life support units (each including a complete SES) and a third rover.
The Habitat ECLSS and numerous other Habitat systems will have been operational for two years. Soon after arrival, regular maintenance by the crew will be performed to ensure continued operation. Many of these tasks can only be done by crew members using the SES, such as removing dust from solar panels and maintaining the rovers.
A short time after the arrival of the first crew, the infrastrructure for the second crew arrives and is installed by the first crew. Four ECLSS modules are now available to nominally sustain the first crew and to complete pressurization of the two new living modules. The two new ECLSS modules provide additional redundancy for the first crew in the event of contingency operations.
1.5.5 Phase 5: Crew Expansion In 2029 Mars Team Two, the second crew of four astroonauts, lands. They are received by their predecessors who have completed the construction of the settlement. As successive Mars One Teams arrive, the settlement will grow in its capacity for scientific research, experiments, and exploration of Mars, with high definition video streams providing viewers on Earth with ample engagement.
Shortly after arrival of the second crew, six Habitat ECLSS modules and 16 SES will be in place and operating/available under nominal conditions. Each time a crew of 4 lands, eight additional SES will accompany them until that strategy evolves to a better solution (e.g. commencement of in-situ manufacturing of spares).
(courtesy mars-one.org)
Page 3 of 36
807300008B
1.6 Reference Documents
Table 1: Paragon Documents Doc Number Title E999019 Configuration Management Plan 807300009 Mars One Habitat ECLSS Conceptual Design Assessment
Table 2: Other Reference Documents Doc Number Title SP‐3006 Bioastronautics Data Book JSC‐20584 Spacecraft Maximum Allowable Concentrations for Airborne Contaminants (SMAC) JSC‐63414 Spacecraft Water Exposure Guidelines (SWEGs) NASA‐STD‐4003 Electrical Bonding for NASA Launch Vehicles, Spacecraft, Payloads, and Flight Equipment MIL‐STD‐461 Requirements for Control of Electromagnetic Interference Characteristics of Subsystems and Equipment JPR 8080.5 JSC Design and Procedural Standards JSC 65828 Structural Design Requirements and Factors of Safety for Space Flight Hardware JSC 65829 Loads and Structural Dynamics Requirements for Space Flight Hardware JSC 28918 EVA Design Requirements and Considerations NASA‐STD‐5017 Design and Development Requirements for Mechanisms NASA‐STD‐5019 Fracture Control Requirements for Spaceflight Hardware NASA‐STD‐6016 Standard Material and Process Requirements for Spacecraft NPR 7150.2A NASA Software Engineering Requirements NASA‐STD‐8719.13 Software Safety Standard NASA‐GB‐8719.13 Software Safety Guidebook NASA‐STD‐5005 Standard for the Design and Fabrication of Ground Support Equipment ANSI/AIAA S‐081A Space Systems ‐ Composite Overwrapped Pressure Vessels (COPVs) July 24, 2006 S‐080‐1998e AIAA Standard for Space Systems ‐ Metallic Pressure Vessels, Pressurized Structures, and Pressure Components AIAA S‐120‐2006 Mass Properties Control for Space Systems ICES paper 2008‐01‐ Trade Study of an Interface for Removable/Replaceable Thermal Micrometeoroid 1990 Garment ICES paper 760954 Study of Development of a Radiation Shielding Kit ICES paper 2006‐01‐ Micrometeoroid and Orbital Debris Enhancements of Shuttle Extravehicular 2285 Mobility Unit Thermal Micrometeoroid Garment ICES paper 03ICES‐27 I‐Suit Advanced Spacesuit Design Improvements and Performance Testing ICES paper 2006‐01‐ Systems Considerations for an Exploration Spacesuit Upper Torso Architecture 2141 ICES paper 2003‐01‐ Test Results of Improved Spacesuit Shielding Components 2330
Page 4 of 36
807300008B
2 System-Level Design Drivers
2.1 Overview The SES is designed to provide a controlled environment for a crew member while conducting surface excursion activities (SEA) outside of the Mars One Habitat or other pressurized surface elements. The following system-level Design Drivers are used in the derivation of the SES requirements and are derived from preliminary information exchanges with Mars One, presentations, physical conditions of the Mars environment, and initial assessments made by Paragon. Some modification of the Mission CONOPs (Section 1.5) and these system-level Design Drivers are expected during the early conceptual development phase and they will impact the subsequent SES requirements. As such, these initial inputs to the development of the SES architecture should be reviewed, vetted and agreed upon early in the design process to avoid significant impacts and costly corrections later in the program.
2.2 Atmospheric and Martian Surface Conditions [SLDD.xxx] Atmospheric Composition Consists primarily of Carbon Dioxide (>95%). Impact to the Design: The inert gases found in the Martian atmosphere have minimal impact to materials currently used in spacesuit design but will have an impact on technology choices for CO2 control.
[SLDD.xxx] Atmospheric Pressure The average atmospheric pressure is 600 Pa (~ 0.087 psia). Impact to the Design: The low atmospheric pressure will necessitate a spacesuit pressure equal to or greater than that historically used in both Lunar and microgravity space suits.
[SLDD.xxx] Temperature and Thermal Environment Annual average temperature range is ‐140°C (‐220°F) to 20°C (70°F). Impact to the Design: Solar cycle is very similar to Earth, but the variation is more extreme. Night excursions during the winter months would require that the spacesuit be designed for worst case conditions. Existing spacesuit technologies are sufficient to compensate for the temperature range; however, evaluations need to be performed regarding convective heat loss to the atmosphere. The spacesuit may be designed to accommodate various thermal kit options that would accommodate a winter night vs. a summer noon. As the typical conditions are very cold, it may make more sense to have a slightly “cold biased” suit that has nominal heating and make special provisions for the rarer times when cooling is needed.
[SLDD.xxx] Wind‐blown Regolith (i.e. dust) Martian weather includes dust storms with potentially high wind velocity and lingering dust clouds. Impact to the Design: Unexpected dust storms are likely to occur during long or short duration surface operations. The reduced visibility may necessitate a navigation system to be integrated to spacesuit. Communication systems must also be capable of operating during these conditions.
[SLDD.xxx] Electrostatic and Abrasive Regolith Martian Dust may be highly charged and varies in consistency and composition.
Page 5 of 36
807300008B
Impact to the Design: The regolith would likely be attracted to most qualified spacesuit design materials. Materials must be evaluated for abrasion, wear, and durability due to exposure to regolith. Testing is required to quantify this effect and identify mitigation strategies. This effort also consists of protection for mobility elements such as bearings. This will also affect suit element integration and cleaning. This is one of the most significant impacts to the spacesuit.
[SLDD.xxx] Superoxides The Martian soil contains "superoxides". Impact to the Design: In the presence of ultraviolet radiation, superoxides break down organic molecules. Materials of construction must be compatible with this environment. Corrosion to metallic parts must also be investigated and evaluated.
[SLDD.xxx] Radiation There is essentially no protection from the atmosphere or any from a planetary magnetic field. Impact to the Design: Unmitigated exposure over hundreds of hours of surface operations will cause long‐term medical harm to the crew and degradation of several known spacesuit materials of construction. Alternate materials will need to be identified and tested for longer durations than previous programs, and/or limited lifetimes established and strictly adhered to. Localized radiation shields may be employed in the spacesuit or undergarment to protect sensitive organs. Radiation exposure lifetime limits may curtail surface operations for crew members and restrict them from further surface exploration if mitigation approaches are not developed.
[SLDD.xxx] CONOPS and Terrain Details of the habitat site and terrain need to be understood. Impact to the Design: The ability to traverse relatively flat terrain and operate a rover in a spacesuit has been previously proven. The ability to climb rocks, construct a habitat in a gravity environment, and initiate a long‐term maintenance and repair capability for habitat systems such as primary structure, electrical power, life support and communications have not been developed. Along with these tasks comes the likelihood of falls and accidents while in the suit. Testing and evaluation need to be conducted to identify durability, mobility and structural requirements for the spacesuit.
2.3 Other Considerations [SLDD.xxx] Gravity Mars has approximately 3/8th gravity of Earth. Impact to the Design: The effective weight of the spacesuit will be more than double of those used on the lunar surface if suits and systems of equivalent mass are utilized. From this perspective, lighter wearable SES elements are more advantageous to reduce crew member fatigue.
[SLDD.xxx] Microbial Load As with most objects in close proximity of working humans, the potential for microbial growth and associated loads on the system are high. Impact to the Design: The spacesuit will need to be designed to inhibit microbial growth but also to accommodate the inevitable cleaning that will be required. Resistance to cleaning Page 6 of 36
807300008B
agents and repair of any abrasions created by the process of cleaning needs to be included and/or reapplication of anti‐microbial treatments.
[SLDD.xxx] Mass and Volume It is anticipated that the mass and volume of the spacesuit, support equipment and spare parts is a significant factor for both launch mass and volume capacity. Impact to the Design: There has always been an emphasis for a lighter, more robust spacesuit across every space program. Separate from mass and volume considerations with regards to surface operations, the transportation costs associated with delivering the SES to the surface will drive the development costs (the lower the allowable mass and volume, the higher the development costs). System mass and volume targets should be relaxed while still achieving required comfort, robustness, mobility, visibility and operational simplicity targets. Decreasing emphasis on maximizing mass and volume reductions minimizes development costs. It is critical that launch mass and volume limitations be defined early in the program as imposed limitations will lead to increased costs in the development of the SES as more complex, efficient and lower mass/volume product solutions are developed to meet launch constraints.
It is proposed that there would be substantial benefit to maintain smaller helmets and eliminating required “hard” elements (e.g. hard upper torso) to minimize storage volume.
[SLDD.xxx] Pressurized Element Airlock Interface There are many other aspects of the Mars One mission that are expected to evolve and impact the SES design and operation. These include, but are not limited to: impact of or prevention of contamination to both Mars and the habitat; inclusion of additional system in the event that there is a PLSS failure in the PLSS; interfaces with other pressurized elements and emergency repair accommodations
Page 7 of 36
807300008B
3 Level I SES Requirements Figure 3 through Figure 5 outline the assumed architecture to illustrate the major functions of the SES and will be used to validate the functionality and interfaces required. There are additional Habitat interfaces that will influence the architecture and design elements of the SES which include but are not limited to the habitat airlock, any mobility vehicles, external recharge ports, etc. that are outside the scope of this work. In addition, elements such as a refurbishment station for cleaning, repairing and recharging the SES will be required but are also out of scope of this initial conceptual design assessment.
Surface Exploration Suit (SES)
PLSS Pressure Suit
Figure 3: Surface SEA Suit System
Pressure Suit
Pressure Drinking Water Protective Thermal Layer Outer Layer Waste Mgmt Food Mgmt Garment Mgmt Covering
Figure 4: Surface Exploration Pressure Suit Funnctional Flow Block Diagram
PLSS
Atmosphere Thermal Comm & Health Power C&DH Mgmt Control Tracking Monitor
Figure 5: Surface SEA PLSS Functioonal Breakdown
3.1 Functional Requirements
3.1.1 Atmosphere Management [SES.xxx‐PGM] Breathable Atmosphere: The SES shall provide and maintain breathable atmosphere for the crew during SEA operations. Rationale: Maintaining proper absolute and partial pressures, temperatures and humidity levels ensures crew comfort and survivability. Verification: (IDAT) – TBD Page 8 of 36
807300008B
3.1.2 Water Management [SES.xxx‐PGM] Potable Water: The SES shall provide source of drinking water for crew during SEA operations. Rationale: Access to water during SEAs is necessary to ensure the crew comfort and health, in addition, lack of water will significantly increase crew fatigue susceptibility. Verification: (IDAT) – TBD
3.1.3 Food Management [SES.xxx‐PGM] Food: The SES shall provide source of high energy food for crew during SEA operations. Rationale: Access to food during longer SEAs will be necessary for crew energy to return to the habitat. This may be accomplished through a liquid system and integrated with the potable water. Verification: (IDAT) – TBD
3.1.4 Crew Waste Management [SES.xxx‐PGM] Waste Management: The SES shall collect and contain feces and urine. Rationale: Fecal waste collection must be performed in a manner that minimizes possible escape of fecal contents into the suit during SEA operations because of the high content of possibly pathogenic bacteria contained in the stool. In addition, there is the potential of injury to crew members and hardware that could result from such dissemination. The voided urine must be contained by the stowage and disposal hardware to prevent inadvertent discharge in the suit that could result in injury to crew member's mucous membranes or equipment. Verification: (IDAT) – TBD
3.1.5 Thermal Management [SES.xxx‐PGM] Thermal Management: The SES shall provide for thermal management of crew during SEA operations. Rationale: Maintaining appropriate temperature ranges maximizes crew productivity and maintains the overall health of the crew. The SES may in some conditions provide heating and in other conditions provide cooling. Verification: (IDAT) – TBD
3.1.6 Communications & Tracking [SES.xxx‐PGM] Integrated Communication: The SES shall provide voice communications between the Suit and the Habitat and between multiple SES units operating at the same time. Rationale: It is vital that suited crew members have two‐way voice communication with other suited crew members as well as crew members in the Habitat. Verification: (IDAT) – TBD
[SES.xxx‐PGM] Tracking: The SES shall provide a means of locating the suited crew member. Rationale: If a crew member(s) fails to return from an SEA or requires assistance, a method of locating that person is needed. A simple radio beacon installed in the suit may satisfy this requirement. Verification: (IDAT) – TBD
Page 9 of 36
807300008B
[SES.xxx‐PGM] HD Video: The SES shall create, record and transmit near real‐time (TBR) high definition motion imagery (TBR) from a mounted camera. Rationale: For safety it is important that video image be recorded and also transmitted to the Habitat. This video may also be streamed to Earth. Verification: (IDAT) – TBD
3.1.7 Electrical Power [SES.xxx‐PGM] Power: The SES shall provide electrical power storage, distribution and may provide emergency generation. Rationale: Subsystems within the SES will require electrical power to perform their functions; as a result the SES will require the ability to store and distribute electrical power. In addition, in the event of an emergency situation, the ability to produce contingency electrical power is desired. The emergency power generation may be enough to maintain minimal life support and activate an emergency beacon, etc. Verification: (IDAT) – TBD
3.1.8 Command & Data Handling [SES.xxx‐PGM] Software Updates: The SES shall accept software updates between SEAs. Rationale: The ability to reprogram devices and update software is needed for maintainability. Updates can be applied when the SES is not in use. Changes to configuration data and software patches are included in the scope of software updates. Firmware updates may be included where deemed feasible. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Status: The SES shall transmit and display the status items. Rationale: These are necessary to ensure the suit operator has adequate information to control the SES systems and to provide telemetry for remote tracking from the Habitat, suit trending, and possible failure investigations. A preliminary list of items which should be included as status items include: operational mode, absolute suit pressure, primary oxygen pressure, secondary oxygen pressure, CO2 helmet inlet partial pressure, battery current, battery voltage, liquid thermal garment (LTG) inlet temperature, ambient environment pressure, oxygen time remaining, power time remaining, and SEA time elapsed. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Indicate Pressure: The SES shall indicate to the suited crew member the internal pressure of the suit without the use of power. Rationale: Internal suit pressure is considered a critical operating parameter and should be available to the crew during any suited pressurized operation. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Caution & Warning Control System (CWCS) Detection: The SES shall detect and indicate to the crew member faults, significant performance degradation and excessive resource usage. Rationale: Indication of these conditions must include both an audible tone and a message on the display which provides additional information about the condition. Examples of conditions
Page 10 of 36
807300008B
which need to be detected include, but are not limited to, sensor failures, oxygen leakage, water leakage, high/low electrical current and abnormal metabolic rate. Verification: (IDAT) – TBD
3.1.9 BioMedical [SES.xxx‐PGM] Biomedical: The SES shall monitor, record, and transmit heart rate of the crew member during suited operations as well as other parameters defined by the Mars One medical team (TBR). Rationale: Biomedical data transmission to the habitat will be required for medical evaluation of crew members, including during suited operation. The collection and transmission of biomed data must not limit the transmission rate of the remaining suit data. Verification: (IDAT) – TBD
3.2 Performance Requirements [SES.xxx‐PGM] Exploration Walking: When in the SES, the crew member shall be capable of walking up a 20 degree incline (TBR) forwards and sideways when 20% (TBR) of the area is covered by 12.5cm (5 inch) (TBR) diameter rocks on the Martian surface. Rationale: Lower body mobility is essential to exploring in terrestrial environments. Balancing center of gravity to ensure proper body control and the ability to recover from falls and kneel is also imperative to exploration. This requirement is intended to capture necessary suit functional capability for walking in a Mars equivalent gravity field. Verification: (IDAT) – TBD
[SES.xxx‐ENG] SEA Nominal Operation Duration: The SES shall sustain the life of the crew member for at least eight (8) hours (TBR) independent of other systems during nominal SEA operations. Rationale: 8 hours has been determined to be acceptable amount of time to complete an SEA objective while considering consumables management and balancing crew exertion. Verification: (IDAT) – TBD
[SES.xxx‐ SMA] Useful Life: The SES shall have a useful life of at least 250 SEAs. Rationale: This is a Mars One program office requirement. The requirement can be met at the system level with the use of spares and allowable preventive and limited life maintenance activities. Verification: (IDAT) – TBD
[SES.xxx‐PGM] Emergency Life Support: The SES shall provide at least 45 minutes (TBR) of emergency life support independent of umbilical services during SEA operations after failure of primary oxygen, vent loop, and/or thermal loop. Rationale: In the case of a suit failure, the suit must be able to provide life support for a sufficient time for the crew to reach a safe haven. Emergency life support includes oxygen for metabolic consumption and leakage make‐up, pressure control to prevent pressures below 3.0 psia, thermal control, and CO2 washout. Verification: (IDAT) – TBD
Page 11 of 36
807300008B
[SES.xxx‐PGM] Emergency Life Support Interfaces: The SES shall interface to external umbilical services for sustaining life support or recharging the SEA system for extended missions. Rationale: In the event the crew leaves the base with a rover, the SES will be required to be in operations for durations greater than the nominal 8 hours while not in contingency operations. For these operational scenarios, umbilical interfaces are required for the crew to switch over from a PLSS to a fixed supply of consumables. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Nominal Suit Pressure : The SES shall have a selectable suit pressure of between 29.65 kPa (0.29 atm, 4.3 psi) and 44.82 kPa (0.44 atm, 6.5 psi) with a minimum of 3 distinct set points. Rationale: The suit pressure takes into consideration potential vehicle operating pressure, decompression sickness (DCS) risk, and operational efficiencies, among other values. The distinct set points should be divided evenly within the pressure range. Verification: (IDAT) – TBD
[SES.xxx‐ENG] System Charging: The rechargeable systems shall be rechargeable from discharge to 100% capacity within four (4) hours (TBR). Rationale: To minimize down time and allow for verification of charging and time between installations, 4 hours is considered acceptable but further studies will be required. This need also imposes requirements on the charging station, which must have sufficient power and consumable fluids to recharge the suit in 4 hours. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Limit Inspired CO2: The SES shall nominally limit average inspired CO2 below 3.8 mmHg (TBR) and below 20.0 mmHg (TBR) during emergency operations.
Rationale: The suit must have a ventilation path such that efficient CO2 washout is achieved in the helmet. Excessive CO2 build up could lead to an onset of cognitive deficit which may pose a hazard to crew during critical operations. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Metabolic Rate: The SES shall accommodate the nominal metabolic profile in TBD with an average metabolic rate of 350 Watts (1200 BTU/hr) (TBR) for the Autonomous Operational Duration.
Rationale: The suit must be capable of providing thermal control, oxygen supply, and CO2 scrubbing under the variable metabolic loads expected during a nominal SEA. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Thermal Protection Performance: The SES shall be compatible with temperatures from ‐128°C (TBR) to 77°C (TBR) for incidental contact and from ‐93°C (TBR) to 57°C (TBR) for extended contact. Rationale: The suit must be designed to withstand these limits without affecting the structural integrity of the pressure garment or burning the crew member. This requirement will drive materials selection for the pressure garment, particularly the gloves. Incidental contact is defined as ~3 second bump contact (7 kPa) or 30 second brush contact (0.7 kPa). Extended contact is not bound by either time durations or pressure range.
Page 12 of 36
807300008B
Verification: (IDAT) – TBD
[SES.xxx‐ENG] Touch Temperatures: The SES shall maintain the internal surface temperature within the range of 10°C (50°F) (TBR) and 45°C (113°F) (TBR) during SEA operations. Rationale: These values are derived from the current ISS suit capability and the touch temperature limits necessary to prevent injury. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Relative Humidity Tolerance: The SES shall restrict average relative humidity levels inside the pressure garment within the range of 15% RH (TBR) and 85% RH (TBR) without the use of a humidifier. Rationale: Average humidity must be maintained above the lower limits stated to ensure that the environment is not too dry for the nominal functioning of mucous membranes. Humidity must be maintained below the upper limits for crew comfort, to allow for effective evaporation, and to limit the formation of condensation. Excess moisture in the glove can contribute to trauma at the fingertips. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Potable Water: The SES shall provide 1kg (TBR) of potable water for consumption by the suited crew member during SEA operations. Rationale: In order to maintain proper hydration during SEA, the suited crew member must be able to consume water or other rehydratable nutritional supplements. 1 kg is approximately 34 fluid ounces which is a standard for an 8hr working EVA on ISS. Further evaluation of workload and water requirements while on a Martian surface is required to finalize this requirement. Verification: (IDAT) – TBD
[SES.xxx‐ENG] ORU Change‐out Time: The SES shall permit any operational replacement unit (ORU) operations to be performed IVA within 30 minutes (TBR) without the use of special tools. Rationale: This requirement is necessary to maximize crew efficiency on SEA days in preparation for the SEA and to limit ORU change‐outs to simple hand motions and eliminate need for special tools. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Data Storage: The SES shall record all sensor readings and faults at a minimum 10 Hz (TBR) during a single SEA. Rationale: Data recording will provide a record of the suit health and status during an SEA and other suit events and will maintain the record should there be an interruption of communication between the suit and the Habitat. This will assist not only for trending data during SEA operations and to facilitate maintenance, but is also intended to function like an aircraft “black box” should retrieval of failure data be necessary after catastrophic events. Recording will last from the time the suit is powered on until the time it is powered off. Verification: (IDAT) – TBD
Page 13 of 36
807300008B
[SES.xxx‐ENG] Speech Intelligibility: The SES auditory speech annunciations and communications shall provide a level of speech intelligibility equivalent to a 95% (TBR) word identification rate. Rationale: This requirement ensures that auditory speech annunciations and communications are sufficiently salient and intelligible. The 5% allowable word identification loss is through the entire suit system and assumes no loss at the interface. Verification: (IDAT) – TBD
[SES.xxx‐PGM] Purge Efficiency: The SES shall have a purge efficiency as good as or better than the ISS space suit capability. Rationale: This requirement has historically driven the need for a vent tree inside the pressure garment. Decreased purge efficiency will result in the usage of additional consumables and longer purge times. Verification: (IDAT) – TBD
3.3 Design & Construction [SES.xxx‐PGM] Unassisted Suit Operation: The SES shall provide for unassisted operation of all suit functions. Rationale: It is necessary that the crew member can use all features of the suit without assistance, including but not limited to donning, doffing, umbilical operations, controls, and status selections. Controls should include, but are not limited to; operational mode, radio mode, radio volume, caution and warning status and acknowledge, display lighting intensity level, power mode, thermal comfort level and auxiliary heating/cooling. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Don/Doff Times: The SES shall be designed to support donning and doffing times of less than 10 minutes (TBR) with assistance, and 30 min (TBR) without assistance. Rationale: To support break times and crew comfort, donning and doffing time duration of 10 min with the assistance of another crew is desired by the Mars One program office. However, in contingency operations another crew member may not be available, and as such, additional time may be required to don or doff the suits without assistance. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Stowed Volume: The SES shall have a PLSS volume that does not exceed TBD dimensions. Rationale: The PLSS must not significantly interfere with crew member mobility and vision. Additionally, the PLSS will be hard volume that cannot be compressed, meaning storage volume will be a significant consideration. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Surface SES Mass: The SES shall have a loaded on back mass of equal to or less than 125 kg (275 lbm) (TBR). Rationale: This control mass is needed to ensure compatibility with mass capability and the suit’s ability to meet functional and performance requirements. Loaded mass is defined as a fully charged unit, with water, oxygen, cooling, and food sources, as well as with any tools or other ancillary hardware. Verification: (IDAT) – TBD
Page 14 of 36
807300008B
3.4 Interfaces
3.4.1 Human Interfaces [SES.xxx‐ENG] Exploration Anthropometry: The SES shall be customizable to fit the full size range of crew members from the 5th (TBR) percentile Japanese (TBR) female to the 95th (TBR) percentile American (TBR) male. Rationale: The full size range of suited crew members must be able to fit, reach, view, and operate required interfaces involved in planned tasks. Designers shall closely examine shoulder mobility issues and hip mobility issues experienced with the EMU in order to protect 5th to 95th percentile crew from injury. It is assumed that actual suit fitting for each crew member will be required for these ranges, but compatibility of common parts is required. Verification: (IDAT) – TBD
[SES.xxx‐ENG] In‐Suit Noise: The SES shall limit the noise measured at the crew member's head to an A‐weighted Sound Pressure Level (SPL) of less than 55 dB (TBR) for continuous noise. Rationale: The noise attenuation effectiveness of hearing protection or communications headsets may not be used to satisfy this requirement. The value defined in this requirement is the amount of sound pressure created by the suit to which the crew member is exposed. Exterior acoustical environments are not considered. Verification: (IDAT) – TBD
[SES.xxx‐PGM] Valsalva: The SES shall allow a suited crew member to perform a hands‐free Valsalva maneuver. Rationale: The Valsalva maneuver is performed by forcibly exhaling against closed lips and pinched nose, forcing air into the middle ear through the Eustachian tube. The maneuver is used by crew members during suit pressurization and depressurization to avoid injury to the inner ear. The Valsalva maneuver must be performed hands‐free due to the crew member being unable to access their nose with their hands to perform the maneuver while wearing the pressurized suit. Verification: (IDAT) – TBD
3.4.2 System Interfaces [SES.xxx‐SMA] Buddy System: The SES shall provide capability to support another SES with one SES on an umbilical for 30 min (TBR). Rationale: In the event of a PLSS failure, one crew member can connect their PLSS to the incapacitated PLSS or suit as an emergency system. Failures of a PLSS should not preclude the ability to operate in the “buddy” mode. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Radio Standard: The SES shall transmit and receive data and voice over a TBD wireless interface. Rationale: Radios will be necessary for communications between suited crew members and the Habitat and Rovers. Verification: (IDAT) – TBD
Page 15 of 36
807300008B
[SES.xxx‐ENG] Radiation Monitoring: The SES shall interface with a real‐time emergency radiation monitoring system. Rationale: This requirement is intended to make the suit compatible with a powered radiation monitoring system near the habitat that notifies the crew for absorbed dose and dose equivalent detecting and may also include individual passive monitoring systems per individual. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Tether points: The SES shall provide structural attachment points for tethers located TBD. Rationale: The crew members may conduct SEA in terrain that requires tethered operations for safety (e.g. areas of extreme incline). Verification: (IDAT) – TBD
[SES.xxx‐ENG] Auxiliary Lighting: The SES shall provide auxiliary lighting of the surroundings. Rationale: The ability to see in the shadows on the planet surface or equipment is necessary to allow the crew member to safely complete tasks. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Electromagnetic Interference and Compatibility: The electromagnetic signals from voice communications, data transmittal, video transmittal and other electronic components shall not interfere with each other or cause malfunction. Rationale: Electromagnetic Interference (EMI) and electromagnetic compatibility (EMC) are key considerations for any electrical system, particularly for systems that transmit and receive signals. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Habitat: The SES shall interface with the habitat for ingress and egress of crew, recharging the SEA consumables, and for servicing of the suits. Rationale: The suit will enter and exit the habitat on a regular basis for crew usage, refurbishment and recharging. It is assumed a standard airlock will be used consisting of a depressurization/pressurization vestibule that will isolate the SEA member from the rest of the habitat. Upon equalization with the external environment when egressing, or the internal environment for ingressing, the crew will perform the don/doffing as required. Alternative architectures such as a rear entry suit may be employed based on future studies that show benefit to reduce mass, crew time, or consumables; or to improve overall safety and reliability of the integration system. Verification: (IDAT) – TBD
3.4.3 Natural and Induced Environments [SES.xxx‐ENG] Exposure to Magnetic Field: The SES shall meet its requirements during and after exposure to a DC Magnetic Field of 250 Gauss (TBR). Rationale: Legacy systems typically require that the vehicle limit magnetic fields within SEA worksites and translation path to 250 Gauss. The suit is not expected to shield the crew member from this field, but it is expected to function nominally in this environment. Verification: (IDAT) – TBD
Page 16 of 36
807300008B
[SES.xxx‐ENG] Solar Ultraviolet: The SES exposed materials shall withstand solar ultraviolet exposure of 100‐ 150nm (TBR) wavelength at an intensity of 7.5x10‐3 w/m2 (TBR) over the useful life of the suit. Rationale: The SES will be exposed to various solar ultraviolet levels during SEA, and the suits must be able to continue nominal operation during and after these exposure periods. NOTE: This will need to be revisited once the Martian environment is explicitly defined. These values are based on a suit designed for LEO and Lunar operations. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Extreme UV Protection: The SES exposed materials shall withstand extreme UV of 10‐100nm (TBR) wavelength at an intensity of 2x10‐3 w/m2 (TBR) over the design life of the suit. Rationale: The suits will be exposed to various solar ultraviolet levels during SEA, and they must be able to continue nominal operation during and after these exposure periods. Exposed materials must withstand this environment. NOTE: This will need to be revisited once the Martian environment is explicitly defined. These values are based on a suit designed for LEO and Lunar operations. Verification: (IDAT) – TBD
[SES.xxx‐ENG] X‐ray Protection: The SES materials shall withstand X‐rays of 1‐10nm (TBR) wavelength at an intensity of 5x10‐5 w/m2 (TBR) over the design life of the suit. Rationale: The suits will be exposed to x‐ray radiation during an SEA, and they must be able to continue nominal operation during and after these exposure periods. Any material that is not specifically shielded from x‐rays must be considered. NOTE: This will need to be revisited once the Martian environment is explicitly defined. These values are based on a suit designed for LEO and Lunar operations. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Solar Ionizing Radiation: The SES shall meet its performance requirements after exposure to the radiation dose environment defined in TBD. Rationale: The suits will be exposed to various ionizing radiation levels during SEA, and they must be able to continue nominal operation during and after these exposure periods. Galactic cosmic particles pose a particular problem. Individual cosmic particles are so energetic as to require impractical amounts of shielding. Hence, a few random failures or temporary anomalies of the electronic system may be expected from this source as long as they do not result in catastrophic events. While utilization of rad hardened components is expected, special shielding of electronics from highly energetic particles is not required. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Plasma: The SES shall protect the crew from electrical shock and meet all its requirements while operating in a plasma environment from ‐80V (TBR) to ‐5V (TBR) floating potential. Rationale: Electrical arcing between systems at different potentials is a possible hazard. This potential difference can arise during SEA operations near power generation sites such as solar power farms. Designs may employ grounding interfaces to control the path of electrical shock to avoid damaging soft goods. Verification: (IDAT) – TBD
Page 17 of 36
807300008B
[SES.xxx‐ENG] High Abrasion Dust: The SES shall meet its performance requirements after exposure to Martian dust. Rationale: Based on experience during the Apollo program, it was recognized that dust on the lunar surface can be especially harsh to equipment and poses a potential hazard to crew members if carried inside the habitable volumes. It is believed that the Martian regolith would have some of the same potential effects. Mitigation strategies may include, but are not limited to, manual cleaning operations, prevention of dust intrusion, dust immobilization, protective personal equipment, design for reliability, etc. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Material Compatibility: The SES shall be designed with materials compatible with other environments defined in TBD. Rationale: As the program matures, a materials compatibility document will need to be developed and matured and will address things such as superoxides and chemical resistance to the Martian environment. Verification: (IDAT) – TBD
[SES.xxx‐ENG] Visibility, Vision, and Clarity: The SES shall provide a viewing range of at least 120 degree horizontal and at least 90 degree vertical with a clarity of TBD under nominal conditions. Rationale: A wide range of vision is necessary for the crew member’s visual situational awareness. Verification: (IDAT) – TBD
3.5 Safety, Quality, and Mission Assurance [SES.xxx‐SMA] High Voltage Exposure: The SES shall protect the suited crew member in the event that any suit surface touches a voltage source of TBD Volts for TBD seconds. Rationale: The Mars One program office intends on using high voltage power systems to minimize system sizing and loads with voltages potentially on the order of 1000VDC. Given the high voltage and rarefied Martian Atmosphere, there is a risk that the suited crew members may be exposed to arcing or inadvertent contact. This issue needs to be resolved with an appropriate control put in place in the suit system by design or operations. Verification: (IDAT) – TBD
[SES.xxx‐ SMA] Mean time Between Failures (MTBF): The SES shall have a mean time between failures (MTBF) of not less than 22,500 hours (TBR) of SEA utilization. Rationale: Only failures which result in loss of crew are considered for this requirement. The number in this requirement is similar to the NASA estimates for a lunar outpost LOC/LOM requirements (LOC=1/17, LOM=1/12 with a hardware usage time of 9404 hours, 3200 of which was EVA time). Verification: (IDAT) – TBD
[SES.xxx‐ SMA] Mean time to Repair (MTTR): The SES shall have a mean time to repair (MTTR) of not more than TBD hours. Rationale: Despite preventative maintenance and rigorous qualification testing, it can be expected that some parts of the SES will break. The suit must be designed to be repaired quickly.
Page 18 of 36
807300008B
Verification: (IDAT) – TBD
[SES.xxx‐SMA] Impact Performance: The SES shall meet its requirements following impact at any point with a 5 cm (TBR) diameter ball having the energy equivalent to the worst case rigidly attached mass of the suit, umbilical, tools, and crew member traveling at a rate of at least 60 cm/s (TBR). Rationale: This requirement ensures that the suit components (whether hard or soft) will continue to operate normally following an impact during SEA. The impact energy must be specified as a function of system mass and anticipated SEA translation and possible fall and/or translation velocities. This requirement must be met at the highest and lowest suit pressures. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Eye Protection: The SES shall limit crew exposure to spectral radiance and irradiance at the crew members' eyes to levels equivalent or lower than current ISS suit performance. Rationale: This requirement is necessary to prevent retinal photochemical injury from exposure. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Power System Duration: The SES shall have a power system life of at least 2 years (TBR) and 750 charge/discharge cycles (TBR). Rationale: Current ISS spacesuit batteries are expected to have a life of 2 years. Batteries are expected to last a full SEA without recharge or swap out. Alternative power sources may be developed or envisioned but will need to accommodate the frequency of SEAs and time between supply drops. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Fault Tolerance: The SES shall be two fault tolerant (TBR) for catastrophic hazards and single fault tolerant (TBR) for critical hazards or shall receive approval for Design for Minimum Risk (DFMR). Rationale: This establishes a minimum of two fault tolerance or DFMR to control catastrophic hazards and single fault tolerance to control critical hazards. It is anticipated that many functions and components of the suit will pursue DFMR (e.g. oxygen storage tanks). Verification: (IDAT) – TBD
[SES.xxx‐SMA] Pre‐SEA Operations Preventative Maintenance: The SES flight hardware shall require no preventive or limited life maintenance prior to first use (TBR). Rationale: This requirement addresses the desire to design suit hardware such that maintenance not be required during the 32 month period prior to first use (time in transit and on the surface prior to first use). Activities associated with wipe down and cleaning to ensure viability of hardware are not considered within the definition of maintenance for this requirement. Battery maintenance is generally excluded from this requirement; however crew‐ time for battery maintenance must be minimized as much as possible. Verification: (IDAT) – TBD
[SES.xxx‐SMA] Post‐SEA Operations Preventative Maintenance: The SES hardware shall require no preventive or limited life maintenance prior to the completion of four 8‐hour SEAs (TBR). Rationale: This requirement addresses the desire to design suit hardware such that preventive or limited life maintenance occurs no more frequently than once every four SEA cycles. Page 19 of 36
807300008B
Activities associated with wipe down and cleaning to ensure viability of hardware are not considered within the definition of maintenance for this requirement. Battery maintenance is generally excluded from this requirement; however crew‐time for battery maintenance must be minimized as much as possible. Verification: (IDAT) – TBD
[SES.xxx‐ENG] SOW Standards: The following technical and process standards are derived from NASA’s human spaceflight program and should be adhered to unless alternative standards are approved by the chief engineer, program manager and customer. Rationale: This list represents a preliminary snapshot of known standards used by NASA and recognized as industry standard. Standards will continue to be used to ensure hazard and quality controls for critical systems. If there are preferred (company or industry) standards, some effort should be expended to ensure they are aligned with the intent of the NASA standards to ensure historical human spaceflight lessons learned are not lost. • NASA‐STD‐4003 Electrical Bonding for NASA Launch Vehicles, Spacecraft, Payloads, and Flight Equipment • MIL‐STD‐461‐F Requirements for Control of Electromagnetic Interference Characteristics of Subsystems and Equipment • JPR 8080.5 JSC Design and Procedural Standards • JSC 28918 EVA Design Requirements and Considerations • JSC 65828, Structural Design Requirements and Factors of Safety for Space Flight Hardware • JSC 65829, Loads and Structural Dynamics Requirements for Space Flight Hardware. NASA‐STD‐5017 Design and Development Requirements for Mechanisms NASA‐STD‐5019 Fracture Control Requirements for Spaceflight Hardware • NASA‐STD‐6016 Standard Material and Process Requirements for Spacecraft• NASA‐ STD‐6016 Standard Materials and Processes Requirements for Spacecraft • NPR 7150.2A NASA Software Engineering Requirements • NASA‐STD‐8719.13 Software Safety Standard • NASA‐GB‐8719.13 Software Safety Guidebook • NASA‐STD‐5005 Standard for the Design and Fabrication of Ground Support Equipment • ANSI/AIAA S‐081A‐ Space Systems ‐ Composite Overwrapped Pressure Vessels (COPVs) July 24, 2006 ANSI/AIAA‐120A Mass Properties Control for Space Systems • S‐080‐1998e AIAA Standard for Space Systems ‐ Metallic Pressure Vessels, Pressurized Structures, and Pressure Components Verification: (IDAT) – TBD
Page 20 of 36
807300008B
4 Functional Baseline Definition The Surface Exploration Suit is divided into two major systems, 1) the Pressure Suit itself and all hardware contained within the suit and 2) the Portable Life Support System which is an interchangeable piece oof hardware that provides services to the Pressure Suit when not attached to the Habitat or other life support umbilical. For the design and development efforts, Safety Reviews will be conducted at the level of the integrated Surface Exploration Suit (SES).
As the Apollo A7LB was the last developed operational planetary suit, some of its primary features are suitable to the Mars One needs.
The following definition provides the initial baseline architecture of the suit, and serves as a point of departure functional baseline to be used as the foundation for trade studies. Figure 6. Typical Spacesuit Configuration. 4.1 Pressure Suit
4.1.1 Helmet The helmet assembly will consist of three major subcomponents. These subcomponents are the pressure bubble, protective bubble and the sun visor. An illustration of the proposed architecture is showwn in Figure 7. The helmet will be a non-conformal elliptical hemispherical shape sized to provide the best compromise for in-transit vehicle operations and Mars SEA. The elliptical hemispherical helmets have been uused on NASA prototype spacesuits developed by ILC Dover since the latte 1990s. Most recently, ILC Dover developed the latest version of this helmet system for NASA’s Z-2 Planetary EVA spacesuit.
The pressure bubble will be fabricated from impact resistant polycarbonate. Figure 7: Mars One Helmet The protective bubble will be fabricated from the same material and be Architecture designed to encase the pressure bubble for maximum protection. The protective bubble will include both opaque and tinted regions to provide adequate protection from sunlight while maximizing visibility. The sun visor will be sandwiched between the pressure and protective visors to protect the sun visor coating from damage from dust and abrasion.
The helmet will also include a lighting system (see Figure 8) to provide illumination during SEA in low light conditions. This system will provide project type illumination to provide adequate visibility for translating on a planetary surface. Secondary illumination will also be provided that will allow the astronaut to view objects close up, such as geologic samples. A prototype lighting system was tested by ILC Dover as part of the NASA D-RATS remote field testing.
Figure 8: Advanced Helmet Lighting System – Waist Entry I‐Suit Page 21 of 36
807300008B
4.1.2 In-Suit Communication System The in-helmet communication system will conssist of a heads-free system of speakers and microphones mounted around the base of the neck ring as shown in Figure 9. It is called heads-free because the components are attached directly to the spacesuit rather than worn on the crew meember’s head like the traditional “snoopy cap”.
4.1.3 Upper Torso The upper torso will be an all-soft waist entry architecture Figure 9: Heads‐ similar to that demonstrated in the Waist Entry I-Suit Free (Figure 10). The approach minimizes mass and provides Communication a system that is very tolerant of impacts associated with System falling during SEA operations. The soft upper torso (SUT) will interface with the base of the helmet neck wedge, shoulder rotary bearings and a hard waist entry closure. The PLSS will have structural attachment points at the back of the neck wedge element and at the top of the waist closure. Life support consumables will pass into and out of the suit through the interfaces at the back of the neck wedge element.
4.1.4 Arms Figure 10: Waist Entry The proposed arm architecture (Figure 11) has been I‐Suit Soft Upper Torso successfully used on both the Waist and Rear Entry I-Suits. (SUT) The shoulder consists of a two bearing toroidal convolute design patented by ILC Dover. The all soft toroidal convolute design minimizes mass and packing volume while also exhibiting a high cycle life. The bearing design was pioneered by ILC Dover during the deevelopment of the original NASA Waist Entry I-Suit program. This design consists of custom packaged commmercial slim bearings coupled with custom pressure and environmental seals. This approach minimizes maintenance time and difficulty. These spacesuit rotary bearings were recently used in the StratEx commercial spacesuit. This suit experienced eight very hard parachute landings, often in nattural terrain, without damage to the suit. The lower arm consists of an all soft gored mobility joint with adjustable axial restraint brackets that provide Vernier sizing for enhanced fit. The Figure 11: I‐Suit wrist end of the lower arm incorporates a bearing/disconnect providing rotational Arm Architecture mobility and the ability to quickly don and doff gloves.
4.1.5 Gloves The gloves will be a modified version of the current Phase VI EVA gloves (Figure 12) that are used on the International Space Station. This glove design has performed well in recent tests by NASA for performing critical surface EVA tasks. This testing also included deliberately pouring JSC Lunar Simulant between the restraint and TMG layers and then performing manned pressurized cycling. No damage was noted to the glove layers during post-test inspections. More of this type of testing will need to be performed to verify the glove design meets Mars SEA requirements. This will be discussed in a later section.
Figure 12: Current Phase VI ISS EMU
Page 22 of 36
807300008B
4.1.6 Waist In order to provide the best trade between mass, mobility and cycle life, the Mars One spacesuit will utilize an all soft toroidal convolute waist joint similar to that developed for the ILC Dover I-Suits and Z-1 spacesuit. This design has structurally redundant axial restraints and requires very little maintenance. This type of mobility joint was first demonstrated in the Waist Entry I-Suit in 1998 during NASA remote field testing in the Mojave Desert as part of the Astronaut Rover Interaction (ASRO) project. It has been used successfully in 9 years of NASA Desert RATS remote field testing in the Arizona desert. This waist architecture provides critical mobility required for operations such as sitting on a rover (Figure 13) and bending over to pick up objects on the ground.
Figure 13: Rear Entry I‐Suit Mobility Evaluation on an ATV
4.1.7 Brief/Hip/Thigh The Mars One spacesuit architecture will consist of a fabric brief and two bearing hip mobility joints. This approach has been show to provide the best trade considering cost, mobility, mass and maintenance. This type of system has been used successfully on the I-Suits and the recent NASA Z-1 spacesuit. Existing designs have shown very good performance during limited testing up to 8.3 psid. The hip and leg bearings will be of the same design previously discussed in the arm section. This approach to lower torso mobility has been shown to eliminate the need for a waist bearing especially when minimizing mass is critical. Figure 14 shows the type of extreme mobility attained by a twwo bearing hip married with a toroidal convolute waist joint. Figure 14: Critical Surface EVA Operations Evaluated during NASA D‐RATS Testing in Arizona 4.1.8 Legs The Mars One spacesuit will utilize an enhanced walking leg joint developed by ILC Dover for the NASA Z-1 and Z-2 spacesuits. This design builds on the lessons learned from the Mk III and I-Suit Page 23 of 36
807300008B programs and more than 15 years of NASA Desert RATS remote field testing. The design is all soft fabric with lightweight titanium axial restraint brackets that provide Vernier sizing similar to those utilized on the lower arm. This type of mobility joint has been used successfully up to 8.3 psid.
4.1.9 Boots The boot architecture will be an evolution of the advanced spacesuit walking boot currently being developed for NASA on the Z-2 program. This boot is being designed to provide long duration walking SEA comfort while also managing operational pressure loads in excess of 8.3 psid. The boot architecture is sized to the astronaut’s foot just as terrestrial hiking boots are today. There is also fit adjustment capability at suit operational pressure via a unique dual ratcchet and cable system.
4.1.10 Liquid Thermal Garment The liquid thermal garment will be similar to the advanced liquid cooling and ventilation garment (LCVG) ILC Dover developed for NASA on a research contract. A picture of the current ILC LCVG is shown in Figure 15. This design is enhanced over the existing ISS EMU LCVG in that it provides improved heating/cooling through better fit and targeted fluid loops. Comfort is improved through incorporation of an improved fabric liner layer, high efficiency low profile vent air return ducts and integral antimicrobial coatings.
4.1.11 Thermal Micrometeoroid Garment (TMG) The TMG is one area of the suit architecture that will Figure 15: ILC Dover EMU LCVG require technology development. The Martian planetary surface and atmosphere bring unique challenges not experienced in previous operational EVA spacesuits. The Martian soil will provide similar challenges experienced on the lunar surface. A very limited amount of research has been performed to develop materials needed to stop the intrusion of Martian soil into the structural and pressure retaining layers of the suit. Novel attachment and termination methods are required to ensure suit mobility is not restricted and suit maintenance time is minimized. ILC Dover has performed some research in this area for NASA, yet more work is required.
The atmospheric pressure on the Martian surface and the extreme thermal gradient required will necessitate the incorporation of new insulation materials in comparison to those used for Lunar and micro-gravity TMGs. This new insulation will have to perform more like a winter parka. Recent TMG work on the StratEx spacesuit has relevant application to a Martian TMG, although more development including thermal analysis and testing is required
The other key challenge is the radiation environment on thhe Martian surface. New materials will have to be incorporated into the layers of the TMG to minimize the radiatioon dosage an astronaut receives while on SEA.
4.2 Portable Life Support System
4.2.1 Overview The portable life support system of the Mars One Surfacce Suit system provides all of the functions necessary for the crew member to comfortably and safelly operate while in the pressure suit. The primary subsystems include Environmental Control and Life Support; power storage, distribution, and possibly power generation; as well as communication between crew members and between the crew member and the habitat. Each of the sections below provides an overview of the major PLSS subsystems.
Page 24 of 36
807300008B
4.2.2 Communications Two-way radios will be used to facilitate voice communications between crew members and the habitat. A multi-channel system in which the user will be able to select the channel, enable or disable the microphone, or as required go into a voice-activated mode will enable multiple crews to function without creating a significant amount of chatter from the Mars One population. The communications subsystem requires a significant amount of interface definition with the other systems and as such the specifics of a baseline are not available.
4.2.3 Power Storage, Distribution, and Generation Power storage would be provided by rechargeable primary batteries, most likely lithium ion. Power would be limited to 28VDC and 5VDC power for pumps/fans and electrical instrumentation, respectively. Small form factor batteries for power storage represent a high technical risk for SEA operations. Due to the limited number of charge/discharge cycles that a battery can endure, a power storage design that utilizes power carts to the maximum extent possible would be considered. In future suit upgrade cycles, it may be possible to integrate thin film solar panels into the suit to produce electrical power and minimize the discharge of the batteries.
Figure 16: Power Subsystem Schematic
4.2.4 Environmental Control and Life Support Environmental control is provided by a system based on Paragon’s patented Metabolic Temperature Swing Adsorption (MTSA) technology, as shown in Figure 17. There are three main loops to this system. The first loop (green) is the air revitalization system that removes CO2, moisture and trace contaminants from the exhaled gas. The second loop shown in blue is a fluid loop that provides temperature control to the suited crew member. Last is a CO2 circuit that uses liquid CO2 to facilitate MTSA operation and provide cooling supplemental cooling.
Page 25 of 36
807300008B
Figure 17: MTSA Pressure, Temperature and Air Revitalization System.
4.2.4.1 Pressure Control and Revitalization The life support system maintains a breathable atmosphere by removing particulates, maintaining humidity levels, temperature and absolute pressures, as well as managing the partial pressures of O2 and CO2.
Utilizing the high pressure O2 and the gas storage systemm on the Mars One Habitat system, tanks of gaseous oxygen are used to maintain the suit O2 levels as well as total pressure.
The pressure control and revitalization loop creates a habitable atmosphere for the crew member inside of the suit. This is a pure oxygen system that is pressurized between 4.3 and 6.5 psia. This pressure is maintained by a suit pressure regulator. A relief valve prevents the suuit from over-pressurization.
The revitalization loop begins with the warm, moist, CO2 rrich gas beiing pulled from the suit into the PLSS by a blower. The exhalant then flows through a MMTSA bed where metabolic heat from the exhalant is used to raise the temperature of one of the saturated CO2 sorbent beds, thus releasing its adsorbed CO2 to the atmosphere. This also cools the exhaled gas and condenses out most of the moisture, which is then directed to an accumulator that can be utilized by the liquid thermal control loop. After leaving the first MTSA bed the exhalant passes through a trace contaminant control assembly and a desiccant bed where the exhalant is warmed by the moisture removal process. At this point the exhaled gas is warm and dry but still rich in CO2. The fllow then goes through a regenerative heat exchanger to cool the gas and then to the second MTSA bed where the CO2 is removed by a CO2 selective adsorbent and the gas is further cooled. This process uses chilled liquid CO2 from an onboard tank to remove heat generated during the exothermic adsorption of the CO2 by the adsorbent in the MTSA bed. The CO2-free gas then flows back to the regen heat exchanger where it is warmed up by the warm side flow. The temperature of the oxygen is adjusted once more as if flows through the thermal control loop heat exchanger. Finally, additional oxygen is added from tanks to replace the oxygen metabolically consumed by the crew member and converted to CO2 and then the flow goes back to the suited crew member.
Page 26 of 36
807300008B
In the preceding paragraph two different MTSA beds were described. Each MTSA bed has a finite capacity to adsorb CO2. When that limit is reached it is switched with the other MTSA bed that has been desorbing. Depending upon the sizing of the beds this switching could be a physical swap or accomplished via manual or automated valves.
4.2.4.2 Temperature Control The temperature control loop keeps the suited crew member comfortable, allowing them to perform their tasks at high efficiency. Warm cooling water exits the suit and enters a reservoir (the same reservoir that accepted the condensed moisture from the air revitalization system). A pump pulls water from the reservoir and forces it through a series of heat exchangers. The first HX thermally conditions the oxygen returning to the crew member. The next two cool the water by utilizing the same CO2 used to cool the second MTSA bed. This thermally conditioned water then returns to the suited crew member. The liquid CO2 required for the environmental control system is produced at the Habitat modules as part of the In Situ Gas Processor.
The environmental control will likely require provisions for both heating and cooling, depending on the environment and operational scenario. Paragon’s experience shows that the wearing of thermal undergarments, the use of cooling and heating loops and/or electrical heaters, etc. are all very specific to the operating environment. The baseline system would be a liquid thermal garment with peripheral heaters for extremities combined with selected undergarments (long underwear, socks and gloves) that would be tried, tested and evaluated by each member of the crew and customized to their preference. While detailed thermal modeling is still required, having a slightly “cold biased” suit will probably be the best approach given the environmental conditions. This means that the nominal thermal control will be heating with cooling only required on occasion. A system-level trade is required to develop the optimum solution as more heating requires additional electrical power.
4.2.5 Command and Data Handling The Command and Data Handling (CDH) system monitors the data being generated by various SES sensors and subsystems, accepts commands from the suited crew member and makes the necessary adjustments to the suit’s operating parameters. Additionally, the CDH also sends data to the Habitat and receives commands in the event that the crew member is incapable of doing so. Finally, the CDH records and displays data, including caution and warning information.
Antenna Antenna
Transmitter Data Modem Video Recorder
Video Camera Data Recorder
Data Acquisition Board Suit Data Inputswith Suit Commands Logical Programming
Crew Data Display
Figure 18: Command and Data Handling Subsystem Schematic
Page 27 of 36
807300008B
4.2.6 Health Monitor The health monitor records and transmits information on the suited crew member’s heart rate, heart rhythm and other potential parameters such as breathing rate, core temperature and skin temperature. There are multiple ways to obtain this information, ranging from sensors attached to the skin, chest straps and swallowed data pills that transmit wirelessly. This data is then fed to the CDH subsystem where it is read, recorded and transmitted to the Habitat. Balancing the needs of medically necessary data with the opportunity to gather scientific information on Martian colonists will ultimately determine the breadth of data recorded.
Page 28 of 36
807300008B
4.3 Master Equipment List (MEL) Table 3 shows a breakdown of the estimated on-back mass of the conceptual SES (including wet mass) broken down to the primary subsystem-level components, and total estimated mass to complete 1000 surface excursions. Per AIAA S-120A, a 30% mass growth allowance (MGA) is added given this early level of design fidelity.
Table 3: SES MEL, On‐back Mass, and Mission Mass Estimates Mass Subsystem Component (kg) Helmet/Protective Visor 3.2 Shoulder (Pair) 3.6 Lower Arm (Pair) 2.7 SUT 2.3 Waist 3.6 Pressure Suit Hip/Brief 5.9 Leg 4.1 Boot 3.2 Cover Layer 2.3 Subtotal 30.9 Structure 17.2 ECLSS 28.6 PLSS Avionics 11.8 Subtotal 57.6 SES Dry Mass Total 88.5
Wet Mass Liquid CO2 Coolant 8.0 Gaseous O2 (primary and emergency) 4.0 Coolant Water 1.0 Food 0.1 Drinking Water 1.0 Subtotal 14.1 On‐back SES Dry + Wet Mass Total 102.6 Spares Estimated mass of spares to complete 1000 SEAs (250 per SES) 1200.0 Four SES (dry mass) 354.0 Pre‐Deployed 90% of Spares 1080.0 SES Assets Subtotal 1434.0 SES Assets Four SES (dry mass) 354.0 Delivered with 10% of Spares 120.0 the Crew Subtotal 474.0 Eight Suits + Spares to Complete 1000 SEAs (250 per SES) 1908.0 SES Total 30% MGA 572.4 Total Estimated Dry Mass with MGA 2480.4
Page 29 of 36
807300008B
5 Risk and Opportunity Management
5.1 Cost and Schedule Risk Drivers
5.1.1 Robustness of Design
5.1.1.1 Service Life Due to the unique nature of the mission, a service life must be established for the SES at the system and subsystem level. Service life will have to account for the fact that replacement parts and suits will require significantly better logistical management due to the time and distance required for transport. Service life needs to be magnitudes higher than any previously developed suit system.
Historically, spacesuit life is driven by cycle life. Simply put, mobility joints can only be flexed so many times and bearings can only be rotated under load for some time before bearings balls or races exhibit unacceptable wear. Cycle life is usually tracked at the component level and sometimes lower. For the ISS EMU program, glove life is defined at the pressure bladder, restraint and TMG level. Each of these subcomponents has a different life based on results of Certification Cycle Testing.
The current ISS EMU is certified for 25 EVAs. NASA requires a factor of safety of 2 on cycle life resulting in a minimum of 50 EVAs worth of manned cycling. During the original ISS EMU suit certification, most of the suit was actually cycled to 100 EVAs because there is a requirement to cycle the suit on both primary axial restraint webbings and secondary restraint webbings. All of this testing was performed at 4.3 psid to a micro-G cycle model developed by reviewing Skylab EVAs and early EMU EVAs. This resulted in a cycle model that is very arm and glove cycle intensive with very little waist and lower torso cycles.
A SEA cycle model does not currently exist. There is some operational experience from Apollo but the duration was very limited with only three days on the lunar surface per mission. NASA has done some recent work looking at what types of motions or activities a suited crew member will have to perform. This includes activities like hammering, digging, lifting, kneeling to pick up an object on the ground, walking, jogging and surface vehicle ingress/egress. Significant forward work will be required to define all activities, number cycles, cycle rates, tool interfaces and surface object interfaces like rocks. It should also be noted that the only operational EVA suit (ISS EMU) has been cycled to at most 100 EVAs. The current requirement for Mars One is 250 SEAs. This is more than twice any previous operational EVA suit has been cycled to. Given that this is a SEA cycle model coupled with a dusty environment, obtaining the required cycle life will be much more challenging than for micro-G EVA. This uncertainty drives the spares mass to be conservatively high at this point in the program phase.
5.1.1.2 Serviceability There is a need to evaluate the ability of using the specialized equipment and materials in the Mars One habitat. The SES subsystems could be specifically designed for ease of serviceability, however, the effort to train the crew members will be substantial. Hard goods should be designed extremely robust to ensure a long service life or be repairable or modified using a “plug and play” mentality of smaller easily transported spare parts. This requirement will take some development effort.
5.1.1.3 Maintainability The suit must be maintainable by the crew with limited supply of tools and equipment as resupply will be costly and infrequent. The time available to maintain the suit is unknown at this time but may be assumed to be short for early missions due to the unknowns of other system requirements, so Mean Time to Replace (MTTR) is particularly important.
The suit must be designed for simplicity, reliability and ruggedness. The first objective should be to reduce the need for maintenance; 2nd should be to make maintenance easy; and 3rd should be to minimize limited life items that require replacement.
Page 30 of 36
807300008B
5.1.1.4 Mass Typical of all launch programs, mass is critical. As a result, the drive to reduce the overall mass of the SES will increase the complexity and cost of the suit. Spacesuit mass is always a significant requirement on any space program. The two primary mission phases that drive mass requirements are vehicle launch mass and suit mass enabling efficient locomotion in partial G SEA. Current chemical rocket technology limits the mass of the vehicle, crew and supplies in order to escape earth’s atmosphere and provide propulsion to make the long trip to Mars. This is normally the driving constraint on deep space programs. Once on the Martian surface, astronauts will experience 3/8G when performing an SEA. The most efficient (lowest energy expended) method of locomotion is affected by the suit system mass and center of gravity (CG). A light weight suit may not allow for normal walking or jogging motions. The suit mass and mobility must be evaluated in environments such as zero G aircraft in order to understand and train for the most efficient Martian surface locomotion.
5.1.1.5 Stowage Volume Stowage volume for the suit will be at a premium, both for the transit phase to Mars and while on the planet. It will be imperative to minimize this volume as much as practical.
5.1.2 Safety and Crew Productivity
5.1.2.1 Suit Pressure The pressure of the suit will drive all structural components of the suit design. Choice of suit pressure is a multivariable trade space, highly linked with choice of habitat pressure, the desired pre-breath cycle time, mobility requirements and CONOPS. Suit pressure is a driving requirement but also one that is often not well understood. In the spacesuit design world, 3.5 psia is about the lowest allowable pressure that can ensure human physiological safety, but operation in this regime requires significant pre-breathe time. Higher pressures reduce the need for pre-breathe, but decrease suit mobility. The current ISS EMU EVA spacesuit operates nominally at 4.3 psia to minimize the forces affecting suit torque and range of motion but this pressure still requires significant oxygen pre-breathe time. If operating from a vehicle or habitat environment at 14.7 psia, NASA considers the lowest pressure requiring zero pre-breathe to be approximately 8.3 psia. However, if the crew members can be acclimated to lower pressures, then both suit pressure and pre-breathe time can be reduced.
5.1.2.2 Anthropometric Range The suit design must accommodate the challenges associated with outfitting the specified anthropometric range. Legacy EVA Suit systems have not been able to preserve the intended functionality for operators who are on the smaller end of the typical NASA anthropometric range. This may drive the program towards custom suits, but this may affect the interchangeability of the suit components. Suits in a few basic sizes that are adjustable over a smaller range may be alternate approach.
5.1.2.3 Mobility The suit must provide adequate mobility to construct and maintain the Martian outpost as well as provide the ability to explore the Martian surface. Tasks that may be performed include fine motor skills (i.e. using tools to build the outpost), walking, climbing (climbing ladders or a Martian cliff), bending over to pick up an item, and driving rovers. It is expected that this requirement will evolve as the CONOPS matures.
5.1.2.4 Dexterity The SES gloves will drive advancements of existing EVA glove technologies. Traditionally, gloved-hand dexterity has come at the expense of accommodating durability and environmental protection requirements – all of which will need to be improved for a manned mission to Mars.
Page 31 of 36
807300008B
5.1.2.5 On-Back Mass On-back mass is the complete mass of the suit system that the crew must wear during excursions. Although Mars gravity is ~37% of Earth’s, the crew may be over-taxed by the weight of the suit when they first get to Mars when it is envisioned that many SEAs are required.
Suit mobility for walking and working requires bearings—especially at the higher pressures needed to preclude or reduce pre-breathing requirements, and bearings have historically been heavy components. Aluminum or composite bearing housings, holding steel bearing races will reduce weight compared to traditional all-steel bearings, and will last considerably longer than all-aluminum bearings.
One option may be to forego the PLSS for some tasks that are in close proximity to the Habitat or perhaps a mobile support cart. The crew members could then be serviced by an umbilical rather than the PLSS, thereby reducing on-back mass. This of course does limit crew member range.
5.1.2.6 Tracking and Communication System Communication is a critical safety feature and will likely require redundancy in the event of a failure. This is especially critical during long excursions on a rover where visual contact to the habitat is lost and support is needed.
Identifying the best means of remotely tracking a crew member will be important as well. This will allow fast recovery should the crew member become stranded or incapacitated over the horizon.
5.1.3 Environmental
5.1.3.1 Dust/Contamination Mitigation The outer layer of the SEA Suit and cleaning systems must provide adequate dust mitigation to protect the suit and maintain functionality. The SEA Suit and cleaning systems must mitigate Martian regolith contamination of the living environment. The don/doff methods and location must mitigate contamination into the suit or onto the undergarments. Methods for cleaning undergarments must be incorporated into the habitat design.
Very little work has been done to understand the impacts to spacesuits from Martian regolith. NASA JSC has constructed a “Martian Rock Yard” to perform analog testing but this regolith does not take into account all the information learned from the JPL Mars Rover programs.
The largest body of data is experience from Project Apollo and testing performed by NASA on and off over the last 20 years as part of Desert RATS planetary analog testing. The Apollo experience exemplifies the concerns with future planetary SEAs as several issues became apparent after only 3 days of lunar EVA:
Spacesuit leakage rose significantly in only 3 days of EVAs
Zippers and hard closure mechanisms started to bind
Dust brought back into the lunar lander created a bad odor when exposed to oxygen
A significant body of work is required to develop materials that will repel and/or keep dust from penetrating into the suit layers. Dust intrusion not only damages suit materials it can also change the outer layer optical properties thereby changing the overall suit emissivity and degrading thermal performance.
5.1.3.1.1 Dust Tolerant Bearing Seals The current state of the art is oil-loaded felt seals. There is limited data on the performance of this technology against Apollo regolith simulant and no testing against Mars regolith simulant. NASA is
Page 32 of 36
807300008B
starting work in this area again but the current focus is lunar soil. Development work is needed to understand the limits of current environmental seals and what technology is needed to obtain a reasonable time before maintenance.
5.1.3.1.2 Dust Tolerant Materials and Attachment Methods for Planetary TMGs Technical paper 2008-01-1990 from the International Conference on Environmental Systems (ICES) discusses some of the recent work performed in this area. This paper is provided with this Mars One Conceptual Design paper.
5.1.3.2 Thermal Comfort Mars has a thin atmosphere that minimizes the effectiveness of MLI, so alternate methods of thermal protection from the environment will be required. In colder conditions the suit may require additional insulating layers similar to a winter jacket (and LTG cooling in warmer conditions) that do not reduce mobility.
5.1.3.3 CO2 Removal The MTSA system for the PLSS requires the use of zeolite beds that have a finite CO2 adsorbtion capability. In the system shown in Figure 17 two beds are in the system. One is adsorbing while the other is desorbing. Detailed design is needed to determine the optimum size of these beds and the method of switching the mode from adsorption to desorption. It may make sense to use smaller beds that are fixed in place with valving to switch modes. Switching could also be done manually, or larger beds could be used that would last the entire mission. In this case the switching would be done as part of post SEA refurbishment.
5.1.3.4 Radiation Protective Materials The need for advanced flexible materials for radiation protection on spacesuits has been around for more than 20 years. The materials must be lightweight, flexible and high in hydrogen. Limited testing and evaluation has been done with polyethylene based materials and tungsten-loaded silicone. The ICES paper “Study of Development of a Radiation Shielding Kit” is provided with the Mars One Suit Conceptual Design paper. This paper discusses flexible radiation material requirements, selection and incorporation into an astronaut protective vest and blanket.
Radiation dosage over the length of Mars mission is a concern that must be addressed. Recent data from the Mars Curiosity Rover shows that radiation dosage for the transit to Mars is much worse than exploration on the Martian surface. However, the total exposure for long duration stays on the surface is still a question. In any event, concerns about an increased risk of cancer from radiation exposure must be tempered by the inherent risks with this mission. The following text is an excerpt from an article in Scientific American December 9, 2013.
A mission consisting of a 180-day cruise to Mars, a 500-day stay on the Red Planet and a 180-day return flight to Earth would expose astronauts to a cumulative radiation dose of about 1.01 Sieverts, measurements by Curiosity's Radiation Assessment Detector (RAD) instrument indicate. To put that in perspective: The European Space Agency generally limits its astronauts to a total career radiation dose of 1 Sievert, which is associated with a 5-percent increase in lifetime fatal cancer risk. A 1-sievert dose from radiation on Mars would violate NASA's current standards, which cap astronauts' excess-cancer risk at 3 percent.
"It's certainly a manageable number," said RAD principal investigator Don Hassler of the Southwest Research Institute in Boulder, Colo., lead author of a study that reports the results Dec. 9 in Science.
NASA is working with the National Academies’ Institute of Medicine to evaluate what appropriate limits would be for a deep-space mission, such as one to Mars.
Page 33 of 36
807300008B
The new results represent the most complete picture yet of the radiation environment en route to Mars and on the Red Planet's surface. They incorporate data that RAD gathered during Curiosity's eight-month cruise through space and the rover's first 300 days on Mars, where it touched down in August 2012.
The RAD measurements cover two different types of energetic-particle radiation — galactic cosmic rays (GCRs), which are accelerated to incredible speeds by far-off supernova explosions (http://www.space.com/11425-photos-supernovas-star- explosions.html), and solar energetic particles (SEPs), which are blasted into space by storms on our own sun.
RAD's data show that astronauts exploring the Martian surface would accumulate about 0.64 millisieverts of radiation per day. The dose rate is nearly three times greater during the journey to Mars, at 1.84 millisieverts per day.
But Mars' radiation environment is dynamic ([Figure 19]), so Curiosity's measurements thus far should not be viewed as the final word, Hassler stressed. For example, RAD's data have been gathered near the peak of the sun's 11-year activity cycle, a time when the GCR flux is relatively low (because solar plasma tends to scatter galactic cosmic rays).
Figure 19: Radiation Climate on Mars (source: Scientific American December 9, 2013)
Using the Curiosity Rover readings and assuming a Maartian habitat would cut the surface SEA exposure in half, the transit to Mars and 250 days of 12 hour SEAs will result in approximately 0.45 Sieverts of radiation. Using European Space Agency limits each astronaut could perform 1150 more SEA days before reaching their total career radiation dose.
Page 34 of 36
807300008B
5.2 Opportunities to Reduce Risk
5.2.1 Future Studies The following studies are recommended prior to significant investments to minimize the risk for development and the ultimate mass of SES hardware transported to the Martian surface.
SEA cycle model development and optimized sparing/refurbishment plan
Certification protocol – tools/interfaces, test scenario definition, cycle rates, etc.
Radiation dosage over total SEA time – limits, Martian surface condition, suit TMG protection level
TMG layup and attachment method (multi-mission: space vacuum & Mars atmosphere)
5.2.2 Precursor Tests (Mars Rover 2020) The following tests are recommended to validate design assumptions required for developing man rated surface suit systems.
Evaluation of rotary bearing dust seals in rover vehicle
Evaluation of ability of proposed suit TMG materials to shed or repel Mars dust
Continued measurements of surface radiation levels at planned Mars One landing site
5.2.3 Minimize Suit Pressure Pressure suit systems such as the current EMU experience development and certification anomalies primarily due to mobility requirements. These anomalies usually result in significant cost and schedule impacts. They usually arise from repetitive motion of the person against the suit bladder, hardware and soft-goods rubbing and abrading, and local stress concentrations at fabric seams and axial restraint attachment interfaces during pressure and/or range of motion cycling. The potential for these anomalies goes up as pressure increases.
Minimizing suit pressure is key to reducing cost, schedule risk, suit complexity, and increasing reliability. Significant testing in industry has occurred for suits at or below 29.65 kPa (0.29 atm, 4.3 psi). As stated in sections 4.1.7 and 4.1.8, ILC has done some testing at 57.23 kPa (0.56 atm, 8.3 psi) but there is no operational experience and there is limited data on reliability. There is some industry experience with soft and hard mobility joints up through operation at 101.35 kPa (1 atm, 14.7 psi) but again the operational use data is limited. The Mars One program would benefit from choosing a vehicle/habitat pressure that allows zero pre-breathe suit operation at or around 29.65 kPa (0.29 atm, 4.3 psi). This merely requires proper acclimatization. The city of El Alto, Bolivia sits at an elevation of 13,615 ft (8.8 psia). Almost one million people live in this city. In the USA, Leadville, Colorado is at over 10,000 ft elevation (10 psia). People have been living and working in this mining town for over 150 years. Therefore it would seem reasonable to have a habitat pressure of 9-10 psia with a 20% oxygen concentration without adverse health effects. This would then allow the suit pressures and pre-breathe times to be reduced.
5.2.4 Additive Manufacturing One technology area that has the potential to greatly reduce cost and risk, and in fact might be considered almost essential for Mars One, is Additive Manufacturing or 3D printing. Given the limited amount of supplies that will be available to the Mars One crew, it will be impossible to bring spares of all parts to account for any potential contingency or needed repair. With developments in 3D printing technology, the crew members would not need to bring any spares; instead they could make the
Page 35 of 36
807300008B needed parts as different needs arise. The crew members would need to bring the 3D printing machines and raw materials with them, and if the need arises for a replacement item such as a spare nut or bolt, a specialty tool, etc. then they could just “manufacture” it as needed. This eliminates the need to prepare the crew members for every possible contingency, and also eliminates the worry that they will get to the surface of Mars and realize they desperately need something that they don’t have – and won’t get for at least two years. Ideally, the parts for the original equipment would already be designed and built using 3D printing to the greatest extent possible to ensure that replacement parts could be generated.
Many current space suit components could be manufactured with 3D printing. Additionally, 3D printing of textiles is just beginning to emerge as a viable technology. Given the structured nature of space suits (as compared to traditional garments); it is possible to envision many of the suit components being manufactured by 3D printing. This technology could significantly reduce the need for serviceability and long service life items. However, for the near-term, suit fabrics and all but rudimentary non-structural parts are only envisioned, but Mars One could push this technology for future missions.
5.2.5 Common Parts As much as practical, use of common parts and interchangeable components throughout the vehicle would enable the crew to reuse components from systems that are broken to support maintenance on other systems. The Mars One program should work to establish standards for use on the Martian outpost (i.e. Metric or English) and be prepared to prioritize commonality over optimization.
5.2.6 Establish Common Interfaces Early As the SEA Suit requirements will be driven by interfaces with the rover, air-lock, SEA tools and recharge system, establishing common interfaces early supported by a strong systems engineering team with excellent communication between the designers will ensure any interfaces issues will be minimized.
Page 36 of 36