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Mars One Surface Exploration Suit (SES) Design Summary

Mars One Surface Exploration Suit (SES) Design Summary

by Suzanne Flinkenflögel on Thursday, 17th November 2016 in Paragon, Technology

On November 15th, 2016, Mars One released the Conceptual Design Assessment of Mars One's Surface Exploration Suit (SES) by Paragon Space Development Corporation®. We hereby present a concise abstract of the independent Paragon report. The abstract was prepared by Mars One Round Three Candidates Josh Richards (AU), Oscar Mathews (US), and Ryan MacDonald (GB).

Abstract—Paragon Space Development Corporation has conducted an initial conceptual design study outlining the baseline requirements for the first surface exploration suit specifically intended for operational use on Mars. Each suit has a dry mass of 88.5 kg and requires 300 kg of spare parts to support 250 surface excursions over its lifetime. With adequate radiation shielding, each crew member can make at least 1150 surface excursions before exceeding ESA’s astronaut radiation career allowance. Mars One will make use of this initial design study to inform, develop and refine its mission of establishing a permanent human settlement on Mars.

1 Background
Typical spacesuit configurationIn March 2013, Paragon Space Development Corporation (Paragon) was contracted by Mars One to conduct a conceptual design study of a Surface Exploration Suit (SES) specifically tailored for long-duration crewed Surface Excursion Activities (SEA) on the Martian surface. This document provides an executive summary of the key findings and conclusions of Paragon’s work to-date and future opportunities. The full technical report is readily available from Mars One’s website

2 Pressure Suit

Mars One’s mission architecture is one of permanent settlement. Surface suits must be highly reliable and maintainable; they must offer sufficient mobility for outpost construction, walking, climbing, and permit extended exploration of the surface.

Surface Exploration Suit operational requirementsMars One’s SES draws upon the heritage of the last operational surface suit (the Apollo A7LB) and combines this with recent advances in suit mobility and endurance, specifically those developed by ILC Dover for NASA’s Z-1/2 spacesuit. Fig. 1 depicts a typical configuration of such a suit consisting of a multi-layer polycarbonate ellipsoidal helmet; bearings in the upper torso, shoulders, arms, wrists, waist, hip and legs for optimal vision and mobility; custom fit boots and gloves (a modified version of the Phase VI EVA gloves currently used on the International Space Station), liquid thermal undergarment for temperature control, along with a thermal micrometeoroid garment designed to prevent the intrusion of Martian regolith into the suit. Advanced radiation shielding will minimize exposure received on SEAs. The baseline operational and physical characteristics of Mars One’s SES are outlined in Tables 1 and 2.

3 Portable Life Support System (PLSS)

Extended excursions on the Martian surface using the SES will require a means to continually replenish the metabolic O2 consumed by the crew member and filter exhaled CO2. This function – among other tasks such as thermal control, waste management, communications, power storage, data handling and health monitoring – is carried out by the Portable Life Support System (PLSS) attached to the suit via an interface at the back of the helmet neck wedge or via an umbilicaled cart for near-habitat operations.

The SES Environmental Control and Life Support is provided by Metabolic Temperature Swing Adsorption (MTSA) technology – patented by Paragon – depicted schematically in Fig. 2. This system utilizes three loops. Firstly, air revitalization (green) removes moisture, trace contaminants, CO2 (using two zeolite beds) and replenishes the pure oxygen environment from onboard storage tanks. Secondly, temperature control (blue) pumps water around the suit to maintain a comfortable temperature for the crew member. Finally, the auxiliary cooling loop (red) which utilizes chilled liquid CO2 to extract excess heat and facilitate the operation of the MTSA.

4 Surface Exploration Suit Challenges

The report recommends simplicity, reliability and ruggedness, and identifies minimizing suit pressure as key to reducing cost, schedule risk, suit complexity, and increasing reliability. Given appropriate crew acclimatization, Paragon believes that Mars One 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), as well as “prioritizing commonality over optimization” in SES development. Optimizing to reduce SES mass is likely to increase complexity and cost, however the current uncertainty in this phase of development has also driven the conservatively high spares mass. The modular nature of the SES is suited to the implementation of additive manufacturing (3D printing) however, which could substantially lower the spares mass requirement. Paragon suggests that SES subsystems could also be designed for ease of serviceability, however a substantial effort would be required to train the crew for this.  

Though Mars One intends to have eight SES systems operational by the time of the first crew landing, the logistical challenge of sending a replacement suit requires them to possess an operational lifetime at least 2.5 times longer than the spacesuits currently used on the ISS today. Paragon calculates suit maintenance will allow eight SES units to carry out 1,000 surface excursions, but will require an estimated spares/suit mass ratio of 1.69 (with a 30% mass-growth allowance) for a total mass requirement of 2,480 kg. Coupling this with the potential for material degradation due to abrasive Martian regolith and corrosion due to superoxide compounds, careful consideration will be needed to reach the target parameters given in Table 1. One of the paramount considerations is preventing airborne dust or microbial contamination of interior habitat volumes, in order to protect the equipment and crew. Care needs to be taken to ensure that the procedure of donning/doffing the SES mitigates the risk of contaminating the suit or living habitat.

Surface Exploration Suit physical characteristicsReadings from the Radiation Assessment Detector onboard NASA’s Curiosity rover indicate ionizing radiation at the level of 1.84 mSv/day during the Earth-Mars transit and 0.64 mSv/day on the surface of Mars. From this, Paragon estimates that at least the equivalent of 1150 surface excursions may be carried out by any one crew member before reaching the European Space Agency astronaut radiation career allowance of 1Sv. While research into lightweight & flexible radiation shielding for spacesuits continues, the report states that concerns about an increased risk of cancer from radiation exposure should be understood in the context of the risks inherent with this mission.

The development of a Thermal Micrometeoroid Garment (TMS) is required to meet the unique challenges of the Martian thermal environment. The SES gloves will also need to meet the environmental protection requirements of Mars while improving dexterity and durability over current designs. Other design challenges identified also include choosing between custom suits or suits in a few basic sizes that are adjustable over a smaller range, reducing overall suit stowage volume, and creating a robust integrated tracking system for crew location, rescue and recovery.

5   Conclusion and Future Work

Paragon’s SES Conceptual Design Study has identified the key design considerations necessary for the creation of the first Mars surface exploration suit. As the next step in the development of Mars One’s exploration suit engineering program, they identified the following avenues of investigation: creating a Materials Compatibility Document for the Martian environment, rear-entry suits to decrease airlock cycling, and, finally, refinement of UV and X-ray surface estimates, with definitions of common interfaces with other aspects of the mission architecture.

Minimizing suit pressure will be a specific focus for future work, reducing the development and certification anomalies experienced by many other pressure suit systems such as the current EMU. The development of the SES gloves will drive advancements of existing EVA glove technologies, while zero-G flight testing will also be required to evaluate suit mass and mobility to understand and train for the most efficient Martian surface locomotion. Finally, 3D printing offers huge potential as an alternative to bringing significant SES spare parts, as well as offering the future potential to manufacture textiles and many other suit components on Mars.

Mars One SES interior life support system
Figure 2. Mars One SES interior life support system
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