MARSSKIN: A MECHANICAL COUNTER PRESSURE MARS ANALOGUE SPACE SUIT
James Waldie, B.Eng, B.Bus1; David Wisely, B.Eng, B.S.2; Daniel Ischia, B.Eng3; Brett Harvey4.
1. Department of Aerospace Engineering, RMIT University, Victoria, Australia;
2. Current Consulting, Melbourne, Australia; 3. Boeing Australia, Fishermans Bend, Victoria, Australia; 4. Dick Smith Electronics, Glen Waverly, Victoria, Australia
In an effort to study field operations for a manned landing on Mars, Mars Society Australia plans to establish a research station in Australia (in addition to those already functioning in Canada and the USA) which will simulate the habitat, equipment and landscape of the predicted mission. Space suits, therefore, must be provided in each habitat to create a realistic mimicry of Martian exploration during simulated extravehicular activity (EVA). The aim of the suits is threefold: first, to restrict the physical capabilities of the astronaut inline with that predicted of an actual suit on Mars; second, to provide the astronaut with capabilities a Mars suit would posses (such as communications and data logging hardware); and third, to study the most effective means of communication, and recording and storing collected data.
Project MarsSkin, Mars Society of Australia’s analogue suit project, is based on an experimental mechanical counter pressure (MCP) suit. This is due to the myriad benefits of MCP over existing suits and the renewed interest in MCP development; it is therefore possible that future Mars explorers will wear MCP suits. A MCP based analogue suit will also be more realistic in terms of rigidity than current analogue suits.
Project MarsSkin comprises three technical groups. The Helmet group is responsible for designing and fabricating the helmet shell in addition to incorporating ancillary items (such as lights and microphones) and enhanced vision and spatial recognition systems. The PULSS group is tasked with producing basic hardware and software for EVA operations (such as communications, cooling system and data logger) with an appropriate load carriage system. The Layers group aims to produce form-fitting MCP and dust layers to simulate current MCP garments.
Mars-Oz is an ambitious plan by the Mars Society of Australia (MSA) to mimic the scenario of a manned landing on the red planet. As such, it will function as a laboratory to study how humans will live and work on Mars. This requires simulating the hardware and equipment of such a mission, but also establishing the base in a geologically similar environment. The best location for Mars-Oz has been determined by the Jarntimarra expedition to be Arkaroola in the South Australian Outback.
The Mars-Oz complex is shown in Figure 1. The core components of the analogue base are the habitat and cargo module (based on the horizontal lander architecture), but it also includes features such as a solar-farm and greenhouses. The concept drawing also shows the Human Operations Prototype (HOP), a Mars rover.
FIGURE 1 - the Mars-Oz facility concept (Jozef Michalek)
During a Mars mission, any excursion outside to the surface (also called extravehicular activity, or EVA) would require a space suit due to the low pressure and extremely low level of oxygen characteristics of the atmosphere. For Mars-Oz, analogue space suits are being created through Project MarsSkin which has 3 goals to fulfil in order to be an integral part of the Mars-Oz infrastructure:
CURRENT MARS ANALOGUE SUITS
Several space suits have been created in order to provide a simulation as to what an actual Mars space suit may be like to wear. They include those developed by the Rocky Mountain Mars Society (USA) and also Hamilton Sundstrand for the Flashline Mars Arctic Research Station on Devon Island (Figure 2).
In actual space suits, the breathing gas is used to pressurise the entire suit: in this way, both pressure and oxygen is effectively supplied to the astronaut. Essentially, an actual suit is a bulky, multi-layered air-tight anthropomorphic balloon inflated with oxygen. Analogue space suits mimic the exotic combination of materials necessary for this modality of suit pressurisation with thick canvas garments (Figure 3).
However, such analogue suits fail to reproduce the actual rigidity of true suits. Whether on-orbit or on the moon (or on the surface of Mars), the minimum pressure inside the suit (about 0.3 bar) is much greater than that outside. The consequence of this pressure differentiation causes the suit to inflate into a taut, neutral position, severely restricting astronaut mobility (especially in the hands). This effect is similar to that observed by pumping up a football: when flat (i.e. the pressure inside the ball is the same as the outside), the leather casing is soft and malleable; when inflated (i.e. the pressure inside the ball is higher than the pressure outside), the leather becomes stiff and inflexible. The rigidity of space suits is well documented in the literature and proved to be significant concern during the Apollo missions, Apollo 17 astronaut Gene Cernan commenting that the suit became as stiff as a cast on a broken arm . Development on the suits has focused on glove mobility since the lunar missions, however little advance has been made. Indeed, current (and flawed) solutions to this problem now centre around mechanically actuated exterior exoskeletons [6,8].
While Mars has a tenuous atmosphere (about 0.01 bar), the pressure difference between the interior and exterior of a gas-pressurised suit would still produce a bulky stiff shell around the astronaut. To recreate this effect on Earth, a simulation suit would need to be inflated to about 1.3 bar. This is easy to do with a air-tight and sealed suit in the static condition, but such suits are difficult to engineer and requires substantial lengths of piping in order to provide pressure on a long traverse EVA.
To create an analogue suit appear realistic, the Mars Society analogue suits are designed to resemble the Apollo mission suits. This is driven by public perception of what a space suit should look like. The major elements of the Apollo suits (the large, boxy backpack and white, ‘Michelin Man’ appearance) are therefore carried over. Current analogue suits, then, successfully simulate the bulky nature and appearance of gas-pressurised suits. However, the rigidity of gas-pressurised suits proved to be a significant hindrance to exploration on the moon, continues to dog current EVAs (when only the gloves need to be flexible!), and will certainly effect the function of future Mars explorers (if such suits are worn). As current analogue suits fail to mimic this crucial stiffness, the validity of the suits is reduced.
Project MarsSkin began in November 2000 with the aim of supplying analogue space suits for Mars-Oz. To differentiate the Australian MarsSkin suits with other analogue suits, it was decided to simulate an experimental form of space suit based on mechanical counter pressure (MCP). MCP suits produce pressure on the body by tight, form-fitting elastics except for the head which is pressurised in a conventional helmet with the breathing oxygen. MCP suits are inherently more flexible, light and safe than conventional suits, and are currently the focus of renewed research and development through Honeywell, NASA, UCSD, Clemson University, MIT and others. The concept and early experiments of a MCP suit were published by Webb , and the first demonstration that highlighted the many advantages of the MCP approach was described by Annis & Webb  (Figure 4). MCP suits and their numerous benefits over gas-pressurised garments in the Mars context are discussed in detail in Waldie .
While MCP suits offer a technology which may be used in the eventual exploration of Mars, there are further benefits to Project MarsSkin in that MCP is easily simulated. Unlike gas-pressurised suits, MCP suits do not stiffen or change characteristically according to interior and/or exterior pressure: the tight elastics maintain constant compression irrespective of the ambient environment, and therefore flexibility remains stagnant .
FIGURE 4 - Early MCP suit. Note the form-fitting design.
While other analogue suits were designed to appear like those of the present and past, MarsSkin suits are designed to look like a MCP suit of the future. This increases the analogue verisimilitude of the suits and therefore Mars-Oz. In essence, though, the suits must still satisfy the premise of being unquestionably ‘a space suit’ to the general public.
Project MarsSkin is branched into four distinct groups:
The Management group is based in Melbourne and comprises James Waldie as Project Leader, Jennifer Laing as PR Director and Guy Murphy (MSA President). This group is tasked with liasing the progress of MarsSkin to the MSA board, co-ordinating the activities of the three other groups, and acquiring funds and sponsorship.
The helmet is essentially a clear dome and backing structure with several ancillary items/systems attached either on the exterior surface or interior. The group, based in Sydney, is led by Michael West (MSA NSW Co-ordinator), and is comprised of undergraduate students from the University of Sydney, Dr. Craig Jin (augmented reality and spatial audio) and Teewoon Tan (image recognition).
The Personal Utility Life Support System (PULSS) is, in other words, the container(s) and the systems therein which support and augment life and the mission during extravehicular activity (EVA). This group is tasked with the design, construction and testing of the PULSS. The members of this Melbourne group include Mark Abela (from Boeing Australia), Brett Harvey (Dick Smith Electronics), Daniel Ischia (Boeing Australia) and David Wisely (Current Consulting).
The Layers group aims to create a system of garments which closely approximates that predicted of an actual Mars MCP suit. This includes the materials for the suit itself, plus the gloves and boots. The group members include James Waldie and Jozef Michalek.
FIGURE 5 - Project MarsSkin logo
DESIGN GOALS AND PROGRESS
The development of the helmet for AMEC 2002 is documented in . Development by the PULSS and Layers groups are documented below.
PULSS - Data Logger
During an EVA on Mars it is imperative that all relevant data is efficiently recorded. Such data could include photos, location (GPS) and heading/elevation, a verbal description by the astronaut, and also sample collection. It is also imperative that this data be communicated either real-time or downloaded at the end of the excursion. For Project MarsSkin, it is proposed that a PC based system with microphone, GPS and web cam hardware could simulate such a data logger. Upon reaching a site, the analogue astronaut could press a ‘new site’ button, and the system automatically record the varied details of the site into an integrated data collection file. It is also proposed that analogue communications between astronauts and the astronauts and the habitat be accomplished by wireless LAN links instead of CB radios. If so, then the details of the EVA could be broadcast back to the habitat in real-time. Further, using internet hardware established in the habitat, it would be possible for anyone in the world to follow along (and indeed interact) with the EVA astronaut via the world-wide-web. Of course, the distances involved in an actual Mars landing would preclude this opportunity, but such publicity would undoubtedly be beneficial to MSA.
The development of the data logger is being carried out by various Mars Societies in the US and Canada, and it is proposed to swap some data loggers with some of our suits at a later stage.
PULSS - Load Carriage System
The big, bulky and boxy design of current life support system backpacks does not distribute mass effectively over the torso. Indeed, even in the 0.17 gravity of the moon, the weight of the backpack caused an abnormal gait and hopping motion during locomotion . A more efficient method (as adopted by almost every army of the world) is to distribute load via webbing as evenly as possible over the body. The design for the PULSS backpack is therefore to reduce the bulk of the backpack to a minimum (while still remaining viable in terms of simulated oxygen storage volume), while carrying other items (such as elements of the data logger, cooling, drinks etc) on webbing and vests over the chest and abdomen. Furthermore, the load is carried in a more flexible manner rather than on a stiff full-back mount: this will provide better flexibility for the astronaut. For AMEC 2002, a backpack has been constructed as an exercise in creating a visual forecast of what the backpack may resemble. As it is not designed to carry any load at all (such as the data logger), the construction is very simple: thermos cores are used to simulate oxygen canisters, while flexible hose is used to mimic valve and pipe-integration equipment. A simple chest pack has also been constructed as a prefix to a full webbing design.
The Honeywell MCP suit concept (Figure 6) is seen as a design benchmark for the appearance of the MarsSkin suit and outer layers. Waldie  stipulates that a likely MCP suit would comprise of two layers: the MCP form-fitting layer and a dust layer. The first aim then is to simulate the MCP layer – this is best achieved by long sleeved and long legged thermal underwear. The garments by Wilderness Wear Australia are made of polypropylene and quickly wick sweat away from the skin. In this manner, it copies the porous nature of actual MCP garments . The material also has high resistance to all mechanical stresses such as rubbing, stretching and tearing which is desired for the active exploration of the Arkaroola terrain.
The next and outer layer is the dust layer, a shell designed (on Mars) to protect the MCP layer from damage, mild radiation and temperature extremes. For Mars-Oz it will perform a similar role in protecting from dust and allowing cool air to circulate around the body between itself and the MCP layer. The jackets are again from Wilderness Wear and are made from Microlite, a durable, waterproof, windproof garment which is again breathable, allowing sweat and moisture to escape and simulating the possible cooling of an actual Mars suit. The jacket and pants are in Navy to form a matching ‘uniform’.
A big benefit of MCP is that standard boots could be worn on Mars as the MCP layer is no thicker than a pair of socks. The boots are AKU Trails and are matched in colour to the outer dust layer. The gloves are perhaps the most important element of the suit to accurately mimic as the hands carry out a large portion of the astronauts desired functionality. Powerstretch gloves from Mountain Hardwear are used to simulate MCP gloves. Again, the material is breathable through a first layer of polyester, while a durable nylon second layer is wind and abrasion resistant. Importantly, the gloves feature a 4-way stretch system, and is similar in thickness to current MCP materials, and so resistance to movement and tactility is very close to the real thing.
FIGURE 6 - Honeywell MCP suit concept
Our thanks go to Bill Oakley of Snowgum, Victoria, for his help in sourcing relevant materials and garments. Thanks also to PR Director Jennifer Laing for a successful ‘Star Wars’ fundraising movie night – much enjoyed! Also, thanks to Michael West for leading the Helmet group with such class.
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