Simeon A Ning and Dr. David D. Allred, Physics and Astronomy
In preparing for a manned mission to Mars, one problem that needs to be addressed is how to do servicing, building and maintenance work on Mars. This problem is related to space suit design. Past NASA explorations have used full pressure suits (FPS). These suits are well designed to provide sufficient partial pressure of oxygen for the astronauts to breathe. This allows the astronauts to survive for limited amounts of time in low pressure, oxygen-poor, cold environments. The downside is that the pressure differential created by the suit makes movement awkward and the large helmet makes visibility low. In addition FPS severely limit dexterity, adaptability, and the ability to move rapidly in and out of the living areas.
We demonstrated the difficulty of working in FPS by a site visit to the company Sprung Instant Structures located in West Valley. Their company builds instant structures similar to what we would like to set up on Mars. We rented mock FPS to wear as we performed different tasks in setting up the structure. The suits severely impeded our ability to perform even basic functions such as climbing ladders and tightening bolts (Fig.1). This difficulty would only be magnified with a real pressurized suit.
In designing a spacesuit, we needed to consider several factors. The difficulty arises in choosing an appropriate pressure level and gas composition. Ideally, the lowest possible pressure is best, because a pressure differential causes the suit to become stiff like an inflated balloon, restricting the astronaut’s movement [1]. However, if the pressure is too low, the astronauts are at risk of hypoxia. We can increase the amount of oxygen, but this is still problematic. High oxygen levels cannot be sustained for much longer than 2 week periods [1], as it is toxic for humans.
After considerable literature research we came up with an original solution to this problem. Our proposed solution is to provide the pressure externally by building a hangar on Mars which could be used to provide counter pressure. We would do this by pressurizing the hangar with the existing Martian atmosphere. If Mars’s atmosphere were compressed to a pressure greater than 30% of sea level (a factor of 50 or more) it would provide sufficient counter pressure so that an astronaut breathing from a gas mask would not require a pressurized suit. Using the Martian air instead of bringing up Earth air will save on resources and expenses. Without the need for the suit to provide pressure, a much thinner suit could be designed. This will allow the astronauts greater mobility, dexterity and visibility, ultimately increasing their ability to do work on Mars.
There all several additional benefits to using a pressurizing hangar as an area for astronauts to do work. A smaller pressure differential between the hangar and living quarters will decrease or possibly eliminate decompression time. This is a huge advantage especially on a prolonged mission where the risk of decompression sickness is great [2]. The hangar environment would also be inert because it would be compressed with Mars air, which is primarily carbon dioxide. This is advantageous in addressing the danger of flammability hazards.
Our next task was to find a solution to providing heat for astronauts in a subzero ambient environment. This problem has the additional constraint that it is desirable to keep the suits thin so that mobility is not restricted. Our solution is to use directed microwaves which could be absorbed by the material of the space suit and then heat the astronauts through conduction. Heating the astronauts directly rather than heating the empty space around them will also save on energy [3]. The microwaves will be regulated by use of electrochromic materials that are switchable in the microwave range. This means that the material can change its state from absorbing radiation of certain frequencies to reflecting it. Thus, when the astronauts get too warm the microwaves can be reflected rather than absorbed by the suit. By supplying heat in this manner, material can be kept thin.
We performed some preliminary testing on electrochromic materal using a “smart window” we received on loan from SAGE Electrochromics. We performed tests to see if the mirror would demonstrate switchable properties in the microwave region (Fig. 2). Our tests showed that the mirror behaved like a metal in the microwave region and attenuated the signal. It did not demonstrate any switchable properties. Further study revealed that this was due to the transparent coatings that are necessary in these types of smart windows. They reflect the microwaves so that they do not even reach the electrochromic material. This opens up an area for further research. Some options include: making our own electrochromic material, using a mirror with co-planar switchable links, or using material that can rotate polarization.
We presented our findings at the 2005 Mars Society Conference and our ideas were well received. Since the conference, we have been collaborating with the Mars Homestead Project, a large group at MIT. We hope that further work together will bring new ideas on this problem to prepare mankind for Mars’ exploration, and offer useful applications to problems here on earth.
References
- Paul D. Campbell, Internal Atmospheric Pressure and Composition for Planet Surface Habitats and Extravehicular Mobility Units, TX, Man-Systems Division NASA, 1991.
- Johnny Conkin, The Mars Project: Avoiding Decompression Sickness on a Distant Planet, TX, National Space Biomedical Research Institute, 2000.
- R. V. Pound, “Radiant Heat for Energy Conservation,” Science, 208, May 1980, pp. 494-495.