Whenever the issue of "human vs robotic" space exploration comes up, someone on the robotic side mentions that humans are very messy creatures. We sweat, we shed, we lose flakes of skin, we generate heat, we create solid and liquid wastes, we require moisture and air pressure, etc, etc.
Keeping these requirements and realities in mind, which of the potential candidates below would make the best Mars explorer?
 Axel Rose |
 Jean-Luc Picard |
If you chose Jean-Luc Picard, you're right... but why? He probably has superior experience, decision-making skills, respect for authority, charisma, and verbal skills... but another great reason for sending Jean-Luc to Mars is his near-lack of facial hair.
One of the greatest challenges in habitat design will be to develop a CELSS, or Closed Environment Life Support System. One of the principles of a CELSS is that all waste is recycled into useful biological inputs. This is much harder than it sounds. In fact, a lot of development has already been undertaken in this area - the Biosphere projects are a great example. Progress is being made, but slowly. Significant problems remain, and many people doubt that we will ever be able to design and build a CELSS with 100% efficiency.
Fortunately, to reach Mars, we don't need our CELSS to be 100% efficient. We only need it to be good enough for our hearty explorers to survive their worst-case scenario on the way to Mars: if they have to use their free-return trajectory to return to Earth without landing, their habitat must keep them alive for two years. This means they need a two-year water supply, air supply, and food supply.
This isn't as bad as it sounds. Water is the heaviest of the required elements, by far. On trek to Mars, our crew requires an abundance of water anyway because water happens to also be one of the best possible shields against solar radiation (like solar flares). The amount of water aboard the spacecraft must be the greater of the amount needed by the CELSS (for a two year journey) or the radiation shielding.
Once the crew reaches Mars, however, the situation changes dramatically. Assuming the crew can obtain an external source of water, which is looking more likely every day, they hardly need a CELSS at all! The carbon dioxide atmosphere of Mars is another major resource. Given enough energy (solar or nuclear) and these simple resources, a crew can survive on Mars for a long time in a low-efficiency CELSS.
On the journey back to Earth, the CELSS becomes important again because we greatly strive to minimize the mass of the Earth Return Vehicle (ERV). Every pound of extra ERV mass, like a pound of water, requires more fuel to launch the rocket, as well as more storage volume and greater structural integrity. The trip home will probably be extremely cramped and spartan. Since no free-return trajectory is possible, a minimal six-month supply of water, air, and food will be provided, and the CELSS must keep the crew alive.
CELSS research is critical to life on Earth, as well. In fact, NASA research in this area can potentially raise the quality of drinking water in many developing nations. Space-age water recycling systems are starting to be used in Iraq to improve the quality (and lower the cost) of drinking water in remote villages.
But what about all those other waste products, like shedding hair and stuff? These will add up, though most can/will be recycled, if possible. Still, the robotics crowd is correct that the need to handle human wastes and other frailties adds cost and complexity to a human exploration system. At least they're right in the short-term.
An interesting long-term trend is slowly developing in the robotics world, however. Robotic explorers, as they become more "advanced," are also becoming more "human" in terms of their CELSS requirements. Byproducts, like heat, need to be strictly controlled to avoid wearing out bearings or contaminating the results from sensitive sensors and scientific equipment. Computational limits of artificial neural networks are pushing researchers towards biological neural networks, which would require strict environmental controls. Greater dexterity is being achieved by using materials that are more fragile under extreme conditions. As our robots become more human, the net long-term (sci-fi?) result will be robotic missions with similar CELSS requirements to human missions. If the trend continues, then robotic-only space exploration is obviously a huge, costly dead-end.
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"Now it was time to repeat the entire process, for Anna. The room was spinning madly about her, yet she felt happy and content as she slumped to the floor. All was well. Far off in the distance, someone was shouting at her, telling her to get up, trying to pull her shirt over her head. [Who is that rude person, and why is he yelling at me?] "
Chapter 1