Whenever Mars exploration is discussed in the media, you'll often hear an assumption that sounds something like this: We can't send human explorers to Mars because the human body wasn't built to endure long periods in Zero-Gravity. The astronauts wouldn't survive the six-month journey, or they would be too weak to do any exploring once they reached Mars. Until NASA conducts decades of research on the International Space Station (ISS) and invests billions of dollars to cure the miriad of Zero-G side affects, human exploration of the solar system is dangerously reckless.
As myths go, this one has achieved legendary status, perhaps because it's mostly true. Past research on ISS has indeed chronicled some of the serious effects of Zero-G on the human physiology... including muscle atrophy, bone loss, and possible reduction in medicine effectiveness. Also, traveling to Mars would require a journey of about six months. And it's completely true that subjecting astronauts to six months of Zero-G, then the stresses of a high-G landing, then two years of isolation far away from adequate medical attention, then another six months of zero-G on the return leg of the trip is dangerously reckless - it's almost a guarantee of mission failure and loss-of-life.
How can we solve these problems? Well, we can't... not yet, anyway. Sometimes, however, the best way to solve a tough problem is to avoid it in the first place. If Zero-G has such disasterous effects on the human body, perhaps we shouldn't travel to Mars in Zero-G !! (Duh)
Mike Griffin, the new NASA administrator, is wise to this myth. Here's a quote from testimony he delivered to the House Science Committee in 2003:
"The most practical long-term microgravity countermeasure may well be to design our spaceships to supply artificial gravity by spinning them to generate a centrifugal force."
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On a six-month journey to Mars, there's plenty of time and incentive to spin the spacecraft, thereby simulating a modest amount of artificial gravity. If one designs the mission and the spacecraft with this in mind, the engineering obstacles should be mostly minor ones. A long, strong tether (cable) mesh is needed, along with a counterbalance - the engines and expended fuel tanks of the third rocket stage would do nicely. |
Note that on the return leg of the trip, artificial gravity would not be as useful. Astronauts have already survived six-months of Zero-G in orbit on ISS. Once they return to Earth, they would receive immediate medical attention and eventually return to full health. A returning Mars crew could expect the best medical care that the Earth can provide.
Traveling to Mars with artificial gravity also bypasses a serious issue with spaceship design: building a crew compartment that is fully functional in both Zero-G and Mars-G. Liquids behave differently in Zero-G. Air circulates differently. Storage volume requirements vary. Handholds are required in different places. The daunting list of internal habitat concerns goes on and on. While we've designed Zero-G habitats before (on ISS, Apollo, and other vehicles), we've never designed a dual-use habitat. Sending the simplest-possible habitat to Mars is a great way to reduce the cost, complexity, and single-points-of-failure of the mission.
Unfortunately, we've never built a fully functional, tethered artificial gravity system before, either. Research is needed in this area... but a few jaunts into Low-Earth-Orbit should suffice to work the bugs out. It's also possible that a reduced amount of gravity isn't sufficient to completely ward off the dehabilitation effects of Zero-G.
NASA has recently funded an artificial gravity study that uses bedrest to simulate a zero-G environment and a centrifuge to simulate a high-G environment. Apparently, subjects will alternate between the two, each day. The goal of this study is to learn... well, I have no idea! The whole scenario doesn't seem to address any real-world issue like the lack of knowledge about partial-G effects on human physiology. It sounds like a disguise for more zero-G research. If anyone out there can educate me about what I'm missing, please do so!
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The Mars Society has proposed a TransLife Project that would send a crew of mice into Low-Earth-Orbit in a spinning habitat. Currently, this project is being funded by NASA and developed at three universities (MIT, Washington, and Queensland). If successfully launched in 2006, we should soon know much more about the engineering of spinning-spacecraft habitats, as well as the effects of reduced gravity on mouse-physiology. |
Stay tuned for more exciting developments!!
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"David laughed. Ben and Cassie both knew about his position within the ultra-secretive Mars movement. He had only held the job for six months, and as far as he was aware, no other outsiders even suspected his involvement. "Me, a terrorist? Very funny." "
Chapter 2