Manned Mission to Mars. Interest grows in an international effort to send humans to Mars early in 21st century
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There is, however, a great deal of technology to be developed and much to be learned about living in space before the world is ready to reach out for Mars. Indeed, all preliminary thinking about manned Mars missions starts with the assumption that permanent space stations have already been established and are part of the working infrastructure of global commerce.Skip to next paragraph
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John Niehoff of Science Applications International Corporation in Chicago says that, given this assumption, a study he made for the Planetary Society suggests that an initial Mars mission would cost about $25 billion to $30 billion in today's costs. For comparison, he quotes estimates made at the NASA Marshall Space Flight Center in Huntsville, Ala., that suggest it would cost $20 billion to $25 billion in inflation-adjusted dollars to launch a single Apollo moon flight. Peak funding for a $30-billion M ars mission, spread over several years, would be about $5 billion in the most expensive year, Mr. Niehoff says. Shared internationally, this should be a manageable expense. Mission studies beginning
It's hard to predict in any detail just what a Mars flight would involve. American mission studies have only just begun again, having been abandoned when the Apollo program wound down. Soviet studies probably are no more advanced, according to Friedman, who has reviewed the Soviet Mars program.
According to Niehoff, mission designers have to balance three critical factors -- round-trip time, staying time at Mars, and the fuel energy required. The traditional approach, which needs the least fuel, is to head for Mars when it is in conjunction on the opposite side of the Sun from Earth. This involves a nine-month trip out to the planet, more than a year and a half at Mars, and a six- to nine-month return. Niehoff observes that, while this may save fuel, staying that long at Mars would be daunting . Twin spaceships
There are faster ways to do it. For example, two space ships could be launched 30 days apart. When the first one reached Mars, the crew would descend to the planet's surface in a transfer vehicle. Thirty days later, it would rendezvous with the second ship, which would then continue on in its solar orbit until it had come back to Earth. The advantage of such a scheme is that the heavy mother ship does not have to slow down and park in a Martian orbit and then be relaunched toward Earth. Niehoff sa ys this plan saves fuel, shortens mission time, and is compatible with current technology.
These and other mission profiles being studied assume there are no unusual human needs that would be costly to meet. In particular, they do not provide for artificial gravity or heavy shielding against cosmic radiation. Yet these two measures may turn out to be necessities, explains John Billingham, chief of the life sciences division at the NASA Ames Research Center.
American and Soviet experience shows that weightlessness produces a 10 percent bone loss for for every eight months in space. There are losses of blood volume and muscle protein as well. No one yet knows whether these losses continue indefinitely or eventually level off in space, Dr. Billingham says. No one knows how serious the central nervous system adaptation to weightless, as evidenced by the frequent astronaut-cosmonaut ``space sickness,'' may be. If there is a critical biomedical danger that canno t be countered by exercise, diet, or medication, then artificial gravity will have to be provided, Billingham says.
That could be awkward and expensive. The only known practical way to do it is to spin the spacecraft to create a centrifugal force. The crew could only cope with very slow rotation, say one to two revolutions a minute. That, Billingham says, would require a large radius to simulate a significant fraction of Earth gravity. The ship might wind up as a dumbbell-like structure with two capsules at the ends of a long connecting tube. This would be a much more costly and more difficult design than usually is contemplated. Danger from cosmic rays