|MadSci Network: Anatomy|
Alicia, It is possible to slow bone and muscle loss in low gravity by increasing the amount of weight a person carries around with them, though doing that won't stop it altogether. The gravity on Mars is around one third of Earth's, so to make a man weigh a normal one hundred fifty pounds, the space suit would need to weigh around 450 pounds on Earth. For the Moon, where gravity is one sixth of Earth's, the suit would have to weigh 720 pounds on Earth. Current suits weigh around 250 pounds. Though making the suits heavier may seem like a good idea, there are lots of reasons to make the suits as light as possible. First, every pound of Earth weight that has to be lifted into space requires approximately fourteen pounds of fuel to get it into an Earth orbit, plus at least another seven pounds of fuel to completely escape Earth's gravity. For a crew of seven which is on the way to Mars (where the suits would have to be two hundred pounds heavier than they are now to make the astronaut weigh the same as on Earth), just getting into orbit with two hundred extra pounds of suit apiece requires another ten tons of fuel. Second, each pound of Earth weight lifted into orbit costs a lot of money: a Shuttle flight, for example, can cost up to ten thousand dollars per pound of weight carried to orbit. That extra fourteen hundred pounds of suits add fourteen million dollars to the trip. Third, there is an absolute limit on the weight a rocket can carry for any given mission. If given a choice between fourteen hundred extra pounds of space suits, fourteen hundred pounds of extra oxygen, or fourteen hundred pounds of food or water, mission designers and astronauts will opt for food, water, or air. Finally, lighter suits are easier to work in. A lighter suit is more flexible and comfortable for the astronaut to wear. A lighter suit also has less inertia than a heavier suit: even though the suit weighs less than its Earth weight, it still has all of its original mass, and its harder to start moving or to stop in a heavier suit. I hope this answers your question. Kevin
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