### Re: Counteracting Atrophy in Low Gravity with Heavy Suits

Date: Fri Jul 31 13:00:33 1998
Posted By: Kevin Reed, Engineer,
Area of science: Anatomy
ID: 900435836.An
Message:
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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.

Kevin

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