SPACEFLIGHT WITH A BOUNCE
Airbags will cushion the MER landings in 2004 as they did with the
Mars Pathfinder mission in 1997. They provide impact protection much
like the airbags in your car. But airbags for space travel are far stronger and larger. They are made of several layers of a tough,
thick material called Vectran and they undergo extensive scrutiny in a procedure called a
"drop test."
Drop tests are exactly what they sound like. A cluster of airbags with a heavy lander tucked inside is dropped to the ground. But since
the real event will happen on Mars, the tests are conducted under Mars-like conditions. They take place in a giant vacuum chamber run by
the NASA Lewis Research Center in Sandusky, Ohio. The facility allows scientists to simulate the lower air pressure found on Mars. Lower
air pressure means the bags can be filled with the same amount of gas that will be used during an actual landing. A platform of jagged
rocks lies at the bottom of the chamber where the airbags are dropped, over and over again, usually smashing into the craggy platform at
about 60 miles per hour. Scientists want to be sure that these critical shock absorbers will do their job when called upon to protect the
delicate lander and rover inside.
The airbag system was developed when NASA needed a landing method that could handle rugged terrain. Scientists and engineers went to work
on an idea that evolved from early Russian space missions. Back in the 1960s the Soviet Union used airbags to land on the Moon.
The Luna 9 landing capsule was equipped with rubber airbags.
A five-meter pole detected the moment of impact with the surface. This triggered engine cutoff and the release of the egg-shaped capsule.
The Luna 9 airbags acted as shock absorbers for the instruments that would transmit the first images ever seen from the lunar surface.
The landers for the MER mission are not shaped like an egg, but rather a tetrahedron. Their airbags are not made of rubber, but a tough
material similar to that used in bulletproof vests. Instead of a pole sensing contact with the surface, computer software monitors
altitude data that comes from a radar altimeter. The software estimates velocity and rate to determine when in the bags should be inflated.
It sends a signal that fires three gas generators to inflate the bags in less than one second. The MER landers will tumble into the world
of martian exploration with a drop, many bounces and a roll.
Web content editor/writer: Pamela R. Smith
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