mars_airbags_000707 WASHINGTON -- Just follow the bouncing ball if you want to safely land on Mars.
A cocoon of airbags was successfully used on the U.S. Mars Pathfinder spacecraft in 1997: After rolling to a stop, the airbags deflated and the lander station released the Sojourner mini-rover that trekked over Martian hill and dale.
Now, airbag landing systems for Mars are set to make a rebound. Not only are they being eyed here in the United States, but in Europe as well.
NASA decides later this month whether a Mars science orbiter or a lander spacecraft gets an agency green light for launch in 2003.
Mars Pathfinder images show airbags to be the saving grace of the mission.
If a Mars lander is the mission of choice, a 286-pound (130-kilogram) rover is to be cushioned on touchdown by airbags, similar to the system flown on Mars Pathfinder.
This time, however, the rover is the only on-duty science officer. A four-petal, self-righting enclosure that deploys the rover to the surface -- like that on the
Mars Pathfinder mission -- won't act as a science or relay support station.No tinkering
Technology company ILC Dover, Inc., based in Frederica, Delaware, is up to their pressure gauges building Mars-bound airbags. ILC created the Mars Pathfinder inflatable-airbag landing system. The firm has now been tasked by the Jet Propulsion Laboratory (JPL) in Pasadena, California to work on airbags for the possible 2003 Mars lander mission, said Mark Grahne, business development manager for the company.
~
"From the standpoint of the technology, using airbags on
the 2003 mission is not part of any go/no-go decision. They are not considered a critical path for the lander concept. If they give us a go-ahead in July, there's ample time to get them ready more time than there was for Pathfinder," Grahne told SPACE.com. 
"Mars Pathfinder opened the eyes of people, just like when the sound barrier was broken."
One goal for the Mars 2003 lander is to reduce the mission's risk factor. Doing so means not tinkering with the already-proven Mars Pathfinder landing design, Grahne said.
Rack 'em up
ILC is relying on JPL's expertise in detailing what future Mars landing sites may be like, particularly the kind of rock distribution that the airbags might encounter. No firm decision has been made as to where the next U.S. Mars lander will be targeted, however.
Copying the Mars Pathfinder airbag system means a Mars 2003 lander would use four independent air bags. Each air bag consists of six intersecting spheres.
The basic airbag geometry takes on the appearance of a huge "billiard rack" of game balls, said David Cadogan, ILC senior design engineer. The woven airbag fabric is Vectran, a liquid crystal polymer fiber. This fabric has a very high strength, similar to Kevlar used in making bulletproof vests, he said.
Once the spacecraft plows through the Martian atmosphere, and after release from parachute, the gaggle of airbags are inflated by gas generators within 1.5 seconds.
The airbags themselves are made of multiple layers of Vectran so they can survive the initial impact with Mars, followed by numerous rough and tumble bounces across the planet's rocky surface.
On the rocks
Before the success of Mars Pathfinder on July 4, 1997, using airbags to crash land sensitive science gear and
a rover on Mars was a hard swallow for lots of space engineers."Here at the company, we've always had confidence in airbag technology. The skeptics were typically just not familiar with the technology, so they were scared because it was an unknown to them," Cadogan said. "The airbags worked perfectly," he said.
Extensive tests of the Mars Pathfinder airbags were done at ILC and at NASA's Plum Brook Station, part of the Glenn Research Center in Cleveland, Ohio. Numerous airbag drops were done under simulated Martian conditions.
Airbags, like the ones used on the Mars Pathfinder mission, are set to make a rebound.
Vertical drops of the airbags, some onto angled platforms loaded with desert counterparts to "Mars rocks", helped to evaluate the landing system, Cadogan said.
~
"Mars Pathfinder opened the eyes of people, just like when the sound barrier was broken," Cadogan said.
Sudden impact
Cadogan and Grahne of ILC Dover said airbags can be ready for the Mars 2003 launch opportunity.
Furthermore, ILC has begun work with engineers putting together the
British-led Beagle 2, a lander to be deployed by the European Space Agency's Mars Express spacecraft, Cadogan said. That European mission heads for Mars in 2003 as well.A modified airbag landing system is also being discussed for a U.S. Mars lander in 2005, Grahne said.
Until selected landing sites are better mapped, airbags appear to add a cushion of safety to overcome risks presented by uncharted and potentially treacherous territory.
"There was a lot of uncertainty about whether the airbags would work," said Brian Muirhead, JPL's Mars Pathfinder project manager. "But the biggest uncertainty is associated with the terrain," he said.
Muirhead said that if a spacecraft heading to places with unknown terrain, "then the airbags are the right technology."
By keeping airbag speed under control prior to impact on Mars, "I think the airbags are capable of going a lot of places no other system can go, at least right now," Muirhead said.
advertisement
