Early in the next century, NASA hopes to send an unmanned probe to Mars that would return to Earth with Martian rocks--and perhaps even evidence of life. Aerospace engineer Michael Roberts, recently retired from the Johnson Space Center in Houston, has been looking for new ways to safely land such a probe, both on Mars and after the return trip to Earth. Current plans call for parachutes to slow a spacecraft’s descent. But Roberts thinks he has a better idea. Instead of dangling from a parachute, a space probe--or even a manned capsule--would sit within a new type of landing device, one without cables to tangle with, that would ensure safer landings on even the roughest terrain. The new lander’s rate of descent would also be somewhat faster than that of a parachute, decreasing the amount of drift.
Although a prototype has yet to be built and tested, Roberts is confident of the design. Four large inflatable legs arranged in a tetrahedral pattern would surround the payload capsule. Before entering Mars’ or Earth’s atmosphere, the uninflated legs would be packed tightly against the spacecraft. During descent, the legs would inflate with compressed air--similar to the workings of an automobile air bag--and tough triangular plastic sails would stretch out between them to slow the craft’s fall. Upon landing, the tetrahedron would settle on three of its legs, with the fourth extending up in the air. Each leg would have a radio beacon or a strobe light to make the lander easier to spot.
Roberts says the lander could be made as large as necessary. If it carried a two-person capsule, for example, he estimates that the lander would have to be about 40 to 50 feet in diameter when inflated. The lander’s payload capsule would be made of traditional aerospace materials such as aluminum, but the sails would be made of a high-strength polymer fiber similar to Kevlar, the material in bulletproof vests. But whereas Kevlar is stiff and sensitive to ultraviolet rays, the lander’s fiber would have to be uv-resistant and flexible enough to be repeatedly folded.
The lander could also have applications beyond space missions, says Roberts. Since the lander depends on the legs to absorb the impact of the fall, it can descend faster than a normal parachute. That makes it ideal for situations in which you need to get a team or emergency supplies down and you don’t want them hanging around in the air. NASA has patented the invention and hopes to have a prototype by the turn of the century.
