Airbags used in the Mars Exploration Rover mission must be strong enough to cushion the spacecraft if it lands on rocks or rough terrain, while allowing it to bounce across Mars' surface at freeway speeds after landing. To add to the complexity, the airbags must inflate seconds before touchdown and deflate once the craft is safely on the ground.
Each Rover uses four airbags with six lobes each, all of which are connected. This connection is important, since it helps abate some of the landing forces by providing a damping mechanism to dissipate the impact energy. The fabric of the airbags is not attached directly to the Rover--ropes that crisscross the bags hold the fabric to the Lander, which, in turn, holds the Rover. While in flight, the bags are stowed with three gas generators that are used for inflation.
Miniature cable-type displacement sensors developed by SpaceAge Control, a sensor supplier that manufactures miniature, ruggedized alternatives to LVDTs and linear potentiometers, were used to test the airbag performance to ensure the airbag compressive stroke did not exceed its design requirements. The flexible displacement cable made for an easier installation process requiring no special fixturing.