Should the astronauts living on the International Space Station (ISS) ever need to evacuate, the plan is that they will be able to board the station’s resident escape spacecraft, which will then take them back to Earth. That escape craft, called Orion, is currently under construction. Like the Apollo spacecraft that it resembles, Orion is intended to land at sea. If it should happen to come down on the land, however... well, those astronauts could be in for a rough landing. With that in mind, a graduate student in MIT’s Department of Aeronautics and Astronautics is developing an air bag system to cushion Orion’s occupants in the event of a dry landing. The system, interestingly enough, was inspired by the structure of seeds.
NASA originally proposed a 499 kg. (1,100 lb.) shock-mounted rigid structure upon which the astronauts’ seats would be mounted, but decided the system would be too heavy for dry landings. MIT student Sydney Do, however, came up with a smaller, lighter alternative: a reusable, 317.5 kg. (700 lb.) air bag system that could inflate during launch and landing, deflate for storage purposes, and partially inflate to provide seating while the vehicle is in space. His system is also purely mechanical, so it wouldn’t be subject to the whims of buggy or misinformed computers.
The origins of the system date back to 2008, when NASA astronaut Charlie Camarda helped students from MIT and Penn State explore how the physics of seeds could be applied to engineering principles. In the case of Do’s air bag system, each astronaut is surrounded in an individual “cushion of air,” just as protective fluid surrounds the embryo in a seed.
Unlike car air bags, which inflate upon impact, Orion’s air bags would already be inflated when the spacecraft hit the ground. The challenge with which Do and his colleagues were presented was one of figuring out the rate at which the gas should be able to vent from the bags. If it vented too fast, or if there wasn’t enough in there in the first place, the force of the landing would send the astronauts and their seats right through the bags and allow them to impact with the ground. If the gas couldn’t be displaced quickly enough, however, the downward kinetic force of the astronaut would compress the gas molecules within the bag, turning it into a spring that could actually rebound them up into Orion’s ceiling.
In order to avoid either of these scenarios, Do and his MIT team designed release valves that open at low pressure. These would allow the gas to keep the seat from hitting the ground on the initial impact, but would also have vented the gas as soon as Orion’s floor came to rest.
Utilizing computer models, Do now has a working prototype of his system, which consists of a seat equipped with four air bags, each one of which features two release valves about 15 cm. (6 in.) wide. He constructed the bags from vectran, a high-strength material that was used to cushion the landings of several of the Mars rovers. His prototype has been successfully put through dozens of dummy-equipped drop tests, from heights of up to three meters (ten feet). He is presently reviewing the test data, before presenting his final design to NASA this fall.
Orion was originally supposed to transport humans to the moon as part of NASA’s Constellation program, but that program was scrapped this February. Even if the spacecraft never even makes it as far as the space station, Do hopes that his system can be used in similar capsule-type space vehicles.
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