On May 27, NASA astronauts Bob Behnken and Doug Hurley are expected to become the first humans to ride a Dragon. The two astronauts will catch a ride to the International Space Station in SpaceX’s Crew Dragon capsule as part of the Demo-2 mission, the final test before NASA officially certifies the vehicle for human spaceflight. It will be the first time in nine years that NASA astronauts have launched to space from the US — and the only time they’ve ever flown on a commercial rocket. Engineers have spent years planning for what happens if things go awry. Here’s a look at what happens if for some unfortunate reason, something goes wrong in space: There are several events that might cause Behnken and Hurley to abort a mission once they’re already in orbit. These range from depressurization to a cabin fire, both of which have occurred on previous crewed missions. In fact, depressurization was the cause of the only deaths known to have occurred in space. In 1971, three cosmonauts returning from a mission to the Salyut 1 space station were killed after a pressure valve in the capsule failed and the cabin turned into a vacuum within seconds. The Crew Dragon has multiple lines of defense against this kind of disaster. In the event of a small leak caused by a faulty component or impact from space debris, the capsule can pump more oxygen and nitrogen into the cabin to maintain pressure until the crew either returns to Earth or arrives at the space station. But if the breach is too large to plug with more gas, Behnken and Hurley’s flight suits can be pressurized and fed oxygen, effectively turning the suits into single-occupant spacecraft. Depending on where they’re at in the mission, it’s possible they could continue on to the space station even if the cabin is a total vacuum.
“The suit is kind of like an escape system, and is designed to be used only if you’re having a very bad day,” says Garrett Reisman, a former NASA astronaut who also spent several years as the director of SpaceX’s crew operations. “It’s nice to know it’s there, but you hope you never have to use it for its intended purpose.” If NASA decides to abort a mission once Behnken and Hurley are in space, they’ll trigger the capsule to perform a deorbit burn that pushes it back into the atmosphere. At that point, drag will start to take effect and pull the spacecraft back toward terra firma. If it’s a dire situation, NASA might choose to deorbit the capsule immediately, even if it means landing in the middle of the Pacific Ocean. Otherwise, mission control will take the time to evaluate the best emergency landing location based on weather and the location of rescue teams. Behnken and Hurley have enough food, water, and oxygen for four days on orbit, so there’s no reason to rush unless the situation demands it. “More often than not, when you feel that you’re rushed, you need to slow down to avoid making a mistake and driving yourself into a difficult situation,” Scoville says.
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