This week, SpaceX successfully tested the engines it will use in its Crew Dragon, the spacecraft it's building to transport NASA astronauts to the International Space Station. The engines, called SuperDracos, were fired up 27 times at the company's test stand in McGregor, Texas. The SuperDracos are meant to help to carry the spacecraft to safety in case something goes wrong during launch.

SpaceX is building the Crew Dragon for NASA through the agency's Commercial Crew Program, which tasks private companies with shuttling astronauts to and from the ISS. The Crew Dragon, which can hold up to seven passengers, is designed to travel to the station on top of a Falcon 9 rocket. SpaceX has successfully flown its Falcon 9 to the ISS many times before, but sometimes accidents happen. This past June, for example, one of the company's rockets exploded en route to space. If a Falcon 9 were to explode during launch with people on board, both NASA and SpaceX want to make sure the astronauts can escape the rocket as quickly as possible.

That's where the SuperDracos come in. Four pairs of these engines will be embedded inside the walls of the Crew Dragon. If a launch turns dangerous at any point — either on the launchpad or during the rocket's ascent — the SuperDracos will fire up and rapidly propel the Crew Dragon away from the rocket. When fired together, the eight SuperDracos create 120,000 pounds of thrust — which takes the Crew Dragon from zero to 100 mph (160 kilometers per hour) in 1.2 seconds. Once the spacecraft is at a safe distance, its parachutes will deploy and land the crew gently in the ocean.

SpaceX successfully demonstrated part of this capability in May during a pad abort test. A test-version of the Crew Dragon fired up its SuperDraco engines on a mock launch pad at Cape Canaveral Air Force Station in Florida. The engines carried the spacecraft up and away from the facility, reaching a top speed of 345 mph (555 kilometers per hour). The Crew Dragon then gently splashed down in the Atlantic Ocean 1.4 miles away from the launch site.

For now, the SuperDracos will only be used during emergencies, but SpaceX eventually plans to use the engines to land the Dragon capsule safely on flat ground. To do this, SpaceX will turn on the engines during the spacecraft's descent to Earth, and then reduce their thrust. This will allow the Crew Dragon to slowly lower itself down to the surface — a technique known as propulsive landing. However, SpaceX hasn't said when it plans to use propulsive landings, and will be sticking with ocean parachute landings for now.

So that means the SuperDracos won't have much to do during missions — if all goes well.