Update July 2nd, 7:35AM ET: The abort test appeared to work as intended, with all three motors firing in the sky and the Orion test capsule slamming into the water. Now NASA will try to collect the boxes of data the capsule jettisoned during the test to determine how well the vehicle held up.

Original story: On Tuesday morning NASA will test its new deep-space crew capsule to see if the vehicle can keep people safe during a botched launch. The agency will activate a special emergency system on the capsule designed to carry the vehicle away from a malfunctioning rocket, to safety. If all goes well, it’ll show that the capsule is ready for flight and pave the way for its first mission to space within the next couple of years.

The crew capsule enduring the test is NASA’s Orion, a key spacecraft the agency has been developing to send crews of four into deep space. Orion is designed to launch on top of a rocket NASA has also been developing called the Space Launch System, or SLS. Together, the spacecraft are meant to transport people to the vicinity of the Moon, all part of NASA’s newly minted Artemis program to return humans to the lunar surface.

But before astronauts are frolicking in Moon dust again, the Orion and SLS need to fly together for the first time. Their inaugural voyage will be an uncrewed mission around the Moon called Artemis 1. And Tuesday’s test is the last big milestone that Orion must pass before Artemis 1 can take place.

The test will be checking out Orion’s “Launch Abort System,” a special setup that’s supposed to kick in mid-flight in case of an emergency. It looks like a tower that’s stacked on top of Orion whenever the vehicle launches on the SLS. Within the tower are three different motors that all work in tandem to rapidly rip the Orion away from the SLS during flight if the rocket starts to misbehave. The motors will transport the Orion to a minimum safe distance away — typically several miles away — where the capsule’s parachutes can safely deploy and gently lower the vehicle to the ground.

“After the Columbia accident, NASA specified that the next human system needed to be 10 times safer on launch than the Shuttle was,” Mike Hawes, the Orion program manager at Lockheed Martin, which is building the capsule, tells The Verge. “And the way we do that with Orion is with this style of launch abort system.” SpaceX and Boeing’s crew capsules will use a similar system in times of an emergency during flights to the International Space Station.

Lockheed Martin already tested an early version of the abort system once before at White Sands Missile Range in New Mexico, but that test was performed on the ground. NASA wants to see how this system performs in the air, which is why the agency will be sending Orion up to 31,000 feet for the exam. The capsule will launch from NASA’s Kennedy Space Center in Florida on top of a special rocket booster provided by Northrop Grumman that will propel the capsule to more than 1,000 miles per hour.

About 55 seconds after launch, the first of the tower’s three motors will start up, pulling Orion away from the booster. At that moment, the capsule will be feeling the highest forces from atmospheric pressure and intense temperatures. “It’s really a test of how well the system operates in its highest stress environment,” says Hawes.

The motor firing is so intense that the capsule will reach up to 7 Gs, or seven times Earth’s gravity. Future astronauts will need to be prepared for this sudden explosion of gravity, but they won’t feel it for long. “The 7 Gs is what’s going to get your attention the quickest, because it happens very quickly,” Randy Bresnik, a NASA astronaut explained during a press conference. “But it’s a short duration.” For comparison, the Russian Soyuz capsule that astronauts currently use to travel to and from the International Space Station can reach above 5 Gs during the descent to Earth.

Once the capsule is separated, the second motors will fire, steering Orion through the air and reorienting it in the direction it needs to go. At this point, the extra Gs begin to subside. Once the system is well enough away from the booster, the third and final motor fires, releasing the Orion from the tower and dropping it to the ground. During this part of the abort, normally Orion would deploy its parachutes to lower itself down gently into the ocean. But for this test, NASA opted to not add parachutes to make the test less complex and less expensive. That means the capsule is going to slam into the Atlantic at 300 miles per hour once the test is over.

All in all, the entire procedure will last just three minutes. The capsule will have a lot of sensors on board to gather data from the flight and let Lockheed Martin know how the vehicle performed. Before Orion hits the ocean, the capsule will eject boxes containing the flight data so that the company can more easily collect them in the water.

After this test is over, the abort system might never see action. “The full abort sequence — which we actually hope to not have to use ever again — is only if there is a problem with the booster,” Hawes says. Signals from the booster, indicating some kind of malfunction, can initiate the system in fractions of a second. The crew can also initiate the system if they notice the rocket is deviating from its planned course. But if it’s a smooth flight, the system will stay quiet.

Once this test is over, Orion’s next big mission will be Artemis 1. That flight is currently planned for summer of 2020, though a recent audit from the Government Accountability Office claims the mission will mostly likely take place as late as June 2021, due to schedule delays from SLS development. Lockheed Martin still has a lot of testing to do before the flight can take place, but Hawes says the company is adding the finishing touches to the crew capsule that will be used for Artemis 1. They plan to hand the capsule to the NASA ground crew by the end of the year. “We’re pretty much all but headed toward the Artemis 1 mission,” says Hawes.

NASA has a four-hour launch window for the abort test on Tuesday, which opens at 7AM ET. The agency plans to stream the whole thing live starting at 6:40AM ET, so check back then and stay tuned to watch a very fast three-minute test in the skies above Florida.