56 days and counting: Two NASA astronauts are still in space as tests on Boeing capsule continue

Their high-stakes mission was supposed to last about a week — but 56 days later, two NASA astronauts are still aboard the International Space Station, waiting as teams on the ground try to figure out how to bring them home safely in the Boeing spaceship they rode to orbit.

The beleaguered Starliner capsule has two problems: its propulsion system is leaking helium and five of its thrusters malfunctioned as it was docking with the ISS. Mission managers were aware of the leaks before the vehicle lifted off, but had said they were unlikely to affect the flight or the astronauts’ safety.

Over the weekend, NASA and Boeing engineers conducted a key test of the Starliner, which launched veteran astronauts Sunita Williams and Butch Wilmore on the vehicle’s first crewed flight on June 5.

The “hot fire test,” as it is known, was the second such test of the Starliner’s thrusters while it has been docked at the space station. It involved firing 27 of the capsule’s 28 jets for bursts of no longer than 1.2 seconds. Engineers on the ground evaluated the thrusters’ performance one at a time and also checked the status of the helium leaks.

In a blog post published Tuesday, NASA said preliminary results were encouraging, with all of the tested thrusters performing well.

“Both teams were very happy with the results,” Chloe Mehring, NASA’s flight director for the Starliner mission, said in a statement.

The agency also said it had verified that the Starliner’s propulsion system was stable and that helium leak rates had not increased in a way that might jeopardize a return trip to Earth. The helium system will be checked again before the Starliner capsule undocks from the space station, according to NASA.

Wilmore and Williams were seated inside the Starliner capsule during the hot fire test as part of their return preparations, NASA said.

The thrusters are crucial for maneuvering the spacecraft in orbit, such as when the capsule approaches the space station and when it backs away from the outpost during the undocking process.

The capsule's reaction control thrusters are also used to guide it into proper position before a different set of engines is fired to begin the journey out of orbit.