by 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, awaiting crews on the ground trying to figure out how to get them home safely in Boeing spacecraft. ride to orbit.
The ill-fated Starliner has two problems: its propulsion system is leaking helium and five of its thrusters have malfunctioned while docked with the space station. Mission managers were aware of the leaks before the vehicle was removed but said they were unlikely to affect the flight or the safety of the astronauts.
Over the weekend, NASA and Boeing engineers conducted an important test of the Starliner, launched by veteran astronauts Sunita Williams and Butch Wilmore on the first crewed flight of the vehicle on June 5.
The “hot fire test,” as it is known, was the second such test of the Starliner’s thrusters while it was deployed to the space station. It involved firing 27 jets of 28 capsules for bursts no longer than 1.2 seconds. Engineers on the ground assessed the performance of the thrusters one at a time and also checked the status of the helium leaks.
In a blog post published on Tuesday, NASA said the preliminary results were encouraging, and all the thrusters tested performed well.
“Both teams were very pleased with the results,” Chloe Mehring, NASA’s flight director for the Starliner mission, said in a statement.
The agency also said it had confirmed that Starliner’s propulsion system was stable and that helium leak rates did not increase in a way that could jeopardize a return trip to Earth. The helium system will be checked again before the Starliner capsule leaves the space station, according to NASA.
Wilmore and Williams were sitting inside the Starliner capsule during the hot-fire test as part of their return preparations, NASA said.
The thrusters are critical for maneuvering the spacecraft in orbit, such as when the capsule approaches the space station and when it backs away from the cavity during the undocking process.
The capsule’s reaction control thrusters are also used to guide it into the correct position before firing another set of engines to begin the trip out of orbit.
The Starliner tests entered orbit after weeks of ground work using a test engine at NASA’s White Sands Test Facility in New Mexico. The teams subjected that engine and thrusters – developed for future Starliner flights – to conditions similar to those experienced by the capsule on its way to the space station. Engineers also replicated conditions that the Starliner will experience as it detaches and prepares to re-enter the atmosphere.
In the coming days, NASA and Boeing officials will evaluate data from all the tests so far and may conduct a formal review to discuss when they will bring the capsule and its astronaut crew home.
NASA has not set a target landing date for the mission, but said there are opportunities during August.
Originally, NASA had set a 45-day time limit for Wilmore and Williams to stay in the space station due to limitations with the Starliner capsule’s batteries. But agency officials said this month that the batteries were being recharged while the spacecraft was docking, which would reduce the risk of extending the capsule’s time in orbit.
With this mission, Boeing hoped to prove that its Starliner capsule could safely transport astronauts to and from the International Space Station – a key step before NASA can authorize the company to launch routine flights to the orbital outpost. The rival company SpaceX has been transporting NASA astronauts since 2020.
The first uncrewed Starliner test flight, in 2019, also had problems and was cut short after software glitches prevented the capsule from attempting to dock with the space station. Several delays caused by fuel valve issues followed before the vehicle successfully approached the unmanned space station in 2022.
Then in the spring, the launch of the NASA astronauts was delayed twice before they took off.
Wilmore and Williams’ long stay on the space station has become increasingly crowded, but mission managers have said there are enough supplies and resources on board to accommodate them.
While awaiting their return to Earth, Williams and Wilmore are conducting science experiments and assisting with various space station duties alongside the seven crew members – four NASA astronauts and three Russian cosmonauts – already stationed there.
“This is a tough business we’re in,” Wilmore said this month in a news briefing from the space station. “Human spaceflight is not easy in any regime, and any spacecraft that’s ever been designed has had its fair share of issues, and that’s the kind of thing we do.”
This article was originally published on NBCNews.com
