Boeing’s Starliner capsule returns to Earth is on hold for an indefinite period while awaiting the results of new propellant tests and the ongoing analysis of helium leaks that appeared during the spacecraft’s rendezvous with the International Space Station, NASA announced Friday.
But agency officials have insisted that Starliner commander Barry “Butch” Wilmore and co-pilot Sunita Williams are not “stranded” in space.
NASA
“We haven’t set a landing date yet,” Steve Stich, manager of NASA’s commercial crew program, told reporters in a conference call. “We are not going to set a specific date until we have completed these tests. »
“So it’s basically completing the testing, completing the fault tree, getting that analysis back to the mission management team, and then doing an agency-level review. Then we’ll work out the rest of the plan, from undocking to landing. I think we are on the right track. »
THE problem for NASA and Boeing is that the Starliner’s service module, which houses the helium lines, thrusters and other critical systems, is discarded before reentry and burns up in the atmosphere.
Engineers won’t be able to study the hardware after the fact, and so they’ll want to collect as much data as possible before Wilmore and Williams return home.
But the crew’s repeated extended stays at the space station as that analysis continued has prompted some observers to say that Wilmore and Williams are stuck in orbit, an impression that appears to have taken root in the absence of updates from NASA as the planned landing date has been repeatedly pushed back.
Stich and Mark Nappi, director of Boeing’s Starliner program, said that description was a mischaracterization.
“It’s quite painful to read what’s going around,” Nappi said. “We have had a very good test flight… and it is perceived rather negatively. We are not stuck on the ISS. The crew is in no danger and there is no increased risk when we let’s decide to bring Suni and Butch back to earth.”
Stich added that he wanted to “make it very clear that Butch and Suni are not stuck in space. Our plan is to continue to bring them back on Starliner and get them home at the right time. We’ll have a little more work to do.” to get there for the final return, but they are safe on the space station. Their spacecraft is working well and they are enjoying their time on the space station.
The Starliner was launched on June 5 in the program’s first manned test flight, with a helium leak already known. The other four developed during the ship’s rendezvous with the space station, when jets were rapidly pulsed to fine-tune the Starliner’s approach.
United Launch Alliance
Once docked at the station, the valves are closed to isolate the helium system, eliminating any further leaks. But once Wilmore and Williams leave and return home, the valves will be reopened to repressurize the lines or manifolds.
Stich said that even with the known leaks, the spacecraft will have 10 times the amount of helium it needs to return home, but engineers want to make sure the leaks don’t get worse once the system is repressurized.
The Starliner’s service module’s five rear-facing thrusters also failed to operate as expected during the June 6 approach to the space station.
After docking, four of the five jets were successfully tested and despite slightly lower power levels than expected, they were considered ready to undock and re-enter. The fifth booster was not “hot fired” because its previous performance indicated that it had in fact failed.
But the managers want to find out the cause of the unexpected behavior of the other four. Starting next week, a new booster identical to those aboard the Starliner will be tested at a government facility in White Sands, New Mexico, exactly as those in orbit were fired during rendezvous and docking of the Starliner.
“We’re going to recreate that profile,” Stich said. “Then we’ll put a pretty aggressive profile in the thruster for the (undocking to reentry) phase.”
NASA
It is possible that the problems with the rear-facing thrusters were caused by higher than normal temperatures due to the Starliner’s orientation relative to the sun, or by the sequence of rapid, repetitive firings commanded by the flight software. Or both.
The ground tests, which are expected to last “a few weeks,” could provide evidence one way or the other.
“This will be a real opportunity to look at a booster like we did in ground space, a detailed inspection,” Stich said. “Once these tests are completed, we will review the landing plan. »
As for the impression that the crew is stranded in space, Stich and Nappi both pointed out that on Wednesday, a defunct Russian satellite, in a slightly lower and more inclined orbit than the space station, suffered a catastrophic “event” that produced more than 100 pieces of traceable debris.
As flight controllers assessed the wreckage’s trajectories, the space station’s nine crew members were ordered to “shelter in place” aboard their respective spacecraft, ready to depart immediately and return to Earth in the event of a damaging impact.
Two Russian cosmonauts and NASA’s Tracy Dyson boarded their Soyuz ferry, while three NASA astronauts and another cosmonaut floated in their SpaceX Crew Dragon. Wilmore and Williams left safely inside the Starliner and were allowed to return home if warranted.
After about an hour, the crew received the green light to resume normal work. If the Starliner had been considered dangerous, Wilmore and Williams would likely have been told to seek refuge in the Crew Dragon. But that was not the case.
“We have the authorization to serve as a lifeboat in case of an emergency on board the ISS,” Nappi said. “That means we can come back at any time with the Starliner, and that was proven this week.”