Boeing's leak-prone Starliner capsule will remain docked to the International Space Station for four additional days, NASA announced Tuesday, returning to Earth with a pre-dawn landing in White Sands, New Mexico, on the 26 of June to close a 20-day test flight: the first with astronauts on board.
The additional docking time will give Starliner Commander Barry “Butch” Wilmore and Copilot Sunita Williams more time to help aboard the station as flight controllers continue to examine telemetry and finalize reentry plans with five leaks of known helium in the capsule's propulsion system. and unexpected behavior in multiple maneuvering jets.
One plane will not be used for the rest of the flight, but the other suspect thrusters were successfully “hot-fired” during a test Saturday, giving managers confidence that they will work as necessary to get the Starliner out of the orbit to re-enter and land. .
NASA
As for the helium leaks, engineers say the spacecraft has more than seven times the amount needed for the rest of the flight. During Saturday's hot-fire test, leak rates were lower than telemetry indicated earlier in the mission, but engineers are still evaluating the data to better understand the system's behavior.
“We've learned that our helium system is not working as designed. While it's manageable, it's still not working the way we designed it,” said Mark Nappi, director of Boeing's Starliner program. “So we have to go find out.”
As for the thrusters, “there are some things about our flight profile and/or our parameters … where our thrusters are not working (as expected). So we have to go figure that out.” . But he said Boeing intends to “completely eliminate” both problems, which he called “annoying,” before the Starliner flies again.
“The great thing about the situation is that we can stay on the ISS a little longer and get as much data as we can so we can fully understand it to the best of our ability.”
Meanwhile, Steve Stich, manager of NASA's commercial crew program, said the Starliner can safely bring Wilmore and Williams back to Earth if a problem arises that requires an immediate departure.
But as it currently stands, Wilmore and Williams will undock from the space station's bow port at 10:10 p.m. EDT on June 25 and fire the craft's aft thrusters to exit orbit in the early hours of next day, deploying a parachute and -Airbag assisted landing at White Sands at 4:51 am EDT.
The day before Wilmore and Williams depart, ISS astronauts Tracy Dyson and Mike Barratt plan to venture outside the station for a spacewalk, or EVA, to retrieve a malfunctioning radio transmitter and to collect swabs near station vents and airlock for microorganisms. have managed to get outside and survive in the harsh environment of space.
During a first attempt on June 13, in what was to be the first of three planned spacewalks, Dyson and Matthew Dominick, their original partner, never left the airlock. Dominick reported a “disturbance problem” with the space suit and the EVA was cancelled.
Rather than take the time to investigate and correct the problem with Dominick's suit, and given the amount of oxygen available, NASA administrators decided to retry the original spacewalk with Dyson and Barratt and combine the tasks planned for the second and third departure of a single excursion on July 2.
NASA
But the spacewalk schedule depends on undocking Starliner, which is the top priority in the near term.
The Starliner was already running four years behind schedule released on June 5a month later than expected due to problems with its Atlas 5 rocket, problems with a countdown computer and an initial helium leak in the system used to pressurize the capsule's thrusters.
NASA and Boeing administrators decided the leak was too small to pose a safety threat, and the ship was cleared for launch. Once in orbit and on the way to the space station, however, four more helium leaks developed and the Starliner's flight computer took seven maneuvering planes offline when telemetry did not match pre-launch expectations.
Stich said Saturday's hot-fire test showed the jets needed for post-decoupling maneuvers and that the critical deorbit “burn” will operate as needed to remove the craft from orbit to return it to to enter. Similarly, he said engineers were confident the helium leaks could be managed even if one or more worsened after decoupling.
But the extra days docked at the space station will give engineers more time to review data and monitor telemetry from the Starliner's service module, which is where the thrusters and helium pressurization pipes are located. Engineers won't be able to study the actual hardware because the service module is discarded before re-entry and will burn up in the atmosphere.
“We're taking extra time given that this is a manned vehicle, we want to make sure we've left no stone unturned,” Stich said. “We also want to look at the systems and the potential interaction between the systems and make sure we haven't missed anything before we go back.”
“I like the vehicle to stay a little longer,” he added. “I like the fact that we're looking at how the vehicle is doing thermally, how the space station is charging the batteries. We're seeing these kinds of cycles, which we absolutely need for later missions. . . . So I think there's a good lining to stay a little (longer on the space station).”
Prior to launch, NASA administrators had hoped that the Starliner test flight would pave the way toward certification of the spacecraft for operational crew rotation missions to the space station beginning in early next year But given the problems previously encountered in the flight, certification could be delayed depending on what is required to address the problems identified so far.
