NASA and Boeing are now targeting Starliner’s return from the International Space Station no earlier than June 26.
According to NASA, the capsule would undock on June 25 and land at White Sands Space Harbor at approximately 4:51 a.m., undocking from the ISS on Tuesday at 10:10 a.m. If the June 26 return does not happen, NASA said there will be a backup opportunity on July 2.
Steve Stich, program manager for NASA’s Commercial Crew Program, said Starliner is “doing very well in orbit, this is a test flight.”
Stich confirmed five aft thrusters failed in total during flight and docking, all of them are reaction control thrusters.
Data showed while docking, some of the thrusters only produced 11% of thrust and even 0% again when fired a second time upon docking.
Stich said NASA decided they would turn off one thruster and not use it again for the rest of the mission.
“So what’s really complicated is we’re going through all the data from this flight and comparing it to OFT 2 [the second uncrewed flight test of Starliner] and looking forward to the remainder of the flight and running simulations.”
Once safely docked, over the past several days NASA “hot-fired” all seven thrusters for about a second to test them.
“When we did that we saw really good chamber pressure, which is a way to measure the health of the thrusters in terms of telemetry,” Stich said. “I think of it as measuring the health of your tires. You check the pressure on your tires to make sure they’re healthy; it needs to be a certain range, and these thrusters when they fire, they normally have a chamber pressure trait that looks very normal.”
During post-docking testing, most thrusters had almost 100% thrust. Stich said this means the thrusters have since recovered after docking.
Stich offered a theory: Starliner’s thrusters don’t work so well when it gets very hot. Perhaps propellants didn’t mix perfectly and vaporize properly.
“So coming out of that we feel very confident in the thrusters, the team is going to make sure to go look at the thrusters in detail across the whole flight and compare them to what happened to OFT 2,” Stich said. “If you remember in OFT 2 during the rendezvous sequence we had two thrusters fail, and both of those thrusters came back at the end of the flight. And the team’s looking at all that data.”
There are two big events required to bring Starliner home: the deorbit burn — slowly down the spacecraft enough for it to fall back towards the Earth’s atmosphere, and then before landing separating the capsule from the rest of the flight hardware. Helium is required for both events to properly pressurize the thrusters.
NASA confirmed there have been five helium leaks in total since before launch.
“We’ve looked at the margin for return and we need about seven hours of helium, and we have about 70 hours of margin to get to the deorbit burn,” Stich said.
Stich said leak rates after nine days docked at the ISS are going down and “leaks seem to be related to the activity of the thrusters.”
NASA has been simulating landing recovery at White Sands to prepare for Starliner’s airbag touchdown.
Butch Wilmore and Suni Williams — retired Navy captains and former space station residents — were the first two astronauts to launch on Starliner. The initial plan was for the flight crew to spend only a week on the space station.
Get today’s headlines in minutes with Your Florida Daily: