With no consensus on the safety of the Starliner crew capsule, NASA officials said Wednesday they need another week or two before deciding whether to bring two astronauts back to Earth on Boeing’s spacecraft or extend their stay on the International Space Station into next year.
Boeing’s Starliner spacecraft, which suffered damage to its thrusters and was plagued by helium leaks, is taking up valuable parking space on the space station. It must leave the orbiting research complex, with or without its two-person crew, before the launch of SpaceX’s next crewed Dragon mission to the station, scheduled for Sept. 24.
“We can juggle and make it all work if we need to scale up, but it’s getting harder,” said Ken Bowersox, associate administrator for NASA’s spaceflight operations directorate. “With the consumables we’re using, with the need to use the ports for cargo missions, those kinds of things, we’re getting to a point where the last week of August is when we really should be making a decision, if not sooner.”
Last week, NASA officials said they expected to make a decision by mid-August, presumably this week, but Bowersox said Wednesday that NASA likely won’t make a final decision on what to do with the Starliner spacecraft until late next week or early the week of Aug. 26.
“We have time available before we bring Starliner home and we want to use that time wisely,” Bowersox said.
NASA astronauts Butch Wilmore and Suni Williams blasted off inside Boeing’s Starliner spacecraft on June 5. Their mission is the first crewed test flight in Boeing’s capsule before NASA clears Starliner for regular crew rotation flights to the space station. But after software hiccups, concerns about the parachute and previous problems with its propulsion system, Boeing’s Starliner program is running more than four years behind SpaceX’s Dragon crewed spacecraft, which first carried astronauts to the station in 2020.
And now, there’s a significant chance that the Starliner crew won’t return home on the spacecraft it launched on. Bowersox, a former astronaut, said NASA brought in propulsion experts from other programs to take another look at the thruster problem.
Engineers are still investigating the root cause of why five of Starliner’s 28 reaction control system thrusters, supplied by Aerojet Rocketdyne, failed during the approach to the space station the day after launch. The thrusters overheated as they pulsed over and over to fine-tune the craft’s rendezvous with the station. Testing of a similar control thruster on the ground suggested that a Teflon seal on an internal valve could swell at higher temperatures, restricting propellant flow to the booster.
Four of the five thrusters that failed before Starliner docked with the station have recovered and generated near-normal levels of thrust during firing tests last month. But many NASA engineers are not convinced the thrusters will function normally on Starliner’s journey from the space station back to Earth. These control thrusters are needed to keep the spacecraft pointed in the right direction when the four largest rocket engines ignite for the deorbit burn that will steer the capsule on a trajectory back into the atmosphere for landing.
Rapid pulses of thrusters, coupled with a prolonged burn of the four largest engines, could raise temperatures inside four doghouse-shaped propulsion capsules around the perimeter of Starliner’s service module. Once the deorbit burn is complete, Starliner will jettison the service module to burn up in the atmosphere, and its crew module will use a different set of thrusters to guide its reentry. It will then deploy parachutes to slow down before landing, likely at White Sands, New Mexico.
High risk
Bowersox said outside engineers brought in from other NASA centers have so far largely agreed with assessments made by the team working full-time on Starliner.
“There are a lot of people who have worked with similar thrusters and seen similar problems,” he said. “We’ve gotten feedback on what we’re seeing and a lot of it confirms what we thought was causing the signals we were seeing in orbit. It’s really difficult when you don’t have the actual hardware to look at, when it’s in space.”