NASA officials said it could take another week or two to decide Wednesday whether to return two astronauts to Earth aboard a Boeing spacecraft or extend their stay on the International Space Station until next year, amid a lack of consensus on the safety of the Starliner crew capsule.
Boeing’s Starliner spacecraft, crippled by suspicious thrusters and helium leaks, is taking up precious parking space on the space station. It must depart the orbital research complex with or without a two-person crew before SpaceX’s next Dragon crewed mission to the station, scheduled for Sept. 24.
“We can adjust and do a better job if we need to, but it’s gotten a lot more difficult,” said Ken Bowersachs, associate administrator for NASA’s Space Flight Operations Directorate. “The consumables we’re using, the need to use ports for cargo missions, those kinds of things, we’re getting to the point where we have to make that call in the last week of August. Or we’re going to have to make that call sooner.”
Last week, NASA officials said they expected a decision in mid-August, possibly this week, but Bowersox said Wednesday that NASA would likely make a final decision on the Starliner spacecraft by the end of next week or early the week of Aug. 26.
“We have time before we have to return Starliner home, and we want to use that time wisely,” Bowersox said.
NASA astronauts Butch Wilmore and Suni Williams launched 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 routine crewed flights to the space station. But software glitches, parachute issues, and previous propulsion system problems have left Boeing’s Starliner program more than four years behind SpaceX’s Dragon crewed spacecraft, which first flew astronauts to the station in 2020.
And now there’s a significant chance that the Starliner crew won’t be able to return to the spacecraft they launched. Bowersox, a former astronaut, said NASA has brought in propulsion experts from other programs to take a fresh look at the propulsion problem.
Engineers are still investigating the root cause of five of the Starliner’s 28 reaction control system thrusters, supplied by Aerojet Rocketdyne, failing during the space station approach the day after launch. The thrusters overheated as they were repeatedly pulsed to fine-tune the spacecraft’s rendezvous with the station. Tests of similar control jets on the ground suggested that Teflon seals in the internal valves could have swelled at higher temperatures, restricting the flow of propellant.
Four of the five failed thrusters recovered before Starliner docked with the space station and produced nearly normal thrust levels during a test launch last month. But many NASA engineers aren’t sure the thrusters will work as they should on Starliner’s journey from the space station to Earth. These control jets are needed to point the spacecraft in the right direction when its four large rocket engines fire for the deorbit burn, steering the capsule onto a trajectory that will land it back in the atmosphere.
The combination of a rapid pulse of the thrusters and a long ignition of the four larger engines will raise the temperature inside the four doghouse-shaped thruster pods surrounding the Starliner’s service module. Once the deorbit burn is complete, Starliner will jettison the service module, burning it in the atmosphere, while the crew module guides reentry using another set of thrusters. It will then deploy parachutes to slow its landing, possibly landing at White Sands, New Mexico.
Increased risk
Bowersachs said outside engineers from other NASA centers have largely agreed with the assessments made so far by the full-time team working on Starliner.
“There are a lot of people who have seen similar problems using similar thrusters,” he said. “So we got feedback on what we were seeing, and a lot of it confirmed what we thought was causing the signatures that we were seeing in orbit. When you’re in space and you don’t have the actual hardware to look at, it’s really hard.”
