After weeks of testing to try to understand the problems afflicting Boeing’s Starliner spacecraft, NASA and company representatives have still not been able to set a return date for the two astronauts who piloted the vehicle — and have been in space for almost two months without being able to return to Earth.
However, engineers finally have some possible answers as to what caused some of Starliner’s problems during the first leg of its journey, which included helium leaks and thrusters abruptly stopping working en route to the International Space Station.
The information came after Boeing and NASA’s ground teams spent the last few weeks working to understand the problem and scheduled plans for some additional tests this weekend, which should serve as “icing on the cake” for understanding the issues. according to Mark Nappi, manager of Boeing’s Commercial Crew Program.
At a site in New Mexico, USA, engineers fired test engines more than 1,000 times, replicating how Starliner’s thrusters would have been fired heading into space. They then fired the booster to test various possibilities for the engines to fire on the way back from space, according to Boeing.
The goal of this test was to better understand why the spacecraft’s thrusters shut down unexpectedly and what dangers — if any — are associated with reactivating those thrusters.
Officials said they were able to recreate the condition of the thrusters in space, which had deteriorated during flight, in their tests on the ground.
And the tests may have helped give engineers a better understanding of the “root cause” of the problem: heat built up inside the boosters may be causing the Teflon seals to swell, restricting fuel flow.
That test “gave us additional confidence to undock in return,” Nappi said.
The findings also led Boeing and NASA to abandon plans to allow astronauts to manually pilot the Starliner spacecraft on the way home, as they did briefly during the trip to the Space Station.
“Some of the manual maneuvers put extra stress on the thrusters,” said Steve Stich, NASA’s commercial crew program manager.
Still, officials did not say definitively on Thursday that the Starliner spacecraft that took veteran NASA astronauts Butch Wilmore and Suni Williams to the Space Station would be the same vehicle that brought the astronauts back. home.
“There are many good reasons to complete this mission and bring Butch and Suni home on Starliner,” Stich said after pointing out that NASA has contingency options if Starliner is not approved to bring astronauts home.
“We need to go through the process,” he added. “We have another critical Starliner mission management team to review all of the thruster data we just talked about.”
“Of course I’m very confident that we have a good vehicle to bring the team back,” said Nappi.
Williams and Wilmore arrived at the International Space Station on June 6 for what was expected to be a roughly weeklong mission. This week, astronauts completed 50 days in space. NASA previously indicated that Starliner can stay in space for a maximum of 90 days.
More tests for Starliner
Separately, engineers may have made progress in understanding the helium leaks that marred the first leg of Starliner’s journey. But Boeing and NASA will take a closer look at this issue again during additional tests of the vehicle in space that will continue this weekend, Stich said.
The tests will include firing 27 Starliner thrusters while the vehicle remains docked at the Space Station.
Analysis of components in ground testing—specifically, of a version of the Starliner service module that has been in New Mexico for three years—showed that helium leaks could be the result of seals that degraded due to exposure to propellant vapor. , according to Nappi.
“The natural solution to this is to simply replace that seal with a material that is not as susceptible” to wear from exposure to propellant, Nappi said, referring to possible changes Boeing could make for future Starliner missions.
However, it remains to be seen whether the leaks aboard Starliner worsened while the vehicle remained docked in space. Because the service module — the part of the spacecraft affected by the helium leaks — was exposed to the fuel for so long, Nappi said it could offer an understanding of how badly the seals could be degraded in a worst-case scenario.
The ongoing effort to understand the helium leak problem is among the main reasons why NASA and Boeing have not yet been able to set a return date for Williams and Wilmore — or give a definitive answer on whether Starliner is ready to fly. them back home.
“The main requirements of flight logic are really that we understand more about helium leaks — we understand the stability of the leaks and how we can manage them if they get bigger,” Stich said, referring to the possibility that helium leaks could occur. helium that affect the Starliner service module could worsen.
NASA and Boeing plan to conduct a review to plan the undocking of Starliner, which “could occur as early as the end of next week,” according to Stich.
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