Starliner ISS keep prolonged to finish thruster and helium leak testing

WASHINGTON — NASA and Boeing have once more prolonged the keep of the CST-100 Starliner on the Worldwide Area Station as engineers wrap up evaluation of thruster issues and helium leaks on the crewed spacecraft.

At a June 18 briefing, NASA introduced that Starliner’s return to Earth on the Crew Flight Take a look at (CFT) mission, which had already been postponed twice to June 22, had been pushed again once more. Starliner is now scheduled to undock from the station at 10:10 p.m. Jap June 25 and land at White Sands, New Mexico, at 4:51 a.m. Jap June 26.

Officers from NASA and Boeing mentioned on the briefing that the prolonged keep on the station will give them extra time to check two key points encountered by the spacecraft throughout its flight to the station practically two weeks in the past: thruster malfunctions and helium leaks within the spacecraft’s propulsion system.

That work included transient firings of a number of aft-facing response management system (RCS) thrusters, 5 of which have been shut down by the spacecraft’s pc as Starliner approached the station. 4 of the thrusters have been restored by controllers to permit the docking to proceed.

The one thruster that was not restored earlier than docking confirmed a “unusual signature” producing virtually no thrust, mentioned Steve Stich, NASA industrial crew program supervisor. That thruster will now not be utilized by the spacecraft throughout undocking and deorbiting maneuvers.

The opposite thrusters, together with each people who malfunctioned through the method and others that behaved usually, confirmed the anticipated profile of chamber pressures throughout a short burn lasting 1 / 4 of a second. The thrusters additionally operated as anticipated throughout an extended burn of 1.2 seconds every the place controllers measured their efficiency by testing the response of the station’s flight management system.

“Popping out of that, we really feel very assured within the thrusters and the staff is simply ensuring to go have a look at the thrusters intimately throughout the entire flight,” he mentioned. That features evaluating their efficiency to that on an uncrewed take a look at flight in Might 2022, referred to as OFT-2, the place two thrusters malfunctioned throughout method however have been restored earlier than the tip of the mission.

Stich mentioned engineers are learning what induced the thrusters to go offline through the method, which can be linked to heavy use. “We’ve got some theories about what’s happening contained in the thruster the place the thruster will get highly regarded,” he mentioned, similar to excessive temperatures stopping correct mixing of gasoline and oxidizer.

Engineers additionally used the thruster take a look at to test on the 5 helium leaks detected within the propulsion system. In each case, he mentioned, leak charges had gone down, in a single case by 50%.

“It appears to be associated to the exercise of the thrusters,” he mentioned of the helium leaks. That may very well be linked to warmth from the thrusters or sliding surfaces that put on down seals. Three of the bigger leaks seemingly have comparable causes, he famous, whereas two smaller ones could as a substitute be just like leaks seen on the OFT-2 mission.

Just like the thruster exams, Stich mentioned the diminished helium leaks give him confidence the spacecraft will be capable of carry out as anticipated throughout undocking and deorbiting maneuvers. “The demand on the thrusters is way, a lot much less” within the later phases of flight, he mentioned.

He mentioned the helium leaks are going down in numerous “doghouses” on the service module from the malfunctioning thrusters. Nevertheless, he said that the “dynamic operations” throughout Starliner’s method to the station could have each induced the thruster malfunctions and helium leaks.

NASA and Boeing engineers plan to proceed evaluation of Starliner till June 22, then deal with preparations for undocking and returning to Earth. That work was an element within the resolution to increase Starliner’s keep on the station. “We don’t get the service module again, so this is a chance to totally perceive the system’s efficiency with out the stress of schedule,” mentioned Mark Nappi, Boeing vice chairman and industrial crew program supervisor. “We’ve got the time.”

He famous that the CFT mission has achieved 77 of 87 flight take a look at targets set out earlier than launch, with the rest related to undocking and touchdown. Engineers included an unspecified variety of further take a look at targets to benefit from the extra time on the station, similar to filming operations of Starliner’s hatch and gathering extra cabin air temperature measurements.

Each Stich and Nappi emphasised, after repeated questioning on the briefing, that they believed Starliner was protected for NASA astronauts Butch Wilmore and Suni Williams to make use of for his or her return to Earth. The additional time, Stich mentioned, permits engineers extra time to check the automobile’s efficiency, together with in a powered-down state that will likely be used throughout future long-duration stays on the station.

He added that NASA had cleared the usage of Starliner to carry Wilmore and Williams again in an emergency, if wanted. “We’re taking slightly further time to evaluate all the info and in addition study as a lot as we are able to whereas now we have the service module in orbit.”

Spacewalk modifications

Wilmore and Williams have been busy on the station serving to take a look at Starliner methods. “They love Starliner, and so they’re so completely satisfied to be part of the mission,” Stich mentioned.

The 2 have additionally been serving to out on the station. “We’ve taken benefit of a few of their further time and further serving to fingers,” mentioned Dana Weigel, NASA ISS program supervisor, similar to conducting analysis.

The 2 assisted a deliberate June 13 spacewalk by NASA astronauts Tracy C. Dyson and Matt Dominick. That spacewalk, although, was referred to as off simply earlier than the scheduled begin due to what NASA referred to as a “spacesuit discomfort concern.”

Weigel mentioned that Dominick was the astronaut that skilled discomfort within the go well with, however didn’t elaborate on the precise concern that prompted the postponement. “We couldn’t resolve it that day,” she mentioned.

NASA has since revised plans for upcoming spacewalks, with Dyson and Mike Barratt now scheduled to carry out a spacewalk June 24 that options the identical duties because the postponed June 13 spacewalk, which embody retrieving a malfunctioning electronics field and acquire samples from the station’s exterior that will likely be used to detect any microorganisms.

Weigel mentioned that Barratt was already slated to carry out an upcoming spacewalk and had a go well with prepared. “We determined it simply made sense to make use of Tracy and Mike,” she mentioned.

That will likely be adopted by a July 2 spacewalk for added station upkeep, though NASA gained’t assign astronauts to it till after the June 24 spacewalk. The company had deliberate a collection of three spacewalks, however Weigel mentioned that will likely be diminished to 2 due to oxygen used making ready for the aborted June 13 spacewalk.

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