While NASA is debating, Boeing Starliner spacecraft safety The agency is “getting more serious” about a backup plan to take the ship’s two crew members after multiple helium leaks and thruster problems. return to earth Officials announced Wednesday that he is aboard SpaceX’s Crew Dragon.
Although no final decision has been made in that case, Starliner Captain Barry “Butch” Wilmore and First Officer Sunita Williams remain on the international space station It will remain there for another six months, descending aboard the Crew Dragon, scheduled to be launched on September 24 to transport the long-stay crew to the outpost.
Two of the four Crew 9 astronauts already assigned to the Crew Dragon flight will be removed from the mission, meaning the ship will launch with two empty seats. Wilmore and Williams will then return to Earth next February, along with two other Crew 9 astronauts.
Shortly before Crew Dragon’s launch, Starliner was scheduled to undock from the station’s forward port without any astronauts on board and return to Earth under computer control. Crew Dragon then docks at a vacant forward port.
Starliner’s first two test flights were unmanned, and both landed safely. Starliner’s current computer systems will need to be updated with new data files and flight controllers will need to brush up on procedures, but that work could be completed in time for the plane’s return in mid-September.
If that scenario comes to fruition, Wilmore and Williams would spend 268 days, or 8.8 months, in space, instead of the week or so they were scheduled to launch atop a United Launch Alliance Atlas 5 rocket on June 5. I will spend it.
There is uncertainty about the exact cause of the thruster problem, but NASA Administrator Ken Bauer said, “Given what has happened over the last week or two, I would say that the chances of Starliner returning uncrewed have increased a little bit.” Sox said. Space operations.
“So we’re looking at those options more carefully and making sure we can address them.”
But he cautioned that a final decision on when and how to bring Starliner crew home will not be made until the agency completes a top-level flight readiness review.
No date has been set, but it could happen late next week or the week after.
“Our first option is to return Butch and Suni to Starliner,” said Steve Stitch, NASA’s commercial crew program manager. “However, we have made the necessary plans to ensure that we have other options. We are working with SpaceX to ensure that Butch and Suni are ready (to return) to Crew 9 if necessary.” I have confirmed that it is working.”
“Right now, we haven’t approved this plan (yet). We’ve done all the work to make sure this plan exists…but we haven’t officially turned it on. We wanted to make sure we had all that flexibility.” On the fly. ”
Before Starliner launched, NASA and Boeing engineers knew there was a small helium leak in the spacecraft’s propulsion system. After ground tests and analysis, the team concluded that the ship could be safely launched as is.
However, the day after liftoff, four more helium leaks occurred and the five aft-facing maneuvering thrusters stopped working as expected. Since then, NASA and Boeing have conducted data reviews and ground tests to understand exactly what caused both problems.
Starliner uses pressurized helium to push propellant into the thrusters. This is important to maintain the correct orientation of the spacecraft. This is especially important when performing a deorbit brake “burn” using large rocket engines to slow the ship for re-entry and landing at the target location.
To authorize a Starliner’s manned return to Earth, engineers must, based on test data and analysis, create an acceptable “flight theory” that provides confidence that the ship can pass through atmospheric reentry and landing with the required safety level. evidence needs to be developed.
“Despite the uncertainty at this time, the Boeing team is very confident that this vehicle will be able to bring crews home immediately,” Bowersox said. “But there are also people who are probably a little more conservative. They’re worried that we don’t know for sure, and they’re estimating the risks higher, and they’re avoiding going home[on the Starliner]. There are other options.
“So, that’s part of the discussion that we’re having right now. But again, I think both views are reasonable within the range of uncertainty that we have. So our efforts are trying to reduce that uncertainty.”
Boeing is adamant that a backup plan for Crew Dragon is not needed, and testing and analysis of helium leaks in Starliner’s propulsion system and initial troubles with its maneuvering thrusters show the spacecraft has the ability to safely return Wilmore and Williams to Earth. It claims that it has been shown that there is sufficient margin for
Boeing says the helium leak is understood, the situation is not worsening, and that there is enough pressurized gas on board to force propellant into the thrusters needed to steer and stabilize the spacecraft. It is said that the critical deorbit brake burn to fall from the spacecraft is taking place. Trajectory for re-entry and landing.
Similarly, engineers have determined that during rendezvous with the space station, several backward-steered jets overheated and fired with less thrust than expected, causing Starliner’s flight computer to stall during approach. I believe I understand.
Ground tests of the new Starliner thrusters involved igniting them hundreds of times under conditions that mimicked those experienced by those aboard the spacecraft, reproducing signs of overheating. This may have been caused by multiple ignitions during testing of the capsule’s manual control system during prolonged exposure to direct sunlight.
Analysis showed that the higher-than-expected heating likely caused a small seal in the thruster valve’s “poppet” to deform and expand, reducing propellant flow. The thrusters aboard Starliner were test-fired in space under more normal conditions and all worked properly. This indicates that the seal has returned to a less obtrusive shape.
New procedures have been introduced to prevent overheating during rendezvous. Additional manual test launches are excluded, prolonged sun exposure is not planned, and station departures require less frequent launches compared to rendezvous.
“We continue to believe in Starliner’s capabilities and flight rationale,” Boeing said in a statement Wednesday. “If NASA decides to make a mission change, we will make the necessary changes to set Starliner up for an uncrewed return.” We will take appropriate measures.”
The helium pipes and thrusters are housed in Starliner’s service module, which will be jettisoned to burn up in the atmosphere before the crew capsule re-enters for landing. Therefore, engineers cannot directly examine the hardware and prove with certainty what went wrong.
For now, that uncertainty appears to favor having Wilmore and Williams return to Earth aboard the Crew Dragon. But that’s not certain yet.
“If we can reproduce the physics in offline testing and understand why this poppet is heating up and pushing out, and why it’s contracting, then we can move forward with more confidence and get Butch and Sonny back on this vehicle. “We can do that,” Stich said.
“That’s what the team is really trying to do. We’re looking at all the data and trying to see if we can give a good physical explanation of what’s going on.”
In the meantime, the wait for a decision one way or another drags on.
“Ultimately, someone has to be appointed the decision maker and that person has to make the decision,” Wayne Hale, former shuttle flight director and program manager, said in a blog post earlier this week.
“Engineers always ask for more testing, more analysis, more time to get more information to get a firmer conclusion. And decision-makers also ask when enough work is done. You have to determine what was done. All these frictions… it’s always a risk to human life.”
Mr. Hale concluded his post with the following: “I don’t envy today’s decision-makers considering the rationale for flight. My only advice is to listen thoroughly, ask questions effectively, and ask for further data when necessary. But when the time comes, you have to make a decision. “
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