NASA and its commercial partners are once again counting down to a launch to send Boeing’s Starliner space capsule to the International Space Station – with a living, breathing crew on board for the first time ever.
The gumball-shaped capsule is expected to rise into space atop a United Launch Alliance Atlas V rocket, scheduled to lift off from the Cape Canaveral space station in Florida at 12:25 p.m. today ET (9:25 a.m. PT). The outlook for acceptable weather conditions has been set at 90%. Launch coverage is streamed via the NASA website and YouTube.
After NASA astronauts Butch Wilmore and Sunita Williams boarded the capsule, mission managers reported that United Launch Alliance was investigating an issue with the ground support system for fueling boosters on the Centaur upper stage of the Atlas V. Engineers worked to reset the fuel fill control system. “We hope this solves the problem,” said Dillon Rice, ULA launch commentator.
If all goes as planned, Wilmore and Williams will place Starliner into low Earth orbit and encounter the space station a little more than 25 hours after launch. During their 10-day trip, they will check Starliner’s systems and deliver supplies to the space station, including a replacement pump for the system the station crew uses to convert urine into drinking water. Then they will return to Earth.
Not everything went as planned with Starliner. Boeing’s spacecraft development efforts faced years of delays and cost overruns of more than $1 billion that the company had to cover.
The Starliner’s first uncrewed flight test was not fully successful in 2019, forcing a second uncrewed test that met its objectives in 2022.
The most recent set of problems occurred during a previous launch attempt on May 6. Mission managers canceled the countdown two hours before launch, due to a faltering oxygen relief valve on the rocket’s Centaur upper stage. While troubleshooting this issue, engineers detected a small helium leak that was traced to a flange on one of the Starliner service module’s thrusters.
NASA and Boeing spent days assessing the leak’s potential impact, and the team decided the safest course was to live with the leak and work around it.
“This is a very, very small leak, and it’s well within the margin that we have,” said Steve Stich, manager of NASA’s Commercial Crew Program.
In a pre-launch briefing, Stich said the flange was at a location in the propellant system where the fuel, oxidizer and helium lines join for pressurization. “It makes the job almost dangerous,” he said.
Engineers also discovered a potential design vulnerability in Starliner’s propulsion system – an issue that could hamper the capsule’s ability to execute a deorbit if two of the four thrusters known as “niches” fail at the same time. time.
The mission team developed a workaround for the test flight. After the Starliner and its crew return, NASA and Boeing will take a closer look at the design of the propulsion system as well as the leaking helium pressurization system.
Another concern emerged at the end of a crewed suborbital space mission led by Jeff Bezos’ Blue Origin space company on May 19. When New Shepard’s crew capsule descended toward landing, one of its three parachutes did not fully open. Starliner’s parachute system uses a similar design, so NASA and Boeing worked with Blue Origin to ensure the problem wouldn’t arise during the orbital test mission.
Stich said Blue Origin attributed the parachute problem to a reefing line designed to prevent the parachute from opening prematurely. There is a mechanism that is supposed to cut the line at the right time, but Stich said “the cutters, for whatever reason, didn’t cut that line.”
“We use a cutter very similar to what Blue Origin uses, so it was important for us to look at this data,” Stich said. “We went back and looked at all of our testing data.”
Stich said the Starliner system’s cutters had been successfully tested 160 times, reassuring the team that the parachutes were ready to operate.
NASA made a last-minute change to the payloads of the Starliner test flight: the space station’s urine recycling system pump unexpectedly failed, forcing the crew to store their urine in bags and tanks. NASA decided to provide some relief, so to speak, by sending a 150-pound replacement tank into the Boeing capsule. To keep Starliner’s mass distribution balanced, two suitcases containing clothing and personal hygiene items for Wilmore and Williams were left behind.
“They will just use our generic supplies that we have on board,” said Dana Weigel, who manages NASA’s International Space Station program. “The reason we have them there is for cases like this.”
After spending about eight days on the space station, Wilmore and Williams will take the Starliner back down for a parachute- and airbag-assisted landing in the American Southwest, at a site to be determined depending on the weather and timing of return.
Boeing will use the data collected during the test flight to refine the design of its spacecraft. These improvements should allow Starliner to take its place alongside SpaceX’s Crew Dragon as a commercial “space taxi” capable of transporting astronauts to and from orbit.
This assumes, of course, that everything goes according to plan.
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