How Bad Luck Foiled Efforts to Get Starliner Back on Course toward Space Station

Bad luck may have played a considerable role in the Boeing CST-100 Starliner crew capsule’s failure to reach the International Space Station (ISS) as planned.

Starliner launched Friday morning (Dec. 20) on an uncrewed mission called Orbital Flight Test (OFT), which was designed to demonstrate the capsule’s ability to get NASA astronauts to and from the ISS. But Starliner encountered problems shortly after liftoff and ended up getting stranded in an orbit that’s incompatible with an ISS rendezvous.

Those problems apparently stemmed from an error with Starliner’s onboard timing system, NASA officials and Boeing representatives said during a postlaunch news conference. Starliner seemed to think it was conducting an orbit-insertion burn when it actually was not. As a result, the capsule performed a series of unnecessary orientation-maintaining firings of its small reaction-control thrusters, using up lots of propellant in the process.

Related: Boeing’s 1st Starliner Flight Test in Photos

The spacecraft’s handlers tried to troubleshoot the issue — and may well have succeeded if Starliner had been in a slightly different patch of sky, NASA Administrator Jim Bridenstine said during Friday’s news conference.

“By the time we were able to get signals up to actually command it to do the orbital insertion burn, it was a bit too late,” he said. “And the reason it was too late is because it appears — and remember, all of this is very early and preliminary, and we’re learning things moment by moment — but it appears as though we were between TDRS communication satellites, which meant we couldn’t get the command signal to tell the spacecraft that it needed to do the orbital insertion burn soon enough.”

TDRS stands for “Tracking and Data Relay Satellites,” and they do just what their name describes: provide a communications link between ground controllers and spacecraft. NASA currently has 10 operational TDRS satellites in geosynchronous orbit, about 22,300 miles (35,800 kilometers) above Earth, so it seems that Starliner was quite unlucky to be out of hailing range during this morning’s crucial moments.

But, as Bridenstine stressed, this is a working hypothesis, not a confirmed diagnosis. And the positioning of Starliner relative to the TDRS flock doesn’t address the root cause of Friday’s problems, which lies with the capsule’s “mission elapsed timing” system. 

Indeed, further analyses have revealed that Starliner apparently wasn’t pointing its antenna toward the TDRS craft as expected, likely as a result of the timing problem, Jim Chilton, senior vice president of Boeing’s Space and Launch Division, explained during a news conference on Saturday (Dec. 21).

The Starliner team is still figuring out what exactly happened with that timing error and how to prevent it from happening again, Bridenstine and others said. (The NASA chief also said that, if astronauts had been on board, they likely would have recognized and fixed the problem in time for Starliner to get back on its way to the ISS.)

The new OFT mission profile has been worked out in a broad sense, however. Starliner won’t dock with the ISS now after all, and the mission will be significantly shorter than its originally planned eight days. The spacecraft team now aims to bring the capsule down on Sunday morning (Dec. 22) at White Sands Missile Range in New Mexico (which was also the primary target site for the originally envisioned OFT).

Pulling off a safe landing will be a major milestone for the revised OFT, NASA officials and Boeing representatives said. And Starliner’s 48 hours in orbit should end up teaching them a lot of useful information about the capsule’s behavior in the space environment, they added.

OFT was supposed to clear the way for Starliner’s first crewed flight, a demonstration mission to the ISS that had been targeted for mid-2020. It’s too early to speculate about how that timeline may change, Bridenstine said. For example, NASA has not yet decided if it will ask Boeing to conduct another version of OFT, or if Starliner’s next flight to the ISS will be the crewed demonstration mission.

Boeing has been developing Starliner with funding from NASA’s Commercial Crew Program, most recently a 2014 contract that awarded the aerospace giant $4.2 billion to finish work on the capsule and fly six operational missions to and from the ISS.

SpaceX got a similar, $2.6 billion deal in 2014 to get its Crew Dragon capsule up and running. The main goal, from NASA’s perspective, is to bring an orbital human spaceflight capability back to American shores. NASA has been dependent on Russian Soyuz spacecraft to get astronauts to and from the ISS since the space shuttle fleet was grounded in July 2011.

Crew Dragon successfully flew its version of OFT, a six-day uncrewed flight called Demo-1, in March of this year. SpaceX is gearing up for a key in-flight test of the capsules’ emergency-escape system next month. If that goes well, the company will start prepping for Demo-2, its crewed demonstration mission to the ISS.

Editor’s note: This story was updated on Saturday to provide new information about the attempts to hail Starliner via TDRS. This information was revealed during a news conference on Saturday.

Mike Wall’s book about the search for alien life, “Out There” (Grand Central Publishing, 2018; illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook

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Source: space.com

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