Working around multiple helium leaks and thruster problems, the crew of Boeing’s Starliner spacecraft wrapped up a challenging rendezvous and a delayed-but-successful docking with the International Space Station Thursday in a major milestone for the new ship’s first piloted test flight.
With commander Barry “Butch” Wilmore and co-pilot Sunita Williams monitoring the Starliner’s automated approach, the Starliner’s docking mechanism engaged its counterpart on the front of the station’s forward Harmony module at 1:34 p.m. EDT as the two spacecraft were sailing 260 miles above the Indian Ocean.
A few moments later, the Boeing ferry ship was pulled in for a “hard” mating, ensuring an airtight structural seal.
“That was an OK, three-wire, fly Navy docking complete!” mission control radioed.
“OK indeed,” replied Wilmore, a veteran astronaut and former Navy test pilot. “Nice to be attached to the big city in the sky.”
After extensive leak checks, hatches were expected to be opened so Wilmore and Williams could float into the lab complex to join the seven Expedition 71 crew members: cosmonauts Oleg Kononenko, Nicolai Chub and Alexander Grebenkin, along with NASA astronauts Matthew Dominick, Michael Barratt, Jeanette Epps and Tracy Dyson.
Wilmore and Williams plan to spend about a week aboard the outpost before returning to Earth June 14 aboard the Starliner. While they’re there, the station crew will install a replacement urine processor pump module that was loaded aboard the Starliner at the last minute to fix the lab’s water recycling system and allow normal use of the toilet in the U.S. segment of the station.
Running years behind schedule after multiple problems that cost Boeing some $1.4 billion to correct, the Starliner was launched Wednesday with a known helium leak in the system used to pressurize the spacecraft’s propulsion system. Launch had been delayed a month, in part because of work to confirm the ship could safely be launched with the leak as is.
After reaching orbit, two more helium leaks developed that prompted flight controllers to close valves leading to the affected manifolds while they analyzed leak rates and potential work arounds. Closing the manifolds took down six of 28 reaction control system jets and three of 20 more powerful thrusters.
As the Starliner closed in on the station Thursday, all three manifolds were re-opened to provide the pressure needed to operate all the available thrusters.
Engineers then had to deal with four RCS jets that either failed or exhibited suspect readings. Flight controllers then commanded test firings to verify performance and all but one of the thrusters were recovered. But by that point, the crew was forced to shift to a backup docking opportunity.
Throughout that process, Wilmore flew the Starliner manually, holding position about 650 feet from the space station. When ground teams concluded the spacecraft had enough thruster redundancy to proceed, the Starliner’s automated control system took over and flew the ship in for a problem-free docking.
Flight controllers planned to close the three suspect helium manifolds to prevent any leakage while attached to the station.
Despite the leaks, NASA officials said enough helium was on board to provide 90 hours of flying time beyond the point of undocking, more than enough time to complete a normal-duration mission.
But the cause of the leaks and the thruster problems could require extensive post-flight inspections and upgrades, another potential headache for Boeing and plans to begin operational Starliner flights to the space station early next year.
Boeing’s Starliner docks at International Space Station
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