Updated at 22:45 East with comments for the post-launch briefing.
TITUSVILLE, Florida – Boeing’s CST-100 Starliner successfully docked with the International Space Station on May 20, just over 24 hours after its launch.
The spacecraft docks with the Harmony module’s front docking port at 20:28 east. Controllers reported a firm dock securing the spacecraft to the station about 20 minutes later, although hatches separating the spacecraft from the station will not open until about 11:45 a.m. east on May 21.
The docking took place more than an hour later than originally scheduled, as controllers tackled a few minor issues. This included the spacecraft’s docking ring, which had to be retracted and extended again before the spacecraft could make its final approach.
“On the joint Boeing-NASA team, the crew of Expedition 67 would like to extend our congratulations on this important occasion,” said NASA astronaut Bob Hines, who is currently at the station after the docking was confirmed. “Today marks a major milestone in securing additional commercial access to low Earth orbit, maintaining the ISS and allowing NASA’s goal to bring people back to the moon and eventually to Mars.
“It was a really critical demonstration mission,” said Katie Luders, NASA’s assistant administrator for space operations, at a briefing an hour after the jump. “To see this vehicle now attached to the ISS is phenomenal.”
Neither NASA nor Boeing provided updates on the status of the Orbital Flight Test (OFT) 2 mission more than 17 hours after a briefing after the May 19 launch, an unusual silence that raised fears that there was a problem with the spacecraft. A Boeing spokesman told SpaceNews that the company would provide an update for the mission “shortly”, but the company released the update just over three hours later.
In this update, Boeing confirmed that the spacecraft is generally in good condition after conducting several tests as planned. One of the problems was the “abnormal behavior” of the spacecraft’s thermal cooling circuit, but the company said the system still maintains stable temperatures.
“The ground team did a great job managing these circuits,” said Steve Stitch, NASA’s sales crew program manager, at a briefing after the jump. He said moisture may have gotten into the coolant circuits, which froze and clogged the filter, causing the circuit to increase pressure. The controllers were able to control the temperature of these coolant circuits and there was a lot of margin in the system.
The other problem was the failure of 2 of the 12 stern-facing orbital maneuvering and attitude control devices (OMACs) during the launch of the spacecraft, which burned down shortly after launch. In a statement, Boeing said a drop in chamber pressure may have caused the pushers to stop.
Mark Napie, Boeing’s vice president and sales crew manager, said the engineers developed error three and identified “three or more” plausible reasons he did not identify, later suggesting the two pushers may have been were damaged for various reasons. “We may never know the real reason for this, because we are not getting this vehicle back,” he said. The engines are located in the service module, which is discarded before re-entry and burns in the atmosphere.
Other OMAC engines continued to perform well, performing several maneuvers as the spacecraft approached the station before the smaller RSC engines took the final approach. OMAC engines will not be reused until the spacecraft’s exit orbit burns out at the end of the mission.
In addition to the two OMAC engine failures, two RCS engines also shut down during the approach to the station after experiencing a drop in chamber pressure. “I don’t think we still know what happened to these pushers, but the vehicle has a lot of reserves,” Stitch said, including for uncoupling and landing.
Starliner is expected to remain at the station until at least May 25. Stitch said the earliest unbundling opportunity would be a landing at the New Sands spaceport in New Mexico at 6:46 p.m. east that day, weather permitting. “We are not in a hurry to return. We want to learn as much as possible about this vehicle while in orbit. “
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