Updated at 10:45 p.m. EST with post-launch commentary.
TITUSVILLE, Fla. – Boeing’s CST-100 Starliner spacecraft successfully docked with the International Space Station on May 20, just over 24 hours after launch.
The spacecraft docked at the station’s Harmony module forward docking port at 8:28 p.m. Eastern Time. Controllers reported hard docking securing the spacecraft to the station about 20 minutes later, although the hatches separating the spacecraft from the station would not open until around 11:45 a.m. on May 21.
The docking took place more than an hour later than the original schedule, as controllers resolved several 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.
“To the joint team of Boeing and NASA, the crew of Expedition 67 would like to extend their congratulations on this momentous occasion,” said NASA astronaut Bob Hines, currently on the station, after the confirmation of mooring. “Today marks an important step toward providing additional commercial access to low Earth orbit, sustaining the ISS, and achieving NASA’s goal of bringing humans back to the Moon and eventually to the Moon. March.”
“It was a really critical demonstration mission,” Kathy Lueders, NASA associate administrator for space operations, said during a briefing an hour after docking. “To see this vehicle now docked to the ISS is nothing short of phenomenal.”
Neither NASA nor Boeing provided updates on the status of the Orbital Flight Test (OFT) 2 mission for more than 17 hours after a post-launch briefing on May 19, an unusual silence that raised fears of a problem with the spaceship. A Boeing spokesperson told SpaceNews the company would provide an update on the mission “in a moment,” but the company did not release that update until more than three hours later.
In this update, Boeing confirmed that the spacecraft was in generally good condition, having completed several tests as planned. One issue was the “off-design behavior” of a thermal cooling loop on the spacecraft, but the company said the system still maintained stable temperatures.
“The ground crew did a great job managing these loops,” said NASA Commercial Crew Program Manager Steve Stich during the post-docking briefing. He said moisture may have entered the coolant loops which had frozen and clogged a filter, causing the pressure in the loop to rise. The controllers were able to handle the temperature of these coolant loops, and there was plenty of headroom in the system.
The other issue was the failure of 2 of the 12 rear-facing Orbital Maneuvering and Attitude Control (OMAC) thrusters during the spacecraft’s orbit shortly after launch. In the statement, Boeing said a drop in chamber pressure likely caused the thrusters to shut down.
Mark Nappi, Boeing vice president and director of the commercial crew program, said engineers had developed fault three and identified “about three” plausible causes, which he did not identify, later suggesting that both thrusters may have failed for different reasons. “We may never know what the real cause of this is because we are not recovering this vehicle,” he said. The thrusters are located in the service module, which is jettisoned prior to reentry and burns up in the atmosphere.
Other OMAC thrusters continued to perform well, performing several maneuvers as the spacecraft approached the station before smaller Reaction Control System (RSC) thrusters took over for the final approach. OMAC thrusters will no longer be used until the spacecraft de-orbits at the end of the mission.
In addition to the two OMAC thruster failures, two RCS thrusters also shut down while approaching the station after experiencing a drop in chamber pressure. “I don’t think we quite know what happened to those thrusters yet, but the vehicle has a lot of redundancy,” Stich said, including for undocking and landing.
Starliner is expected to remain at the station until at least May 25. Stich said the first undocking opportunity would set up a landing at White Sands Space Harbor in New Mexico at 6:46 p.m. Eastern time that day, weather permitting. “We are in no rush to come back. We want to learn as much as possible from this vehicle while it is in orbit.
#Starliner #docks #ISS #time #SpaceNews