Leaving behind the two NASA astronauts it took to the International Space Station three months ago, Boeing’s troubled Starliner spacecraft is set to begin its return to Earth on Friday evening.
Six hours after it undocks from the station, it is to parachute to a landing at the White Sands Space Harbor in New Mexico. If bad weather or technical issues cause a delay, Starliner’s return could happen on Sept. 10, Sept. 14 or Sept. 18.
After lengthy analysis and ground tests, NASA officials said they still did not fully understand the cause of the propulsion system problems that arose as Starliner approached the space station in June.
Both Boeing and NASA officials have said that they expect that the trip back will be uneventful for the empty Starliner. And they maintain that the spacecraft could have probably still brought back safely the two NASA astronauts, Suni Williams and Butch Wilmore, whose stays on the space station have been extended.
“We have confidence in the vehicle,” Steve Stich, the manager of the commercial crew program at NASA, said during a news conference on Wednesday. He noted that Starliner had successfully landed during earlier test flights with no crew.
“We’ve had two good landings with Starliner so far, and we’re expecting another one Friday,” Mr. Stich said.
Even so, lingering unease led officials to choose what they considered to be the safer option: to keep Ms. Williams and Mr. Wilmore on the space station for another five months and have them return in February on the Crew Dragon, a spacecraft built by SpaceX, a competitor founded by Elon Musk.
Dana Weigel, the program manager for the space station at NASA, said Ms. Williams and Mr. Wilmore had undergone training for a longer mission including performing spacewalks and operating the robotic arm.
“We had them well prepared to move into this role,” Ms. Weigel said.
After Starliner undocks, it will fire its thrusters to back away and then move above the space station. The maneuver was changed from what would have been used had the astronauts been aboard. “It’s a quicker way away from station, way less stress on the thrusters,” Mr. Stich said.
The departure uses short thruster pulses, which are less likely to cause the heating that is believed to have reduced the performance of some of 28 small thrusters in June. The spacecraft also experienced leaks of helium, an inert gas used to push propellant. But it still has much more helium than is needed for the return trip.
The key maneuver is a firing by larger thrusters that causes the spacecraft to drop out of orbit. The smaller thrusters, including the ones that malfunctioned during docking, are used to keep the spacecraft pointed in the correct direction.
The large thrusters have not had any problems so far, but in case they malfunction, the smaller thrusters also serve as a backup for dropping the spacecraft out of orbit. .
If the landing goes smoothly, what happens next with the Starliner program remains somewhat uncertain. June’s flight was the first with astronauts aboard, and was to be the last step in NASA’s process of certifying that Starliner was ready to begin regular once-a-year trips carrying astronauts to the space station.
NASA could request that Boeing perform another crewed flight test. The company agreed to redo a crewless flight test after the first launch of Starliner in December 2019 almost immediately ran into technical trouble.
Bill Nelson, the NASA administrator, said at a news conference last month that the new chief executive of Boeing, Kelly Ortberg, had assured him that Boeing would continue working on Starliner.
However, that would come at considerable cost for Boeing. The $4.2 billion contract that Boeing signed with NASA in 2014 set fixed amounts for meeting milestones like certification, and the company does not receive payment until it meets those benchmarks. Unlike many traditional so-called cost-plus contracts, Boeing is responsible for picking up the cost of overruns and delays under the agreement with the agency.
Boeing has already written off $1.6 billion of its costs for the Starliner program.
The post Boeing Starliner Set to Leave Space Station Without Its Crew appeared first on New York Times.
