Boeing’s Starliner spacecraft returned to Earth on Wednesday after a largely successful uncrewed test flight that included four and a half days docked at the International Space Station.
“It was a picture-perfect landing,” Steve Stich, manager of the commercial crew program at NASA, said during a news conference a couple of hours later. “The test flight was extremely successful. We met all the mission objectives.”
Starliner, which Boeing developed for NASA, provides the space agency with a second transportation system for taking astronauts to and from the space station. SpaceX, the rocket company founded by Elon Musk, has been flying astronauts to the space station on its Crew Dragon spacecraft for a couple of years.
Streaking across the sky over the Pacific Ocean, then crossing over Mexico’s Baja California Peninsula, Boeing’s capsule parachuted to a landing at the White Sands Missile Range in New Mexico. The conclusion of the this test flight comes after a couple of years of setbacks and sets the stage for the next Starliner mission, which is to have astronauts aboard.
Mr. Stich said the spacecraft experienced a few glitches during landing — it dropped communication with global positioning satellites for a while before reconnecting, and one of the capsule’s thrusters may have malfunctioned.
On Tuesday, astronauts on the space station closed the hatch to the Starliner capsule after filling it with 600 pounds of cargo to be returned to Earth.
The spacecraft undocked from the orbiting outpost on schedule at 2:36 p.m. Eastern time on Wednesday. Less than 20 minutes later, it was more than 300 feet from the station and preparing for its journey back to the ground as the side of the Earth facing the sun came into view.
“It was a great stay by Starliner. We’re a little sad to see her go,” said Bob Hines, a NASA astronaut currently aboard the space station, after confirming the departure was successful.
After it departed, Starliner lined up its trajectory with the selected landing site in New Mexico.
As the capsule traveled through space, mission managers used the time before the spacecraft re-entered the atmosphere to remotely troubleshoot issues with its thrusters.
During launch on Thursday last week, just before Starliner entered orbit, two of the spacecraft’s thrusters failed. Other thrusters kicked in automatically to compensate.
During the troubleshooting on Wednesday, the two balky thrusters were fired and still exhibited problems, putting out only about one-quarter of the expected thrust. “We’ll have to go work on that after the flight,” Mr. Stich said.
Two other smaller thrusters, used during the approach to the space station, failed on Sunday, but those worked as expected when tested on Wednesday. Mr. Stich said four other of the smaller thrusters were also tested, without problem.
At 6:05 p.m., the capsule ignited its propulsion system for 58 seconds to drop out of orbit.
It then discarded its service module, the part below the cone-shaped capsule that contains most of the spacecraft’s propulsion and power systems. The service module re-entered the atmosphere separately and burned up. The malfunctioning thrusters were on the service module, so engineers will not be able to directly examine them.
The Starliner capsule sliced through the atmosphere; the compression of air against the blunt bottom seared the heat shield to 3,000 degrees Fahrenheit.
At an altitude of about 30,000 feet, two small parachutes called drogues deployed. The three main parachutes deployed about a minute later. A couple of minutes later, it hit the ground, cushioned by airbags.
Although Russian and Chinese astronaut transports have long parachuted onto land instead of splashing in the ocean, Starliner is the first American capsule to use that approach. Avoiding salt water should help simplify refurbishment of the capsule, which is designed to be used up to 10 times.
The mission, which launched on Thursday, avoided the major problems that occurred during an earlier test flight in December 2019. Software flaws during that flight caused the mission to be cut short without Starliner docking at the space station.
Because of the unfinished testing, NASA required Boeing to undertake a second uncrewed test flight. Boeing was ready to launch it in August 2021 until stuck valves on the spacecraft scuttled the countdown. Boeing then had to spend months investigating and remediating the valves.
This time, Starliner mostly worked as designed and achieved its objectives. In addition to the malfunctioning thrusters, the cooling system operated a bit sluggishly. But these appear to be the sort of problems that a test flight is designed to uncover and not major surprises.
Boeing and NASA can now start planning for the crewed flight, a final test before Starliner can enter routine operations.
“When I look at what happened in the flight and the kind of things we’ll need to work through over the next few months, I don’t see any reason why we can’t proceed toward the crewed flight test next,” Mr. Stich said.
NASA will wait until summer to announce who will be on that flight and whether it will carry two or three astronauts. Boeing and the agency have suggested that flight could occur before the end of the year, but Mark Nappi, vice president and program manager of Boeing’s commercial crew program, said it would probably be several months before they could set a target date for launch.
“Certainly, it could move into the first quarter of next year,” Mr. Stich said.
The contracts to Boeing and SpaceX were issued in 2014, three years after NASA retired the space shuttles. The agency had to rely on Russia to transport astronauts for nearly a decade.
A second transportation option offers NASA redundancy in case either spacecraft suffers an accident, and it prevents further reliance on Russia, which has become politically complicated since it invaded Ukraine earlier this year.
Soruce : https://www.nytimes.com/2022/05/25/science/boeing-starliner-landing-nasa.html