Explanation – How can the Boeing Starliner return its astronauts to Earth?

Problems with Boeing’s Starliner capsule, which is still docked with the International Space Station (ISS), have derailed original plans for the astronauts’ return to Earth, while last-minute repairs and tests have delayed a mission considered crucial for the future. From the aviation division of Boeing.

NASA has postponed the planned return three times and has not yet set a date. Since launch on June 5, the capsule has suffered five helium leaks, five maneuvering thrusters failed, and a thrust valve failed to close fully, causing the space crew and mission managers in Houston to spend more time than expected troubleshooting the mission.

Here’s an explanation of potential paths forward for Starliner astronauts and veteran NASA astronauts Barry “Butch” Wilmore and Sunita “Sonny” Williams.

current situation

Starliner could remain docked with the International Space Station for up to 45 days, NASA Commercial Crew Manager Steve Stich told reporters. But if it’s absolutely necessary, such as when more issues arise that mission officials can’t resolve in time, the Starliner could remain at dock for up to 72 days, relying on various backup systems, according to a person familiar with the flight planning.

Internally at NASA, the latest date for Starliner’s return is July 6, according to this source, who spoke on condition of anonymity. This return date means that the mission, which was scheduled to last eight days, will instead last for a month.

The Starliner’s expendable propulsion system is part of the aircraft’s “service module.” Current problems focus on this system, which is necessary to propel the capsule away from the International Space Station and dive through the Earth’s atmosphere. Many Starliner engines overheat during launch, and leaks of helium — used to pressurize the engines — appear to be related to how often they are used, according to Stich.

Recent rocket firing tests while Starliner remained at dock gave mission teams confidence in a safe return, though tests and evaluations are continuing, Stitch said. The mission management team, made up of NASA and Boeing personnel, is studying data on the propulsion problems, running simulations in Houston and considering how to fix them, such as updating the software or changing hardware usage.

Once NASA officials give the team the green light to return, the Starliner engines will be used to detach the capsule from the International Space Station and begin the roughly six-hour journey home, with the orbit gradually shortening before the capsule plunges into Earth’s atmosphere for the duration of a parachute- and airbag-assisted landing at one of the sites. Potential in the southwestern United States.

This is the first Starliner mission to orbit with astronauts on board, the final test required before NASA can certify it as the US space agency’s second flight to the International Space Station. It will join SpaceX’s Crew Dragon, which has dominated the emerging government and private markets for human spaceflight amid years-long Starliner delays.

When the unexpected happens

Even with problems with the propulsion system, NASA said the Starliner would still be able to return astronauts to Earth if necessary — that is, if the capsule needed to be used as an escape point from the International Space Station in emergency service or if any of the Starliner’s damaged parts showed up. – Like solar panels – signs of expiration earlier than planned.

Unlike the current Starliner mission, NASA has not set a specific return date for the first Crew Dragon mission with astronauts in 2020. This mission ultimately took 62 days because the astronauts had to help maintain the International Space Station as the space station was closed at the time. .

If this is not possible use Starliner

If the Starliner vehicle is deemed unable to safely return Wilmore and Williams to Earth, one option would be to send them home aboard Crew Dragon, which brought four astronauts to the station in March and has more in case of emergency.

This scenario, considered unlikely, would undoubtedly be embarrassing for Boeing. But NASA and Boeing officials, as well as engineers familiar with the program, told Reuters that nothing in the Starliner’s current problems suggests this would be necessary.

In such a scenario, the Starliner’s fate depends on several factors, including the extent of the technical problems.

The last time a NASA astronaut needed a backup flight home was in 2022, when a Russian Soyuz capsule suffered a coolant leak after bringing two astronauts and US astronaut Frank Rubio to the station.

NASA considered Crew Dragon as a replacement flight for Rubio home, but he ended up using an empty Soyuz capsule launched by Russia as a rescue vehicle. Rubio’s mission was extended from six months to just over a year – 371 days – a record length of time for an American in space.