欧美文化:NASA delays Boeing Starliner launch to no earlier than May 21

LOS ANGELES, May 14 (Xinhua) -- NASA and Boeing are now targeting no earlier than Tuesday, May 21, for launch of the first crewed mission of the Starliner spacecraft to the International Space Station (ISS), the agency said on Tuesday.

The spacecraft was previously scheduled to launch on a United Launch Alliance (ULA) Atlas V rocket on May 6 from Cape Canaveral Space Force Station in the U.S. state of Florida.

The launch attempt was scrubbed due to technical issues.

On May 11, the ULA team successfully replaced a pressure regulation valve on the liquid oxygen tank on the Atlas V rocket's Centaur upper stage. The team also performed re-pressurization and system purges, and tested the new valve, which performed normally, according to NASA.

Starliner teams are working to resolve a small helium leak detected in the spacecraft's service module traced to a flange on a single reaction control system thruster. Helium is used in spacecraft thruster systems to allow the thrusters to fire and is not combustible or toxic.

NASA and Boeing are developing spacecraft testing and operational solutions to address the issue.

The flight test will carry NASA astronauts Butch Wilmore and Suni Williams to ISS. The duo are the first to launch aboard Boeing's Starliner to the space station as part of the agency's Commercial Crew Program.

The astronauts will spend about a week at the orbiting laboratory before returning to Earth and making a parachute and airbag-assisted landing in the southwestern United States, according to NASA.

After successful completion of the mission, NASA will begin the final process of certifying Starliner and its systems for crewed rotation missions to the space station.