Washington (AFP)

Boeing's Starliner capsule will not launch for the International Space Station on Wednesday due to a problem in the propulsion system that caused the cancellation of an unmanned test flight the day before, the company said without set the date for a next mission.

"Unexpected" indications on the position of the valves of the Starliner propulsion system indeed led to the temporary shutdown of the mission, Boeing said in a statement.

Engineering teams have ruled out several possible causes, including a software error, but need more time to understand the phenomenon, NASA added.

"We're going to let the data guide us," said John Vollmer, head of Boeing.

"Our team has worked diligently to ensure the safety and success of this mission, and we will proceed with a launch only if our vehicle is functioning properly and our teams are confident in its ability to fly," he said.

The test mission was originally scheduled to take place on Friday but had to be postponed to Tuesday after a Russian science module unexpectedly activated its thrusters after docking with the International Space Station (ISS), changing its orientation.

This incident is far from being the first setback experienced by Boeing since the establishment of its contract with NASA.

After ending its own space shuttle program in 2011, NASA has in fact secured the services of Boeing and SpaceX in order to no longer need Russian rockets to reach the ISS.

SpaceX has already transported no less than ten astronauts to the Space Station, including Frenchman Thomas Pesquet, aboard its Crew Dragon spacecraft.

For its part, Boeing has fallen behind.

In December 2019, during a first test flight, a software problem had caused a problem in the way the capsule had ignited its thrusters.

As a result, Starliner had not had enough fuel to reach the ISS and had to turn back to Earth prematurely.

Subsequently, an investigation showed that the capsule had almost experienced a serious flight anomaly on entering the atmosphere.

NASA had described the mission as a "high visibility close call", a rare name reserved for flights that came close to disaster.

It is crucial for Boeing to successfully complete an unmanned flight mission to the ISS before it can safely ferry astronauts.

© 2021 AFP