Boeing Starliner launch delayed to Tuesday due to helium leak

May 15 (UPI) -- Boeing's Starliner flight to the International Space Station was delayed again due to a helium leak.

NASA, Boeing and the United Launch Alliance said in a statemen Tuesday that the launch date will now come no earlier than Tuesday at 4:43 p.m. EDT.

"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," they said.

Boeing's statement said that it is working with NASA "developing spacecraft testing and operational solutions to address the issue."

"As a part of the testing, Boeing will bring the propulsion system up to flight pressurization just as it does prior to launch, and then allow the helium system to vent naturally to validate existing data and strengthen flight rationale," it said.

The previous delay was to replace a bad oxygen tank pressure regulation valve on the Atlas V rocket's Centaur upper stage. That valve passed a test, but the new issue has delayed the launch again.

The Boeing Starliner is being prepared for a crew flight test to the International Space Station.

NASA astronauts Butch Wilmore and Suni Williams have been in pre-flight quarantine. They returned to Houston May 10 to spend more time with their families as the prelaunch procedures continue. In a few days they will return to NASA's Kennedy Space Center in Florida.

The Atlas V and Starliner are in the Vertical Integration Facility at Space Launch Complex 41 at Cape Canaveral Space Force Station in Florida.

Starliner has had multiple problems that have repeatedly delayed launches.

In June problems with parachutes and wiring insulation delayed a launch that had been planned for July 21.

Two Starliner missions landed safely in the New Mexico desert in two test flights in 2019 and 2022. But since the first launch in 2019, a number of problems have delayed the Starliner schedule.