Boeing, NASA prepare for second flight test of new Starliner despite leak on spacecraft

After a failed launch attempt of Boeing's new Starliner crew capsule on May 6, NASA and the aerospace company are prepared for a second go — even though the spacecraft will be flying with a small helium leak.

On Wednesday, Boeing and the National Aeronautics and Space Administration called a "go" for launch after a flight test readiness review. The launch is set for Saturday at 12:25 p.m. ET. If this launch is delayed, there are other opportunities on June 2, 5 and 6.

The initial launch attempt of Starliner (also known as CST-100) was scrubbed due to an oxygen leak. The launch was called off  just as NASA's two astronauts — Suni Williams and Butch Wilmore, who will be the test crew for this capsule — were getting strapped into their seats on the new spacecraft on the night of May 6.

The leak was detected on the United Launch Alliance (ULA) Atlas V rocket on which the capsule is hitching a ride.

After the rocket and capsule were rolled back to ULA's Vertical Integration Facility for further examination, the oxygen leak was traced back to a thruster valve that was eventually replaced.

However, other issues were discovered, including a helium leak in Starliner.

At a press update last week, Mark Nappi, Boeing's Starliner program manager, said that had the helium leak been discovered during launch procedures, it wouldn't have caused a scrub. He also said the discovery had a "silver lining."

"Had we launched ... it would have been a safe flight and a successful flight," he said, "but we would have not known as much as we know today."

The leak was discovered in a small control jet that helps the capsule make small adjustments while in orbit. However, there are 28 of these jets, and the teams working on the issue ensured that none of the others could fail. Helium is an inert gas and not combustible.

The reason given for not fixing the leak was that it would have caused further delays to a launch that has faced years of setbacks.

The teams would have had to remove Starliner from Atlas V, take it to a separate facility and drain the service module (which provides power and propulsion for the capsule). Then they'd have to start at the beginning and refill the capsule with propellant and reinstall it atop the rocket.

Although the leak is small, they determined that even if it were to leak further, it would "not be a safety-of-flight-issue," Nappi said.

Meanwhile, teams also discovered another issue, this time with the flight re-entry system, something Nappi called a "design vulnerability."

When Starliner re-enters the atmosphere, it needs to lose a great deal of speed. It has three different ways of doing this — referred to as redundancy capabilities. One approach uses four special thrusters (which includes one with the helium leak), another uses just two and the third approach uses eight smaller thrusters.