Boeing's 1st Starliner astronaut launch delayed again, to May 25

The first astronaut mission of Boeing's new Starliner spacecraft has been pushed back by an additional four days, to May 25.

Tuesday (May 21) had been the latest target date for the launch of Starliner's Crew Flight Test (CFT), which will send NASA astronauts Suni Williams and Butch Wilmore to the International Space Station (ISS) for a roughly week-long stay. 

But NASA announced today (May 17) that it's now eyeing May 25 for the liftoff, which will take place atop a United Launch Alliance (ULA) Atlas V rocket from Cape Canaveral Space Force Station, on Florida's Space Coast.

"The additional time allows teams to further assess a small helium leak in the Boeing Starliner spacecraft's service module traced to a flange on a single reaction control system thruster," agency officials wrote in an update today.

Related: Boeing Starliner 1st astronaut flight: Live updates

That leak was discovered earlier this week, prompting the mission team to push CFT's planned launch from today to May 21. Further analysis of the leak suggests that it's not a huge problem, but NASA, Boeing and ULA want more time to assess the situation, agency officials wrote in today's update.

"Pressure testing performed on May 15 on the spacecraft's helium system showed the leak in the flange is stable and would not pose a risk at that level during the flight," the update reads. 

"The testing also indicated the rest of the thruster system is sealed effectively across the entire service module," it continues. "Boeing teams are working to develop operational procedures to ensure the system retains sufficient performance capability and appropriate redundancy during the flight." 

CFT was originally supposed to launch on May 6, but that attempt was scrubbed a few hours before liftoff when the launch team noticed a "buzzing" valve in the Atlas V's upper stage. ULA eventually decided to replace the valve, a process that required rolling the Atlas V and Starliner off the pad and back to an assembly building. That operation pushed the target launch date to today, which became untenable after the helium leak cropped up.

Starliner and its rocket ride remain in the assembly building. Williams and Wilmore, meanwhile, are in quarantine in Houston. They'll return to Florida's Space Coast when the target launch date draws near, NASA officials said in today's update.

Boeing developed, and is flying, Starliner under a $4.2 billion contract awarded by NASA's Commercial Crew Program in 2014. SpaceX got a similar deal, worth $2.6 billion, for work on its Dragon capsule.

SpaceX is in the middle of its eighth contracted, long-duration astronaut mission to the ISS for NASA. CFT will be Starliner's first crewed effort, the equivalent of SpaceX's Demo-2 mission, a test flight that launched in May 2020.