The first Boeing Starliner astronauts have returned to the launch site.
NASA Crewed Flight Test (CFT) astronauts Butch Wilmore and Suni Williams arrived at NASA’s Kennedy Space Center in Florida on Tuesday (May 28) ahead of the Boeing Starliner’s scheduled liftoff on Saturday (June 1).
NASA will hold a delta flight readiness review later today (May 29) to review the launch, officials said; This is a slightly more detailed review than a standard review, to address the Starliner’s technical issues resulting from a helium leak.
Assuming the mission passes this review and schedules are met, the CFT will launch from the nearby Cape Canaveral space station no earlier than 12:25 p.m. EDT (4:25 p.m. GMT), and you can watch the historic launch here on Space.com, via NASA Television. . NASA will provide an update to journalists Friday, May 31 at 1 p.m. EDT (5 p.m. GMT), which you can also watch live here.
Related: “It’s so complicated”: Boeing Starliner teams diagnose helium leak before astronaut launch on June 1
This is not the first time the crew has flown to KSC aboard NASA T-38 trainer aircraft for a launch attempt; they first arrived on April 25 for what was supposed to be a May 6 launch, but that effort was canceled just two hours before liftoff.
As the stacked Starliner and United Launch Alliance Atlas V rockets underwent troubleshooting, the crew – still in quarantine – returned to NASA’s Johnson Space Center in Houston for a few weeks to continue training and wait for a later launch date. farm.
The Starliner CFT made a long journey to the launch pad. NASA tasked SpaceX and Boeing with billion-dollar contracts in 2014 to send astronauts to the International Space Station by 2017. Both vehicles were delayed in that goal due to technical and financial problems.
SpaceX, borrowing from its Dragon cargo design that has been flying missions to the ISS since 2012, completed its first crewed test in 2020. SpaceX has since flown 11 other missions to the ISS. Starliner, a brand new spacecraft, took longer.
Starliner’s first ISS mission in 2019 without astronauts got stuck in the wrong orbit due to software issues and failed to reach its destination. A follow-up mission in 2022 managed to succeed after dozens of fixes and delays due to the pandemic.
Related: 2 astronaut taxis: why NASA wants both the Boeing Starliner and the SpaceX Dragon
CFT encountered another delay in 2023 after the parachutes were found to carry less load than expected and flammable tape was found on the wiring. NASA and Starliner officials stressed that the mission is under development – which means not only that safety takes priority over any schedule issues, which is true for all missions, but that corrections caps will be needed as the design matures.
The two CFT astronauts are also former US Navy test pilots and have thus participated in the development of other aerospace projects over the decades.
Everything seemed on track for a launch attempt on May 6, but late in the countdown, a “buzzing” valve was discovered aboard the Atlas V, meaning the oxygen relief valve opened and closed quickly. This problem prompted ULA, Boeing and NASA to cancel the mission. Hours of troubleshooting resulted in the decision to return the rocket to its Cape Canaveral facility for a valve replacement.
That valve swap went ahead as planned on May 12, but a small helium leak in an Aerojet Rocketdyne booster aboard the Starliner — discovered after the scrub — later came under scrutiny. Team representatives told reporters in a briefing last week that they learned a few things during this process.
The leak does not constitute an immediate risk for a launch, since helium is an inert gas; Both Crew Dragon and the space shuttle lifted off safely despite helium leaks, they noted. The concern is how this leak would affect the Reaction Control System (RCS); it is a set of 28 small engines aboard the Starliner for modest maneuvers in orbit.
The leak is in a button-sized area in the Starliner spacecraft, less than 10 sheets of paper thick, in a rubber seal between two metal parts of a flange. The leak is about 50 to 70 psi depending on the pressure around it, but this (apparently) high rate is relative to a tiny space, NASA and Boeing pointed out during the briefing.
It wasn’t safe to open this location with Starliner stacked on Atlas V, but extensive computer analysis showed the leak appeared stable. The team also performed pressure changes in this area, to simulate spaceflight changes, and were pleased with the performance they saw.
Additionally, the other 27 boosters have no leaks, creating a large buffer if further leaks occur, NASA’s Steve Stich, manager of the agency’s commercial crew program, pointed out during the call. May 24.
He added that engineers, however, discovered a “design vulnerability” while troubleshooting the helium. Simply put, Starliner has three certified modes for returning astronauts to Earth: one mode using the RCS thrusters and two modes using the Orbital Maneuvering and Attitude Control (OMAC) thrusters; OMAC modes require two or four of these thrusters, depending on the situation.
The RCS re-entry mode requires eight thrusters in adjacent “niches”: there are four of these assemblies around Starliner. But in rare helium leak circumstances, all thrusters in adjacent niches may fail simultaneously, meaning the RCS would no longer be available to back up the OMAC. The team thus created, and simulated with the CFT astronauts, a new re-entry mode which would only require four RCS thrusters at a time. The delta flight preparation exam will confirm, among other things, the certification of this new re-entry technique.