by The first Boeing Starliner astronauts are back at the launch site.
NASA Crew Flight Test (CFT) astronauts Butch Wilmore and Suni Williams arrived at NASA’s Kennedy Space Center in Florida on Tuesday (May 28) ahead of their expected Boeing Starliner liftoff on Saturday (June 1).
NASA will conduct a delta flight readiness review later today (May 29) to review the launch, officials said; this is a bit more detailed than a standard review, to address technical concerns on Starliner resulting from a helium leak.
Assuming the mission passes the review and keeps to the schedules, CFT will be launched from the nearby Cape Canaveral Space Force Station no earlier than 12:25 pm EDT (1625 GMT), and you can watch on the historic launch here at Space.com, via NASA Television . NASA will provide an update to reporters on Friday (May 31) at 1 pm EDT (1700 GMT) which you can also watch live here.
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This is not the first time the crew has flown into KSC on NASA T-38 trainer jets for a launch attempt; they first flew in on April 25 for an expected May 6 launch, but that attempt was scrubbed just two hours before liftoff.
As the Starliner stack rocket and United Launch Alliance Atlas V undergo 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 firm.
Starliner CFT had a long journey to the launch pad. NASA awarded both SpaceX and Boeing billion-dollar contracts in 2014 to send astronauts to the International Space Station by 2017. Both vehicles have been delayed in that goal due to technical and funding challenges.
SpaceX, borrowing from its cargo Dragon design that has flown ISS missions since 2012, completed its first crewed test in 2020. SpaceX has flown 11 more missions to the ISS since then. 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 glitches and failed to reach its destination. A follow-up mission in 2022 made it safely after numerous fixes, and delays due to the pandemic.
Related: 2 astronaut taxis: Why NASA wants Boeing’s Starliner and SpaceX’s Dragon
CFT was further delayed in 2023 when the parachutes were found to be able to carry less load than expected, and flammable tape was found on the wiring. NASA and Starliner officials emphasized that the mission is under development — meaning not only that safety is prioritized over any schedule concerns, which is true of all missions, but that course corrections will be needed as the design matures. .
Both CFT astronauts are also former US Navy test pilots, so they have participated in the development of other aerospace projects for many years.
Everything appeared to be on track for a May 6 launch attempt, but late in the countdown a “buzzing” valve was discovered aboard the Atlas V, meaning the oxygen relief valve was opening and closing rapidly. That issue prompted ULA, Boeing and NASA to scrap the mission. Hours of troubleshooting led to the decision to tow the rocket back to its Cape Canaveral facility for a valve replacement.
That valve swap went as planned by May 12, but a small helium leak in an Aerojet Rocketdyne thruster aboard the Starliner – found after the crash – was thoroughly investigated. Team representatives told reporters in a briefing last week that they had learned a few things in that process.
The leak is not an immediate risk to shipping, since helium is an inert gas; both Crew Dragon and the space shuttle have been safely launched with helium leaks, they noted. The concern is how that leak would affect the reaction control system (RCS); that is a set of 28 small engines on board Starliner for moderate maneuvers in orbit.
The leak in a button-sized area in the Starliner spacecraft is less than 10 sheets of thick paper, in a rubber seal between two metal flange parts. The leak is about 50 psi to 70 psi depending on the pressure around it, but that high rate is (apparently) relative to a tiny space, NASA and Boeing emphasized in the briefing.
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It was unsafe to open this spot with Starliner stacked on Atlas V, but extensive computer analysis showed that the leak appeared to be stable. The team also made pressure changes in this area, to simulate changes in spaceflight, and were pleased with the performance they saw.
In addition, the other 27 thrusters have no leaks at all, which creates a large buffer if another leak develops, emphasized NASA’s Steve Stich, the agency’s commercial crew program manager. on call 24 May.
He added that engineers, however, encountered a “design vulnerability” during the helium troubleshooting. Simply put, Starliner has three certified methods of returning the astronauts to Earth: One method using the RCS thrusters, and two methods using orbital maneuvering and attitude control (OMAC) thrusters; OMAC modes require two or four of those thrusters, depending on the situation.
The RCS reentry method requires eight thrusters in “doghouses:” Four of these assemblies surround the Starliner. But in the rare event of a helium leak, all litters in adjacent doghouses could fail at the same time, meaning RCS would no longer be available to support OMAC. So the team, and simulated with the CFT astronauts, created a new re-entry method that would require only four RCS thrusters at a time. The delta flight readiness review will confirm the certification of that new re-entry technique, among other things.
