NASA delays SLS tanking test, next launch opportunity

NASA’s Space Launch System moon rocket on its launch pad. Credit: Michael Cain / Spaceflight Now / Coldlife Photography

NASA said Monday it is now targeting Wednesday, Sept. 21, for a critical fueling test on the Space Launch System moon rocket, which could allow for another attempt to launch the unpiloted Artemis 1 lunar test flight as soon as Sept. 27, assuming engineers find no problems and the Space Force approves an extension for the rocket’s range safety system. The updated schedule is a four-day delay for the SLS tanking test and next launch opportunity.

“The updated dates represent careful consideration of multiple logistical topics, including the additional value of having more time to prepare for the cryogenic demonstration test, and subsequently more time to prepare for the launch,” NASA said Monday. “The dates also allow managers to ensure teams have enough rest and to replenish supplies of cryogenic propellants.”

Ground crews at NASA’s Kennedy Space Center completed repairs to a hydrogen leak at the launch pad over the weekend, the agency said Monday. Teams discovered the leak during a launch attempt Sept. 3, forcing NASA to delay the start of the Artemis 1 lunar test flight until the next launch period. NASA has cycles of roughly two weeks of launch opportunities each month due to a range of technical factors, primarily the position of the moon in its orbit around the Earth.

Technicians last week replaced two seals in liquid hydrogen lines routed between the rocket’s mobile launch platform and the core stage, then re-connected the fuel feed line between the launch pad and the launch vehicle over the weekend. Testing is on tap this week to ensure there is a tight bond between the ground-side and rocket-side umbilical plates at ambient conditions.

The cryogenic loading test on the rocket now planned for Sept. 21 will expose the umbilical connection to super-cold temperatures as liquid hydrogen flows into the rocket. The liquid hydrogen is chilled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius).

The shape and size of seals and gaskets can change when exposed to super-cold temperatures, creating a leak path that wasn’t detectable at ambient temperatures. A molecule of liquid hydrogen, created by bonding two hydrogen atoms together, is one of the tiniest known in the universe, and leak through gaps impermeable to other molecules.

The SLS moon rocket’s core stage contains 537,000 gallons of liquid hydrogen fuel and 196,000 gallons of super-cold liquid oxygen as an oxidizer. The same propellants power the SLS upper stage, with much smaller tanks. All four propellant tanks will be loaded in the Sept. 21 tanking test.

“The demonstration will allow teams to confirm the hydrogen leak has been repaired, evaluate updated propellant loading procedures designed to reduce thermal and pressure-related stress on the system, conduct a kick-start bleed test, and evaluate pre-pressurization procedures,” NASA said Monday.

The kick-start bleed test and pre-pressurization procedures will verify countdown steps that were unaccomplished during dress rehearsals earlier this year. The hydrogen bleed line needed to thermally condition the four core stage engines leaked during a June countdown rehearsal, and was repaired when the rocket returned to the Vehicle Assembly Building. NASA scrubbed the first Artemis 1 launch attempt Aug. 29 when sensor data indicated one of the engines was not reaching the proper temperature during the hydrogen bleed procedure.

NASA determined the temperature reading on the engine was from a bad sensor, and pressed ahead with a second launch attempt Sept. 3. But the launch team never got to the kick-start bleed milestone in the Sept. 3 countdown due to the hydrogen leak encountered during fuel loading.

The launch dates and windows for Launch Period 26 for the Artemis 1 mission, opening Sept. 19 and closing Oct. 4. Credit: NASA / Spaceflight Now

The space agency also continues to work with the U.S. Space Force’s Eastern Range on a request to extend the range’s certification of batteries on the SLS moon rocket’s flight termination system, which would destroy the launcher if it veered off course after liftoff. The range must approve the battery certification — initially 20 days, then increased to 25 days and now would need to cover at least 45 days — in order for NASA to proceed with attempts in late September and early October.

“NASA is continuing to respect the Eastern Range’s process for review of the agency’s request for an extension of the current testing requirement for the flight termination system and is providing additional information and data as needed,” the agency said Monday. “In parallel, the agency is continuing preparations for the cryogenic demonstration test and potential launch opportunities, should the request be approved.”

If the range doesn’t approve the battery certification extension, NASA will need to roll the SLS moon rocket back to the Vehicle Assembly Building, pushing the Artemis 1 launch date into the second half of October or November. The next launch period opens Oct. 17 and runs through Oct. 31, followed by another series of launch dates starting Nov. 12.

NASA said a launch attempt Sept. 27, if approved by the range, would have a launch window opening at 11:37 a.m. EDT (1537 GMT). If the mission blasts off Sept. 27, the Orion spacecraft would wrap up its unpiloted test flight to the moon and back with a splashdown in the Pacific Ocean on Nov. 5.

A backup launch opportunity could be available Oct. 2, with a 109-minute launch window opening at 2:52 p.m. EDT (1852 GMT), resulting in splashdown of the Orion spacecraft Nov. 11.

NASA’s Artemis team is also working around schedules for other launches. NASA and SpaceX plan to launch the next crew to the International Space Station on Oct. 3 on a Falcon 9 rocket from pad 39A at Kennedy, less than 2 miles south of pad 39B, where the Artemis 1 moon rocket is located. Launch operations at each pad can temporarily halt work at the neighboring launch facility, which must be evacuated when a rocket is taking off nearby.

“Teams are working the upcoming commercial crew launch in parallel to the Artemis 1 planning and both launch schedules will continue to be assessed over the coming weeks,” NASA said. “NASA and SpaceX will review the Artemis 1 and Crew-5 prelaunch processing milestones to understand any potential impacts.”

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