EDITOR’S NOTE: Updated June 23 with additional information and quotes from NASA spokespersons.
Forgoing another repeat of the countdown, NASA plans to return the Space Launch System’s first rocket to its assembly hangar at Kennedy Space Center next week for a hydrogen leak repair and continued preparations for liftoff of the Artemis 1 lunar mission.
With dress rehearsals for the countdown complete, Kennedy ground crews prepare to roll the 322-foot-tall (98-meter) Space Launch System lunar rocket toward the Vehicle Assembly Building. The return to VAB will end the Wet Dress Rehearsal, or WDR, campaign as NASA nears the launch of the long-delayed Artemis 1 test flight around the moon, sources said Wednesday night.
Kathryn Hambleton, a NASA spokeswoman, confirmed on Thursday that the SLS team declares the WDR campaign over, and said officials are “working on plans to meet some remaining (test) goals before returning to VAB. “.
The launch of Artemis 1 will kick off an unpiloted demonstration mission of the powerful SLS lunar rocket and Orion spacecraft before future Artemis flights carry astronauts to the Moon. The Space Launch System has been in development for more than a decade, costing more than $20 billion to date, making it one of NASA’s costliest programs to date.
NASA’s launch team encountered several technical issues that prevented the SLS moon rocket’s cryogenic propellant tanks from being fully loaded during three training countdowns in April. But a fourth dress rehearsal on Monday continued deeper into the countdown, and the launch team filled the rocket with its 755,000-gallon supply of super-cold liquid hydrogen and liquid oxygen for the first time. .
But engineers discovered a hydrogen leak in a 4-inch quick-disconnect fitting on Monday, forcing the launch team to change procedures in the final stages of the practice countdown.
The NASA launch team originally wanted to run the final 10-minute terminal countdown sequence twice, reaching T-minus 9.3 seconds on the final run, just before the moment the main engines from the center stage would ignite during an actual launch attempt. Engineers spent several hours assessing the hydrogen leak, and officials ultimately decided to continue the countdown with just one pass in the final 10-minute sequence.
Engineers reconfigured the countdown timer on the ground to mask the hydrogen leak, which would normally trigger a blackout of the countdown clock. With the workaround in place to tell the ground launch sequencer computer to ignore the leak, the clock continued at T-minus 29 seconds, one second after the countdown control had was transferred from the ground controller to an automated sequencer on board the SLS. moon rocket.
The rocket’s onboard computers commanded hold at T-minus 29 seconds, when sensors showed the core stage engines were not ready to fire, NASA officials said Tuesday. The leaking hydrogen connector discovered on Monday is associated with a central stage RS-25 main engine cooling or thermal conditioning system.
Despite the leak and the countdown being cut short of reaching T-minus 9 seconds, NASA officials said the dress rehearsal met most of its objectives.
“I would say we’re in the 90th percentile as far as where we need to be overall,” Mike Sarafin, NASA’s Artemis 1 mission manager, said in a conference call with reporters on Tuesday.
But Sarafin said there were still “open elements” left unfulfilled during Monday’s countdown rehearsal. According to John Blevins, chief engineer of the SLS program at Marshall Space Flight Center.
Blevins said Tuesday engineers would assess the risk of proceeding with the launch without skipping the final 20 seconds of the countdown repeater. The worst case scenario of continuing without further repetition is a glitch that causes an abort in the final seconds of the launch day countdown.
“We’ll either have a successful launch or a scrub because we have protection in the system for the goals that we didn’t hit, if they don’t work properly on launch day,” Blevins said. “So they’re not really aimed at making the vehicle safer to drive. It’s really about whether we can hit our optimal window launch target for our lunar mission.
NASA Exploration Systems Manager Tom Whitmeyer said on Tuesday he was “very encouraged” by the outcome of the countdown repeat.
“We think we had a really successful rehearsal,” Whitmeyer said.
“There’s a relative risk in continuing to exercise the material on the pad (for another rep),” Whitmeyer said Tuesday. “It’s not necessarily a risk-free situation.”
The powerful Space Launch System, powered by the Space Shuttle’s remaining engines and thrusters, is central to NASA’s lunar mission planning. The rocket will send crews to the moon on the Orion capsule, which will be attached to a landing deck delivered to lunar orbit in a separate launch. The lander will then ferry astronauts to the moon’s surface and return them to the Orion spacecraft for return to Earth.
The program’s first moon landing will take place after the Artemis 2 flight, a mission that will send four astronauts on a trajectory past the far side of the moon and back to Earth. The Artemis 1 mission is a precursor to Artemis 2.
Once the Artemis 1 rocket is back inside the Vehicle Assembly Building, the Artemis ground crew will troubleshoot the leaking hydrogen connector detected on Monday. Technicians will also complete preparations for the flight termination system, which would be activated to destroy the rocket if it veered off course after liftoff.
Final inspections and shutdowns are also underway inside the VAB, and the ground crew will recharge the batteries on some of the CubeSat secondary payloads mounted under the Orion spacecraft.
NASA has not set a target launch date for the Artemis 1 mission, but agency officials said last week the flight could be ready for launch in late August. NASA has Artemis 1 launch dates available in roughly two-week periods when the moon is in the correct position in its orbit, and the trajectory ensures that the Orion spacecraft’s power-generating solar panels don’t are not shaded for more than 90 minutes at a time.
Other constraints include requirements to meet specific parameters for re-entry and a daylight splashdown of the Orion capsule at the end of the mission.
The next viable launch period for Artemis 1 opens on August 23 and ends on September 6, then more launch opportunities are available from September 19.
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