NASA does not plan another Artemis 1 countdown rehearsal – Spaceflight Now

EDITOR’S NOTE: Updated June 23 with additional information and quotes from a NASA spokesperson.

NASA’s Artemis 1 moon rocket at Launch Complex 39B earlier this month. Credit: NASA/Ben Smegelsky

Abandoning another countdown rehearsal, NASA plans to return the first Space Launch System rocket to its assembly hangar at Kennedy Space Center next week for a hydrogen leak repair and ongoing preparations for liftoff on the Artemis 1 lunar mission. .

With the countdown dress rehearsals complete, ground crews at Kennedy are preparing to launch the 300-foot Space Launch System lunar rocket to the Vehicle Assembly Building. The return to the VAB will end the Wet Dress Rehearsal, or WDR, campaign as NASA approaches the launch of the long-delayed Artemis 1 test flight around the moon, sources said Wednesday.

Kathryn Hambleton, a NASA spokeswoman, confirmed on Thursday that the SLS team is declaring the WDR campaign complete and said managers are “working plans to address some remaining (test) objectives before returning to the VAB.” .

The launch of Artemis 1 will kick off an unmanned demonstration mission of the powerful SLS lunar rocket and the Orion spacecraft before future Artemis flights take astronauts to the moon. The Space Launch System has been in development for over a decade, costing over $20 billion to date, making it one of NASA’s most expensive programs at the time.

The NASA launch team encountered several technical issues that prevented the SLS lunar rocket’s cryogenic booster tanks from fully loading in three training countdowns in April. But a fourth dress rehearsal on Monday deepened 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 modify procedures in the final stages of the practical countdown.

NASA’s launch team originally wanted to proceed with the terminal’s final 10-minute countdown sequence twice, hitting T-9.3 seconds in the final run, just before the time when the main stage’s main engines would fire during an actual launch attempt. The engineers spent several hours evaluating the hydrogen leak and the managers finally decided to continue the countdown with just one run in the final 10-minute sequence.

Engineers reconfigured the countdown sequencer on the ground to mask hydrogen leakage, which would normally trigger a countdown clock cutoff. With the solution in place to tell the ground launch sequencer computer to ignore the leak, the clock continued to T-minus 29 seconds, one second after the countdown control passed from the ground controller to an automated sequencer onboard the SLS. moon rocket.

The rocket’s onboard computers commanded the wait at T-minus 29 seconds, when sensors showed the midstage engines were not ready to ignite, NASA officials said Tuesday. The leaky hydrogen connector discovered on Monday is associated with a system for thermally conditioning, or cooling, the mid-stage RS-25 prime movers.

Despite the leak and the slashing of the countdown before it reached T-minus 9 seconds, NASA officials said the dress rehearsal achieved most of its goals.

“I would say we’re in the 90th percentile in terms of 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 some “open items” unrealized during Monday’s countdown rehearsal. One was the start-up of the hydraulic power units on the SLS solid rocket thrusters, which was to have taken place within the final 30 seconds of the countdown to firing the propulsion nozzles via a steering check of the gimbal with its thrust vector control mechanisms. thrust, according to John Blevins, chief engineer for the SLS program at the Marshall Space Flight Center.

Blevins said on Tuesday that engineers would assess the risk of proceeding to launch without going through the last 20 seconds of the countdown trial. He the worst case scenario of continuing without another rehearsal is an issue that causes a miscarriage in the final seconds of the countdown on launch day.

“We’re going to have a successful launch or a scrub because we have protection in the system for those goals that we don’t meet if they don’t perform properly on launch day,” Blevins said. “So they’re not really about making the vehicle safer to fly. They’re really about whether we can hit the launch target for our window that’s ideal for our lunar mission.”

Tom Whitmeyer, NASA’s exploration systems manager, said Tuesday that he was “very encouraged” by the outcome of the countdown trial.

“We think we had a really successful trial,” Whitmeyer said.

“There is a relative risk in continuing to exercise the hardware on the block (for another trial),” Whitmeyer said Tuesday. “This is not necessarily a risk-free situation.”

The mighty Space Launch System, powered by leftover Space Shuttle engines and thrusters, is central to NASA’s lunar mission planning. The rocket will send crews to the moon in the Orion capsule, which will connect to a landing stage delivered to lunar orbit in a separate launch. The lander will then transport the astronauts to the surface of the moon and back to the Orion spacecraft to return to Earth.

The program’s first moon landing will follow the Artemis 2 flight, a mission that will send four astronauts on a trajectory beyond 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 will activate to destroy the rocket if it goes off course after takeoff.

Final inspections and closures are also available within 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 an anticipated launch date for the Artemis 1 mission, but agency officials said last week that the earliest the flight could be ready for launch is in late August. NASA has Artemis 1 launch dates available for periods lasting about two weeks, when the moon is in the correct position in its orbit, and the trajectory ensures that the Orion spacecraft’s power-generating solar panels are not shadowed for more than 90 minutes at a time.

Other restrictions include requirements to meet specific parameters for re-entry and a daylight dive of the Orion capsule at the end of the mission.

The next viable release period for Artemis 1 opens on August 23rd and closes on September 6th, so more launch opportunities will be available from September 19th.

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Follow Stephen Clark on Twitter: @StephenClark1.

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