Scrubbed Artemis 1 release raises concerns about unfinished trials

Scrubbed Artemis 1 release raises concerns about unfinished trials
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SLS on the launch pad at the Kennedy Space Center in Florida.

SLS on the launch pad at the Kennedy Space Center in Florida.
Photo: POT

On Monday, NASA failed in its first attempt to launch the uncrewed Artemis 1 mission, with engineers struggling to resolve an engine cooling problem. It’s an entirely surprising result, given that NASA failed to complete a single wet dress rehearsal, four of which were attempted earlier in the year. The space agency appears to be improvising, with the failed launch attempt effectively serving as the fifth wet dress rehearsal, in what is a worrying sign.

NASA’s Space Launch System (SLS) was supposed to take flight on Monday morning, but instead we were left wondering about the status of the program as a whole. NASA will provide more updates on the rocket later tonight, including whether a launch on Friday or Monday is possible, or whether the 322-foot-tall (98-meter) rocket will have to make its now-familiar 4-mile (6.4-meter) kilometers) walk back to the vehicle assembly building for repairs.

The unflown SLS mega rocket is critical to NASA Artemis Program, which seeks a permanent and sustainable return to the Moon. For him Artemis 1 mission, an uncrewed Orion rocket will be sent on a multi-week mission to the Moon and back. A successful integrated test of SLS and Orion would set the stage for a manned Artemis 2 mission in about two years, and a manned mission to land on the lunar surface later this decade.

A launch on Friday seems unlikely, and not just because of the gloomy weather forecast. NASA launch attempt monday it was nowhere near successful, with the countdown clock advancing no more than T-40 minutes. An “engine bleeding” problem prevented one of the rocket’s four RS-25 engines reached the ultracold temperature required for liftoff, resulting in delamination.

Thousands of spectators had gathered near the launch site, as had hundreds of reporters. Vice President Kamala Harris was also present at the Kennedy Space Center in Florida. Everyone left disappointed, but it doesn’t take a rocket scientist to admit that a Monday launch was always going to be unlikely. Given that ground crews failed to complete a single full wet dress rehearsal, it seemed like a stretch to believe that NASA would somehow get everything right during the first attempt to launch the Artemis 1 mission.

In fact, the problems began almost immediately early Monday morning, with the threat of lightning delaying tanking operations by almost an hour. Working under an accelerated timeline, ground crews proceeded through the six-hour fueling process. An issue arose when the team transitioned from slow to fast tanks, with a leaky 8-inch inlet valve causing elevated hydrogen readings. The leak was resolved by going back to slow fill and running the process again, allowing the core stage hydrogen tank to fill completely.

However, using the propellant to cool all four RS-25 engines, the team discovered that one of the engines, engine number three, refused to cool down to the required ultra-low temperatures. Engineers worked their way through previously established troubleshooting guidelines in an attempt to coax more liquid hydrogen into the engine. They tried to increase the pressure in the tank, but this led to the detection of another problem: an apparently leaking vent valve located between the liquid hydrogen and liquid oxygen tanks.

Speaking to reporters yesterday, Mike Sarafin, director of the Artemis mission at NASA, said engineers “wanted to increase the pressure in the tank to set the hydrogen bleed” but the “vent valve was not cooperating”. That was the straw that broke the camel’s back and the team “decided it was appropriate to declare the elimination because we just weren’t going to meet the two-hour window,” Sarafin said, adding that it was “one of those situations where you just knew.” that we needed more time.” He insisted that the problem is not the engine itself, but the “bleeding system that thermally conditions the engine”.

The engine bleeding issue is one of an unknown number of items that were not tested during wet dress rehearsals. Following the conclusion of the final wet dress that took place in June, NASA officials said 90% of all test objectives were met, without disclosing any details about the remaining 10%. The final wet dress was not completed due to an unresolved hydrogen leak related to a faulty quick connect fitting. For that test, NASA officials hoped to run the countdown clock to T-10 seconds, but it never got past T-29 seconds, leaving many in doubt about the final stage of launch.

After the partial completion of the third wet dress in April, SLS was sent back to the vehicle assembly building for repairs, returning to launch pad 39B in early June. Across the four trials, engineers noted a number of seemingly minor problems, a list that includes faulty fans on the mobile launcher, a misconfigured manual vent valve, excessively cold temperatures and frost during propellant loading, a small leak of hydrogen at the umbilical tail service mast, problems with the gaseous nitrogen supplier, and a faulty helium check valve that needed to be replaced.

That said, it was during the fourth wet dress that the SLS was finally fully loaded with propellants, with more than 755,000 gallons of liquid oxygen and liquid hydrogen added to the rocket’s two stages. Despite failing to achieve 10% of the test objectives, Tom Whitmeyer, NASA exploration systems manager, said “We think we had a really successful trial” and that there were risks in doing a fifth trial.

Speaking to reporters yesterday, Jim Free, NASA’s associate administrator for exploration systems development, echoed this earlier sentiment, saying another wet dress rehearsal was not necessary. “It would have taken another cycle of deployment and retreat,” he said, and that would have introduced more risks, including attrition. “We won’t know until we know, but we won’t know until we try,” Free added. “We felt we were in the best position to try.”

Keith Cowing, editor of and a former NASA rocket scientist, said the space agency treated the first Artemis 1 launch attempt as essentially the fifth dress rehearsal. Cowing, who spoke to me on the phone, said that NASA should have done all the required tests in advance to avoid these new problems.

“These things happen,” Cowing said. “But this is legacy hardware, with different rocket parts that have flown before.” By legacy hardware, Cowing is referring to the fact that the current SLS configuration “uses existing hardware from the Space Shuttle inventory, as much as possible, to save cost and speed up the schedule.” according to to NASA. These elements include the core stage thrusters and engines, along with the integrated spacecraft and payload element. “NASA shouldn’t expect everything to work as expected, as there will be problems with integration,” Cowing told me. To which he added: “Testing is good and needs to be done methodically so that when you finally try to shoot, you know what you’ve tested, rather than using shooting attempts as de facto wet dresses.

Cowing is concerned about the state of the program and the already archaic nature of SLS. Unlike SpaceX rockets, which can be modified and repaired at the launch pad, SLS must return to the Vehicle Assembly Building for hardware adjustments (this could be the case with the leaky vent valve mentioned above, but we will have to wait for the official word from NASA). And at an estimated cost of $4.1 billion per launch, Cowing predicts that SLS launches will be rare events, citing NASA Inspector General Paul Martin, who earlier this year described the price tag as “unsustainable.”

NASA officials are likely to feel the pressure, hence the desire to finally get SLS off the ground. It’s turning into uncomfortable theater though, and Monday’s scrub is a case in point. The odds of a launch were exceptionally low (at least that’s how I assessed it), but NASA was not shy about publicizing the event and inviting a host of dignitaries and celebrities.

The megarocket doesn’t appear to be ready for launch, but NASA is doing its best to convince us that it is. Sadly, the “mock” launch attempt from earlier this week probably won’t be the last.

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