Sunday, June 23, 2024
    HomeScienceScrubbed Artemis 1 Launch Prompts Concerns About Unfinished Rehearsals

    Scrubbed Artemis 1 Launch Prompts Concerns About Unfinished Rehearsals

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

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

    On Monday, NASA failed in its first attempt to launch the uncrewed Artemis 1 mission, with engineers struggling to resolve an engine cooling issue. It’s a wholly unsurprising result, given that NASA was unable to complete a single wet dress rehearsal, of which four were attempted earlier in the year. The space agency appears to be winging it, with the botched launch attempt effectively serving as the fifth wet dress rehearsal, in what is a troubling sign.

    NASA’s Space Launch System (SLS) was supposed to take flight on Monday morning, but instead we’re left wondering about the state of the program as a whole. NASA will provide more updates about the rocket later this evening, including whether a launch on Friday or Monday might be possible, or whether the 322-foot-tall (98-meter) rocket will have to make its now-familiar 4-mile (6.4-kilometer) trek back to the Vehicle Assembly Building for repairs.

    The unflown SLS megarocket is critical to NASA’s Artemis program, which seeks a permanent and sustainable return to the Moon. For the 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 crewed Artemis 2 mission in roughly two years, and a crewed mission to land on the lunar surface later this decade.

    A launch on Friday seems unlikely, and not just because of the grim weather forecast. NASA’s launch attempt on Monday came nowhere near to succeeding, with the countdown clock proceeding no further than T-40 minutes. An “engine bleed” issue prevented one of the rocket’s four RS-25 engines from reaching the required ultra-cold temperature for liftoff, resulting in the scrub.

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

    Indeed, the problems started almost immediately on early Monday morning, with the threat of lightning delaying tanking operations by nearly an hour. Working under an accelerated timeline, ground teams proceeded with the six-hour fueling process. A problem emerged when the team transitioned from slow to fast tanking, with a leaky 8-inch inlet valve causing elevated hydrogen readings. The leak was resolved by reverting back to slow fill and going through the process again, allowing the core stage hydrogen tank to be fully topped off.

    When using the propellant to chill the four RS-25 engines, however, the team found that one of the engines—engine number three—refused to cool down to the ultra-low temperatures required. 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 leaky vent valve positioned between the liquid hydrogen and liquid oxygen tanks.

    Speaking to reporters yesterday, Mike Sarafin, Artemis mission manager at NASA, said engineers “wanted to increase the pressure in the tank in order to establish the hydrogen bleed,” but the “vent valve wasn’t cooperating.” That was the final straw, and the team “decided that it was appropriate to declare the scrub because we just weren’t going to make the two-hour window,” Sarafin said, adding that it was “one of those situations where we just knew we needed more time.” He insisted that the problem is not with the engine itself, but rather the “bleed system that thermally conditions the engine.”

    The engine bleed issue is one of an unknown number of items that were not tested during the wet dress rehearsals. Upon the conclusion of the final wet dress held in June, NASA officials said 90% of all test objectives were met, while not disclosing any details about the remaining 10%. The final wet dress was not completed due to an unresolved hydrogen leak linked to a faulty quick-connect fitting. For that rehearsal, NASA officials had hoped to run the countdown clock to T-10 seconds, but it never got past T-29 seconds, leaving much about the final launch stage in doubt.

    Upon 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 rehearsals, engineers recorded a slew of apparently minor issues, a list that includes faulty ventilation fans on the mobile launcher, a misconfigured manual vent valve, overly cold temperatures and frost during propellant loading, a small hydrogen leak on the tail service mast umbilical, issues with the supplier of gaseous nitrogen, and a faulty helium check valve that needed to be replaced.

    That said, it was during the fourth wet dress that SLS was finally loaded fully with propellants, with upwards of 755,000 gallons of liquid oxygen and liquid hydrogen added to the rocket’s two stages. Despite not achieving 10% of test objectives, Tom Whitmeyer, NASA’s exploration systems manager, said “we think that we had a really successful rehearsal,” and that there were risks to running a fifth trial run.

    Speaking to reporters yesterday, Jim Free, NASA associate administrator for exploration systems development, echoed this earlier sentiment, saying another wet dress rehearsal wasn’t necessary. “We would have taken another cycle of rolling out and back,” he said, and that would’ve introduced further risks, including wear-and-tear. “We won’t know until we know, but we also won’t know until we try,” Free added. “We felt like we were in the best position to try.”

    Keith Cowing, editor of and a former rocket scientist at NASA, said the space agency treated the first Artemis 1 launch attempt as essentially the fifth wet dress rehearsal. Cowing, who spoke to me by phone, said NASA should’ve done all the required testing up front to avoid these new problems.

    “These things happen,” Cowing said. “But this is heritage hardware, with different pieces of rockets that have flown before.” By heritage hardware, Cowing is referring to the fact that the current SLS configuration “utilizes existing hardware from the Space Shuttle inventory, as much as possible, to save cost and expedite the schedule,” according to NASA. These elements include the core stage boosters and engines, along with the Integrated Spacecraft and Payload Element. “NASA shouldn’t expect that it’s all going to work as expected, as there’s going to be problems with the integration,” Cowing told me. To which he added: “Testing is good, and it needs to be done methodically, so when you finally attempt to launch you know what you’ve tested out—instead of using launch attempts as de facto wet dresses.”

    Cowing is worried about the state of the program and the already-archaic nature of SLS. Unlike SpaceX rockets, which can be tweaked and repaired on the launch pad, SLS must return to the Vehicle Assembly Building for hardware adjustments (this might be the case with the aforementioned leaky vent valve, but we’ll 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’s inspector general Paul Martin, who earlier this year described the price tag as “unsustainable.”

    NASA officials are likely feeling the pressure, hence the desire to finally get SLS off the ground. It’s making for some awkward theater, however, with Monday’s scrub being a good example. The odds of a launch were exceptionally low (at least that’s how I assessed it), yet NASA had no qualms about publicizing the event and inviting a host of dignitaries and celebrity guests.

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



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