NASA engineers hope to have their massive moon-bound Space Launch System ready for launch in a few months, but so far they’ve encountered some bumps in the road. On March 17, NASA rolled the world’s most powerful rocket to the launch pad at the Kennedy Space Center in Florida to prepare it for the Artemis program’s inaugural lunar mission later this year. Since then, engineers have performed numerous checks on the massive rocket’s systems, but after three attempts, they failed the final test, a practice countdown dubbed the “wet dress rehearsal test.”

The main issues were a faulty helium check valve and a liquid hydrogen leak, leading to several pushbacks from the test countdown. Finally, over the weekend, NASA officials decided to disconnect the rocket and gently roll the SLS and Orion crew pod back to the Vehicle Assembly Building, a facility that contains the equipment they need to conduct rocket operations. They could return to the trail as early as next week to complete the countdown, but the first Artemis mission around the moon – originally scheduled for early June – may be postponed.

“The mega-moon rocket is still doing very well. The one check valve is literally the only real problem we’ve seen so far. We are very proud of the rocket,” Tom Whitmeyer, deputy assistant administrator at NASA headquarters in Washington, said at a news conference this afternoon. “But we still have some work to do.”

The precautions are not surprising; NASA doesn’t want to risk their most expensive rocket or their debut Artemis launch fails. “It comes down to what we consider to be the acceptable level of risk,” Mike Sarafin, the Artemis mission manager, said at an earlier press conference on April 15.

The test itself began on April 1, after the rocket was transported via a huge track from the assembly building to Launch Complex 39B. Jeff Spaulding, the senior NASA test director, and his team started their process by plugging in the rocket’s electrical power and pressure systems and filling the pair of white boosters on the side with propellants. Then they began loading the large orange fuel tank with more than 700,000 gallons of liquid hydrogen and liquid oxygen, supercooled to -423 and -297 degrees Fahrenheit, respectively. (That’s the “wet” in the “wet dress rehearsal”.) Their goal was to simulate the entire countdown to just under T-10 seconds — the closest thing to a real launch without the core stage RS-25 motors. to start.

During the test, Spaulding and his colleagues monitored instruments, pressures, temperatures and valves to make sure all systems were operating within acceptable parameters. (“If it turns out they’re a bit out of bounds, now we want to know — if there’s anything we need to fix or adjust,” he’d said in the days leading up to rehearsal.)

The test showed that several adjustments were needed. The trial was delayed the first time on April 2 by lightning bolts, which hit the towers surrounding the missile. The next day, NASA officials experienced problems with launch tower fans and their backups, according to Charlie Blackwell-Thompson, the launch director for Artemis. These fans provide pressure in the mobile launcher, the high construction next to the rocket, to keep out dangerous gases. This led to a delay in resolving the fan failure.


This post NASA rolls back its SLS rocket for repairs was original published at “https://www.wired.com/story/nasa-rolls-back-its-sls-rocket-for-repairs”

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