Third Time Not the Charm for Artemis I Test

Third Time Not the Charm for Artemis I Test

NASA’s third attempt to conduct a test countdown for the Artemis I launch was scrubbed today. The Space Launch System rocket, derived from the space shuttle, is getting ready for flight later this year. In preparation, NASA wants to fuel the rocket and practice countdowns. The so-called Wet Dress Rehearsal test began over a week ago, but has been bedeviled by one problem or another. Today was no exception.

Artemis I will be the first launch of the SLS and Orion spacecraft on an uncrewed test flight around the Moon. NASA is targeting June for the actual launch, but will not decide on a date until this WDR test is completed and the data analyzed.

The first two attempts had to be scrubbed. Minor issues were overcome, but bigger problems emerged that forced NASA to end the test each day.

On April 3, primary and backup fans needed to pressurize the Mobile Launcher to keep out hazardous fumes didn’t work.

That problem was rectified and the test resumed on April 4, but then a helium check valve on the second stage malfunctioned.

The Artemis I Space Launch System rocket and Orion spacecraft, attached to the Mobile Launcher, atop the Crawler-Transporter, on their way to Launch Complex 39-B, March 17, 2022. The core stage is orange. Two white Solid Rocket Boosters are mounted on the left and right. The white Interim Cryogenic Propulsion Stage (ICPS) is on top of the core stage, and the white Orion capsule on top of that. Credit: NASA

SLS has two stages: the large, orange core stage built by Boeing, and a second stage (or upper stage) called the Interim Cryogenic Propulsion Stage (ICPS). ICPS is essentially the same as the upper stage of the United Launch Alliance’s Delta IV Heavy rocket.

Both stages use Liquid Hydrogen (LH2) and Liquid Oxygen (LOX) for propellant. As orginally planned, one major goal of the WDR test was “tanking” both stages — filling them with LH2 and LOX.

NASA cannot fix the vent valve on the ICPS while the rocket is on the launch pad, however. Rather than roll the vehicle back to the Vehicle Assembly Building to repair the valve, NASA decided to forgo tanking the ICPS and proceed with the rest of the test.

Launch Director Charlie Blackwell-Thompson said the WDR test has two primary objectives and five secondary objectives and that after the first two scrubs, one primary objective and three of the secondary objectives had been met.

Among those not met are tanking and conducting two practice countdowns, one to within 30 seconds of launch, and the other to within 9.3 seconds of launch, so the launch team can gain experience in stopping and recycling to a specific point in the countdown sequence.

Resuming the WDR test had to wait until the Axiom-1 private astronaut mission lifted off to the International Space Station because that rocket was on an adjacent launch pad and the test and the launch could not take place on the same day. Axiom-1 launched on April 8.

NASA set April 13 for resuming the two-day WDR test with a “T-0,” the point in a countdown when launch ordinarily would occur, of 2:40 pm ET today. As with the first two tries, minor issues were encountered early in the day. First a problem with the supply of gaseous nitrogen (GN2) needed to purge the propellant lines, then LOX loading exceeded a temperature limit. Those were overcome and a new T-0 was set for 3:57 pm ET.

But it was not to be. The final straw for the day was a hydrogen leak in the Tail Service Mast Umbilical on the Mobile Launcher that connects to the core stage. SpaceflightNow tweeted an illustration of where it is located.

At about 4:00 pm ET, NASA conceded it would not be able to complete the test today. At that point, the core stage’s LH2 tank had been filled just 5 percent and the LOX tank 49 percent.

Although they could not load propellants into the ICPS, they did gather data by conducting a “chilldown” test where ICPS propellant lines were cooled to the temperatures needed as if they were going send LOX and LH2 through.

The agency is keeping a positive outlook in its tweets and blog posts, the only public window into what is happening in real time. NASA is not providing live commentary.

The last tweet references the “Shuttle WDR,” a reference to comparable tests of NASA’s space shuttle system, which is a forebear of the SLS. SLS’s core stage is derived from the space shuttle’s External Tank. The two Solid Rocket Boosters on the SLS are 5-segment versions of the 4-segment shuttle SRBs. Despite the shuttle heritage, every system is different, which is why tests like this are needed.

Launch Director Blackwell-Thompson and Artemis Mission Manager Mike Sarafin will hold a media teleconference tomorrow afternoon to discuss what comes next.

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