NASA declares SLS Megarocket tank test a success

Engineers repairing the area where a liquid hydrogen leak was detected during SLS's second launch attempt on September 3.  This photo was taken on September 8th at Kennedy Space Center in Florida.

Engineers repairing the area where a liquid hydrogen leak was detected during SLS’s second launch attempt on September 3. This photo was taken on September 8th at Kennedy Space Center in Florida.
photo: NASA

A demonstration to confirm a repaired hydrogen leak appears to have gone well, and NASA declared Wednesday’s cryogenic tank test a success. Engineers have yet to verify the results, but the space agency may be on track to complete its third launch attempt of its SLS megarocket in just six days — a mission that would officially launch the Artemis lunar program.

Launch Director Charlie Blackwell-Thompson declared “go” to refuel at 7:30 a.m. (all times Eastern), approximately 30 minutes after the scheduled launch time. Ground teams began loading more than 700,000 gallons of propellant into the megarocket, beginning with the core phase. Today’s cryogenic tank test, as it was called, took place while the 98-meter-tall rocket stood on Pad 39B at Kennedy Space Center in Florida.

The test follows two previous launch attempts, both of which ended in scrubs for different reasons. That first scrubon August 29, the result of a faulty sensor that recorded incorrect engine temperature readingswhile second scrub, on September 3, was the result of a significant hydrogen leak, which NASA subsequently traced to damaged seals on the quick connect coupling between a liquid hydrogen fuel line and the core stage. SLS uses a mixture of oxygen and liquid hydrogen, the latter of which has one tendency to leak because of its small atomic size.

Not yet ready to make a third launch attempt, NASA officials decided to conduct a cryogenic tank test, the main objective of which was to “look at the two new seals,” as Tom Whitmeyer, deputy assistant administrator for the development of joint exploration systems, said. said at NASA, told reporters Monday. NASA officials refrained from calling today’s test a wet dress rehearsal because key wet-dress objectives, such as entering the final counting phase of the countdown and powering the Orion spacecraft and lateral boosters, were not included on Wednesday‘s testing.

For today’s test, a key strategy was for ground teams to employ a “friendlier, gentler“Approach to refueling. Engineers felt that a slower approach would reduce the likelihood of thermal shock, since components at tempera come into contact with ultra-cold propellantsTemperatures down to -423 degrees Fahrenheit (-217 degrees Celsius). It is possible that a thermal shock or accidental over-pressurization on September 3rd caused the hydrogen leak, but the real cause is the failed 8-inch gasket, which had a possible indentation less than 0.01 inch in size not yet known known.

Around 9:45 a.m., the ground teams switched from slow fill to fast fill. An hour later, teams reported a hydrogen leak at the quick-disconnect coupling between the rocket and the utility tower at the stern, which was an ominous sign. Blackwell-Thompson signed the resulting plan to heat the line and reset the junction, and the teams were back in business about an hour later. Speaking to Blackwell-Thompson after the test, NASA launch commentator Derrol Nail said, “You could feel the space deflating a little, but how [the ground teams] beyond that, you felt a certain elevation of the room.”

Refueling thereafter moved quickly and smoothly after the missile’s thermal conditioning was complete four RS-25 engines took place just before 1:00 p.m. The teams managed to fill the core stage and the Interim Cryogenic Propulsion Stage (ICPS), also known as the upper stage, completely with fuel. At 15:45 the launch controllers had completed the pre-pressure test, shortly thereafter the defuelling activities began. “All objectives for the Artemis 1 cryo demonstration have been met,” tweeted NASA’s Exploration Ground Systems at 4:33 p.m., and the test was declared complete 20 minutes later.

“I think the test went really well,” Blackwell-Thompson told Nail. “We wanted to learn, we wanted to evaluate [tail service mast umbilicals] under cryogenic conditions.” She said the teams were also working with a new loading process, called the kinder, gentler approach, which Blackwell-Thompson described as “very targeted.” Ultimately, “all testing objectives were met today,” she said.

NASA needs to review today’s test results and decide how to proceed. Ideally, the engineers will like what they saw and prepare the conditions for launch in just six days. Assuming the test is as successful as it seems, NASA could do so Start SLS already on September 27th, with a 70-minute launch window opening at 11:37 a.m. ET. To do so, however, the space agency must still obtain an exemption from the Space Force’s Eastern Range, which manages launches along Florida’s east coast. NASA is currently attempting to launch the Artemis 1 missionin which the SLS rocket will take an unmanned Orion capsule on a journey to and from the moon.

A successful start would be the beginning of the It was Artemis, in which NASA seeks a sustained and permanent presence in the lunar environment. Artemis 1 is a demonstration mission that would set the stage for Artemis 2, where a manned Orion spacecraft will make a similar journey in late 2024.

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