Tough final tests for NASA’s giant SLS rocket

Eric Bottlaender

Space specialist

April 05, 2022 at 4:45 p.m.


SLS Artemis 1 WDR test © NASA

SLS at its launch site, although it will (still) have to wait a few months for take-off © NASA

Since the arrival of the launcher of the mission Artemis I on its launch site, the teams of the American agency are preparing the WDR, a countdown test with filling of the tanks. Despite extensive testing, they manipulate several systems for the first time. The test has been stopped dead twice already.

Test, correct, try again: this sequence is designed for that!

No joke for the countdown

1er April, the ground teams who take care of the Space Launch System (SLS), NASA’s new giant launcher, gave the green light to start the test from this weekend. After electrical and pneumatic tests, this is the last major test campaign for SLS: a ” Wet Dress Rehearsal ”, that is to say a countdown test as in the take-off condition, which is stopped at t-9 seconds, before the ignition of the engines.

Everything else must follow the same parameters as the day of the flight. But, since last Friday, concerns have marred the days of the technicians, engineers and managers present on the site. Starting with a huge thunderstorm overnight from Friday to Saturday, which highlighted the site’s new protective equipment: 4 lightning strikes hit the structures, including a huge lightning strike on one of the cables between the large towers provided for this purpose. It was immediately necessary to take stock… But, fortunately, after a few hours of inspection, the teams again obtained the ” go “.

A storm, two technical stops, and it’s only Tuesday

Since then, the countdown has twice ventured below 6:40, but could not stay there for long, due to various technical problems. This is the limit from which the filling of the tanks (nitrogen, liquid oxygen, then liquid hydrogen) must start.

Sunday, April 3, ventilation equipment is not working on the launch tower. However, the latter is necessary for the other equipment, which is used to pressurize the cryogenic lines… The first attempt is then stopped.

A little over a day later, the countdown resumes, and this time everything seems to be going according to plan. Nitrogen (used to pressurize the launcher’s large tanks) and liquid oxygen tanks fill up. But ultimately, it is the control of a pressure relief valve located on the launcher, on the hydrogen side, which no longer responds (this is onboard/ground equipment, controlled by the launch tower). Rebelote, the test is cancelled.

SLS Artemis 1 spring rollout © NASA

The new lunar launcher is no longer really within a few days © NASA

let’s take it easy

If this test campaign with SLS, which seems ready to take off, is sluggish, it is more or less in the order of things. Indeed, it is not so much a question of repeating the countdown as of finding the few errors and technical problems that could endanger the real shooting campaign…

But the objective is also to prepare the teams and the equipment for the following launches. Indeed, the next SLS, after Artemis I, will have the heavy task of taking three astronauts to spend a few weeks in lunar orbit. A responsibility that everyone takes very seriously. Finally, we can laugh at these few postponements in the face of the years of delay that the project already supports. Sometimes it’s better to take the time…

On the same subject :
NASA will put SpaceX in competition to bring astronauts to the lunar surface


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