NASA makes third attempt to partially fuel moon rocket into practice countdown

NASA on Tuesday restarted a two-day dress rehearsal countdown for the agency’s new Space Launch System launches monthly after a series of unrelated glitches, mostly with ground systems, blocked two previous attempts to fully tank the enormous launcher to verify its readiness for flight.

The only rocket-related problem – problems with a one-way helium pressure valve in the second stage of the booster – can not be repaired at the launch site, and engineers will not be able to pump super-cold cryogenic propellants into the stage. during fuel operations Thursday as originally planned.

Instead, the team will concentrate on loading the SLS core stage with 537,000 gallons of liquid hydrogen fuel and 196,000 gallons of liquid oxygen Thursday morning, testing their ability to control and monitor the flow of propellants, checking control space commands and validating software. via two terminals countdown test runs.

The Space Launch System rockets Monday, seen Tuesday above Path 39B at the Kennedy Space Center. After two previous attempts to complete a dress rehearsal countdown and tank test, NASA began a third practice countdown on Tuesday.

CBS News

In one check, the countdown will tick down to the T-minus 33-second mark for a recycle back to T-minus 10 minutes for any test procedures that might be needed if a problem interrupts an actual launch countdown.

A second run will then tick all the way down to T-minus 9.3 seconds, the moment before main engine ignition command would be sent for an actual launch. At that point, the ground start sequencer computer will stop counting down and the test will end.

The original goals of the countdown test included charging both stages with liquid oxygen and hydrogen.

But it was also about testing the Launch Control Center, all (ground support equipment), our sister control centers … Blackwell-Thompson, NASA’s first female launch director.

Seeing the problem with helium valve, the team “looked at some of those goals we can achieve without loading the top stage,” she said. “We want to get as much data as we can while we’re on the road. The data will guide us and tell us what to do.”

It is not yet known if an additional fuel test may be required at some point before launch, but the top SLS phase, known as the Interim Cryogenic Propulsion Stage, or ICPS, cannot be loaded with fuels unless the nuclear phase is also full.

In any case, the revised dress rehearsal countdown test began at 5:30 p.m. Tuesday as scheduled. If all goes well, fuel operations in the nuclear phase will begin on Thursday at 7 a.m. with a cut-off focused at 2:40 p.m.

While the top stage is not loaded with propellants, liquid oxygen and hydrogen will flow through launch lines and into the ICPS plumbing to ensure the system is leak free.

After the test is completed, engineers will spend approximately 10 days preparing the rocket and its mobile launch platform for the 4.2-mile journey back to the Vehicle Assembly Building where the helium valve will be replaced.

What happens next is not yet known. NASA wants to launch the SLS on its first flight, boosting an unpiloted Orion crew capsule past the moon and back, sometime this summer, but the timeline will depend on what additional tests are needed.

“This is the first flight of a program that is meant to last for years, to take us back to the moon … and one day to continue to Mars,” Blackwell-Thompson said. “And so when you think about that investment, and you think about the first flight, you have to expect that you will learn things.

“You can not have a first flight and not learn anything. And so what do you do when something happens? You adapt, you look at the data, you develop a plan and you let the data lead you to the next step. And that is what we will do in preparing this great car to fly. “

The Space Launch System rocket is the most powerful launcher ever built for NASA, a key element of the agency’s Artemis program to send astronauts back to the moon.

Equipped with two extended solid fuel boosters and a core stage powered by four modified space shuttle main engines, the SLS rocket will tip the scales at 5.75 million pounds when lifted and generate a ground shake of 8.8 million pounds of thrust, making it the most powerful rocket yet flying.

The 322-foot-tall SLS was towed to launch site 39B on March 18 and engineers began the first attempt at a dress rehearsal countdown on April 1st.

But before the fuel could start at the nuclear stage two days later, the team ran into problems with fans needed to put pressure on the rocket’s mobile launch platform, a routine step to prevent free hydrogen gas from making its way came in several compartments and formed a fire hazard.

The problem could not be repaired quickly and the fueling operation was over one day delayed until April 4th, Two more ground system problems caused additional delays before the helium valve problem was identified. Engineers then opted to push ahead Tuesday with a modified countdown.

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