NASA restarts lunar rocket wet sample countdown – Spaceflight now


NASA’s Space Launch System lunar rocket on pillow 39B. Credit: NASA / Ben Smegelsky

NASA restarted a two-day rehearsal countdown Tuesday for the agency’s new Space Launch System lunar rocket after a series of unrelated bugs, mostly involving Earth systems, blocked two previous attempts to fully fuel the huge launch vehicle to confirm its readiness for flight.

The lone rocket-related problem – problems with a one-way helium pressure valve in the booster’s second stage – cannot be solved by the launch pad, and engineers will be unable to pump super-cold cryogenic propellants into the scene during fuel operations Thursday as originally planned.

Instead, the team will concentrate on filling 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 monitor and control the flow of propellants, verify control room command and validate software through two terminal countdown test runs.

In one, the countdown will tick down to the T-minus 33-second mark before reusing back to the T-minus 10 minutes to test procedures that might be necessary if a problem should interrupt an actual launch countdown.

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

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

But it was also about testing the Launch Control Center, everything (ground support equipment), our sister control centers… and making sure we’re all capable of operating in a day-to-day launch environment, said Charlie Blackwell-Thompson, NASA’s first female launch director.

Given the problem with the helium valve, “the team looked at which of these goals we can achieve without straining the top phase. We want to get as much data as we can while we are at the table. The data will guide us and tell tell us what to do next. “

It is not yet known if an additional fuel test may be required at some point before launch, but the SLS upper stage, known as the Interim Cryogenic Propulsion Stage or ICPS, cannot be filled with propellants unless the core stage is also filled.

In any case, the revised dress rehearsal countdown test began at. 17.30 Tuesday as planned. If all goes well, fuel operations will begin at the core stage around noon. 07.00 Thursday with cut-off targeted at. 14.40

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

After the test is completed, engineers will spend about 10 days preparing the rocket and its mobile launching platform for the 4.2-mile ride 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 virgin flight and boost an un piloted Orion crew capsule beyond the moon and back, sometime this summer, but that will depend on what additional testing is required.

“This is the first flight in a program designed to last for years, to take us back to the moon … and one day to move on 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 are going to learn things.

“You can not have a first flight and not learn anything. And what do you do when something happens? You adapt, you look at the data, you develop a plan and you let the data take you to the next step. And that is what we will do to prepare this amazing vehicle for flying. “

The Space Launch System rocket is the most powerful launch vehicle 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 amplifiers and a core stage powered by four modified space shuttle main engines, the SLS rocket will tip the scale to 5.75 million pounds on takeoff and generate a ground-shaking 8.8 million pounds of propulsion, making it the most powerful rocket that yet has flown.

The 322-foot-tall SLS was pulled out to launch pad 39B on March 18 and engineers began the first attempt at a rehearsal count on April 1.

But before fuel at the core stage could begin two days later, the team ran into problems with fans needed to put pressure on the rocket’s mobile launching platform, a routine step to prevent free hydrogen gas from penetrating various spaces and posing a fire hazard.

The problem could not be solved quickly and refueling was delayed one day until April 4th. Two more ground system problems caused further delays before the helium valve problem was identified. Engineers then chose to continue Tuesday with a changed countdown.

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