NASA is trying again to complete the countdown to the lunar rocket – Spaceflight Now


The moon hangs in the sky behind NASA’s Orion spacecraft and the Space Launch System lunar rocket on the launch pad at the Kennedy Space Center. Credit: NASA / Ben Smegelski

Countdown clocks began ticking on Saturday for NASA’s fourth attempt to complete a dress rehearsal and charge test for its Space Launch System lunar rocket, a requirement before the huge accelerator can be approved for launch on the long-awaited first flight.

“There is no one who wants to go through this more than the EGS (Exploration Ground Systems) team and all our teams … to get this vehicle to tank, to find out how far we are in the number of terminals and then to back … to launch, said Jim Free, director of research development at NASA headquarters.

The countdown began at 5:30 p.m. EDT, and if all goes well, the two-day test will enter its final hours on Monday morning, when engineers plan to remotely load the first and second stages of the rocket with three-quarters of a million gallons of supercold liquid oxygen and hydrogen fuel.

Launch Director Charlie Blackwell-Thompson and her team plan to count to T-minus 33 seconds and then recycle, which will mimic unplanned retention before counting to T-minus 10 seconds. At this point, just before the rocket’s four main engines begin their launch sequence in actual launch, the computers will stop the test.

The aim is to ensure that the sophisticated launch control software, electrical, mechanical and fuel systems of the rocket, together with their interfaces with launch site maintenance equipment, will work together as necessary to safely launch the most powerful an accelerator once created for NASA.

These complexities have been demonstrated in three previous attempts to power the SLS, as engineers encountered problems with launch site subsystems, unexpected changes in fuel temperature and pressure, a stuck helium valve on the upper stage, and leaks in the fitting that connects the hydrogen pipeline. to the rocket. First stage.

Originally towed to 39B at the Kennedy Space Center on March 18, NASA moved the 330-foot SLS rocket back to the vehicle assembly building on April 25 to replace the helium valve, repair the hydrogen leak and make several other upgrades. and improvements.

Hydrogen leaks are known to be difficult to detect and eliminate, as they do not usually occur until the hardware is exposed to cryogenic temperatures. But Free is optimistic that the work of tightening the flange in the fuel pipe connector has solved the problem.

“We fixed some things we saw in the area where we saw the leak, including going back to some of the procedures we used and know-how from the shuttle days that we really took advantage of,” he said. “Obviously, we won’t know the results of this until we actually transfer the liquid hydrogen to the substrate.

“We also worked on some of the loading procedures,” he continued. “We’ve seen some things with LOX (liquid oxygen) and hydrogen that our team has actually been able to come back to automate these procedures that we know will help us during the upcoming flow.”

Along with dealing with the hydrogen leak, the engineers replaced the helium valve after finding some rubber debris stuck in the mechanism. They are also modifying refueling procedures to eliminate some of the pressure and temperature problems previously tested.

Mounted on a powerful chain conveyor, the SLS rocket and its mobile launch pad were pulled back to the launch pad on June 6, laying the groundwork for the fourth attempt to complete the rehearsal this weekend.

Assuming the test goes well, NASA will move the rocket back to VAB once again for final flight preparation.

NASA hopes to finally launch the SLS in late August, reinforcing an unmanned capsule of the Orion crew on a test flight beyond the moon and back. The first manned mission, a flight with four astronauts around the moon, is planned for 2023 with a landing in 2025.

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