Countdown clocks began ticking on Saturday for NASA’s fourth attempt to complete the countdown for the general test and charge test of its lunar rocket Space Launch System, a condition before the big booster can be approved for launch on its 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 charge this vehicle, understand where we arrive in the number of terminals and then return … 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 pass into its final hours on Monday morning, when engineers plan to remotely fill 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 down to T-minus 33 seconds and then recycle that will mimic unplanned retention before counting down to T-minus 10 seconds. At that point, just before the rocket’s four main engines begin their actual launch, the computers will stop the test.
The goal is to ensure that the complex launch control software, electrical, mechanical and rocket propulsion systems, along with their interfaces with launch pad support equipment, work together as needed to safely launch the most powerful booster ever made for NASA.
These complexities have been exposed in three previous attempts to refuel SLS as engineers encountered problems with the launch pad subsystems, unexpected changes in propellant temperature and pressure, a stuck helium valve in the upper stage and a leak in the connector connecting the hydrogen fuel pipe with rocket First phase.
Originally towed to base 39B at the Kennedy Space Center on March 18, NASA returned a 330-foot SLS rocket to a vehicle assembly building on April 25 to replace a helium valve, repair a hydrogen leak, and make several other upgrades. and improvements.
Hydrogen leaks are known to be difficult to determine and eliminate because they do not usually occur until the hardware is exposed to cryogenic temperatures. But Free is optimistic that work on 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 the shuttle day knowledge, which we really benefited from,” he said. “Obviously, we won’t know the results of that until we actually drop liquid hydrogen on the pad.”
“We also worked on some loading procedures,” he continued. “We saw some things with LOX (liquid oxygen) and hydrogen that our team could actually go back to (and) automate those procedures, which we know will help us during the upcoming course.
Along with resolving the hydrogen leak, the engineers replaced the helium valve after finding some rubber debris in the mechanism. They have also modified refueling procedures to eliminate some of the pressure and temperature problems they have experienced before.
Mounted on a powerful crawler transporter, the SLS rocket and its mobile launch phase were pulled back to the launch pad on June 6, setting the stage for a fourth attempt this weekend to complete the test.
Assuming the test passes well, NASA will once again return the rocket to VAB for final preparations for the flight.
NASA hopes to finally launch the SLS at the end of August, reinforcing the unmanned capsule of the Orion crew on a test flight behind the Moon and back. The first manned mission, a flight with four astronauts around the moon, is planned for 2023 with a landing in the time frame of 2025.
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