NASA made a third attempt to power its new Space Launch System moon rocket during a test countdown on Thursday, but once again a series of technical issues triggered multiple delays, preventing engineers from pumping out 730,000 gallons of liquid hydrogen and oxygen in the booster’s massive first stage. foreseen.
Problems with a helium pressurization valve in the upper stage of the SLS rocket, discovered during a refueling attempt last week, limited Thursday’s propellant loading attempt to just the middle stage, but engineers were only able to fill its hydrogen tank to the 5% level and the oxygen tank to about 49%.
This is due to problems with a nitrogen gas supply line, violations of oxygen temperature during initial charging, unexpected “overpressure” when passing liquid hydrogen flow at high speeds and to indications of a hydrogen leak in a launch pad umbilical during an attempted “rapid fill” recovery from a shutdown.
Two planned terminal countdown “runs” were planned to bring the count down to T-minus 33 seconds, then, after a recycle, to T-minus 9.3 seconds to check propellant management and procedures of the launch day. But the countdown never resumed after a final built-in wait.
Despite the significance of the tests, NASA declined to comment on real-time launch control, fearing export control laws could be violated if technical information is released before it can be reviewed. Instead, the agency uses social media – tweets and blog posts – to inform journalists and the public.
The helium valve problem that prevented upper stage refueling cannot be fixed on the launch pad and it is not yet clear whether NASA will attempt a fourth stage refueling test or choose to bring the rocket back. to Kennedy Space Center’s iconic Vehicle Assembly Building for repairs.
At this point, the agency could bring it back to the pad for another refueling test or press for launch. Or both. NASA officials have declined to present even tentative plans beyond the now-delayed refueling test, saying they want that data in hand before making decisions on how to proceed.
The Space Launch System rocket is the most powerful launch vehicle ever built for NASA, a key part of the agency’s Artemis program to return astronauts to the Moon. With the ‘mega rocket’ years behind schedule and billions over budget, NASA plans to launch an unpiloted Orion crew capsule beyond the moon and back on an inaugural test flight this summer.
The dress rehearsal countdown and refueling exercise is a critical step on the road to launch, allowing managers and engineers to put complex ground systems and the SLS rocket through the paces. from launch day for the first time.
The problems are not unexpected given the massive amounts of super-cold cryogenic propellants involved and the complex systems needed to safely manage them. A scheduled six-day countdown test for the first Apollo Saturn 5 moon rocket lasted 17 days. Surprisingly, perhaps, the SLS dress rehearsal now looks set to take even longer.