Space Launch System dress rehearsal canceled for repairs

If at first you don't succeed... you're probably NASA

NASA's third attempt at an Artemis I wet dress rehearsal has ended with a plan to roll the agency's Moon rocket back to the Vehicle Assembly Building (VAB) for repairs.

It is the latest in a long line of setbacks for the Space Launch System (SLS) on which NASA hopes to send astronauts to the Moon.

The first attempt at the start of this month was halted due to problems with the fans required to pressurize the mobile launcher. Positive pressure is required in enclosed areas to keep out hazardous gases. Without it, the loading of propellants into the core stage and Interim Cryogenic Propulsion Stage could not proceed.

Fan fixed, the team tried again but again the test was called off. This time it was a problem with a helium check valve, which is designed to prevent helium flowing back out of the rocket. Deciding that the valve could be swapped once the rocket was safely back in the VAB after the test, NASA opted to change what success meant and "modified" the dress rehearsal. The focus would instead be on filling the core stage and performing minimal propellant operations on the ICPS (in this case, chilling down the lines).

What could possibly go wrong?

The answer was a hydrogen leak in the latest effort. As the liquid oxygen tank of the core stage reached approximately 49 percent full and the liquid hydrogen tank was loaded to five percent capacity, a liquid hydrogen leak was detected on the tail service mast umbilical, located at the base of the mobile launcher and connected to the core stage.

Space Shuttle veterans sympathized. Kind of.

Having lived through 'the summer of hydrogen leaks' on the shuttle I can sympathize. And that was after 35 or so launches. A leak the first time is almost to be expected. But not satisfactory. https://t.co/BKLn0X5Qj7

— Wayne Hale (@waynehale) April 15, 2022

Hale is most likely referring to 1990, when Shuttle launches were repeatedly postponed as engineers hunted for the source of hydrogen leaks.

NASA has elected to roll the SLS back to the VAB to both replace the faulty upper stage check value and deal with the umbilical leak. The agency is also planning to improve the supply of nitrogen gas to the pad, which was also a factor in the issues.

The rollback will likely occur next week and a date for a return to the pad for another dress rehearsal has yet to be set. Whether NASA will then leave the rocket at the pad ready for launch or return it to the VAB once again (as originally planned) has yet to be decided. The problems, however, have made a launch for the uncrewed test flight in the first half of June highly unlikely. Dates in July or later are more probable. ®