SLS rehearsal scrubbed, Artemis likely delayed

NASA canceled the month-long wet dress rehearsal of its Space Launch System (SLS) at Kennedy Space Center (KSC) on Monday, April 18, 2022. The scrub will further delay the initial launch of the Artemis 1 mission, which many hoped would be ready to blast off in June. Artemis 1 is NASA’s first step in a return to the moon. There have been many delays. A pair of faulty systems caused this week’s delay, which will have a knock-on effect creating additional delays of future Artemis mission events.

Trip around the moon on hold due to SLS problems

Mission controllers have been hoping for a June launch of NASA’s unmanned SLS heavy lift craft – carrying the Orion crew capsule – for a shakedown journey around the moon. But the launch can’t go forward until technicians address failures of two of the ship’s critical systems.

NASA announced the decision to end the rehearsal, which would have included testing all steps in the launch, with the exception of ignition, during a simulated countdown, during a live mission status update on Monday, April 18, 2022. During that update, Antonia Jaramillo, a spokesperson for NASA’s Office of Communications, described the next steps for the SLS, as well as why they’re being taken:

NASA’s planning to roll the Space Launch System rocket and Orion spacecraft back to the Vehicle Assembly Building. While in the Vehicle Assembly Building, teams will replace a faulty upper-stage check valve and a small leak on the tail surface mast umbilical on the mobile launcher, while an outside supplier of gaseous nitrogen used for the Artemis 1 wet dress rehearsal makes upgrades to their system.

Currently, the SLS remains in a safe configuration on its launch pad at KSC, awaiting transport back to the VAB. Rollback is scheduled for April 26.

The first launch window for Artemis 1 is June 6-16; additional windows are open June 29-July 12 and July 26-August 9.

Culprit is a bad 3-inch valve in SLS

Engineers identified the first of the problems earlier in the countdown rehearsal, announcing they would continue testing with a modified checklist during an update on April 9:

Engineers have identified a helium check valve that is not functioning as expected, requiring these changes to ensure safety of the flight hardware. Helium is used for several different operations, including purging the engine, or clearing the lines, prior to loading propellants during tanking, as well as draining propellant. A check valve is a type of valve that allows liquid or gas to flow in a particular direction and prevents backflow. The helium check valve is about three inches long and prevents the helium from flowing back out of the rocket.

During this week’s announcement of the rollback, Tom Whitmire, deputy associate administrator for Common Exploration Systems Development at NASA headquarters, was hopeful as he described the difficulties engineers and techs face while they prepare to put the SLS into space for the first time:

It’s a very delicate dance in order to bring a rocket alive, fuel it up, look at all the pressures, temperatures, and all the valves, the commands we send to the vehicle, the responses we see back from the vehicle. It’s a really complicated thing to do. We’re putting the pieces of the puzzle together. I think we figured out a few more pieces on Thursday, but we’ve got a few more pieces in front of us.

A liquid hydrogen leak in the tail service mast umbilical is a challenge still to be addressed.

We’ll be back, says NASA

Despite yet another delay in getting off the ground, development of the SLS and the continuation of the Artemis Mission will go on. According to Whitmire:

We will absolutely go back out. We’re absolutely going to do a wet dress rehearsal. We’re going to demonstrate cryo-loading of the spheres, and we also will demonstrate terminal countdown. It’s just a matter of what’s the right time and what’s the right way to do that, and how that might fit in our forward scheduling.

In the meantime, the SLS program’s engineers and technicians will be busy preparing the rocket for its return to the launch pad. According to Charlie Blackwell-Thomson, Artemis launch director at NASA’s KSC:

The troubleshooting plan going forward, again it’s the same plan we would have performed at the pad, but given that we’re returning to the VAB, we’re going to hold off until we get there. And that will be to remove that perge can. We will do another set of leak checks with some probes and some instrumentation to see if we can find evidence of a leak. We’ll also do inspections of the floor green seals that are there on the flange. There are some soft goods that we can replace.

Bottom line: NASA found critical faults in two systems on the SLS, causing technicians to cancel a dress rehearsal of the ship’s launch procedure and move the craft back to the VAB. The delay will likely delay the launch of the Artemis 1 mission, and so further slow the return of humans to the moon.

Via NASA