Artemis I Tanking Test Meets Objectives, But Is It Ready for Launch?

Artemis I Tanking Test Meets Objectives, But Is It Ready for Launch?

NASA’s tanking test of the Artemis I Space Launch System rocket met all its objectives today, but it still experienced hydrogen leaks. One would have violated launch rules so it remains unclear if the rocket is ready for launch as soon as next Tuesday, the current target date. The agency also continues to await a decision from the Space Force on whether it must replace a battery for the Flight Termination System. Weather might be iffy, too.

After a long day of ups and downs, Artemis I Launch Director Charlie Blackwell-Thompson said the test “went very well” and “all of the objectives that we set out to do we were able to accomplish today.”

The Artemis I Space Launch System rocket and Orion spacecraft at Launch Complex-39B as the September 21, 2022 “tanking test” got underway at 7:30 am ET. The SLS Core Stage is orange. The white Interim Cryogenic Propulsion Stage, or upper stage, is between the Core Stage and white Orion capsule at the very top. Screengrab.

Speaking with Derrol Nail from NASA’s Communications Office on the NASA webcast after the test, she was not willing to speculate on whether they will be ready to launch on September 27, however.

The launch was scrubbed on August 29 and September 3. In both cases, and in practice countdowns in April and June, problems were encountered with seals on Quick Disconnect (QD) fittings for lines that carry cryogenic liquid hydrogen (LH2) from ground equipment into the SLS fuel tanks. The lines are in the Tail Service Mast Umbilical that connect the rocket to the Mobile Launcher at the base of the rocket.

Fuel is fed into the Core Stage through lines between the Tail Service Mast Umbilical (the grey structure) and the rocket. Screengrab, September 21, 2022.

The cryogenic LH2 and liquid oxygen (LOX) used as propellant must be topped off almost until the moment of launch because it boils off. The QDs instantly separate the lines from the rocket at liftoff.

LH2 is at -423°F and the QD seals can be disturbed by the super-cold fuel. If they are not seated properly, hydrogen leaks out. LH2 is very flammable so if the concentration exceeds 4 percent, fueling must stop.

NASA adopted a “kinder, gentler” approach to fueling today allowing more time for the seals to adjust to changes in temperature and pressure.

The leaks on August 29 were not enough to cancel the launch. Instead, that attempt was scrubbed because a faulty sensor indicated one of the four engines was not chilled enough. But on September 3, a leak around the 8-inch QD for the LH2 fill-and-drain line to the Core Stage reached 8 percent. Engineers tried warming up the line hoping it would reseat itself, but the leak reappeared when they tried again and the launch was called off.

NASA also was concerned about the seal on a 4-inch QD for a “bleed line” used to redirect some of the propellant during tanking operations. Both were replaced over the past two weeks.

The only way to know if that solved the problem was to run the cryogenic fuel through the lines again and fill the LH2 and LOX tanks — a “tanking test.” That’s what they did today.

Even using the kinder, gentler fueling approach, a 7% leak was detected on the 8-inch QD when fueling got underway on the Core Stage. They stopped, warmed up the line and resumed fueling, this time at a much lower pressure. That worked. Eventually they were able to fill both the Core Stage and the Interim Cryogenic Propulsion Stage tanks.

The Interim Cryogenic Propulsion Stage, or upper stage, being filled with propellants through umbilicals similar to those from the Tail Service Mast at the base of the rocket for the Core Stage.  Screengrab, September 21, 2022.

At that point they were ready for the “pre-press” test where they pressurize the Core Stage to the same level needed to actually launch the rocket. During that test, a leak that got up to “a little over 5%” was detected at the 4-inch QD. The seals are designed to seat themselves more securely as pressure increases and in this case it stabilized itself at an acceptable level for the test.

Nail, who was the interface between the launch team and the public today, narrating and explaining what was happening, said the leak on the 4-inch QD would have violated rules for an actual launch, however. So although the test was a success, that does not necessarily mean the rocket is ready to launch.

Charlie Blackwell-Thompson, Artemis I Launch Director. Photo credit: NASA

Blackwell-Thompson declined to estimate when the launch will happen until she and her team can study the data.

“I think you always take the data and go look at what it tells you. … I don’t like to get ahead of the data.”

NASA also is waiting for the Space Force to decide if it will extend a waiver for replacing a critical battery in the Flight Termination System. It can only be replaced if the rocket is rolled back to the Vehicle Assembly Building  (VAB) where work platforms can be set up to allow access to various levels of the 322-foot tall rocket.

That would require quite a bit of time. NASA also would like to avoid moving the rocket back and forth between the launch pad and the VAB unless absolutely necessary since it puts stress on the rocket each time. But the Space Force is responsible for public safety and needs to be absolutely certain the Flight Termination System would work if the rocket veered off course and had to be destroyed.

Another factor could be a tropical disturbance in the Atlantic that might turn into a hurricane. Designated Invest 98L, it is too early to accurately forecast what it will do, but Florida could be in its sights. NASA officials have said they would need to decide 3 days in advance to roll SLS back to the VAB if a hurricane is predicted. How that will affect launch planning is unknown at this time.

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