An issue in one of the refurbished shuttle main engines that are used in SLS’s core stage caused the launch today to be scrubbed.
The launch director halted today’s Artemis I launch attempt at approximately 8:34 a.m. EDT. The Space Launch System rocket and Orion spacecraft remain in a safe and stable configuration. Launch controllers were continuing to evaluate why a bleed test to get the RS-25 engines on the bottom of the core stage to the proper temperature range for liftoff was not successful, and ran out of time in the two-hour launch window. Engineers are continuing to gather additional data.
More information here and here. From the second link:
The four RS-25 engines on Artemis I are ones that were still in service at the end of the Shuttle program. But, for Artemis I, at least one component on each of the Core Stage engines comes from the three engines that powered Columbia to orbit on STS-1 on April 12, 1981. “It might be a valve, it might be a bolt, for others, it’s pieces of wiring, little things like that,” said Aerojet Rocketdyne’s Bill Muddle, RS-25 lead field integration engineer, in an interview with NASASpaceflight. “But there is something from the STS-1 engines on each of these [for Artemis I].”
Originally NASA had wanted to do this same bleed test during one of the two wet dress rehearsal countdowns prior to today’s launch attempt, but other issues with the rocket during those rehearsals made it impossible. As a result, the agency discovered this issue during the launch countdown.
Nor was this engine problem the only issue during this morning’s countdown.
The Engine No. 3 conditioning issue cropped up as NASA worked through a series of glitches during the countdown, including a liquid hydrogen leak early in the fueling process and a possible crack in a part of core booster known as the intertank flange, which connects the SLS’s giant liquid hydrogen and liquid oxygen tanks. The tanks can hold a combined 730,000 gallons (3.3 million liters) of propellant. “The flanges are connection joints that function like a seam on a shirt, are affixed at the top and bottom of the intertank so the two tanks can be attached to it,” NASA said in the update.
NASA engineers found that the crack was actually in the insulating foam on the flange, not in the rocket’s metal structure. “That ice that formed is essentially air that’s being chilled by the tank that gets trapped inside of a crack in the foam but not the actual tank,” Nail said. Nail added that NASA personnel had seen similar cracks in the foam when it was used on the space shuttles before their retirement in 2011.
The Engine No. 3 problems and the feared crack followed concerns about a liquid hydrogen leak in the rocket. The leak during the fueling process appeared similar to one that occurred during an SLS fueling test earlier this year, Nail noted. But NASA officials were not quick to judge. “Although a similar issue was identified in an earlier wet dress rehearsal, it may not necessarily be the same cause,” NASA officials wrote in a subsequent update.
NASA stopped and restarted the flow of liquid hydrogen into the tank in an attempt to verify the leak and even proceeded with fueling the 322-foot-tall (98 meters) rocket’s upper stage while engineers worked the issue.
None of these issues should be a surprise. First, this is the first launch of a new rocket. Such problems should be expected. Second, based on the entire past history of this rocket and NASA’s sloppy development of it, it would have been a miracle if nothing went wrong. The entire SLS program has been riddled with delays due to mismanagement and faulty engineering.
The real problem with today’s scrub comes from that NASA management and the way the government operates. Cutting-edge engineering projects traditionally do such tests during early development, though such live tests should continue throughout the entire project. Witness how SpaceX and Rocket Lab have developed their rockets. The live tests come early, including some explosive failures. Since such failures are expected, the project moves on quickly with upgraded prototypes.
Doing it this way however means the early development costs are high, only to drop as the engineers work out the kinks and the project moves forward.
Government projects however don’t want high initial costs. Instead, government officials prefer early costs to be low, so that they can get Congress easily committed to a big and expensive project. Thus, with SLS NASA instead followed its standard “buy-in” procedure it has followed beginning with the shuttle. No or very few tests are done until the spacecraft or rocket is completely finished and ready for operation. All testing instead is done on the computer, during development. When the agency thinks it has something that looks good on paper, it then tries to build it. The result is a very long and very expensive development process producing an untested rocket like SLS, with most of the biggest costs at the back end when Congress feels forced to throw good money after bad.
And when NASA engineers finally try to fly it they are saddled with these issues, many of which a normal development program would have found early on.
If engineers can figure out the engine problem the agency can try again to launch on September 2nd or September 5th. After that the next opportunity will be in October. At that point the solid rocket strap-on boosters will have been stacked for just under two years, almost one full year past their use-by date, posing new risks during launch.
If engineers can’t fix the problem on the launchpad and need to bring the rocket back to the assembly building to tear it down, expect even longer delays, which might even extend well into 2023.
NOTE: This launch was scheduled for 8:33 am (Eastern), which was 5:33 am (Pacific) in Arizona. I decided it wasn’t worth it to get up in the wee hours, since I figured the odds were very high the launch would be scrubbed. Turned out to be a good decision.
One last comment: None of this should be a surprise. I said the same things back in 2011, calling SLS a bad idea and a vast waste of money that should be canceled then. A rereading of that 2011 essay proves everything I said then was right on the money, to a degree that even I find it startling.