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SLS launch scrubbed

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.

Genesis cover

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  • pawn

    I think a hydrogen detection of >600 ppm was a launch constraint for STS. There were all kinds of transients that those system detected, some real some not. The change over from slow to fast fill was always a moment of tension at the console.

    Does anybody have the skinny on what was seen?

  • Richard M

    “Use the Shuttle engines, get the Shuttle constraints.” — Wayne Hale

  • LocalFluff

    The proven RS-25 engines would be a strong point of the SLS. I’ve heard so many good things about RS-25. But of course, they have messed with them. And I’m surprised to now find that there were 7 main engine incidents with the Shuttle, including valve failures and faulty sensors. One caused an abort-to-orbit, which however still didn’t compromise the mission objectives. One caused a scrubbed launch and engine replacement. I don’t know if those incidents had any causes similar to this one.

    Is it likely that a hydrogen leak and cracks in the insulating foam can be fixed on the launch pad? Perhaps they will be judged to be inconsequential.

  • Tregonsee

    I have very mixed thoughts on this. The SLS system may, MAY, have made sense when it was conceived, but both technology and private industry have moved past Apollo-era technology. The sooner this thing is put out of our misery, the better for the real space program. Hopefully it will go out with a whimper rather than a catastrophic bang!

  • Richard M


    And more to the point, Shuttle was regularly bedeviled with hydrogen feed issues. That great ISP comes with some very high costs.

    It’s quite telling that none of the commerciaL medium and heavy lift vehicles in development (Starship, New Glenn, Terran R, Neutron, Antares 300) are using it. (Or, uh, 40 year old engine designs.)

  • Ray Van Dune

    Great explication of the pitfalls of the SLS development process, Bob!

    It would seem that only if reusing of major existing components actually results in a faster deployment does it make sense., and even then maybe not. Here, reuse of the main engines dictated a hydrolox rocket, which meant the “simple” build techniques used by SpaceX (welded stainless steel cylinders) could not be used.

    You can bet that the lamps are burning late at SpaceX, because they probably sense that they have a chance to fly first. A friend said “Yeah, but SLS is headed for the moon”, to which I replied “But it ain’t coming back, and the next one won’t fly for another couple of years!”

  • Ray Van Dune: “…SpaceX…probably sense that they have a chance to fly first.”

    SpaceX already flew first. Falcon Heavy flew back in 2018. A heavy-lift rocket capable of interplanetary flights; Falcon Heavy has been operational for over four years.

    SLS is the one playing catch-up.

  • Col Beausabre

    The Fallacy of Sunk Costs rears its ugly head once again. “We can’t cancel it now, look at all the money we’ve spent!” Which, of course is totally irrelevant. What is relevant is what you want to spend in the future and what you will then end up with. This is Freshman Economics, Finance 101, fer cripes sake!

  • pawn

    “Well, were going to save so much money going with the Lego… err, already developed rocket!”

    I wonder how much a clean sheet designed one would have cost?

    Let me answer that. Less, because it would still be on the drawing board or it never would have gotten funded.

    Given how things turned out, that might have been the best decision. whether it makes it to orbit in one piece or not.

    But the lesson here for future designs is, “This is what you get when you live in a “minimum risk” world.

    Of course, Hindsight is Golden.

  • Jerry Greenwood

    “ That ice that formed is essentially air that’s being chilled by the tank that gets trapped inside of a crack in the foam”.

    It’s not air that is freezing. It’s water from exposure to the humid air of Florida much like condensation on a glass of iced tea. The water in the bottom of your lawn mower gas tank you discover in the spring is a good example of this phenomenon. Under months of exposure at ambient conditions a substantial amounts of water can accumulate and when exposed to freezing temperatures it will expand and break whatever it is trapped in hence the cracked foam. I’m pretty sure NASA knows this but they’re not telling.

  • LocalFluff

    Soviet Buran/Energia/Zenith made more sense as it was launched without the orbiter in 1987. With the main engines on the main tank instead of the orbiter, it could fly also without the orbiter. And the (fueled, not solid) boosters flew smaller satellites to orbit on their own too. A much more modular and economical design. SLS is a three decades later attempt to recapture parts of the Buran/Energia design advantage. Energia was actually more capable than SLS in terms of mass to orbit. SLS would’ve made a 25 years record lifting, not a Saturn V 50 years old.

  • David Eastman

    pawn asks “I wonder how much a clean sheet designed one would have cost?”

    That was never in the cards. The competing proposal to what eventually became SLS would have been to use the existing Atlas/Delta fleet, perhaps with minor upgrades, and do on-orbit refueling. It really hurts to consider where we would be now in terms of capabilities if we’d gone that route. Boeing and Lockheed would have had incentive to upgrade Delta and Atlas, ACES would presumably have been flying long since, SpaceX and other commercial entities would have been able to use propellant delivery missions for development funding, the list goes on. Instead we poured billions down the drain to build a system that pushed no new boundaries, developed no new technologies, spawned no competition, and is obsolete before it’s first flight.

  • James Street

    At least with the NASA jobs program we get a good show. Every few years they’ll roll it out of the hangar, do a countdown, stop the countdown, and roll it back to the hangar. With other government jobs programs (ending racism, ending global warming, ending homelessness, etc) we get nothing for our money. And those programs cost us trillions, not billions, so the NASA jobs program is a bargain.

  • GaryMike

    China has always stolen what they need then claimed it as domestic accomplishment.

    Where’s the Chinese equivalent of SLS?

  • GaryMike

    After all, they’ve had more than a decade to pilfer what they needed.

  • David Ross

    “they’ve had more than a decade to pilfer what they needed.”
    Assuming that SLS wasn’t itself (and isn’t) a massive plundering caper upon the Treasury.
    I did, actually, awaken on time to watch the countdown. I drove off to some coffee shop and did some work instead. It seems like I didn’t miss anything, excepting the money I didn’t earn from my paycheck.

  • Jeff Wright

    SpaceX’s problems-chopsticks crushing scaffolding that should have been moved…not burning off methane? That mickey mouse crap is more concerning. The ‘sunk-cost fallacy’ crud says a new building would have been cheaper than fixing the Pentagon building…also a national asset.

  • George C

    As a software engineer I like early hardware testing too, because it validates the simulation software which itself is costly and tricky to debug.

  • GaryMike

    How valid is simulation software if it’s the Simulation that makes you think you’re creating the code?

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