News: 1611081311

  ARM Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life (Terry Pratchett, Jingo)

Engineers blame 'intentionally conservative' test parameters for premature end to Space Launch System hotfire

(2021/01/19)


After the weekend's shorter-than-hoped-for test firing of the core stage of NASA's monstrous Space Launch System (SLS) rocket, engineers have confirmed the hardware remains in "excellent condition" and [1]blamed "test parameters that were intentionally conservative."

The parameters were designed for ground testing and were exceeded by a hydraulic system during gimballing by thrust vector control hardware, resulting in the shutdown. "If this scenario occurred during a flight," the agency explained, "the rocket would have continued to fly using the remaining CAPUs [Core Stage Auxiliary Power Units] to power the thrust vector control systems for the engines."

[2]

"The specific logic that stopped the test is unique to the ground test when the core stage is mounted in the B-2 test stand at Stennis," added the agency. Alas, the intentional stressing of the system that resulted in the CAPU shutdown (and transfer of power to the other CAPUs) exceeded those pre-sets and triggered the premature end of the hotfire.

"The data is being assessed as part of the process of finalizing the pre-set test limits prior to the next usage of the core stage."

[3]

And that alarming Major Component Failure (MCF) call? It was due to the loss of one leg of redundancy in the instrumentation of Engine 4. In addition, the engines managed to hit their full power of 109 per cent during the test.

However, and here lies the rub, there is no escaping the fact that 67.2 seconds is quite some way short of the eight minutes engineers aimed for. While the initial findings will provide a little relief for the troubled Artemis programme and its schedule constraints, they do not yet justify ditching a second test and shipping the stage to Kennedy Space Center.

"Data analysis is continuing to help the team determine if a second hotfire test is required," said the agency. Those parameters around the thrust vector control can be tweaked by the team to prevent another automatic shutdown should the decision be taken to run the test again.

[4]

However, going for a second test would severely damage the already slim chances of a 2021 launch for the uncrewed Artemis I. ®

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[1] https://blogs.nasa.gov/artemis/2021/01/19/green-run-update-data-and-inspections-indicate-core-stage-in-good-condition/?utm_source=TWITTER&utm_medium=KathyLueders&utm_campaign=NASASocial&linkId=109487603

[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_science/front&sz=300x250&tile=2&c=2YAdkiGBZ5GwPUEBrEMzPTQAAAAc&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0

[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_science/front&sz=300x250%7C300x252%7C300x600&tile=3&c=33YAdkiGBZ5GwPUEBrEMzPTQAAAAc&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dtop%26test%3D0

[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_science/front&sz=300x100%7C300x250%7C300x251&tile=4&c=44YAdkiGBZ5GwPUEBrEMzPTQAAAAc&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[5] https://whitepapers.theregister.com/

Well That Doesn't Sound Too Bad

Anonymous Coward

Better this as an outcome than it having got to 67sec and "boom boom a boom".

Re: Well That Doesn't Sound Too Bad

eldel

I'm not so sure - and that may be the reason that Space X and Blue Origin to a lessor extent are moving much faster than Boeing. They leave it to fail and gather more information.

In this test Boeing stopped it at the first sign of trouble - no doubt to try and protect a politically imposed launch date - but now have no idea if the problem would stabilize or get worse and cause a catastrophic failure and when. Space X would just let the bastard blow up and thus characterize the whole thing.Yeah it ain't cheap - but when you have stuff rolling off an assembly line instead of hand crafted by a cost plus band of artisans then it's a quick turnaround and another learning experience.

SLS has effectively been in development since 2005 (if you include the Constellation program) - only 3 years less than Space X has been in existence. Not only that they even had the engines 'gifted' to them so they didn't have to develop them. Since 2011 the development costs for the first stage booster alone are running at somewhere north of $20B and all they have to show for it are some politicians getting fat bribes. For reference Space X developed the Falcon 1 and 9 for around $400M.

Re: Well That Doesn't Sound Too Bad

Jon 37

You misunderstand. The purpose of NASA is pork - i.e. to spend money in lots of political districts so politicians can say how good they are at creating and/or keeping jobs. The short-term purpose of SpaceX is to build a successful, cheap, profitable rocket launching business, including unmanned and manned launches, as a stepping-stone to their longer-term goal of establishing a colony on Mars.

Both organizations are being very successful at achieving their goals. They're just completely different goals.

(Edit to add: I know there are lots of really smart people working at NASA who genuinely believe in advancing scientific knowledge and/or sending humans to explore. However, their mission and budget are set by politicians, and they set the goals of NASA to align with their desires for pork).

Re: Well That Doesn't Sound Too Bad

Martin Gregorie

Don't you mean something like:

"The purpose of NASA used to be space and aerospace research until the politicians took over and turned it into their own pork barrel".

Re: Well That Doesn't Sound Too Bad

admiraljkb

> even had the engines 'gifted' to them so they didn't have to develop them

That is actually a large part of the problem from what I can figure out. This program is trying to take hand me downs designed and built by engineers that are dead or long retired now and having to reverse engineer them to fit them in. Many times this is much harder than just going pure greenfield and do something new. They HAVE to be ultra conservative on tests, because many of the parts just aren't replaceable currently. The consequence of that is later when failures happen with the old space shuttle components (again) with live humans aboard (again).

Figured out a while back as a software engineer that legacy code will eventually hit a point where F it, it's time to create something new as it takes too much time to maintain that mass of spaghetti.. Also found similar on my house, where after starting "renovations" it turned into a rebuild, and would have been cheaper, easier and FASTER to bulldoze and build new.

Re: Well That Doesn't Sound Too Bad

Anonymous Coward

Figured out a while back as a software engineer that legacy code will eventually hit a point where F it, it's time to create something new as it takes too much time to maintain that mass of spaghetti..

Doesn't really work that way with rocket engines. These burn H2 and LOX - the recipe for the best in-vacuum performance. H2 is bastard hard stuff to work with, and a fresh design is going to be at best only incrementally better than the existing design. Redesigning those things is likely not going to produce any worthwhile benefits.

SpaceX are avoiding H2 by using methane - basically a compromise between very difficult engineering and performance. It performs better than kerosene, but isn't as hard to engineer for as H2. That's fine, because the only performance targets they need to meet are their own. But AFAIK they won't be able to achieve as high interplanetary velocities as the SLS.

It doesn't really work that way with many other things too. If you want a Mach 2 airliner, it's always going to end up looking a bit like, and share many of the same basic technologies, as Concorde. No one's really improved on the car.

Re: Well That Doesn't Sound Too Bad

bombastic bob

exactly - a 'Total Inability To Sustain Usual Parameters' event resulting in a ginormous "ooh, aahh" ball of "system integrity loss" would have cost a LOT more and set them back a LOT further. 400 additional seconds of fuel would make ONE HUMONGOUS FIREBALL, after all.

A look at Apollo 2 through 6 would confirm this approach (wikipedia articles on them are interesting and appear to be accurate). After Apollo 1, they needed to be more careful to identify potential problem before they become fireballs. Similarly with the shuttle losses. Space is (currently) a dangerous business, just like flying was 100 years ago.

Chris G

Rather than a second test, shirley they could write a software fix for it, to avoid delays and to get it in the air?

What could go wrong?

Edited to say, at $20Bn that is not just a gravy train, they have the meat and two veg and the apple pie and custard.

admiraljkb

quick software workaround for the sensor, and put it back in the air without disclosing anything at all? That sounds like the (modern) Boeing way, sadly.

hit their full power of 109 per cent

fwthinks

So they have a power dial that can go to 11, but they only got to 10.9 before they hit the big red button

There once was this One Ring

Grikath

And thus they spake: It Will Be All Right.....

Much of the excitement we get out of our work is that we don't really
know what we are doing.
-- E. Dijkstra