SLS test failure 2

[thebard3]

More trouble for NASA, probably good news for SpaceX and Blue Horizons.

https://www.space.com/nasa-sls-megarocket-artemis-1-engine-test-fire

Brad Waybright

The more you know, the more you know you don't know.

 

[MacGyverS2000]

I'd hardly call this an engineering failure or a disaster. This is what happens during testing of a new system... nothing blew up, no one was harmed, the safety systems kicked in and shut the system down.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[1503-44]

You both win. Its an engineering failure (did not perform according to design intent) without disaster. Fortunately the SSS did perform according to design intent.

 

[IRstuff]

I read with amusement the definition of MCF; I can think of a NSFW version

TTFN (ta ta for now)
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[GregLocock]

Protos break, that's why we still have them. The failure is when a design gets through validation and is then in service when it fails.

OTOH if a test fail delays the in-service date, you had a management failure, a management that assumed that everything would go to plan and left no slack in the schedule or not enough contingency budget. Or that's how I'd play it if I were on the engineering team, and had written evidence that we'd seen schedule compression or scope creep.

Cheers

Greg Locock


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[IRstuff]

That's usually machts nichts in governmental aerospace, Greg. We've had programs that had everything shifted to the right because of customer FUBARS, except the test phase and final delivery date never move because THEY would be in trouble with THEIR customers, be it Congress, or whoever.

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[rb1957]

Apparently they set some shut-down sensors to low levels expecting success (the fools) but this also saved the test article from damage (the smart people). I think they'll be running again soon.

Funny, aren't these the same engines are previous. Ok, "same" except for the differences ...

Still a year (at least) from test flight.

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[FacEngrPE]

Updated Info

https://spaceflightnow.com/2021/01/...early-engine-shutdown-during-sls-test-firing/

Excerpts follow
[ul]
[li]"During gimballing, the hydraulic system associated with the core stage’s power unit for Engine 2, also known as engine E2056, exceeded the pre-set test limits that had been established,” NASA said. “As they were programmed to do, the flight computers automatically ended the test.”[/li]

[li]… There was one measurement within the hydraulic system that got out of parameters, and that sent the signal to shut down all four engines. That parameter that was tested, that’s not a parameter that would even be measured on a flight. That was a test parameter that was being measured.”[/li]

[li]NASA said Tuesday a sensor reading that indicated the MCF on Engine 4 was not related to the hot fire shutdown. The sensor reading involved the loss of “one leg redundancy” in the instrumentation for Engine 4 about 1.4 seconds after ignition, the agency said.[/li]

[li]“Test constraints for hot fire were set up to allow the test to proceed with this condition, because the engine control system still has sufficient redundancy to ensure safe engine operation during the test,” NASA said. “The team plans to investigate and resolve the Engine 4 instrumentation issue before the next use of the core stage.”[/li]

[/ul]
So I tend to agree (now that more information is becoming available) this test shutdown should be considered a "part of the expected range of test events".

NASA: Green Run Update: Data and Inspections Indicate Core Stage in Good Condition

https://blogs.nasa.gov/artemis/2021...ctions-indicate-core-stage-in-good-condition/

[ul]
[li]After analyzing initial data, the team determined that the shutdown after firing the engines for 67.2-seconds on Jan.16 was triggered by test parameters that were intentionally conservative to ensure the safety of the core stage during the test.[/li]

[/ul]
Fred

 

[MacGyverS2000]

The failure is when a design gets through validation and is then in service when it fails.

^^^^^ This.

There was one measurement within the hydraulic system that got out of parameters, and that sent the signal to shut down all four engines. That parameter that was tested, that’s not a parameter that would even be measured on a flight. That was a test parameter that was being measured.

This statement concerns me... they decided a particular exceeded-parameter was important enough to shut down a test, but that parameter won't be measured during actual flight.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[thebard3]

https://bgr.com/2021/01/19/sls-test-failure-nasa/

Whether or not you might declare this a failure or successful/unsuccessful test, this seems eerily similar to the Boeing Starliner test which failed to reach proper orbit with the ISS due to a software flaw, and subsequent forensics led to another flaw which could have allowed components to impact each other after separation. At the time, NASA declared the mission mostly successful and that a follow-on test might not be necessary. Now, after more than a year, NASA is scheduling a follow-on test in March with requalified software. This is a duplicate of the original test. If there's another problem with it I'd say it will be an engineering and corporate disaster for Boeing.

Brad Waybright

The more you know, the more you know you don't know.

 

[Eufalconimorph]

SLS was sold to the public as being good because it re-uses a lot of Shuttle components, which should make for straightforward design/integration and provide jobs in every state. The schedules were planned with the idea that integrating a bunch of existing components into a new design should be "easy", at least compared to something that needs lots of iterative testing like the original Saturn development. Boeing is a big experienced company, they can surely just simulate everything they need so that a lot of the expensive physical tests can be skipped. Cheap enough for taxpayers to accept, pork for some critical senators, showy results in reasonable time.

Boeing and NASA are seemingly discovering that adding in computer simulations to their rocket engineering doesn't actually decrease the complexity any, it just means you've now got an additional complex simulation step that can get things wrong. Rocket engineering is hard enough without doing it virtually as well! Then the physical test happened, reality met the simulation, the simulation was found wanting, and the schedule slipped.

This is opposed to SpaceX's way, where they plan for lots of iterative testing and failures, and then Musk goes and spouts off some utterly unrealistic deadline and the schedule slips. But at least it's cheaper, and still tends to be faster.

 

[rb1957]

yeah ... "easy" ... "how hard can it be ?" ... computer simulation in lieu of 3D testing ... sigh

another day in paradise, or is paradise one day closer ?

 

[GregLocock]

My previous post was channeling Feynman. This time it's some oil company guy.

You can run projects to a tight schedule using simulation to partially replace development prototypes, such that your prototypes become Verification Prototypes (does the machine perform in line with the predictions) rather than as actual development tools. But in order to meet those timelines you have to be prepared to throw tremendous resources in occasionally. What happens in practice is that the first project to be run like this is a success, partly because it is getting a lot of oversight, and sets the new standard for timing and processes. But subsequent projects will be expected to meet the new standard without the extra resources.

Cheers

Greg Locock


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