Author Topic: Static Test Firing  (Read 5238 times)

Offline TJL

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Static Test Firing
« on: 03/23/2019 01:50 pm »
Was wondering why only SpaceX requires a static test fire of its launch vehicle before every launch and other launch providers do not?  Thank you.

Online ZachS09

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Re: Static Test Firing
« Reply #1 on: 03/23/2019 04:41 pm »
Before SpaceX did these static fires, NASA's Space Shuttles also did static fires. However, they did this only before a brand-new orbiter flew on its maiden voyage. An exception was after the Challenger disaster and before the STS-26 mission when Discovery test-fired its engines.
« Last Edit: 03/26/2019 11:48 pm by ZachS09 »
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Offline skater

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Re: Static Test Firing
« Reply #2 on: 03/23/2019 05:11 pm »
Delta IV can't do it due to the ablative nozzle.

Offline space_snap828

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Re: Static Test Firing
« Reply #3 on: 03/23/2019 05:46 pm »
I've looked into this before, and it seems that many(maybe most) rocket engines are incapable of being fired more than once without a ton of refurbishment. However, I found that for the Saturn V, every F-1 engine was test fired, but then had to be cleaned out a good deal, and then be sent to the rocket. SpaceX also does this, although Merlin engines need far less refurbishment.

Online ZachS09

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Re: Static Test Firing
« Reply #4 on: 03/23/2019 11:07 pm »
Delta IV can't do it due to the ablative nozzle.

Technically, Delta IV DID do a static fire before its maiden voyage. But to add on to your point, they probably changed engines after the test.
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Offline Slarty1080

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Re: Static Test Firing
« Reply #5 on: 03/24/2019 09:13 am »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?
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Offline Jcc

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Re: Static Test Firing
« Reply #6 on: 03/24/2019 10:36 am »
I think they will continue to test fire every engine in McGregor, but if they get to the point where they can reuse stages within 24 hours (in other words, without refurbishment), then static firing of the full stack will be redundant.

Offline CorvusCorax

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Re: Static Test Firing
« Reply #7 on: 03/24/2019 10:49 am »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?

Usually, any launch provider conducts whats called a "wet dress rehearsal" before launch. Thats a complete countdown including fueling, where both the rocket hardware (which is often brand new and as such untested, or has been flown but through a straining reentry procedure plus several months of sitting around) and the procedures/team are tested as if. Except the rocket doesnt take off

Igniting the engines as part of that is a great idea, becauseotherwise you might miss something and only notice on launch day

( scrubs are annoying, especially if you have instantanious launch windows )

assume a mission like the voyager probes, requiring planetary alignments you only get once in a few hundred years!

For other launches, a delay is less of a problem, but still something you would want to avoid.

Issue is, most engines cannot be easily static fired. most launchers use solids, which are by definition single use only. Others have engines that require extensive overhaul, but after such extensive maintenance you might as well need another test fire so whats the point?

So long story short, if you have engines that can be easily and repeatedly testfired ( for Raptor that is even more the case than for Merlin ) you would really really want to do a static fire whenever you do a dress rehearsal of any kind.


Now the interesting question with starship is, do you really need a dress rehearsal every flight. And the answer is likely no.

You'd only want that if
- the vehicle is brand new or has seen significant changes/upgrades/modifications
- you have a severe change in profile/procedures or new team, which you want to rehearse
- the vehicle was standing around for an extended time without use
- you have a high profile mission where you can't afford a launch scrub or just want to be extra save (crew on board)

that means, if spaceship gets to the point they launch daily with only refueling and reloading cargo in between, they likely wont do a static fire or dress reheatsal for every flight. But They will still do them when it makes sense.










Offline Lars-J

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Re: Static Test Firing
« Reply #8 on: 03/25/2019 06:14 am »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?

Why in the world would they stop testing them? They are building REUSABLE engines for REUSABLE rockets. If test/hot firing them is a problem, they have done something wrong.

Think of other reusable engines. Do you think jet engines are started for the first time a in real takeoff?

SpaceX is where they are because of a meticulous text program. If you think they will abandon that then you need to think again.

Offline guckyfan

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Re: Static Test Firing
« Reply #9 on: 03/25/2019 07:24 am »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?

Why in the world would they stop testing them? They are building REUSABLE engines for REUSABLE rockets. If test/hot firing them is a problem, they have done something wrong.

Think of other reusable engines. Do you think jet engines are started for the first time a in real takeoff?

SpaceX is where they are because of a meticulous text program. If you think they will abandon that then you need to think again.

For new rockets, sure there will be tests. But I expect them to skip static fires of flown boosters in the not too distant future, probably beginning with Starlink flights. Make the launch the static fire and shut off if really needed.

Offline wannamoonbase

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Re: Static Test Firing
« Reply #10 on: 03/25/2019 12:15 pm »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?

Why in the world would they stop testing them? They are building REUSABLE engines for REUSABLE rockets. If test/hot firing them is a problem, they have done something wrong.

Think of other reusable engines. Do you think jet engines are started for the first time a in real takeoff?

SpaceX is where they are because of a meticulous text program. If you think they will abandon that then you need to think again.

For new rockets, sure there will be tests. But I expect them to skip static fires of flown boosters in the not too distant future, probably beginning with Starlink flights. Make the launch the static fire and shut off if really needed.

I agree with a caveat that it may depend on how quickly it is turned from 1 launch to the next.
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Online envy887

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Re: Static Test Firing
« Reply #11 on: 03/25/2019 01:07 pm »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?

Somewhere between zero and zero.

SpaceX will probably eliminate the preflight static fire, and might eliminate the full stage full duration test fire (possibly replacing it with an actual orbital test flight of the fully reusable stack). But they will never stop testing Raptors individually.

Offline wannamoonbase

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Re: Static Test Firing
« Reply #12 on: 03/25/2019 03:59 pm »
So what are the chances that when Raptor operations become routine that they will abandon test firing them and just use them straight off of the production line? If not why not?

Somewhere between zero and zero.

SpaceX will probably eliminate the preflight static fire, and might eliminate the full stage full duration test fire (possibly replacing it with an actual orbital test flight of the fully reusable stack). But they will never stop testing Raptors individually.

I've thought the full duration test fires should be phased out already.  They must have enough test data by now to determine whether a booster is ready without a full burn.

But they are the rocket guys and it's there money they are spending on subcooled propellants.
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Offline guckyfan

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Re: Static Test Firing
« Reply #13 on: 03/25/2019 04:38 pm »
I've thought the full duration test fires should be phased out already.  They must have enough test data by now to determine whether a booster is ready without a full burn.

They seem to use the term full duration somewhat loosely. For example when they plan a 10 second test of a new stage and it burns 10 seconds, it is a full duration test.

Offline whitelancer64

Re: Static Test Firing
« Reply #14 on: 03/25/2019 05:11 pm »
Delta IV can't do it due to the ablative nozzle.

Delta IV can and has done static fires. They were called "hot fires" by ULA. Notably, the Delta IV Heavy did a couple of hot fire tests prior to its maiden launch.

Several other rockets can and have done similar static fires, usually before their maiden launches.

Atlas V used to do a full wet dress rehearsal before every launch. ULA has now phased them out because they only infrequently turned up issues. They now only do wet dress rehearsals for NASA / DOD flights or by customer request.

SpaceX is still doing static fires, and part of the reason they do them is because they iterate their builds. It was not common for a Falcon 9 to be the exact same build as the one before it. Now that the Block 5 is a pretty stable design, we may finally see the static fires be phased out.
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Offline CraigLieb

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Re: Static Test Firing
« Reply #15 on: 03/28/2019 12:57 pm »
As they gain deep experience with reuse, would they consider an extended hold-down before launch to verify for a little bit longer everything is working? You might end up with extra scrubs but save a full fueling cycle.
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Offline Jim

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Re: Static Test Firing
« Reply #16 on: 03/28/2019 02:18 pm »
Delta IV can't do it due to the ablative nozzle.

Technically, Delta IV DID do a static fire before its maiden voyage. But to add on to your point, they probably changed engines after the test.

Delta IV did only one.
it was a test stage and not a flight stage.  That stage is now in the AF Space Museum
« Last Edit: 03/28/2019 02:20 pm by Jim »

Offline Jim

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Re: Static Test Firing
« Reply #17 on: 03/28/2019 02:19 pm »

Usually, any launch provider conducts whats called a "wet dress rehearsal" before launch. Thats a complete countdown including fueling, where both the rocket hardware (which is often brand new and as such untested, or has been flown but through a straining reentry procedure plus several months of sitting around) and the procedures/team are tested as if. Except the rocket doesnt take off


Atlas doesn't do them anymore

Online envy887

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Re: Static Test Firing
« Reply #18 on: 03/28/2019 03:27 pm »

Usually, any launch provider conducts whats called a "wet dress rehearsal" before launch. Thats a complete countdown including fueling, where both the rocket hardware (which is often brand new and as such untested, or has been flown but through a straining reentry procedure plus several months of sitting around) and the procedures/team are tested as if. Except the rocket doesnt take off


Atlas doesn't do them anymore

Not as a matter of course. But they did one for Insight.

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