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Watching video of today's test of Northrop Grumman's OmegA first stage SRB after the test is over and the flames have died down a bit, it looks like they are sticking something into the back end of this rocket to probe it.

Question: What is the device shown in the rocket's nozzle, and what purpose does it serve?

Screenshot from OmegA Milestone: First Stage Static Test Fire

OmegA Rocket First Stage Static Test Fire

OmegA Rocket First Stage Static Test Fire

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uhoh
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2 Answers2

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It's a quenching probe.

After burnout of the booster was confirmed, a CO2 fire extinguisher was moved into the nozzle area to inject carbon dioxide into the booster to kill any remaining fire in order to preserve the systems in their condition at burnout, allowing for a detailed study of the components of the SRB. 

Source: http://www.spaceflight101.net/sls-srb---qm-1-updates.html

(This is from an article on a Space Launch System SRB test)

Presumably required due to the non-flight-like horizontal attitude at burnout.

Organic Marble
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  • I discovered some additional information at the end of the video, it makes more sense to me after reading this. You might want to include a reference to it Starting here there are a few Q&A's: https://youtu.be/8MTM-ANa7FI?t=5055 – uhoh May 31 '19 at 09:53
  • So the quenching probe is the CO2 fire extinguisher? – Uwe May 31 '19 at 10:14
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    It may be required in order to preserve the engine (as much as possible) for inspection afterwards. – ceejayoz May 31 '19 at 13:09
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    @ceejayoz that is indeed the purpose as stated in the quote in my answer. – Organic Marble May 31 '19 at 21:19
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    @OrganicMarble I'm pretty sure a comment got deleted somewhere that I was replying to. – ceejayoz May 31 '19 at 21:28
  • @ceejayoz Maybe so but the answer is three hours older than your comment and has always categorically said that the purpose is to preserve the engine for inspection. So I don't really see why you're saying "Maybe". – David Richerby May 31 '19 at 22:39
  • @DavidRicherby "Maybe" is not the same as "may be" = "might be"! – CJ Dennis Jun 01 '19 at 00:38
  • @CJDennis OK, "May be". It doesn't make any difference in this case: they're still posting a comment acknowledging that something is a possibility, under an answer that states that it's the actual reason. – David Richerby Jun 01 '19 at 01:55
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    I'm guessing this is unburnt "ash"? Actual solid fuel contains an oxidiser and would keep burning in a CO2 atmosphere, wouldn't it? – Rich Jun 01 '19 at 03:25
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    So they're probing the rocket's action end. For science. – Machavity Jun 01 '19 at 03:28
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Structural failure of the nozzle happens prior to the probe being inserted. Without the nozzle, parts of the tail end of the rocket were burning and were not supposed to be. The fire was then extinguished with the probe to save the rocket itself and to save any evidence of why the nozzle exploded.

J. P. Smith
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