NASA TESTS RS-25 ENGINE for Space Launch System

Has anyone watched the YouTube video of the test of the RS-25 engine ? There are two interesting observations. One, the cars that are parked in close proximity to the testing facility and two the large plume of vapor emanating from just above the ground in the foreground of the video. My guess is that NASA stores the liquid oxygen and hydrogen for these tests in underground tanks and the plume is caused by the ground above these tanks being chilled by the gases evaporating in these underground tanks.

Are there any other possible causes for the phenomena?

I assume you're talking about this video

[video=youtube;lFqfCDEp6iw]https://www.youtube.com/watch?v=lFqfCDEp6iw[/video]

Looking at the Stennis site on Google maps, I think what you're seeing is vapor (boil-off) that's sitting on top of a pond.

https://www.google.com/maps/@30.3645121,-89.5935328,357m/data=!3m1!1e3

Looking at other places at the site, I think their cryo facilities are somewhere else.

Yeah, there are care parked around the test stand, but these things were built with the expectation of motor explosions.

more info on NASA Stennis:
https://searchpub.nssc.nasa.gov/ser..._2012.docx?rhid=1000&did=493501&type=released

bobk99 said:

I'm still not sure about the physics behind the thick heavy cloud. If it was boil-off, wouldn't the cloud be more dispersed ? It looks like it's much heavier than air for it to be staying so close to the surface of the pond.

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It's cold. Diatomic oxygen is heavier than "air". O2 = 32 , N2 = 28 (grams/mole)

Don't they use a water deluge system on test and launch missions?

Steven said:

Don't they use a water deluge system on test and launch missions?

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Certainly. If you look closely, in some of the shots, you can see the stream of water in the gap under the engine. Most of the white stuff coming out the side of the test stand is steam. Deluge system helps control noise as well as temp.

sooner.boomer said:

Certainly. If you look closely, in some of the shots, you can see the stream of water in the gap under the engine. Most of the white stuff coming out the side of the test stand is steam. Deluge system helps control noise as well as temp.

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Sure. I just wanted to answer the second question of the OP's as to what was causing the white plume. Got it.

sooner.boomer said:

Certainly. If you look closely, in some of the shots, you can see the stream of water in the gap under the engine. Most of the white stuff coming out the side of the test stand is steam. Deluge system helps control noise as well as temp.

Click to expand...

Not to be all Captain Technicality here, but since RS-25 is LH2 and LOX, all of the stuff coming out of the test stand is steam. I guess there's probably some stray NOx and stuff from combustion, too.

I didn't know the deluge controlled noise too. Learn something new every day.

boatgeek said:

Not to be all Captain Technicality here, but since RS-25 is LH2 and LOX, all of the stuff coming out of the test stand is steam. I guess there's probably some stray NOx and stuff from combustion, too.

I didn't know the deluge controlled noise too. Learn something new every day.

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All the water from the deluge system turns to steam as well. Quit a bit of was used on the Apollo missions.

[video=youtube;p8DOXrhkHE8]https://www.youtube.com/watch?v=p8DOXrhkHE8[/video] Here's a perfect example showing how much water comes out prior to ignition.

boatgeek said:

Not to be all Captain Technicality here, but since RS-25 is LH2 and LOX, all of the stuff coming out of the test stand is steam. I guess there's probably some stray NOx and stuff from combustion, too.

I didn't know the deluge controlled noise too. Learn something new every day.

Click to expand...

There's quite a bit of NOx's produced. Almost any combustion in "air" (nitrogen) will produce them, even if air is not used in the combustion.

I was looking at the wikipedia article on this engine - https://en.wikipedia.org/wiki/Space_Shuttle_main_engine

WOW, is it complex! The F-1 and F-1A engines use a single-shaft turbopump for the fuel and oxidizer. The J-2 engines use seperate turbopumps, powered from a common gas generator. The RS-25 used a low pressure, then a high pressure turbopump for the fuel/oxidizer (total of 4). The electronic controls are more complex, as are the valves. I guess they work, though (to the delight of many subcontractors...).

Later in the video is an aerial shot with a rectangular pond fully exposed and there is a line running directly to the flame chute, I wonder if that line in part of the chute cooling system like a water jacket in addition to the deluge and as the water is circulated in the pond it starts to boil off (think nuclear reactor cooling pond). Odds are the video is not edited in linear time but has shots taken for effect placed at varoius times in the actual burn. Just because the pond is visible at 7:20 in the video doesnt mean that it didnt actually happen at 3 minutes into the reak burn.

Look at the Google maps reference above. It looks like there are two "dump" areas - the pond and a concrete circle.