Author Topic: Rocket plume colors  (Read 20692 times)

Offline Antares

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Re: Rocket plume colors
« Reply #20 on: 11/15/2007 04:55 PM »
1) Regarding glowing and not glowing exhaust, if I connect my knowledge of static and total temperature with my knowledge of radiating hot gas (dangerous, I know), I think that the visibly radiating part of a plume has been shocked to a lower speed but higher static temperature.  Visible radiation occurs at that higher static temperature.
Or,
The not glowing part of the exhaust is so high in static temperature that it is actually radiating at higher energy than the visible spectrum.  But that doesn't make as much sense to me: it should be radiating broadband.

2) Green plume at ignition: hypergols, undoubtedly.
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Offline Jim

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Re: Rocket plume colors
« Reply #21 on: 11/15/2007 07:28 PM »
Quote
Citabria - 15/11/2007  12:31 PM

That's right. The gas generator exhaust is much cooler (and fuel-rich) than mainstage exhaust and so it is routed through those large tapered ducts you see surrounding the F-1 nozzle where it exits and cools the inside of the nozzle extension. The effect is even more apparent in films of Saturn 1 launches, because the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.

BTW, the Titan II hypergolic exhaust did not glow as much as RP-1, so the Mach diamonds were more visible.

The gas generator exhaust gas becomes bright when it mixes with enough O2 to ignite

Offline luke strawwalker

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Re: Rocket plume colors
« Reply #22 on: 11/19/2007 11:22 PM »
Quote
Jim - 15/11/2007  2:28 PM

Quote
Citabria - 15/11/2007  12:31 PM

That's right. The gas generator exhaust is much cooler (and fuel-rich) than mainstage exhaust and so it is routed through those large tapered ducts you see surrounding the F-1 nozzle where it exits and cools the inside of the nozzle extension. The effect is even more apparent in films of Saturn 1 launches, because the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.

BTW, the Titan II hypergolic exhaust did not glow as much as RP-1, so the Mach diamonds were more visible.

The gas generator exhaust gas becomes bright when it mixes with enough O2 to ignite

That makes sense to me, since this 'cooling flow' surrounding the main exhaust of the F-1 would stay laminar for a bit after exiting the nozzle and then start to eddy and mix with atmospheric oxygen and burn brightly shortly after exiting the nozzle, which would produce a 'chasing' effect on the plume (like watching a smooth waterfall flow trip into turbulence as it goes over the edge/past rocks or debris)  

I've seen the dark exhaust stripes/ Mach Diamond effect on solid motor plumes too, though, most notably on a video I have somewhere of a Mace or Matador nuclear cruise missile launch, lifting off from it's underground bunker on top of a belly-mounted SRM boost motor.... OL JR :)
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Offline DecoLV

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Re: Rocket plume colors
« Reply #23 on: 11/22/2017 01:56 AM »
Speaking of green...wasn't there a copper-based fuel tested in a rocket in the 1960s? Or was it TEA-TEB? I remember seeing the green flame and thinking it looked ridiculous.

Offline Welsh Dragon

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Re: Rocket plume colors
« Reply #24 on: 11/22/2017 07:55 AM »
Boron containing propellants. Pentaborane was called Green Dragon

Offline Boost

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Re: Rocket plume colors
« Reply #25 on: 11/22/2017 01:15 PM »
the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.
Does anyone have any reference about this ? I'd like to know more about these tapered duct difference between the central and the outer H-1 engines, but the only source I have found so far on internet is... this post by Citabria. In addition, I would have thought the central engines had more thermal constraints and needed more this cooling system than the outer engines.

A good source of information dealing with exhaust gases for the Saturn I/IB that I have found so far is this one: https://fr.scribd.com/document/47291629/Review-of-Our-National-Heritage-of-Launch-Vehicles-Using-Aerodynamic-Surfaces-and-Current-Use-of-These-by-Other-Nations , page 21 of the PDF, noted page 15 on screen. One can read:

Quote
For the four fixed center engines, the fuel-rich exhaust gases were piped to the edge of the booster skirt and dumped overboard into a region of high-velocity air flow. In the later vehicles, the exhaust gases were dumped exactly into the “anterstar” created by the four fixed engines. The gimbaled outboard engines required a different approach. The turbopump was fixed to the gimbaled engines; therefore, an overboard duct for them would have required a flexible coupling that could withstand the high temperature of the turbine exhaust gases. Instead, MSFC devised outboard engine attachments called aspirators, which forced the turbine exhaust into hoods on the stub fins as shown in figure 12.

But I see no mention that for the 4 central engines, part of the exhaust was reinjected inside the nozzle.

Offline Jim

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Re: Rocket plume colors
« Reply #26 on: 11/22/2017 01:39 PM »
the outer 4 H-1 engines have those ducts and the inner 4 do not. You can see the darker exhaust from the outer engines but the inner engines show less or none of the darker band.
Does anyone have any reference about this ? I'd like to know more about these tapered duct difference between the central and the outer H-1 engines, but the only source I have found so far on internet is... this post by Citabria. In addition, I would have thought the central engines had more thermal constraints and needed more this cooling system than the outer engines.

A good source of information dealing with exhaust gases for the Saturn I/IB that I have found so far is this one: https://fr.scribd.com/document/47291629/Review-of-Our-National-Heritage-of-Launch-Vehicles-Using-Aerodynamic-Surfaces-and-Current-Use-of-These-by-Other-Nations , page 21 of the PDF, noted page 15 on screen. One can read:

Quote
For the four fixed center engines, the fuel-rich exhaust gases were piped to the edge of the booster skirt and dumped overboard into a region of high-velocity air flow. In the later vehicles, the exhaust gases were dumped exactly into the “anterstar” created by the four fixed engines. The gimbaled outboard engines required a different approach. The turbopump was fixed to the gimbaled engines; therefore, an overboard duct for them would have required a flexible coupling that could withstand the high temperature of the turbine exhaust gases. Instead, MSFC devised outboard engine attachments called aspirators, which forced the turbine exhaust into hoods on the stub fins as shown in figure 12.

But I see no mention that for the 4 central engines, part of the exhaust was reinjected inside the nozzle.

No, S-1 and S-IB did not have any part of the exhaust was reinjected inside the nozzle.  The outboard engine used aspirators which surrounded the nozzle but released the gas beyond the exit plane of the nozzle.  It can be see in the photo

« Last Edit: 11/22/2017 01:39 PM by Jim »

Offline Jim

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Re: Rocket plume colors
« Reply #27 on: 11/22/2017 01:41 PM »
The link shows the difference between inboard and outboard engines of the later S-IBs.

http://heroicrelics.org/info/h-1/h-1-c-d.html


« Last Edit: 11/22/2017 01:45 PM by Jim »

Offline Jim

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Re: Rocket plume colors
« Reply #28 on: 11/22/2017 01:44 PM »
The S-I did not dump into the “anterstar” but overboard and the plumes can be seen here

Offline Boost

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Re: Rocket plume colors
« Reply #29 on: 11/22/2017 01:58 PM »
Yes, but the quote from the article says the same thing, so everybody agrees no ?
Thanks for the link, so Citabria was wrong, and for the outboard engines the exhaust was reinjected into the chamber. I guess this explains the after-burn observed in the plume for these engines wrt the central ones.
« Last Edit: 11/22/2017 02:03 PM by Boost »

Offline Jim

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Re: Rocket plume colors
« Reply #30 on: 11/22/2017 02:31 PM »

Thanks for the link, so Citabria was wrong, and for the outboard engines the exhaust was reinjected into the chamber.

He is right.

No, it is not reinjected into the nozzle (chamber or thrust chamber is higher up on the engine).  The aspirator is a jacket around the nozzle and its flow (the turbo pump exhaust) mixes with the main flow after it leaves the nozzle.


This is a different than the Saturn V F-1.  The turbo pump exhaust is ducted into the nozzle extension to cool it and it mixed with the main flow while in the nozzle
« Last Edit: 11/22/2017 02:33 PM by Jim »

Offline Alpha Control

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Re: Rocket plume colors
« Reply #31 on: 11/22/2017 08:26 PM »
Interesting read.  I think it's the first time I've seen this thread.

And does this thread get the award for Longest Gap of Time Between Posts?

Ten years! Wow.  :)

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Offline smoliarm

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Re: Rocket plume colors
« Reply #32 on: 12/06/2017 12:05 PM »
Copper?
Green flame in the beginning of kero-LOX engine work - it's due to BORON. The igniters usually employ TEA/TEB mixture, and TEB is an organic compound of boron. Presence of boron ions gives bright green color to flames.


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