Yes, I see what you mean. Obviously not an issue with DAC exposure.

Differences in incandescence are quite common in any rocket plume, especially with multiple engines and confluent plumes. But this is quite a marked difference, and I don't think it's due simply to flow characteristics as it is in other rockets.

I think this might have something to do with the nature of the F-1 nozzle cooling, but I'll have to dig through a bunch of stuff before I can say for sure. Thanks for your sharp eyes!

If the engine bell of the F1 engines were cooled by LOX and the exhaust exited the nozzle in a near perfect plane, then wouldn't the outer part of the plume be relatively cold? Then, the flame would only become incandescent when turbulance mixes up the exhaust gas six feet below the exit point.

Or something like that. Nice pic, BTW.

I like your theory... it would also explain why you can see lighter "flickers" in the close-up film. The inner, hotter part of the flow would tend to "shine through" a bit.

Other things I thought of are: an effect of the ablative coating from the inside of the bell (sort of a "smoke shroud"), or an acoustic shock effect like the one which can briefly black-out the light of a nuclear explosion.

Another thing that's rather clear in the video is that the transition from "dark plume" to incandescence is associated with a change in the plume's size and character -- from a highly laminar, columnar flow to a broader, more ragged, turbulent state.

The photo credit is NASA (KSC-68PC-327) - it's the Apollo 8 launch.

Further thought. RP-1 and Lox would burn to produce CO2 and H2O, so why would the plume be black? I seem to remember reading that the F1s ran slightly fuel rich, as part of the fix for instability. I suppose this would produce a slightly 'sooty' exhaust.

There's another supplementary method of cooling where, in addition to piping cryogenic oxidizer around the nozzle, you drip oxidizer down the inside of the bell. I don't remember right off if the F-1 used this method too. But it might also account for an annular layer. The dark layer is indeed annular; If you look at the night launches, you can see that it's got incandescent gas behind it.

Exhaust plumes are neither isobaric nor isothermal. This can be clearly seen in the space shuttle plume. So some variances in incandescence are explicable by the simple flow characteristics in the plume.

I'm not as excited about the possibility of confluence. In the Titan launches you can see a difference in incandescence due to plume confluence, but I don't think that's what's happening here.

I agree the flow ceases to be blatantly laminar at the boundary, but my opinion is that the plume diameter does not expand by much, nor does it expand significantly as the plume lengthens. This is proof positive that Wood's theory of additional, nonpropulsive combustion is in error.

I think the photo above give pretty clear evidence that the transition from dark to incandescent occurs well above the point of confluence. There must be some other explanation! And I want to know the answer, dammit! [img]/phpBB/images/smiles/icon_biggrin.gif[/img]

I agree that the dark region seems to be annular. That suggests that johnwitts may be on to the truth... it's got to be some sort of boundary effect for the part of the plume that's in contact with the nozzle.

There sure doesn't seem to be a lot of technical information about the F-1 on line...

There sure doesn't seem to be a lot of technical information about the F-1 on line...

Probably because in the wrong hands F1 engines would spell trouble.

ASME reports that its propulsion technical committee has never had a "Bill Wood" or a "William Wood" in it, let alone as its chair.

Of course, the FTC or FDA might have something to say about that.

Actually, those types of weightloss gimmicks also can be expanded to homeopathy, using copper bracelets to drain away magnetic energy, and all those other fraudulant scams.

I lump them together with the Moon Hoax idea: you need to be skeptical when presented with ideas. If you believe what people tell you just because they say it, then at best you'll be lied to, and at worst it'll kill you and a lot of others.

ACME reports that its propulsion technical committee has never had a "Bill Wood" or a "William Wood" in it, let alone as its chair.

Isn't that the company that makes all the stuff that Wiley Coyote used to not catch the Roadrunner?

Phil, it's funny you should mention that, because I've been involved in a couple ongoing threads on another forum with some anti-vaccinationists and anti-fluoridationists. Their religious-like zealotry is very similar to the HBs. And their arguments follow essentially the same pattern as HBs. If you go their websites, you see the exact same incorrect information spread around and treated as fact.

It really is a similar mindset. VERY conspiracy oriented.

Phil, it's funny you should mention that, because I've been involved in a couple ongoing threads on another forum with some anti-vaccinationists and anti-fluoridationists.

So there are actually people who think we shouldn't go on holiday or clean our teeth? [img]/phpBB/images/smiles/icon_smile.gif[/img]

Yep. I keep showing them my vacation pictures, but they say they're obviously faked, something about divergent shadows?

(and I hate to think what their mouths look like, yeeech!)

That dark plume from the F1s is very dark, even when compared to the silvery nozzle. It's puzzling me more and more.

I've just had a trawl through Kipps pictures at the Project Apollo Image Gallery and the dark plume is visible during all the launches of a Saturn V. They vary a bit in size, but they always apear very dark. (The exception is Apollo 17, where there is no good pic of the engines during launch).

Also, am I correct in remembering that all the orange smoke emitted before the engines light proper is just the exhaust from the fuel pump turbines? Some pumps!!!

I know the answer to this one... [img]/phpBB/images/smiles/icon_smile.gif[/img]

The turbine was a monster -- 55,000 horsepower! That's as powerful as a commercial jet engine. I think (but am not sure) that there was one turbine per F-1.

The orange smoke was produced by the turbine exhaust, but it's a bit more complicated than that. The exhaust was routed into the F-1 combustion chambers, where the LOX streams had already started. There it was ignited and burned, producing a preheating effect. (Later, after the engines were running, that same exhaust gas produced cooling for the bell, since it was "only" 800 degrees F.)

So the orange smoke wasn't the turbine exhaust; it was produced by the combustion of the turbine exhaust as it prepared the engines for the thermal shock of ignition.

The Saturn V is a machine that's loaded with superlatives. Each F-1 engine produced 1.5 million pounds of thrust, had a combustion chamber pressure of 1060 psi... everything about it is just jaw-dropping. But to me, the most amazing statistic about the S-IC is its fuel consumption. Each of the five engines burned one ton of fuel and two tons of LOX... per second.


<font size=-1>[ This Message was edited by: Donnie B. on 2002-07-10 21:05 ]</font>

Big numbers indeed. I thought I'd got it sort of right.

CzC...

Do you get as angry when charlatans try to con the unwary oughta money with products as get-rich-quick, super fast weight loss and other products along those lines? Or is your indignation just reserved for the HB charlatans?

I get angry at any attempt to deceive. It's just that I only write about the Moon Hoax charlatans on Moon Hoax sites.

Don't start me off on Psychologists...

The orange smoke is from the hypergolic igniters which start the turbines and initiate the combustion. The F-1 ignition sequence is a little more complicated than

1. Open fuel valves.
2. Flick lighter.

John, when you get to KSC in August and tour the Saturn Center, you will be amazed at how much bigger the stuff looks in real life than you ever imagined. Unfortunately, you don't get to see a "fuel pump" from a Saturn V there - nearest place is Washington's Smithsonian to see one outside the rocket assembly, but the sucker is HUGE.

If I get to KSC... It's looking shakey at the moment. Boo Hoo.

Out of interest, what powered the turbines?

And I'm a little puzzled by the idea of igniting exhaust. If it's already an exhaust product, how's it gonna ignite?

The turbines were powered by the fuel that also powered the engine - no extra fuel tanks just for the turbines. Just small ones with some hypergolic stuff to get the whole chicken-egg thingy started.
IIRC, the gas for the turbines was burnt with excessive fule, otherwise it would have gotten too hot for the turbine. Afterwards, you can burn the rest of the fuel in the gas by adding oxygen.

Harald

Harald,

You're correct. The turbines "ran rich", so there was plenty of unburned fuel in their exhaust. You might say that the pre-burn in the F-1 engines was like a deliberate "backfire" (now there's something you don't get very often with modern, lean-burning, computer-controlled car engines).

Another theory about the "dark plume" region...

The exhaust is composed of high-temperature, high-velocity gasses, in smooth laminar flow. This establishes a sharp boundary between the exhaust flow and the cooler ambient air.

Such a boundary may cause significant refraction, just as the boundary between air and water refracts light and changes the apparent position of objects underwater.

If the refraction were great enough, a significant fraction of the light might be deflected away from the viewer's eyes (say, downward). Further away from the engine bell, turbulence would begin to disrupt the boundary and the effect would be lost.

In other words, the apparent darkness of the plume might be a mirage -- quite literally.

I do not know if this is the correct explanation, but I'm throwing it out for your consideration. I really want to understand what's going on here!

There was a thread about this on sci.space.tech:

http://groups.google.com/groups?hl=e....net&frame=off
or
http://groups.google.com/groups?q=pl...k.bc.ca&rnum=3
The last one was posted by Henry Hillbrath
Saturn V Propulsion Design Engineer

A short excerpt:

One of the F-1 innovations was the "Gas Cooled Skirt." There is a big, tapered toroidial manifold around the engine part way down the nozzle exit. That is where the turbine exhaust
gas is put back in the nozzle. Down stream of there, there is no regenerative liquid cooling, the skirt is "cooled" by the turbine exhaust gas, which is only at a few hundred degrees F.

The turbine exhaust stream and the core stream are more or less kept separate by layer of "shingles" on the inside of the nozzle (there is some leakage, by design, at the joints.)
The turbine exhaust gas is cool, relatively speaking, and is it the dirtiest, greasiest, sootiest, mess you can imagine.
Being kerosene burned with only enough oxygen to get it up only a thousand or so degrees F before going through the turbine (I don't remember the number, and am too lazy to look for it.)
So, right at the exit plane, and for a short distance down stream, the plume looks darker than it does further down, because it is cooler. Eventually, it mixes, both with the core flow, and with the ambient air, and then it is quite warm.


Harald

Thanks, Harald... the real answer is much more prosaic than mine, but it's good to know.

Too bad. I am taking my family to Florida in August, hoping to see the Aug 22 shuttle launch if it doesn't get delayed. I hope it does work out for you - it would be neat to get together for a beer after a year of chatting on these bulletin boards.

Oh wait - I've just figured it out. Now that there's a possibility of some independent third party actually verifying that your trips are real, you are backpedaling so the hoax you've been spinning doesn't unravel. It's not like you'd need to expose that Fiat Uno in Florida, so what is it you're trying to hide? [img]/phpBB/images/smiles/icon_smile.gif[/img]

It got delayed!

While looking at the sites above, I found this reference to TEA, used to start the F1 engines (when mixed with fuel)...

F1 information from Henry Hillbrath

I don't know of too many things that are hypergolic with LOX.
The stuff that all Rocketdyne engines use is fairly exotic,
"TEA," not something you want with crumpets. ("Tri ethyl
aluminum.) TEA is REALLY nasty stuff. It makes the legendary
hydrazine (actually not much of a hazard) seem warm and fuzzy
in comparison. For one thing, it is very likely to ignite on
contact with air. And it is not good for the complexion, or
human bodies in general, and when it burns, or is just left
lying about, it leaves a residue of aluminum oxide, which is
not nice stuff in valve seats, etc.


I have never seen TEA burn, and I never was aware that you
can see any evidence of TEA ignition in an F-1 or other
engine. However, I certainly assume that, like any other
aluminum containing fuel, it burns with a brilliant white
flame. TEA also has quite a bit of carbon in it, as well as
hydrogen, and when burned off mixture ratio, the aluminum is
going to get all the oxygen available, so it would be sooty,
too. However, there is only a few tens of cubic inches of TEA
total in the ignition slug, and there are great gobs of
kerosene, so I suspect that any effect from the TEA is
masked.

[note from B.D.; Huzel and Huang indicate the volume of TEA used in the F1
as being only 35 cubic inches, or about 600 ml.]

Henry Hillbrath
Saturn V Propulsion Design Engineer (and I kid...)

600ml!!! To start an F1!!! That's less than 2 pints. TEA must be wicked viscious stuff indeed. Where can I get some for my bike?

Where can I get some for my bike?
I assume thats a motor bike. I just had a surreal vision of someone on a bicycle with some kind of homemade contraptions on it whizzing off into the distance at warp speed. Not that its anymore surreal for a motorbike.