Response Video to the latest MoonFaker

[Vincent McConnell]

Jarrah White has claimed that the Lunar Module had no ascent plume. In this video, if you CHOOSE to watch (Don't incessantly bitch because I posted a link) I tackle the claims brought up in MoonFaker: "Where's the Plume?".

The video covers the invisibility of the propellants used, the color differences between two videos of the same engine, atmospheric gases, cables and impossible wires, etc.

The arguments are better presented within the video itself. If you care to, please watch and leave comment with your feedback on the actual youtube page.

[gillianren]

Why? I understand that YouTube is set up so that you can't have a reasoned, cogent discussion there.

[JayUtah]

Nov 6, 2011 13:35:47 GMT -4 Vincent McConnell said:

Jarrah White has claimed that the Lunar Module had no ascent plume.

Nor should have, as all experienced rocketeers know.

[Vincent McConnell]

Nov 6, 2011 14:41:29 GMT -4 JayUtah said:

Nov 6, 2011 13:35:47 GMT -4 Vincent McConnell said:

Jarrah White has claimed that the Lunar Module had no ascent plume.

Nor should have, as all experienced rocketeers know.

Hmm... Partially Wrong, MOSTLY right. At the moment of ignition, there is a quick jet of plasma gas and then immediately afterward, the fuel burns invisibly and can only be seen if looking DIRECTLY into the combustion chamber.

[JayUtah]

Yes, you can expect some visible effect during the startup transient, which for that motor is about a third of a second. However it's difficult to distinguish the plume from material that's being ejected from between the stages.

And yes, after pitchover allows you see up into the thrust chamber, glowing gases can be seen inside it. We mention that somewhere on Clavius, and it has been part of the debunking landscape for about 10 years. Thanks for refreshing it. However that's not a plume in the classic sense. It doesn't become a plume until it passes the exit plane and is then subject to a new regime of physical law.

The chemistry and radiometry of rocket plumes is very important these days because the majority of rocket motors are made for the military. The visibility of the plume in any detectable wavelength becomes a means for tracking rockets and possibly intercepting them.

[tedward]

Forgive me for not knowing what he is saying in this latest vid. Not looked in.

If memory serves the effects are not wholly invisible in that the debris is visible being scattered by the force. I believe a bit of gold coloured material shifts somewhat in a clip from an ascent. Try that on a film set, it would not go half the distance.

[theteacher]

Nov 6, 2011 13:35:47 GMT -4 Vincent McConnell said:

The video covers the invisibility of the propellants used, ...

Your video would be more convincing, if you let the clip showing the ascent from the Moon run past the pitch-over, after which the burning of the propellants is clearly visible through the nozzle of the ascent stage.

[JayUtah]

The N₂0₄/hydrazine formulation produces a transparent plume from a de Laval nozzle at steady state in a vacuum. This will generally be true of any propellant formulation whose exhaust products are gaseous under the plume thermodynamics.

(In contrast LOX/RP-1 has some solid combustion products, but under most vacuum conditions plume expansion prevents them from incandescing in the visible spectrum. They may be visible if backlit. They are spectacularly bright in the middle of the visible spectrum when fired in the atmosphere.)

For any plume under any conditions, the strongest emissions will be in the infrared, including the near-infrared if water vapor is a significant component of the exhaust product. During the ignition transient in methylated hydrazine fuels in a vacuum you should see emissions in the short reds and long oranges -- the lower portion of the visible spectrum. Where ambient pressure allows the plume to incandesce, it appears pink-orange and transparent.

However the television image does not reproduce color faithfully enough to determine whether anything we see there is conclusively a visible portion of the transient plume. Since the transient for the APS is only 0.300 to 0.350 second long, it is doubtful the television camera recorded an actual transient.

The top of the descent stage was heavily layered with H-film and Mylar. Pieces of this material are obviously what we see ejected, entrained by the plume as it strikes the deflector atop the center compartment of the descent stage. I have been given high quality reproductions of the LM ascent stage ignition video frames, and I cannot conclusively distinguish descent-stage debris from any APS plume.

[Halcyon Dayz, FCD]

Do I understand correctly that because of the absence of air pressure the exhaust gasses expand faster, cooling it off, so it actually isn't glowing hot?

[Count Zero]

The RP1/LOX plume is incandescent in the atmosphere, but is not in near vacuum. Watch this video of the Apollo launch. Shortly after launch the plume is long, thin and bright.
By T+1:45 (altitude ~20km) the plume has spread-out considerably due to the lower pressure, but is still glowing.
By T+2:20 (altitude 46km), the plume is very wide and the particles (basically soot) are no longer incandescent.

[JayUtah]

Nov 6, 2011 19:35:33 GMT -4 Halcyon Dayz, FCD said:

Do I understand correctly that because of the absence of air pressure the exhaust gasses expand faster, cooling it off, so it actually isn't glowing hot?

Exactly correct.

[ka9q]

Jarrah showed a clip of a Titan II being launched from a silo to claim that the LM's fuel/oxidizer combination (Aerozine 50/N2O4) should have produced a visible plume. Apparently he was too entranced by the thick, smoky flames shooting up from the flame diverter vents as the missile rose from the silo to notice that the plumes from the engines themselves were indeed almost invisible.

But this does raise an interesting point -- why are there thick smoky flames from the diverter vents? It can't be an inherent property of a hypergolic rocket plume as the Titan's entire plume is later seen to be invisible when it's clear of the silo.

I think the most likely source of the smoky flames was the combustion of an ablative protective coating on the flame diverter at the bottom of the silo and/or the exhaust vents. An ablative coating would not be much of a drawback in a silo normally used only once. At Vandenberg where the same silos were reused for several test shots, any ablative coating could be manually replaced after each launch. Maybe only the Vandenberg silos had an ablative coating while the regular operational silos were destroyed by a single launch. Anybody know?

Another possibility is that the Titan II generated a smoky, flaming plume only for the first few seconds of operation, settling down to a clean, transparent one before the missile cleared the silo. Unless the ICBM Titans were appreciably different for those built for Gemini, this seems less likely. Videos of Gemini Titan launches do not show appreciable smoke or flame at launch, though we do see large clouds of water vapor from the water being dumped on the pad structures for protective cooling. In some cases there are also small orangish clouds of unreacted oxidizer, but still no flames or dark smoke.

[JayUtah]

Nov 6, 2011 23:22:40 GMT -4 ka9q said:

Another possibility is that the Titan II generated a smoky, flaming plume only for the first few seconds of operation, settling down to a clean, transparent one before the missile cleared the silo.

Yes, that would be the answer.

www.clavius.org/techengine.html

The Titan 2 versus LM argument is one that Jarrah has basically lifted from Bill Kaysing. I wrote the page above when Kaysing made the claim. Jarrah just repeats it for a new generation of believers without acknowledging that the issue has a resolution.

In some cases there are also small orangish clouds of unreacted oxidizer, but still no flames or dark smoke.

Kaysing's example showed lots of orange smoke, and mentioned it specifically.

Nitrogen tetroxide reacts with air to produce that smoke. Hydrazine does the same, only with white smoke. In that particular propellant formulation (and many others), you pre-inject oxidizer to smooth the ignition.

I'm not aware of any ablative coatings on the flame deflectors that would produce that effect, but I happen to have a good friend who's a logistics officer for the Titan 2 and will know the answer.

[ka9q]

Watch the clip. At 5:27 not just smoke comes out of the silo vents; there's actual flame. Perhaps the confined path through which these gases flow keeps them from cooling, heating materials to incandescence that would not do so in an unconfined setting.

But not only does Jarrah's own clip prove him wrong (because the engine plume is seen to be faint and transparent) but also dishonest. Footage of all 12 Gemini/Titan II launches is readily available. He could have shown any of them, but they don't show any actual flame -- just lots of water vapor from the pad water jets plus some small clouds of nitrogen dioxide. He only shows one small still from a GT launch just after liftoff with the water vapor clouds dominating the scene.

Instead he picked an obscure clip from a twilight silo launch, presumably at Vandenberg. And he edits it to show only the period before the missile clears the silo. He follows that with a still from what appears to be a different daytime launch from the same silo taken after the Titan II has cleared the silo. He apparently chose it because the sun is backlighting the plumes to make them more conspicuous than usual, and because we can only see the portion of the plume immediately below the engines. The engines are obviously in mainstage operation, yet flames and black smoke continue to pour from the vents. That's what made me suspect that something other than the actual rocket combustion products were responsible (like an ablative coating). Determining that this is so would put yet another coffin nail in JW's claims.

I've also noticed that the portion of a Titan II plume where the two nozzle plumes overlap is noticeably brighter than the individual plumes. Why is that? Since none of the Apollo spacecraft engines had twin nozzles, this effect would not be present in any Apollo footage so it's another reason Jarrah's selection of Titan II footage is dishonest, as is the fact that all of that Titan II footage is in a sea level atmosphere.

[JayUtah]

Nov 7, 2011 16:14:29 GMT -4 ka9q said:

Perhaps the confined path through which these gases flow keeps them from cooling, heating materials to incandescence that would not do so in an unconfined setting.

Yes, that's a confirmed effect. If you confine a plume, you keep it mechanically compressed and you reduce its opportunity to radiate heat. However, there are fluid-dynamics effects too around fittings. See below.

I've also noticed that the portion of a Titan II plume where the two nozzle plumes overlap is noticeably brighter than the individual plumes. Why is that?

We typically run engines fuel-rich. That means the exhaust plume has uncombusted fuel species (e.g., H₂, CH₂). In the mixing layer (i.e., the annular layer outside the inviscid supersonic flow) these fuel species ordinarily combust with atmospheric oxygen in a turbulent pattern. However in the Titan configuration, the confluence zone remains fuel-rich. The fuel species incandesce (rather than burn) due to the increased radiative heat load from the plume cores and mechanical compression from being relatively pinned between the cores.

The latter effect also occurs in plumes that encounter mechanical obstacles and are thus subjected to local compression or rarefaction. We note this, for example, in camera E3 on Pad 39A where the pad fixtures interact with the plumes to form lee zones of varying plume incandesce. This also occurs in the familiar Saturn V diagnostic films. The otherwise invisible J-2 plumes strike the departing interstage and cause brief zones of of varying illumination due to fluid dynamic effects that alter local plume pressure and temperature.

...as is the fact that all of that Titan II footage is in a sea level atmosphere.

Yes, I wish we had made this point earlier. Any comparison to firings in an atmosphere are largely invalid.