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Another SR-71 thread

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posted on Jul, 28 2019 @ 09:47 PM
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I know the SR-71 has been around for a while and most people are fairly familiar with it. I was too, but I learned a few things in this article that I thought were pretty cool so I thought I would share it here. For instance, I had no idea the fuel was circulated throughout the plane as coolant prior to being routed to the engine to be burned. To keep it from burning off at the high operating temps of the aircraft the fuel was made inert, which made it perfect for use as coolant. The addition of a chemical igniter in the form of triethylborane was needed to burn the fuel since it had such a high flash-point and low volatility.

There is a neat, but very low quality, video showing one of the engines on a stand at full afterburner. That is 32,500 pound of thrust, or, 160,000 shaft horsepower. Very impressive...

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(post by FlukeSkywalker removed for a manners violation)

posted on Jul, 28 2019 @ 11:20 PM
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a reply to: Vroomfondel


The fuel was high flashpoint JP7 and was not inert or it wouldn't burn.



posted on Jul, 28 2019 @ 11:48 PM
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originally posted by: pteridine
a reply to: Vroomfondel


The fuel was high flashpoint JP7 and was not inert or it wouldn't burn.

From the link...
"A new type of aviation fuel, JP-7, was invented that would not “cook off” at high operating temperatures, having such a low volatility and high flash point that it required the use of triethylborane as a chemical ignitor in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning. "



posted on Jul, 29 2019 @ 02:29 AM
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a reply to: BlackIbanez

😎



posted on Jul, 29 2019 @ 07:43 AM
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originally posted by: BlackIbanez

originally posted by: pteridine
a reply to: Vroomfondel


The fuel was high flashpoint JP7 and was not inert or it wouldn't burn.

From the link...
"A new type of aviation fuel, JP-7, was invented that would not “cook off” at high operating temperatures, having such a low volatility and high flash point that it required the use of triethylborane as a chemical ignitor in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning. "



The nitrogen reduced oxidation as the fuel was being used as a coolant; the nitrogen is called an 'inert atmosphere.' Nitrogen and argon are commonly used for such; nitrogen in industrial processes and argon in the lab because it will displace air. The author of this selected a poorly written phrase to explain what was being done.



posted on Jul, 29 2019 @ 12:52 PM
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originally posted by: pteridine

originally posted by: BlackIbanez

originally posted by: pteridine
a reply to: Vroomfondel


The fuel was high flashpoint JP7 and was not inert or it wouldn't burn.

From the link...
"A new type of aviation fuel, JP-7, was invented that would not “cook off” at high operating temperatures, having such a low volatility and high flash point that it required the use of triethylborane as a chemical ignitor in order for combustion to take place. The fuel itself was rendered inert by the infusion of nitrogen and then circulated around various components within the airframe as a coolant before being routed into the J58 engines for burning. "



The nitrogen reduced oxidation as the fuel was being used as a coolant; the nitrogen is called an 'inert atmosphere.' Nitrogen and argon are commonly used for such; nitrogen in industrial processes and argon in the lab because it will displace air. The author of this selected a poorly written phrase to explain what was being done.


You googled "inert nitrogen" and found something regarding an inert atmosphere. Congratulations. You found something completely unrelated to this article.

An inert atmosphere is exactly that - an atmosphere, gaseous. It is used to shield materials from an atmosphere that contains compounds that may be harmful under certain conditions. This is done typically within a vessel of some kind although gas shielding for welding is similar in nature. In a liquid there is no "inert nitrogen atmosphere". The introduction of nitrogen made the fuel inert - unreactive in a specific set of conditions, the aircraft's operating parameters. The low volatility and high flash-point made the fuel unreactive during normal operation of the aircraft. To be consumed as fuel, triethylborane as a chemical ignitor must be used. The triethylborane did not change the fuels volatility or flash-point, it created an atmosphere in excess of the fuels flash-point allowing it to burn. The triethylborane played the role of a cigarette lighter being applied to the fuse of a fire cracker. It raised local conditions to beyond the flash-point of the fuel allowing ignition to take place.

Thank you for contributing rambling incoherence to this thread.



posted on Jul, 29 2019 @ 02:00 PM
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a reply to: Vroomfondel


Actually, Vroom, the nitrogen displaced the dissolved oxygen in the fuel and, without oxygen, the fuel can be used as a heat sink without decomposing [oxidizing] as it is heated. Compounds in the fuel, such as substituted aromatics, are susceptible to oxidation at the alpha carbons and can then form gums and varnishes on the heat exchangers. This reduces the effectiveness of the heat exchangers and causes leading edge overheating. This is bad. Combat aircraft use fuel as a heat sink for all their electronics and need additives to reduce gum formation on the heat exchangers. Heat dissipation is a limiting factor in several applications; mainly radar.

If it wasn't a T&C violation, I'd send you some papers and presentations I authored on fuel chemistry.
edit on 7/29/2019 by pteridine because: (no reason given)



posted on Jul, 29 2019 @ 02:02 PM
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Inert means chemically inactive and the fuel was certainly chemically active and it also had self sustaining combustion after using the triethylborane to start the engines. The triethylborane was not continually added to the fuel.



posted on Jul, 29 2019 @ 03:56 PM
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a reply to: pteridine

If the fuel in question was never stripped then you have half a chance of being correct. Are you forgetting high temp/high pressure stripping? The x-fins are gone at that point. No gum. No varnish. JP-7 is created with a blend of feed stocks which result in a low volatility fuel with a very high flash point, perfect for use as a heat sink. Other combat aircraft fuels need additives to perform the same function.

Once the fins are stripped the fuel is perfect for this application and clean compared to typical jet fuel. Once the fuel reaches its flash point it can maintain that condition indefinitely. However, in these engines 80% of the thrust at high speeds comes from the ram-jet effect of the barrel cone, not the fuel.



posted on Jul, 29 2019 @ 03:59 PM
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a reply to: Flipper35

Inert "at specific conditions", the aircrafts operating parameters. The fuel did not burn without first creating conditions above its flash-point. In other words, during normal operation the fuel was stable and not susceptible to flash combustion or "cooking off" at the high heat encountered in normal operation of the craft. Inert does not mean it can not burn. It means stable at a specified set of conditions.



posted on Jul, 29 2019 @ 09:48 PM
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Listening to this while reading ATS...



posted on Jul, 29 2019 @ 10:12 PM
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originally posted by: Vroomfondel
a reply to: pteridine

If the fuel in question was never stripped then you have half a chance of being correct. Are you forgetting high temp/high pressure stripping? The x-fins are gone at that point. No gum. No varnish. JP-7 is created with a blend of feed stocks which result in a low volatility fuel with a very high flash point, perfect for use as a heat sink. Other combat aircraft fuels need additives to perform the same function.

Once the fins are stripped the fuel is perfect for this application and clean compared to typical jet fuel. Once the fuel reaches its flash point it can maintain that condition indefinitely. However, in these engines 80% of the thrust at high speeds comes from the ram-jet effect of the barrel cone, not the fuel.



If by x-fin stripping you mean removal of olefins, that is a certainty. Can you define high temp/high pressure stripping? It sounds as though you are referring to catalytic hydrogenation. JP-7 is also low in nitrogen and sulfur containing compounds.
It is other hydrocarbons that are of concern. Alkyl benzenes, indanes, and tetralins, components of JP-7, all have benzylic carbons which are susceptible to oxidation and subsequent formation of gums and varnishes. Sparging the fuel with nitrogen displaces the dissolved oxygen that would react with the benzylic carbons and allows the fuel to be used as a heat sink, hydraulic fluid, and lubricant.



posted on Jul, 30 2019 @ 12:17 AM
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a reply to: pteridine

Its a catalytic cracking process. Stripping x-fins (olefins, paraffins) requires high heat and high pressure, catalysts, an adsorber molecular sieve, and time.

One of the significant features of JP-7 is the extremely low, < 3%, quantity of benzenes, toluenes, etc, and almost no sulfur or oxygen impurities. Oxidation was minimal at best. Where most fuels would oxidise, this fuel required that heat just to flow freely due to its viscosity. After circulating through the craft as coolant when it reached approx. 550F it would be routed to the engines as fuel.

If you are not Chem-E, you are very convincing. I'll give you that.

edit on 30-7-2019 by Vroomfondel because: (no reason given)



posted on Jul, 30 2019 @ 04:03 AM
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Dont forget the ionisation that was put into the fuel to help with its Stealth.



posted on Jul, 30 2019 @ 01:04 PM
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originally posted by: VroomfondelThat is 32,500 pound of thrust, or, 160,000 shaft horsepower. Very impressive...


What's even more impressive is how little thrust that actually is. What made the J58 special wasn't necessarily how much thrust it actually made, but the speeds and temperatures that it could make that trust at without either flaming out or melting.

To put it in perspective, the General Electric GE-4 turbojet, which was to be the engine for the ill-fated Boeing 2707 program, made 50,000lbs of dry thrust and 65,000lbs with afterburners. And the 2707 would have had 4 of them.

Even that's nothing compared to a modern high-bypass turbofan. The A380's Rolls Royce Trent 900s are each rated at 77,000lbs of thrust at takeoff, A350's Trent XWBs are each rated at 97,000lbs of thrust at takeoff, and the 777X's General Electric GE9X's are rated at an absolutely massive 105,000lbs of takeoff thrust apiece.



posted on Jul, 30 2019 @ 01:54 PM
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a reply to: Vroomfondel


Cat cracking does several things at once but is usually part of fuel production. Paraffins are saturated hydrocarbons and are more stable. Light paraffins would be removed in a distillation process. There was consideration given to cat cracking on leading edge heat exchangers which would convert hydroaromatics to hydrogen and aromatics. These would be immediately combusted and have the effect of using the heat of air friction to produce a more energetic fuel. The complexities and failure modes of such a scheme may not be worth the effort.

JP-7 has paraffins, cycloparaffins, alkyl benzenes, tetralins, indanes, and other such compounds. As I mentioned above, the compounds with benzylic carbons are susceptible to oxidation, hence the sparging of the fuel with nitrogen to displace dissolved oxygen.

JP-7 is not more dense than other jet fuels but it is carefully blended [rather than just a distillate cut] to produce a fuel with a high flash point and thermal stability. The nitrogen sparge to remove oxygen is just added insurance.

The Mig 25 was said to use a higher density fuel and, at one time, adding micronized carbon to jet fuels to increase volumetric energy was considered but disadvantages seem to have overcome any advantages. Decalin has a density of 0.9 which would be an improvement of about 6% in fuel density but is not worth the much higher costs. It would seem that fuel density is not a limiting factor.



posted on Jul, 30 2019 @ 03:23 PM
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a reply to: Vroomfondel

My point was, once the engines are started it no longer uses any external additives to keep it going. It was an excellent fuel for the Blackbird because of its qualities, but the way the article reads, even gasoline would be inert in the fuel tanks.



posted on Jul, 30 2019 @ 05:44 PM
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a reply to: pteridine

So JP-7 was basically the jet fuel equivalent of high-performance synthetic motor oil?



posted on Jul, 30 2019 @ 08:45 PM
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a reply to: Flipper35

I didn't take it that way at all. JP-7 specifically was inert under those operating conditions, meaning it wouldn't cook off or spontaneously combust, not that it was incapable of burning as fuel when the proper conditions were met in the engines. It took an additive to create those conditions, but once there the fuel could maintain combustion without the additives. But not much fuel was being burned at cruising speed anyway. 80% of the thrust over mach 3 was from the turbo-ram jet aspect of the engines, not from the consumption of fuel.




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