More SR71 coolness

James Snover

James Snover

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Yep. It also pre-heated the fuel to
make it easier to ignite. Because JP-7 hates to ignite. So they accomplished two things.

On the ground, to start it they had to use a chemical called tetra-ethyl borane to light the engines. In flight, to start the afterburners, required a shot if TEB. If the engines flamed out inflight, that was another shot of TEB. On the throttle is a small counter. It counted down from 50 to 0. That was the shots of TEB remaining.

If they got down to a minimum number, they made an emergency landing. Because when you were out of TEB, and if your engines then flamed out, you were out of options.

They used to do a demo where they would take an open can of JP-7, and toss a match in it. The match would go out. No fire.


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James Snover

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And that wasn’t the only trick they did with the fuel! They trimmed the aircraft by changing its center of gravity by transferring fuel among seven tanks.


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James Snover

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My94GT said:
So now I feel better about the fuel Mileage of my truck lol
Click to expand...
In fact, the Blackbird had to be flown like the most miserly hyper-miler in a four-cylinder econobox. That's why the inlet spikes are there: to recapture energy from the air that had to be pushed out of the way; That's why all the tricks using center of gravity to triim the plane as much as possible, so they don't get a lot of drag from control surface deflections in cruise. It's why the inlet spikes extended and rectracted with speed: to keep them as efficient as possible while at cruise. It's why there are several sets of bypass/bleed-air doors, why the afterburner nozzles dilate and contract. Efficiency is what it was all for, and what enabled it to cruise for hours in afterburner.

It worked so well, that above Mach 2.3, the faster the airplane went, the more fuel efficient it became.
 
James Snover

James Snover

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Ok, one last bit: the Blackbird held almost 100,000 pounds of fuel. It took about 20 minutes to refuel. The whole time the pilot is having to watch the airspeed, his angle of attack, the airplane's center of gravity ... for 20 minutes. With half his windshield fogged over, because for some reason the designers only installed a defroster in half of the windshield and when she hit the lower altitudes and speeds to match the tanker, one half of the windshield almost immediately fogged over.
 
James Snover

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One last bit: at 80,000 feet, the atmospheric pressure is about 0.5psi. 1/2 pound per square inch. And it is (generally) -60F.

The only way to get work ( for example, make an airplane fly) out of air is to put energy (heat) into it.

The inlets, with those spikes, captured the supersonic shockwave of the air the plane had to push out of its way, shoved it down the throat of the intake, and decelerated the air to subsonic speeds.

In the process, that produced 45psi at 950F at the face of the engine! Those spikes let you reclaim what you otherwise had to push out of the way, and with engines in full afterburner STILL developed 45psi and 1,100 degrees of heat! That jump in pressure and temperature is what let the Blackbird do what it did: fly in continuous afterburner for hours on end.


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Revvv

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James Snover said:
One last bit: at 80,000 feet, the atmospheric pressure is about 0.5psi. 1/2 pound per square inch. And it is (generally) -60F.

The only way to get work ( for example, make an airplane fly) out of air is to put energy (heat) into it.

The inlets, with those spikes, captured the supersonic shockwave of the air the plane had to push out of its way, shoved it down the throat of the intake, and decelerated the air to subsonic speeds.

In the process, that produced 45psi at 950F at the face of the engine! Those spikes let you reclaim what you otherwise had to push out of the way, and with engines in full afterburner STILL developed 45psi and 1,100 degrees of heat! That jump in pressure and temperature is what let the Blackbird do what it did: fly in continuous afterburner for hours on end.


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Click to expand...
Now that is impressive.

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MG0h3

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Saw one at the Boeing Airfield when I was @8yrs old. I remember the gent giving us the rundown explaining how it leaked fuel while on the ground. Basically the plane/fuel tanks were designed for the pressure and heat for super sonic speeds and to compensate it was “loose” on the ground.

Saw the B2 at the same airfield much later. You could be looking right at that thing and when it banked it almost disappeared.

Lots of cool flight stuff played in our area growing up.


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