Scramjets
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Scramjets
This might not be quite Tech Log, but it is interesting aviation technology in the making (doubtless the mods will move it to a better home if need be!).
Seems that materials science has been advancing quietly in the background, and various tests to prove the viability of Mach 6+ engines are looking promising.
From a PopSci article titled The Hypersonic Age is Near
"[...] With any luck, sometime in 2009, the X51-A will shatter all previous records for sustained scramjet ignition. The PWR team imagines that a B-52 bomber will take off from Edwards Air Force Base in California's Mojave Desert, head toward the coast and, at 45,000 feet, drop the X-51A from the plane. A solid-fuel rocket attached to the X-51A will fire, blasting it up to 60,000 feet and past Mach 4.5, and then drop off to let the scramjet ignite. For five minutes, the scramjet will accelerate the X-51A to a peak speed past Mach 6 and an altitude above 80,000 feet. Then it will fly into the Pacific, its data safely telemetered to engineers on the ground. The test will also mark the moment when scramjets move from flash-in-the-pan science experiments to useful tools. "This is an airplane," Berger emphasizes, "not just something where you light a scramjet and fire it and see where it goes. This is really beyond something you might do for a weapon application. The whole idea is to prove the practicality of a free-flying, scalable, scramjet-powered vehicle. [...]"
Not sure there'll be anything for pilots to do in this brave new world. If something goes wonky at Mach 6 and 80k feet...
R
Seems that materials science has been advancing quietly in the background, and various tests to prove the viability of Mach 6+ engines are looking promising.
From a PopSci article titled The Hypersonic Age is Near
"[...] With any luck, sometime in 2009, the X51-A will shatter all previous records for sustained scramjet ignition. The PWR team imagines that a B-52 bomber will take off from Edwards Air Force Base in California's Mojave Desert, head toward the coast and, at 45,000 feet, drop the X-51A from the plane. A solid-fuel rocket attached to the X-51A will fire, blasting it up to 60,000 feet and past Mach 4.5, and then drop off to let the scramjet ignite. For five minutes, the scramjet will accelerate the X-51A to a peak speed past Mach 6 and an altitude above 80,000 feet. Then it will fly into the Pacific, its data safely telemetered to engineers on the ground. The test will also mark the moment when scramjets move from flash-in-the-pan science experiments to useful tools. "This is an airplane," Berger emphasizes, "not just something where you light a scramjet and fire it and see where it goes. This is really beyond something you might do for a weapon application. The whole idea is to prove the practicality of a free-flying, scalable, scramjet-powered vehicle. [...]"
Not sure there'll be anything for pilots to do in this brave new world. If something goes wonky at Mach 6 and 80k feet...
R
The X-15 did so, but with a rocket engine and for a very brief duration. A Scramjet is air-breathing, making high speed with long duration possible.
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I think that the engine is the key here, while the X15 used hypergolic rocket fuel and early Solid Rockets to achieve these performance levels. An engine capable of running a sustainable supersonic flow using atmospheric oxygen without melting in 5 milliseconds would be a real achievement IMHO.
oops Wiz - you just beat me to it!
oops Wiz - you just beat me to it!
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I know what engine the X15 used, and I am aware of the possibilities that the scram jet presents.
My comment about the X15's performance was in reply to SLF's last two sentences.
My comment about the X15's performance was in reply to SLF's last two sentences.
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Dear Henry,
Wiz and I are trying to compare like for like here. The X15 though a very admirable project was essentially the precursor to the STS Space Shuttle which achieves orbital velocity and LEO, something the X15 never did, (though with a little more money - who knows). Scramjet has been a much harder technical achievement mainly due to such problems as materials technology and combustion stability. Not having to lug your own supply of very heavy oxidizer along with you will be the real breakthrough.
TOD
Wiz and I are trying to compare like for like here. The X15 though a very admirable project was essentially the precursor to the STS Space Shuttle which achieves orbital velocity and LEO, something the X15 never did, (though with a little more money - who knows). Scramjet has been a much harder technical achievement mainly due to such problems as materials technology and combustion stability. Not having to lug your own supply of very heavy oxidizer along with you will be the real breakthrough.
TOD
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Dear Thridle: I understand and agree with what you say.
I was merely trying to point out that if something goes wonky at 350,000ft while doing 6.7, it might well be a bit worse than something going wonky at Mach 6 and 80k feet...
In either situation it is not going to be very pleasant.
I was merely trying to point out that if something goes wonky at 350,000ft while doing 6.7, it might well be a bit worse than something going wonky at Mach 6 and 80k feet...
In either situation it is not going to be very pleasant.
Plastic PPRuNer
'.....while the X15 used hypergolic rocket fuel and...."
I hope I'm not being too picky, but the XLR99 engine that powered the X-15 was not hypergolic (i.e. used propellants that burn spontaneously when mixed).
The XLR99 used anhydrous ammonia and liquid oxygen which require an initial igniter.
See: http://www.bobholland.com/me/reaction.htm for the XLR99 and http://www.permanent.com/t-mikesc.htm for hypergolic propellants.
I hope I'm not being too picky, but the XLR99 engine that powered the X-15 was not hypergolic (i.e. used propellants that burn spontaneously when mixed).
The XLR99 used anhydrous ammonia and liquid oxygen which require an initial igniter.
See: http://www.bobholland.com/me/reaction.htm for the XLR99 and http://www.permanent.com/t-mikesc.htm for hypergolic propellants.
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Before launch from the B-52 the X-15 used an igniter to light off a small stream of propellants in a small combustion chamber attached to the main combustion chamber. When lit this was referred to as "igniter idle". After drop this was then used to light the main combustion chamber.
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Dear Mac,
Yes I stand corrected, all I can blame is a rusty memory! I suspect Scott Crossfield may be briefly forgiven for thinking otherwise when he had the ground test accident - lucky guy.
The thing that most got me when I watch the landing sequences is the acute timing required for de-rotation on touchdown. It makes me appreciate my nice big elevator I have to stop the nosegear crashing onto the ground and the fuselage shearing in two (I do sometimes try I regret to say).
Regards
TOD
Yes I stand corrected, all I can blame is a rusty memory! I suspect Scott Crossfield may be briefly forgiven for thinking otherwise when he had the ground test accident - lucky guy.
The thing that most got me when I watch the landing sequences is the acute timing required for de-rotation on touchdown. It makes me appreciate my nice big elevator I have to stop the nosegear crashing onto the ground and the fuselage shearing in two (I do sometimes try I regret to say).
Regards
TOD
