martinbo

So what of "Aurora" and it's slated Scramjet propulsion?

Curb Zone

 

Bozzor

Actually it is something called a Pulse Detonation Wave Engine...

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BMW_Dude

Looks like you guys know a lot about airplanes, a small interest of mine, except I don't know much about it!

Interestingly I watch a program on TV about the SR-71 and they indicated it could do Mach 5-6! Does that sound true?

Beemer B773ER

In short, no, that's not true at all. It could only push a little over Mach 3.

Here's a short extract from a page I'm at right now:

The X-43A flight easily set a world speed record for an air-breathing or jet engine aircraft. The previous known record was held by a ramjet powered missile, which achieved slightly over Mach 5. High-speed air-breathing engines, like a ramjet, mix compressed air from the atmosphere with fuel to provide combustion. The same is true of the scramjet or supersonic combustion ramjet that powers the X-43A. The highest speed attained by a rocket-powered airplane, NASA's X-15 aircraft, was Mach 6.7. The fastest air-breathing manned vehicle, the SR-71, achieved slightly more than Mach 3. The X-43A more than doubled the top speed of the jet-powered SR-71.

Editors Note: The X-43A was un-manned, carried aloft by a B-52 and rocket assisted to an altitude of 110,000 feet before the scramjet engine on the X-43A ignited and boosted the speed of the craft to Mach 9.7. The X-43A is now in the Guinness Book of World records as the fastest air-breathing aircraft in the world. The SR-71 is still the fastest air-breathing, manned aircraft in the world.

So there it is, amazingly, the SR-71 still holds the record for manned flying... which is amazing for an aircraft of its age.


PS to Boz: Thanks for the heads-up on the development of BWB's. Damn fascinating reading about the benefits of such an aircraft over the A380. I hope we end up seeing Boeing take up this evolutionary design. Evolutionary and not revolutionary because to me this idea spawned from John Northrop's historic flying wing idea. Amazing to see how right he was so long ago.

Gotta love where commercial aircraft design is heading... up, up, up and AWAY!!

Alfie

Mach 3.6 if I'm correct.

Bozzor

It could sustain a cruise at above Mach 3.2, but not sure by how much. Mach 3.6 might be a bit high for sustained cruise, though short bursts may be possible...not really too sure...

martinbo

Yes, officially [and this is off the top of my head now... I don't feel like googling it] the top speed of the SR-71 was quoted by the USAF as being (around) 3571.16 km/h. That's at least how I remember it!

Interestingly:

The SR71's titanium skin was design to expand and seal joints and high temperatures; on the ground the SR-71 leaked copius quantities of the JP7 fuel though this was hardly an issue as the fuel wouldn't ignite even if a lit match was thrown at it.

Even better, the majority of the thrust produced by the J58 turbo/ramjets at full chat didn't come from the reheat exhaust but from the high pressure pulse produced by the engine inlet cone configuration. The aperture of the variable geometry engine intakes was adjusted by moving the cone fore and aft depending on the speed of the aircraft. Cool huh? Imagine the thrust of those hydraulic cylinders required to push that intake cone forward in such airflow!

martinbo

Ja ja ok, curiosity got the better of me and I was out by a couple of clicks. Official top speed is 3529 km/h. Too much Aviagraphica for me and not enough spec sheets!

Here's a tremendously useful repository for Blackbird info:
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Bozzor

Btw, I have the real, declassified SR-71 flight manual in PDF format...all 150 MB of it. Let me know if anyone wants it and will place it in my emule folder...

Beemer B773ER

Yes, I remembering reading similar information a while ago. It truely is amazing how this aircraft operates. How the guys at Skunkworks had to develop intuitive designs and mechanisms to simply keep this thing flying in a straight line let alone achieve speeds inexcess of Mach 3.
When I did see the SR-71 in the metal, I was a little suprised as the poor build quality in terms of the joints and so forth, and I simply put that down to it being a relatively old aircraft and also because it simply sits outdoors prone to the elements .... but I think I was to aww-struck to remember the real reason for it. Just imagine the intense heat of the aircraft as it approached its terminal velocity.

Nonetheless, once the plane landed no one could approach it for some time as its canopy was still hotter than 300 degrees Celsius.

At around Mach 3, the increased heating from the shock cone compression, plus the heating from the compressor fans, were already enough to get the core air to dangerously high temperatures, and no fuel was added in the combustion chamber. This means the whole compressor-combustor-turbine set-up in the core of the engine provided no power, and the Blackbird flies on afterburners alone, using the compression from the shock cones: the engines became ramjets. No other aircraft does this.
Truely a unique aircraft, not just by its form, but its function. Simply put.. it's a masterpiece in aircarft engineering considering the context of its development.

** Thanks to Martin for the link. Some incredible information there.

Curb Zone