

Hypersonic aircraft shatters aviation records - ilamont
http://www.latimes.com/business/la-fi-hypersonic-20100527,0,764506.story?track=rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+latimes%2Fmostviewed+%28L.A.+Times+-+Most+Viewed+Stories%29

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run4yourlives
Speed is not really the issue here: the X-15 was a hell of a lot faster 40
years ago. As usual the media misses the point due to their own ignorance.

There are two news-worthy items here:

1\. The ramjet/scramjet engine. (No moving parts)

2\. The lack of a test pilot.

This is what makes this test significant.

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archon
That and the fact that the speed was sustained for a longer period with this
test vehicle than with previous vehicles.

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run4yourlives
meh. Build a bigger gas-tank. :-)

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Tuna-Fish
Not an issue. What makes it fail is the insane erosion it suffers when it rams
into air at 2km/s.

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run4yourlives
Given that we've been launching rockets and missiles into the atmosphere at
speeds much faster than Mach 4 for the better part of a century now, I think
we've solved that issue as far as practically required. :-)

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rbanffy
It all depends on the altitude. If you are using a rocket, you can avoid the
friction problem by going out of most of the atmosphere. Do that with an air-
breathing engine and it will not function.

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run4yourlives
As I said, solved as far as practically required, as your comment illustrates.

The viability of the scramjet being actually useful for anything is up for
debate. Either you can fly slower with a jet, or leave the atmosphere
altogether with a rocket.

Flying at orbital speeds within the atmosphere is of very, very marginal
utility, given the number of complexities involved.

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rbanffy
Maybe scramjets could be used as auxiliary propulsion for launchers. A pound
of oxidizer saved is a pound gained.

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primemod3
More impressive to me is the X-15, which flew faster than the aircraft in this
video, had a pilot, and flew in the 1960s.
[http://en.wikipedia.org/wiki/North_American_X-15#Fastest_fli...](http://en.wikipedia.org/wiki/North_American_X-15#Fastest_flights)

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retube
that was a rocket engine though. this is air-breathing.

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arethuza
"With the technology, the military could strike anywhere on planet within an
hour or less"

Even at 4000 miles at out it wouldn't it still take up to 3 hours to get
anywhere on the planet (24900 mile circumference)?

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eavc
But we have bases all over the world.

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arethuza
So nowhere on the planet is less than 4000 miles from a US base?

Somehow I expect the answer to that question to be "yes".

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eavc
And ships are capable of launching missiles and aircraft as well.

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mustpax
This is the engine that powers this aircraft:
<http://en.wikipedia.org/wiki/Scramjet>

Right now, it can only operate at high speeds, hence the bomber-based launch.

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retube
a scramjet will only _ever_ be able to operate at high speeds. The compression
of intake air for combustion is achieved by the forward velocity of the engine
itself (the engine has no moving parts) unlike a normal jet engine which uses
a fan to compress the intake.

Any scramjet, current or future, will require some combination of other
engines in order to accelerate the aircraft to a velocity at which the
scramjet becomes self-sustaining (typically 3000+ mph I think).

Edit: needless to say, a stable self-sustaining scramjet is an INSANELY hard
fluid dynamics problem.

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rbanffy
You could use a conventional jet engine to pump its exhaust into the scramjet
intake. It would have less oxygen, but a turbofan engine could compress enough
air through the scramjet fast enough. The trick in this is to transition from
subsonic flow in the turbofan to full supersonic engine operation.

Looks like an interesting concept.

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run4yourlives
Putting a conventional jet engine in front of a scramjet defeats any real
benefit you derive from having the scramjet there in the first place.

The scramjet's main advantages are cost and efficiency; to accomplish these
gains it comes with a myriad of technical problems and hurdles.

The viability of the technology is actually still very much up for debate.

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rbanffy
You don't keep the turbofans in front of the scramjet all the time - you use
them to give the scramjet enough air to start. As the speed increases, the
turbofan engines would eventually cease to operate and could be shut off
completely, leaving the scramjet to operate freely.

The turbofans are dead weight when you are cruising at Mach 7 in the upper
atmosphere, but are useful for take off and landing.

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blhack
At what point are these things no longer airplanes and just rockets?

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psadauskas
When they carry 100% of their own fuel. This one gets oxygen from the
atmosphere.

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blhack
Aha! I was mostly commenting on the wings being useless though (until it slows
down)...

Well...not useless, but not really being used to generate any lift.

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teamonkey
This plane is a Waverider. It uses its own supersonic shockwave to generate
lift.

<http://en.wikipedia.org/wiki/Waverider>

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Qz
Make sure to watch the video, it's pretty awesome.

