Slashdot Mirror
HyShot Scramjet Test Declared a Success
An anonymous reader writes: "ABC news is reporting
that analysis of the flight data from the recent
HyShot scramjet test (covered by Slashdot
previously) suggests that the test was successful and that the engine achieved combustion in flight after reaching Mach 7.6. The University of Queensland is also reporting the news."
BBC story
There's a ton of photos at http://photos.cc.uq.edu.au/HYSHOT/ and also at http://www.mech.uq.edu.au/hyper/hyshot/HyShot_phot os.html. The former link has some friggin huge jpegs.
There is also a page about the HyShot program itself at http://www.mech.uq.edu.au/hyper/hyshot/
It's not how fast, but how did they fly that fast.
The Scramjet theory has to have occurred. Which is basically an engine with no moving parts. The intake air has to hit the fuel so fast, and at such high density that some sort of "Critical Mass" combustion takes place that produces more thrust that drag of the air molecules hitting the craft at about 10kph.
When you're on a shoe-string budget, it's hard to figure out if that really happened. It'll take a much more expensive project to figure this out for sure, hence, NASA's much more expensive project.
Who needs this anyway, with
Sydney's Mardi-Gras going bankrupt!
Hello Frisco!
Untrue. Sound travels slower because the air is colder, not thinner. The speed of sound in the Earth's atmosphere is proportional to the square root of the temperature, nothing else. http://www.allstar.fiu.edu/aero/mach.htm
Here's an atmosphere simulator where you can pick an altitude and see the speed of sound. As it says, "the speed of sound depends on the temperature and the gas," not on pressure.
It's only a high rate of acceleration that causes passengers to experience excessive G force. Once you've reached Mach 7, so long as you remain at a constant velocity nobody should notice how fast you're going.
Assuming you weren't trolling:
Mach 7.6 is a speed, not an acceleration. A hypersonic passenger vehicle will presumably travel with moderate acceleration until reaching high speed.
At 1/2-earth-gravity acceleration, you get one sea-level Mach number per minute, more or less, so you'll be at Mach 7.6 a few minutes after launch.
2*3*3*3*3*11*251
Note that the figures at
fas.org indicate that the speed of the Minuteman III at burnout is approx. Mach 23.
What you do have the potential for (given significant further progress) is very fast cruise missiles, not ICBM's.
John_Chalisque
Mach is a measure of speed relative to the speed of sound at a given elevation, it is not a measure of acceleration. So, at sea level, Mach 7.6 is roughly 5800mph (~2600m/s), but at 25000ft, where the air is thinner, Mach 7.6 is about 5000mph (~2250m/s).
The gravitation of earth (ie, the amount of force we feel from gravity) is 9.8m/s^2. So, a constant 1G force (which the body won't find too uncomfortable) would accellerate a body to 2250m/s in about four minutes... If a genter push is desired, say .5G, that level of acceleration would need to be maintained for a bit over seven and a half minutes...
Unless, of course, my physics is rusty.. :^)
there will probably be "low-speed" versions for shorter distances
Probably not. To understand why requires some knowledge of how a scramjet differs from a normal turbofan engine. There are no spinning parts in a scramjet or ramjet engine. The (sc)ram engine requires a strong standing shock to me maintained in the intake. This standing shock replaces the compressor section of a normal turbo fan. There is a minimum speed which will produce a sufficiently strong, stable shock that will allow this to work.
The SC part is for supersonic combustion which makes that standing shock also replace the combustor portion of the turbo fan. Chemical reactions and transonic fluid dynamics can interact in very complicated ways. This can make this supersonic combustion unstable. The best way to stabilize it is to go faster and increase the strength of the shock.
So, to sum up, operating scramjets at lower speeds is more difficult, so if anything, we will probably see them operating at the highest possible speeds that the airframe and aerodynamics will allow.
One of the interesting footnotes from aviation is the first attempt at breaking the sound barrier. As you approach the speed of sound turbulence increases dramatically. However, when you break it you are in a new aerodynamic regime and suddenly the turbulence plummets. A very pleasant surprise to Chuck Yeager, the first supersonic pilot.
t ml
You can find more information about the "Wall of Air" that was believed to prevent supersonic flight, as well as Yeager's breaking on the barrier here:
http://www.capstonestudio.com/supersonic/main.h
Life is short: void the warranty.
At a constant 1G acceleration, you'd hit Mach 7.6 in about 4 minutes and travel about 260 KM. The Space Shuttle goes supersonic within 75 seconds of liftoff, so it really doesn't take too long. I think by the time the boosters drop off (2-1/2 minutes) it's doing Mach 3 or better.
The X-15 hit Mach 6.72, and its maximum burn time was under 5 minutes (it was a rocket plane though), so it makes sense for something like a hypersonic engine to be used for real flights, even NY-LA would be practical...under 1 hour door-to-door, no need for a crappy airline meal! The SR-71 has already done NY-LA in about 1 hour at Mach 3.5.
A man's reach must exceed his grasp, or what's an erection for?
As I read the comments, it seems that some people don't get the implications. In a normal jet engine the flow has to be slowed to less than Mach 1 for compustion to occur. Faster, and it goes out. This limits the range of velocity that can be attained. So, there is a range of velocity that can only be attained with rockets. With a working Scramjet it becomes possible to fly most of the way to orbit. From an energy consideration, once you are in low earth orbit you are half way to anywhere in the solar system and can use low acceleration, high efficency engines to get anywhere.
Scramjets are the realistic key to space exploration.
Eschew Obfuscation
Our monkey brains can't really appreciate the size of this Earth. Circumference = 24,000 miles. Mach 7.6 = 5000 mph. So it'd take about 5 hours to circumnavigate the globe -- or about 2.5 hours to reach the opposite point on the other side of the world.
Depending on lift ability, this could have fascinating implications for rapid-response troops.
But more importantly, it's potentially an excellent way to lower costs to get things into orbit. And air travel is all well and nice, but the future is in space travel, at least to LEO.
The Mongrel Dogs Who Teach
Bzzzt. But thank you for playing. Since forces are dependent on acceleration, moving at constant speed is indistinguishable from being at rest. That's not even Einstein -- that's Galileo.
Bzzzt again. This just isn't your day. First, modern physicists don't even talk about mass increasing as velocity increases. Mass is mass is mass; ie., what used to be called "rest mass". The observed kinetic energy increased with velocity, of course. But we don't use relativist mass because it implies things like, "Oh, Newton's laws are OK if you just put a factor of gamma in", which is not true. It can be shown that in fact, there would be two relativistic masses, a "parallel component" one and a "transverse component" one. This complicates the idea of mass and force so much it's of no use whatsoever.
Second, even if your mass seems to increase as measured by an observer, it wouldn't for you... All of your molecules will be traveling at the same speed, so each sees the others at rest and therefore, by the first principle of relativity, can see no mass effect.
Third -- and now I'm just being obnoxious -- you seem to confuse "mass" and "weight".
The Mongrel Dogs Who Teach
No. Years of Star Trek have mislead people by analogy, but the "sonic boom" is not the sound of you piercing the sound barrier. It's the result of a massive spike-and-fall of pressure across your ears. You are right that it comes from a superposition of pressure maxima (a "piling up") but that happens along a cone of air.
Without touting my own horn too much -- and believe me, there are equally good or better animations -- but I have a set of animated GIFs that show this.
The Mongrel Dogs Who Teach
If you're flying at about 5,000 mph, you could cover the London-New York distance in about 40 minutes. Add a bit more time for acceleration and decceleration.
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