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Second Test of X-43A Scramjet Tomorrow
pinkUZI writes "NASA says its new Hyper-X, a jet capable of flying some 5,000mph - seven times the speed of sound - will be ready to take a test cruise across the Pacific this Saturday. This is actually NASA's second attempt; the first, in 2001, failed when stabilizing fins flew off the plane's booster rocket and controllers ordered the craft destroyed. CNN has the story." NASA's mission web page has more information, photos, etc.
http://science.slashdot.org/article.pl?sid=04/03/2 5/141238&mode=nested&tid=134&tid=160
Why are you posting AGAIN ??? and on the same subject?
Um, this is primarily a test of an engine, not an aircraft.
The X1 was also launched from a plane and was the first aircraft to break the sound barrier. Planes such as the SR-71 have far surpassed this speed and takeoff in the conventional fashion.
I'm not sure what you're referring to when you state "always be launching them from the underbellies of a big plane".
They're not (directly) working on cruise missiles, although the tech could be used for that. They're trying to invent a cheaper way to get to orbit. This is just a test bed to figure out the scram jet. The plan is for a standard jet engine to get you to supersonic speeds, the scram jet to get you to hypersonic speeds and the edge of the atmosphere. Once you're going, say, Mach 7 and most of the atmosphere is below you, you fire the rocket engine to get you the rest of the way to orbit. This approach wouldn't require the rocket to carry as much oxydizer, thus less weight, less cost.
Yes, they will be able to do that. For subsonic flight, it would use regular engines. Once it got fast enough, the SCRAMJET would take over. This one gets around all that by using a rocket to accelerate it to the right speed before engine ignition.
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Obviously if this method of propulsion is used in aircraft that are anything but proof-of-concept, they'll have to take off on their own power. However most of these experimental aircraft are dropped from the belly of an aircraft already at altitude, even manned aircraft like the X-1 and X-15 (both rocket-powered, dropped from a B-29 and B-52 respectively). For the most part, getting the aircraft to the needed altiude on its own would require too much fuel (making the need to design a much bigger aircraft, etc.).
Happened in Arizona, reputedly. I quick google yields: http://www.snopes.com/autos/dream/jato.asp
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It's a test flight, not a full-fledged production vehicle we're talking about here. The plan is that eventually aircraft will take off under normal jet propulsion, use scramjets to accelerate to escape velocity, and use chemical-powered propusion once they have left the atmosphere.
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They're testing it over the pacific ocean.
Yes, you would hear the sonic boom of the test flight. (If you are close enough to hear it at all, of course).
At supersonic speeds, the edge of the soundwaves that are produced by an object is a cone in the object's inertial frame. Regardless of the speed. The speed only changes the angle of this cone..
The trajectory of a conventional rocket accomplishes 2 things...getting up...and getting to orbital speed. This approach really replaces the first nearly vertical portion with a more conventional lifting air breathing propulsion vehicle.
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well, if you get your rocket to reach really high speeds at a fairly high altitude inside the atmosphere, you have less altitude for the rocket to fly and less energy that needs to be expended merely to accelerate the rocket. overall this means less rocket fuel needed to reach orbit. also, because you are starting your rocket at a higher altitude you can optimise your rocket motor for a higher altitude which would increase its effiecieny. overall, a Good Thing
Disclaimer, IANARSBIAITTBO (I am not a rocket scientist, but i am in training to become one)
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As anyone who has taken high school physics should know, to get into orbit does not just require "going up." It requires reaching orbital velocity about 25,000 mph.
physlink.com
A scram jet could be used for part of an orbital flight from about 7 to 10 times the speed of sound. A rocket would probably be used before and after the scram jet, but there would be considerable fuel savings. Of coure once you are outside the atmosphere, a jet is useless and a rocket engine would have to be use.
Well this is "news for nurds."
No, orbits are horizontal. When you watch a rocket launch vertically, it's only the first couple miles up that are vertical, after that they start to curve towards the orbit they are aiming for, and they start accelerating horizontally and decelerating vertically.
For those who want to know what a scramjet is, and how it works, check this page.
A ramjet has no moving parts and achieves compression of intake air by the forward speed of the air vehicle. Air entering the intake of a supersonic aircraft is slowed by aerodynamic diffusion created by the inlet and diffuser to velocities comparable to those in a turbojet augmentor. The expansion of hot gases after fuel injection and combustion accelerates the exhaust air to a velocity higher than that at the inlet and creates positive push.
Scramjet is an acronym for Supersonic Combustion Ramjet. The scramjet differs from the ramjet in that combustion takes place at supersonic air velocities through the engine. It is mechanically simple, but vastly more complex aerodynamically than a jet engine. Hydrogen is normally the fuel used.
This is all very different from conventional airliner engines, which are a gas turbine/fan nacelle called a "turbofan". (A "turboprop" is a gas turbine driving a propeller instead of a fan, BTW.)
Mach 7 is velocity. The only thing you could feel is the acceleration. But flying at mach 7 would feel the same as flying at mach 0. (Excluding external influences). You would only need inertial dampeners when the acceleration would be high.
Inertial damperners aren't exactly that hard to build. Consider that the inertial force is proportional to both mass and acceleration, the only thing you would need to acomplish is reducing mass to near zero. I'll leave that as an exercice for the reader.
BTW, this is why the X-prize will need to have a follow-up contest (Y-prize?) to really open up space: the X-prize teams are trying for altitude, and then falling right back down. They aren't achieving orbit, because they aren't adding the tangental speed.
Yes, I'm still a junky. Are you still a bitch?
In real layman's terms......
weigh yourself at sea level
then weigh yourself again at the top of mount everest
unless you are using *really* accurate scales the two readings will be the same.
now go back to both locations where you weighed yourself and measure the atmospheric pressure in both places.
unlike your weight you'll find the pressure is about a third of what it was at sea level.
pressure in a known and unchanged mixture of gases is another way of counting how many molecules of gas there are in any given cubic meter, or to put it another way, the mass of a given cubic metre.
so your aerofoil (wing) at the top of everest has about one third of the mass of gas to ride on as it does at sea level.... if your aerofoil is a fixed wing then you can always travel three times as fast (hence needing a scramjet) whereas if your aerofoil is a rotary wing (helicopter) you come up against a hard limit when the out edges of the rotors approach the speed of sound, hence the much lower maximum altitude ever recorded in a helicopter as opposed to a swing wing.
NB all of the above is really really simplified and therefore full of errors to a physicist / aerodynamics / bernoulli / etc etc etc
HTH etc
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I already posted this in another discussion here, but probably it is worth mentioning again. The bigger cousin of X-43A, X-43C, is being cancelled because it does not fit in the new space plans.
Current fighters top out at somewhat over Mach 2, perhaps Mach 2.5 for the F-15.
The upcoming F-22's top speed is classified, but it might be as high as Mach 3 (this is purely a guess on my part). It is quite a bit higher performance than the F-15, and can cruise at supersonic speed (somewhere over Mach 1, again classified) without afterburner. It's the first aircraft ever to have this capability, dubbed "supercruise" (not after Tom...I think).
The SR-71 is the current air-breathing airplane speed record holder, with a top speed of around Mach 3.5, though the actual top speed is still classified as far as I can tell.
The X-15 had a speed record of Mach 6.72 (in 1968!) but was a rocket, not an air-breathing aircaft.
Hope that helped! :-)
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Even if you survive the crash, you'd die of hypothermia in a few hours. I don't know if you've ever swam in the North Atlantic but I spent a few days at the beach in Nova Scotia in the middle of August and let me assure you that the water was not much over 60F. You die when your body core temp reaches 80F. In 60F water, you've got about 3 hours of survival time immersed. So, in an ideal scenario, unless the rescuers get to you in under 3 hours, you're gonna die anyhow.
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Speaking of Hypersonic bombers blowing shit back to the Stone-age, you might want to look up Project Pluto. These military guys can be some real heartless bastards at times. Still, they make the target go boom, so who can complain?
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the SR-71 (aka Habu or Blackbird) uses small wings and is very specialized.
The SR-71 has tiny wings,
Small wings? Have you ever looked at an SR-71? With a wing span of 55 and a half feet, and a wing area of 1795 square feet, its wings are far short of "small". A 737 only has a wing area of 1344 square feet.
Low lift wings maybe, making for less wind resistance and friction, but small, not hardly.
No, they didn't. It was a rocket test.
and maybe I'm slightly mistaken here
Yes, you are.
but I find it almost typical of NASA to so completely ignore these other countries who in this case actually got there first and are possibly (?) more advanced than NASA in this area.
No, NASA's statement, as it was worded, was correct. It is you who are in error.
Of course if your world view is limited to America and the occassional country it chooses to bomb
Would you please fuck off and die, you ideological bigot? Can't we keep the worst of the international politics out of the sciences, or has ideology fucked over your brain that much?
Well, that was the orbiting velocity of the Space Shuttle. That's over Mach 20. It's rather easier to go fast in space - there isn't all that air you have to shove out of the way.
The fastest combat jet is the MiG-25, which has been radar tracked at 3,395km/h.
If by "conventional" you mean "needs exotic accelerant to burn fuel and immediate refueling after take-off", then yeah, sure, ok.
um no, some very simple math indicates that if you go up 1 mile, the circumference is only about 6 miles longer. You have a point, but it's not nearly as big an effect (especially considering thinner air -> efficiency at high altitudes).
31,000 miles?
How do you work that out? a circumference of 25,000 miles gives us a radius of 3,978 miles. Go a mile up, and the effective radius is 3,979 miles, which gives us a circumference of...
25,006 miles. Not much of a difference.
evil math within Nature's Cubic Creation!
The SR71 needed that stuff because it flew over mach 3 at almost 100k feet. the friction and heat buildup from going that fast that high was beyond the metals used back in the days the SR-71 were designed. New spy planes (aurora) can do the same without the loosly put together skin. (which is why the SR-71 leaked like a siv on the ground.
A more useful comparison would be with an F15-e or F16, more than capable of traveling at mach 2ish, no refueling right after takeoff, regular old jet fuel.
Just three more hours seapeople and you can finally take me away from this crappy God Damned planet full of hippies
"Mach seven" really doesn't sound all that impressive.
The SR-71 Blackbird has an official top speed of around Mach 3.5, and unofficially several pilots have reported taking the plane to substantially higher speeds. The plane's airspeed indicator goes up to Mach 5, if that means anything.
At Mach 3.5, air resistance raises the plane's temperature to nearly a thousand degrees fahrenheit. Conventional aircraft aluminum would soften and lose its structural integrity at that temperature. For that reason, the SR-71's skin is made out of titanium. Thermal expansion causes the plane to be around six inches bigger while it's flying versus on the ground, which naturally caused nightmares for the plane's designers. The plane has a special cooling system which uses its jet fuel as a coolant liquid, circulated under the skin. After landing, ground crew must wait for a while before they can safely touch it, because the surface is so hot.
And that's only Mach 3.5. Does Mach 7 still not sound impressive to you?
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No, they just don't like it when a project that cost a fraction (arround AU$1.5 million) of what theirs did suceeded before theirs did, by a bunch of mechanical engineers at a university that nobody knows about. More details about the project are available at the Center for Hypersonics and UQ news.
We had some lectures from the head of the engineering faculty in first year, and he went into a fair bit of detail on how the system worked. Last I heard was that the project has received further funding, but that was shortly after their mostly sucessful trial run (they couldn't find their rocket for a few weeks in the Australian desert). I've heard nothing else about it since, though. But that's probably because all anybody talks about now is mice in space.
Assuming the same coffficient of lift, Cl, in order to generate the same amount of lift you would have to have the same "dynamic pressure" (to borrow a Boeing term), then (from Bernoulli equation)
If the ratio of densitySL/densityEverest is 1/3, then solving for velocityEverest:
or approximately 1.73 times the speed at sea level.
Hey, Windows users, there is no such thing as "forward" slash, there is only slash and backslash.
SCRAMJETs will not use kerosene-derived propellant. They will combust hydrogen with oxygen from the atmosphere (maybe you should have done 2 seconds of research).
A flight on a Mach 5 aircraft will be shorter than the same flight on a Mach
If what you mean by "somewhat" is "not really." I can't see the 20 Concordes built adding significantly the net pollution of thousands of supersonic military aircraft in service around the world.
They don't need to.