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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
the b-52 to launch the plane. Will they be able to develop on of there that can take off on its own? or will we always be launching them from the underbellies of a big plane.
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Da-dum-ching!
Gordon D. Pusch wrote in sci.space.tech: "Hypersonic travel combines all the disadvantages of airplanes with all the disadvantages of rocket flight and all the disadvantages of re-entry --- continuously."
The article starts off with this:
The space agency's dogged pursuit of extreme speed, officials hope, will ultimately make space flight easier to accomplish.
OK, so exactly how is this supposed to aid space flight efforts? There is no mention made of that in the article at all.
I would have thought that the ability to reach incredible speeds in horizontal flight inside the atmosphere is unrelated to both:
1) Entering orbit (horizontal flight).
2) Flying in vaccum (different conditions than in atmosphere).
I'm confused ... any thoughts?
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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, 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 only possible use I can think of is hyper-range weapons. Ground-controlled planes armed with lethal cargo (nuclear or not) could be flown around the globe faster than any ICBM, and guided with better accuracy.
I'm all for "Science for Science's sake" but I think this is worthless for any practical purposes.
Slight off-topic, but why do I have to go to Jet Propulsion Laboratory to find out about the Mars rovers, and then I have to go to National Aeronautics and Space Administration to find out about fancy new jet engines?!
Is it a cunning plan to out-fox those secret stealing ruskies?
The danger here is that the darn thing will carry all of these systems and have no capacity left over for payload. I recall the Boeing SST back in the late 60's early 70's was based on a swing wing concept. The scale of the mechanical systems to swing the large wing faced them with a difficult choice of a swing wing or passengers...but not both.
In the physics world one has a sense that they are on to something when the math becomes elegant and simple...I think in the "no moving parts" nature of the scram jet are appealing...a turbofan/scram/rocket combination is not
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But if the earth's circumference is around 25,000 miles, and this jet can go 5,000 miles an hour, that would mean it would take only 2.5 hours to get from any location to any other.
Okay, if it only takes 2.5 hours at top speed to go anywhere on the planet, how much time is spent accelerating and decelerating versus actually flying at Mach 10? And how much fuel are you burning in the process? I remember working at LaRC when they were just starting to test scramjets and I still think the science is good for orbit, but bad for commercial applications.
Almost as interesting as the X programs is the B-52 mothership that launches them. There was an Air & Space article years ago (no online version at airspacemag.com) about it.
It's an aging early-model B-52B, evidenced by the non-pointy nose and is 49 years old. There are virtually no spare parts remaining for it, and most of the current inventory (Gs, Hs) don't have any parts commonality.
Plus, we never sold any of them to other countries, so it's not like there's a stockpile somplace else on the globe. The cost to replace it is prohibitive, given the structural reinforcements needed to carry the craft aloft. Also, the airframe is very young from an hours perspective. In fact, it's the lowest hour B-52 in the inventory.
The USAF has loaned an H-model to NASA to become the next generation launch platform, but I haven't heard much about it since the 2001 announcement.
It's a supremely important beast in the research arsenal. And, given our penchant for resurrecting C-64s as web servers and using mame to emulate decades-old cabinet games, it seems like the sort of thing that would interest the average computer geek.
Like so many things, it's the logistical details of maintaining an archaic aircraft against all odds (and lack of funding) that really become the story rather than the whizz-bang doodad that always gets the front page pictures.
Amateurs discuss tactics. Professionals discuss logistics.
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.)
Let's assume for a moment here that I'm not Buckaroo Banzai and I'm a little bit vague on what the upper limit has been for manned flight (or travel in any medium, salt-plain automobiles or whatever). "Mach seven" really doesn't sound all that impressive. THIS IS 2004! We should be on mach ten-hundred by now.
For Christ's-sake, in that episode of ST:TNG where Riker had salt-and-peper hair and he didn't play trombone, I clearly heard him say: "WARP THIRTEEN! ENGAGE!" What the hell mach was Tom Cruise going before he entered into coitus with that blonde? What is the top theoretical speed of the current US fighter/and or/stealth aircraft?
What are the records here, that my tax-dollars are allegedly breaking?
Don't mod this retarded shit up, this is the uninformed wanting to become informed.
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Mostly I agree, but your first question starts with an incorrect assumption: a 600mph vertical dive. Pilots are trained at ditching an airplane at sea, and planes do float for a short time after this happens. In fact (though I don't know of any specific cases off hand) it has happened before, and many passangers have survived ditching at sea. Vertical dives do not happen in a significant amount of emergency situations, wings are simple devices and don't break all that often, and a wing is all you need to prevent a vertical dive.
Airplanes have backup batteries, and backup radios. You can be sure that before the plane hits the water emergency people know that it is going down, and about where. They might not be able to get to you in time to save you, but they at least know where to look just in case.
I'd prefer to float around the North Atlantic than die. Though I think it is safe to assume that if it really is several days before rescure workers find you they will find a dead body. However depending on where the crash happens, rescure workers may find you sooner.
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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