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NASA Prototype Plane Scheduled To Attempt Mach 5+
Logic Bomb writes: "Mach 5 -- 5 times the speed of sound, or 5000 mph -- is a speed that so far has eluded jet-powered aircraft (the existing record for a production craft is about mach 2.1). NASA, however, has high hopes for its latest attempt, the X-43A. Using a booster rocket, the prototype will be accelerated to mach 5, at which point its engine will be scooping enough oxygen to power the craft at those speeds on its own. Hopefully, it will fly at speeds up to almost mach 7 for 10-15 seconds before shutting off and plunging into the Pacific. An article from the Los Angeles Times has more details." Not to be confused with the X-33 and X-34 projects.
The sonic boom is only produced at the precise moment where the speed of travel for the plane is equal to the speed of sound. At that speed, the sound waves emitted over a period of time "bunch up" and hit together, causing a sonic boom. However, this doesn't apply once the speed gets above the speed of sound - in fact, the faster above the speed of sound that the plane gets, the less of a sonic boom effect it will produce. After Mach 2, the sonic boom effect will be less than if it were standing still.
The shockwave is only a _plane_ when you're at exactly Mach 1. However, you still do indeed get a shockwave at higher speeds. It's a cone instead of a plane, that gets a narrower and narrower aspect ratio as the plane travels faster (the cone expands radially at Mach 1, but the tip [the plane] is moving much faster).
Draw the tip of a stick across still water and watch the ripples to see what I mean. Try this at different speeds (from very slow to very fast).
As it's still a shockwave - an abrupt (discontinuous) change in the velocity and density of the air - it'll still sound like a thundercrack, and will still break windows, because it deposits all of its energy at once (when the shock passes the listener/window).
You'll actually get _more_ damage at higher Mach numbers, because the energy shed into the atmosphere is roughly proportional to the cube of the plane's speed (one of the reasons heating's a problem in hypersonic craft).
For quite a while there have been persistent rumours of a US military aircraft that flies at Mach 5 using liquid methane as a fuel. That would nix the "first aircraft to travel at this speed" claim.
Are there actual records of the US craft's existence, or does it remained a rumour?
The SR-71's top speed record was Mach 3.24, which is still the record for air breathing propulsion powered aircraft. (Of course there've been plenty of rumors of top secret planes even faster.)
The F-15 can fly Mach 2.5 at high altitude, & many current fighter aircraft can fly Mach 2.1.
The X-15 (which was rocket powered) reached speeds of over Mach 7, which was the fastest human piloted aircraft ever. The space shuttle reaches Mach 25 (~17,000 mph) in order to reach orbit.
Logic Bomb seems to be under the impression that The speed of sound is 1000mph. It's more like 730-750mph last time I checked.... Mach 7 is 5000 mph, not Mach 5.
The mph speeds are correct as stated, but all of the mach speeds are off. The SR-71 does go 2100mph, but thats nearly Mach 3, not Mach 2.1. And the new craft in question which will go 5000mph is Mach 7, not 5.
Just nitpicking here folks, but someone should clarify this....
-Julius X
-Julius X
remove "-whatkindofspamdoyoutakemefor-" from email to send
Ya what a WASTE of time to fly real fast! Its a shame we throw away money on stuff like that! I mean, who wants to go gallavanting around really fast! And in the AIR too! WHAT MADNESS! If God intended us to fly he'd have given us wings! If God intended us to go faster than 20mph he'd have given us turboprop thighs!
I, for one am OFFENDED that we are wasting money on fruitless projects like flying fast. It would be better spend on expanding the west wing of my 8 bendroom mansion, or paying some immigrant to scrape barnacles off my yacht.
Actually, Mach is only one of three measurement commonly used for speed of aircraft. There's Mach, indicated airspeed and actual airspeed, all different. Mach and indicated airspeed are used because that's what the aircraft actually feels. As an aircraft approaches mach 1 (civil airliners cruise at .7-.73 generally) there's something called drag divergence. That's why the civil jets fly at the speed they do, much above that and drag starts to seriously go up exponentially almost. mach varies depending on temperature, not density, but temperature.
Indicated airspeed varies depending on density. For most small aircraft, homebuilts or general aviation aircraft that you and I could fly, this is the most important number as it determines when the aircraft will stall or when the wings will rip off. Mostly used at low speeds when air can generally be considered incompressible. If you go faster where you have to start taking into accoutn compression, then you start dealing more with Mach generally.
And finally actual airspeed which is actually a fixed number no matter where you are, at any location, any altitude, any temperature. But unfortunately, this really doesn't matter to much to the airframe or wings, that's why it's least used, except in planning the actual flight path of the aircraft.
Clarify anything?
New York to Los Angeles in a half hour. Wow.
In completely unrelated news:
Every window from New Jersey to Nevada was broken today, which officials are at a loss to explain. It appears to have been a sharp earthquake which rattled houses and businesses across the country. Seismologists have reported that every one of their seismographs recorded a large spike, possibly a new type of fault slippage previously unknown.
Officials at UnitedSpace were unavailable for comment.
the AC
Hemos is like...sci-fi fans;he thinks technology is cool, but he hasn't bothered to understand the science it's based on
So the claims of the space shuttle reaching Mach25 aren't that impressive? Does that mean that while in orbit it is effectively orbiting at Mach infinity (as sound has zero propagation speed in space...)?
For some reason I thought Mach was defined as the speed of sound at such a presure and humidity, analogously to c, which is constant, vs the Speed Of Light, which varies.
OT sig ref: I hate, you milk man dan!
"Hopefully, it will fly at speeds up to almost mach 7 for 10-15 seconds before shutting off and plunging into the Pacific"
Fortunately the seat cushions can be used as a floatation device.
--Brogdon
This tagline is umop apisdn.
I guess we'll have to wait for the documents to become declassified.
Until then... "Go! Speed Racer! Go-Go! Speed Racer!"
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crazy dynamite monkey
Why do we use Mach as a measurement of speed when it varies with altitude? No one would ever use a measurement of length that varied with what country you were in? Hmmm... I'll make a measurement called "Schnach" which is 1 meter in Australia, but is 3 inches in the US. Brilliant idea, eh?
It's a common engineering error to confuse units -- especially when they are close to each other in standard units.
1000ft/s = 305m/s
1000mi/hr = 447m/s
Seastead this.
Actually, if memory serves, Mach 1.0 at mean sea level and mean atmospheric conditions is about 714 MPH at sea level.
However, the speed of sound varies proportionally to the density of the medium, in this case, air. So at higher temperatures, and higher altitudes, the speed of sound increases. At the sort of near-space altitudes at which this thing will probably operate, Mach 5 is close to 5000 MPH.
Learn from the mistakes of others. You won't live long enough to make them all yourself.
Using a booster rocket, the prototype will be accelerated to mach 5, at which point the pilot's face will be torn from his skull. Hopefully, the plane will fly at speeds up to almost mach 7 for 10-15 seconds before getting hit by a Chinese hotdog pilot.
Got Rhinos?
"a 12-foot experimental airplane is scheduled to make its maiden flight next month, flying over the Pacific Ocean at more than 5,000 mph."
Nothing like spending billions of dollars on something that can send two midgets across the pacific in record time.
-gerbik
Don't boxers say the same thing? "I wanna dodge, block, or just plain ignore every punch you throw - and I wanna throw punches you can't dodge, block, or ignore at all, sucka!"
I'm sure what you meant to say was "they want a bomber flying at Mach 5 which will be too fast for anybody else to shoot down" and "they want a missile defense system capable of destroying everybody else's theater and ballistic missiles".
You're forgetting that people say "Military Intelligence is an oxymoron" because it's funny, not because it's true. HTH.
Any sufficiently well-organized community is indistinguishable from Government.
Although the author seems to be confused about the value of Mach 1, some of the responses aren't much more informed. Mach 1 is the speed of sound, which varies greatly depending on the density of the air. At sea level it is usually around 730 mph or so. So it is difficult to say what Mach number the blackbird achieved when it was flying 2,100 mph. You'd have to know the density altitude for the flight. Also, a scramjet engine is not quite the same as a ramjet. The idea is the same, but since air is highly compressible, it behaves differently at different speeds. There are basically four areas of flow: subsonic, transonic, supersonic, and hypersonic. What holds true for supersonic flow is not necessarily true for hypersonic flow. The divisions between these areas of flow depends on the Mach number of the fluid, which is why speeds are rated in Mach numbers and not mph or km/s. So, a different design is required for hypersonic flow compared to supersonic flow. Hope this clears some things up.
Nope, you're wrong too. Speed of sound decreases with increasing altitude (less dense air).
See:
- http://www.grc.nasa.gov/WWW/K-12/airplane/atmos
i .h tml
- http://www.grc.nasa.gov/WWW/K-12/airplane/sound
. ht ml
for the basic information and a cool little demonstrator app. However, even at high altitude, the SOS doesn't change much (-14% is "not much" to me). Now, speed of sound through solid rock, THAT'S fast!One source of confusion is that SOS is about 1100 feet per sec or about 750 miles per hour. People often get the numbers and units swapped.
- Chris
P.S. Wow, I actually used my Aerospace Engineering degree today!
P.P.S. SR-71 has gone to Mach 3 according to public knowledge, but it's widely expected that it went MUCH faster. Hell, most fighter jets can push Mach 2.0, and the SR-71's design point is Speed At All Costs.
One simple rule for its versus it's
The moveable spike does add a lot of the thrust. But what's being discussed is a scramjet, and as such, it gets all its air without compression. The ramjet is a compromise between the scramjet and the turbojet, really. Also, the ramjet has realistic speed limits, because there is some compression needed to fly, and the craft can't make it to scramjet operational speeds with air-breathing engines.
I'd rant further, but I sold back my propulsion texts when I realized I was going into the church business. Oh well.
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-- Geof F. Morris
Actually, a [the speed of sound] varies with altitude, as temperature and density have an effect on the speed of sound. You can go supersonic, technically, simply by holding speed but changing altitude.
Most Mach references are to sea level a of 340 m/s.
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-- Geof F. Morris
Per the article, the X-15 got to Mach 6+.
Yes, the SR-71 got to Mach 3+, but not a whole lot faster--the engines were losing efficiency at that point and couldn't push any harder. Even moving the spike in the aerospike didn't help--you were still using some mechanical compression, and the mechanical compression was what was slowing the flow down. Shutting down the turbine blades wouldn't work, either. The theoretical limit is somewhere in the Mach 3.6+ range. I once saw a better analysis, but that was in a book I sold back. =)
But the "been there, done that..." scenario doesn't hold. The X-15 was a rocket plane, and as such had to carry its own fuel. Also, the X-15 was dropped from a bomber after being carried to altitude. The SR-71 had its theoretical limits as above. This is a step beyond either--something that would take off on its own and fly faster than the X-15. Granted, I don't enjoy aerospace engineering anymore, but even I think this is tres cool.
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-- Geof F. Morris
This is important aerospace research, and if you read the article, it's pretty easy to see why. The ability to fly at such speeds for intercontinental, oceanic flights is of great societal benefit. Speed of transport will make this work commercially.
The military aspects are a bit more challenging, though. If you're going to build a bomber so fast it can't be shot down, fine--but then you have to either slow down the craft so that the munitions can exit the slipstream, or you have to come up with some design that will allow you to drop iron at high speeds--such as the Valkyrie, which dropped munitions out the tail.
Either is a huge design problem. If you slow the craft down, you have to design a craft that performs at all speed ranges with in-theater fidelity. If you kick the munitions out of the back, you have to compensate for the mass changes with aerodynamics, because you change the center of gravity all the way through the release profile, and you better hold the craft steady during release, lest you hit the bomb on the way out. "Somebody set us up the bomb," indeed!
But this won't replace STS. Yes, a scramjet is nice. Yes, this is similar to rocket-based combined cycle. But we could more cheaply build a reliable, two-stage system to get into orbit. Mass fractions are all you have to look at to wonder why Single Stage To Orbit [SSTO] is some perverted NASA priority. As a NASA sub, I know they don't live in reality, but damn...
But this is, for once, a positive example of your tax dollars at work.
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-- Geof F. Morris
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Oh bother.
the mach number is a constant that compressable flow is dependant upon.
you need to complain to god or something. at speeds close to the speed of sound in that medium, the mach number is a very important number. it can be used to very easily characterize the way that the medium will flow around an object.
in aircraft design, an optimum airfoil and engine geometry is characterized by the mach number.
one other technical thing. the mach number is not a unit. that is like saying the number 1 is a unit. the mach number has no units. that is why it is so convenient for engineering. it doesn't matter whether you use metric or imperial.
i can't decide whether you are trolling or just plain stupid, so i'm posting.
Bored with your projects?
Try Einsteinium
"We at Gillette want our products to be cutting edge," Kilts said, "Absolutely at the bleeding edge of technology."
The product name has yet to be announced, but Kilts claims, "They will have 5 or more blades."
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