DARPA releases video of HTV-2 hypersonic glider flight

Aug 25, 2011 By JOHN ANTCZAK , Associated Press

An unmanned glider streaks over the Pacific Ocean at 20 times the speed of sound in a video released Thursday by a U.S. defense research agency experimenting with technology that could give the military the ability to strike any part of the globe within an hour.

The Aug. 11 test ended early when a problem caused the craft's to force it down into the ocean but the said valuable data was collected in the nearly three minutes of free flight at the of Mach 20 - about 13,000 mph.

The Falcon Hypersonic Test Vehicle-2 was launched from Vandenberg Air Force Base, Calif., atop a Minotaur 4 rocket that carried it to the edge of space, performed what described as a series of aggressive banks and turns, and then released the glider.

This video is not supported by your browser at this time.
This video depicts a speed comparison between DARPA's HTV-2, a C-5 and an F-18.

The video taken by a crewmember on a tracking ship shows the rocket and vehicle together as a fast-moving contrail and then the HTV-2 as a faint dot zipping away on its own.

"It gives us a visceral feel for what it means to fly at Mach 20," DARPA Director Regina Dugan said in a statement.

Hypersonic is the term for speeds greater than Mach 5. Various hypersonic programs have typically produced brief flights - measured in seconds or minutes.

This month's test was the second of two missions in DARPA's HTV-2 program, which is aimed at learning how to fly at such speeds and advancing the technologies needed for long-duration hypersonic flight.

This video is not supported by your browser at this time.

The HTV-2's dimensions are among details kept secret by the agency, which seeks to provide technology breakthroughs for the Defense Department.

The first HTV-2 was launched on April 22, 2010. It returned nine minutes of data, including 139 seconds of aerodynamic data at speeds between 17 and 22 times the , DARPA said. That craft detected an anomaly, aborted its flight and plunged into the ocean, the agency said.

DARPA said preliminary analysis of this month's flight showed that the Minotaur rocket placed the HTV-2 at the planned release point and at the proper velocity and orientation, and the separation from the booster was clean.

In a statement, Air Force Maj. Chris Schulz, the HTV-2 program manager, likened the rocket's performance to making "a three-point shot from the California coastline into a basket between California and Hawaii."

The test also returned more than nine minutes of data. Dugan said that included approximately three minutes of "stable aerodynamically controlled Mach 20 hypersonic flight."

When the problem occurred, the HTV-2's flight safety system autonomously guided it in a controlled descent to splashdown along the planned trajectory, DARPA said.

After the first flight, changes were made to the second HTV-2 and its problem was not believed to be related to the previous one, DARPA said.

Explore further: Fiber-optic microscope will help physicians detect cancer, diseases at early stages

More information: Online: http://www.darpa.mil/

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jmlvu
1.5 / 5 (8) Aug 25, 2011
The top video is a simulation. The boring one at the bottom is real life. I'm guessing the builders are trying to justify the billions spent on a jet that crashed.
GSwift7
4.3 / 5 (20) Aug 25, 2011
The test also returned more than nine minutes of data. Dugan said that included approximately three minutes of "stable aerodynamically controlled Mach 20 hypersonic flight."

When the problem occurred, the HTV-2's flight safety system autonomously guided it in a controlled descent to splashdown along the planned trajectory, DARPA said.

After the first flight, changes were made to the second HTV-2 and its flight problem was not believed to be related to the previous one, DARPA said.


That sounds like a huge success then. In the early stages of this kind of thing, they expect failures. What's important is learning how to avoid the same thing next time, then move on to the next possible failure. This is stuff that'll be in engineering textbooks one day. It's not about trying to build a single aircraft; it's about learning new basic principles of engineering. The value is immeasurable, so a few billion is nothing. Besides, DARPA is one of the most effective agencies we have
GSwift7
4.1 / 5 (15) Aug 25, 2011
I'm guessing the builders are trying to justify the billions spent on a jet that crashed


DARPA doesn't have to worry about that. They are independently funded by the Pentagon. They don't get hardly any interference from Congress or the President.

When they have bad news, it never makes it into the press. They have the ability to keep all their work in complete secrecy. For some reason they have been very public about this. Maybe sending a message to China or some other country.
Star_Gazer
4.1 / 5 (15) Aug 25, 2011
I'm guessing the builders are trying to justify the billions spent on a jet that crashed.


It is my understanding that they were not planning on safely landing the plane anyway. And they spent billions on the technology and know how, not the specific piece of hardware. What they got is invaluable information on how to improve next version. IMO Failure > Success, because you learn from failure.
fmfbrestel
4.7 / 5 (16) Aug 25, 2011
First off, not a jet, not a plane. It is a hypersonic glider. It has control surfaces, but was not powered after separation from the rocket.

Second off, it was supposed to crash. It "crashed" a little early, but even the "crash" was a controlled dive.

Thirdly, it transmitted 3 minutes of aerodynamically stable, controlled, mach 20, telemetry data. You try sending a text message at mach 20 and see if it goes through. Just getting the data was a MAJOR victory for the program.
Kedas
1 / 5 (10) Aug 25, 2011
Don't we already know how to make rockets?
GSwift7
3.8 / 5 (10) Aug 25, 2011
Don't we already know how to make rockets


facepalm.

Yes, lol. Go read the wiki page for crying out loud:

http://en.wikiped..._Project

It's a two part project. One part is perfecting the launch system. That includes designing the launch pad, fuel storage system, launch controls and protocols, rocket control systems, fuselage cowling, etc. It requires a little bit of modification to the original ICBM they're using for the tests.

That's the easy part.

That rocket is used as a launch vehicle for the hard part of the project. As the rocket dives back into the atmosphere after reaching its highest point, it releases the glider it was carrying in its nose cone. That glider is then expected to achieve manueverable flight at mach 20 . Current tests are planned to end in a controlled "crash" into the sea, resulting in complete destruction of the glider. The idea is to get as much flight data as possible first.

continued:
GSwift7
3.2 / 5 (9) Aug 25, 2011
continued:

They do eventually hope to figure out how to steer the glider well enough so that they can have it land in a controlled way and be recovered and reused after completing its bombing mission.

That brings up an interesting point though. There's no way you could release bombs at hypersonic speeds, so it's gotta slow down a lot before it can hit a target, unless they've changed their minds and they use the glider like a cruise missile. Slowing down over a target would make it vulnerable to air defenses.
Sonhouse
5 / 5 (3) Aug 25, 2011
I wonder how much kinetic energy could be deposited on a target just by crashing into it? It could be a bomb with no explosives inside just by coming in at mach 10 or something.
emsquared
3.5 / 5 (4) Aug 25, 2011
I wonder how much kinetic energy could be deposited on a target just by crashing into it? It could be a bomb with no explosives inside just by coming in at mach 10 or something.

Ever heard of a rail gun?
fmfbrestel
4.2 / 5 (5) Aug 25, 2011
Sonhouse -- A LOT. Google "rods from god" or "space based kinetic impactor". Put a telephone pole sized rod of tungsten with a few control fins (major reason why they are doing this research right here) and a deorbit rocket on the back. Hits like a nuke, but no one gets cancer.
fmfbrestel
4 / 5 (3) Aug 25, 2011
The reason they want this tech, is that if you orbit a tungsten rod, you have to wait until the orbit comes close enough to your target. If you can just launch a missile and achieve near orbital velocities, you dont need to maintain a constellation of tungsten rods in space.

Draw back being that if we launch a missile with a kinetic impactor at a state that is friendly with Russia or China... well they might think it is an incoming nuke an launch a retaliatory strike.

They claim the launch characteristics are different enough for that not to be a concern, but I'm not convinced. Lets say China launched an ICBM at Taiwan, we're not going to wait around to see if it's a nuke or not, we're going to retaliate even if the launch looks slightly funny.
jselin
2.9 / 5 (8) Aug 25, 2011
First off, not a jet, not a plane. It is a hypersonic glider. It has control surfaces, but was not powered after separation from the rocket.

That's incorrect... HTV-2 is a scramjet powered vehicle. You can't maintain that kind of speed for that long just coasting.
Ricochet
5 / 5 (2) Aug 25, 2011
Sure we do, but our rockets aren't made for mach 20 atmospheric flight. The space shuttle starts about mach 26 when it's barely hitting the atmosphere, and it slows to under mach 3 by the time it reaches 83,000 ft.
Ricochet
5 / 5 (6) Aug 25, 2011
First off, not a jet, not a plane. It is a hypersonic glider. It has control surfaces, but was not powered after separation from the rocket.

That's incorrect... HTV-2 is a scramjet powered vehicle. You can't maintain that kind of speed for that long just coasting.

No, it was launched via rocket, then glided along its test-path. If you take a gander at the link below, you'll see it actually had to slow itself down a bit to obtain its test speed.
http://www.darpa....011.html
The end-result of this entire project would probably be a scramjet or similarly powered vehicle to obtain/maintain its flight, yes, but this TEST vehicle was not powered beyond its RCS thrusters.
jselin
4.3 / 5 (6) Aug 25, 2011
My apologies fmfbrestel... apparently I've been wrong about this for quite some time :/
Ricochet
5 / 5 (2) Aug 25, 2011
Speaking of DARPA and their top secret projects, they do have quite a bit on their website, including this:
http://www.darpa....MS).aspx
Remember that remote control cockroach in The 5th Element? Yeah, they're working on it...
fmfbrestel
5 / 5 (4) Aug 25, 2011
No worries jselen, darpa has a lot of hypersonic programs right now. easy to get them confused.
komone
5 / 5 (2) Aug 25, 2011
I happen to believe that it is a great thing that even in these days of economic constraint, we are still literally pushing the envelope of possibility. Any exploration of limits is bound to be a learning experience, and it would be unbelievable to make it work right first time. Go for it DARPA!
Star_Gazer
1 / 5 (1) Aug 25, 2011
My apologies fmfbrestel... apparently I've been wrong about this for quite some time :/


I thought it was a scramjet too =(
mankydp
2 / 5 (4) Aug 25, 2011
I am sorry but the first video is made on a computer. The second could be anything. Since we do not have actual video from the unit we do not if any of this is real. I am sure that there is a need to move quickly but for what reason? We do not have the cash for a cheap high speed rail system in the country. Or for that matter getting all the the methane hydrates from our coasts rather than fracking. Just a rant on propaganda.
Osiris1
1.1 / 5 (8) Aug 25, 2011
In this age of satellites and cameras of high res everywhere there are no secrets; attempts at secrecy only get fast publication by the 'other side' whoever that is! No pilot! What a surprise that is?! At mach 20 no pilot can hope to really control it except through a 'pooter'....same as the shuttle. However a full size one could launch a shuttle on its back without need of the big fat dumb expensive booster that leaks fuel, blows up, and shreds foam from its tank(s).
Rod from God, get a life! That is for the Chinese to build on the moon when they get there first and claim it....a rail gun to send helium three back to earth cheaply....and other 'peaceful' purposes.
fmfbrestel
5 / 5 (4) Aug 25, 2011
However a full size one could launch a shuttle on its back without need of the big fat dumb expensive booster that leaks fuel, blows up, and shreds foam from its tank(s).

really? did you even read the article? It is a GLIDER.

No pilot! What a surprise that is?! At mach 20 no pilot can hope to really control it except through a 'pooter'....same as the shuttle.

first off, "pooter"? welcome to second grade. Second off, so what? Thats the point of the technology a "pooter" that can control something going mach 20 is half of what makes this impressive.



harryhill
1.4 / 5 (11) Aug 26, 2011
Another military 'make nothing' project. Only object to either engage in or start another losing war. Only way it could be effective is to use nuclear weapons. That is called suicidal.
Start of 'The War to End all Wars' or: 'World Without Humans'
eachus
3.7 / 5 (3) Aug 26, 2011
This is a glider, so was the space shuttle. The difference is that the space shuttle was deliberately built with a low lift to drag ratio so that it wouldn't "flip" at high speeds. Even so, the space shuttle went through over a dozen flight domains from Mach 23 to around Mach 3--from there it could be tested in wind tunnels during development.

Only one test pilot landed the (shuttle) simulator with the computers disabled out of about 150 tests. After that they just made the computers level 1 critical, and the final system had three computers voting every few milliseconds on what to do next. If all three disagreed, the system took whatever a fourth computer told it.

Did it work? Yes. But I just started laughing hysterically as the TV reporters were intently following the details of the landing from the point where the shuttle crossed the outer marker--that part any of the astronauts could have done in their sleep, it was the part over the Pacific and the coast that was risky.
antialias_physorg
5 / 5 (2) Aug 26, 2011
Don't we already know how to make rockets?

Yes, but the number of (intercontinental) rockets you may have are limited by international treaties - the number of gliders aren't.
Skultch
1 / 5 (1) Aug 26, 2011
They claim the launch characteristics are different enough for that not to be a concern, but I'm not convinced. Lets say China launched an ICBM at Taiwan, we're not going to wait around to see if it's a nuke or not, we're going to retaliate even if the launch looks slightly funny.


Yep. Not just launch, but trajectory as well, I think. Sometimes you just can't get the launch evidence. Someone correct me if I'm wrong, but isn't it very difficult to deduce payload from trajectory with 90% certainty? I remember being in Kuwait in March'03 when we were briefed on our ability to detect chemical payloads on-board SCUD missiles. The system gave a false positive once, and that was the day I started smoking. (I've since quit, thank Jebus) :)

What's the degree of certainty with ICBMs? Could it be that with such new tech and unusual trajectory that the uncertainty is even that much higher for those that don't have any data to compare?
El_Nose
2 / 5 (4) Aug 26, 2011
these videos would be better served posted on taliban and al queda and iranian or yemen government message boards. Its not that these are weapons we are using, this is just how we blow our money -- what exactly to you spend your budget on -- oh that's right buying our 30 year old weaponary... well if you think that is on par with fighting the US then well sorry about your luck. -- ohh look i got this new mechanical dragonfly that is also a homing becon or explosive delivery platform -- you still buying our guns. Too each their own.
parder_dade
1 / 5 (4) Aug 26, 2011
Am I mistaken or didn't the Space Shuttle re-enter at mach 25 or something like that? Is the big deal the engine or control of the vehicle or both? I dislike this kind of reporting.
Thex1138
1 / 5 (6) Aug 26, 2011
Worlds most expensive skyrocket. Sorry but this is a pretty big waste of money. The skunkworks that designed and developed the SR-71 built scores of planes that pelt along at up to Mach 3. And that was in the 1950's/1960's. This is HTV project is not really as impressive a feat as what was achieved 60 years ago to push a plane at Mach 3.2 with turbines. .
_nigmatic10
1 / 5 (1) Aug 27, 2011
Looks very interesting.
Jeddy_Mctedder
1.6 / 5 (7) Aug 27, 2011
what i want to know is how how quickly does an unpowered glider go. mach 20 seems a bit ridiculously fast to be travelling under 80,000 feet. but above 60,000 feet there is almost no oxygen for a scram jet to breath.

as far as high speed transport.
darpa should work on developing room temperature super conductors so that we can build a near zero pressure vaccu-tube tunnel system for transporting heavy cargo across the country at mach 10 for 1% the amount of energy that is used by these high speed jets.

if you could deliver a tank column of 30 tanks across the country in under 1 hour, that would be strategically valuable. and the applications to civilian tech, and military supply logistics would pay not only for themselves but help establish american technology dominance abroad.
et3.com
Jmaximus
1 / 5 (2) Aug 28, 2011
So we are cutting SS for this? We don't need any more billion dollar weapons. My guess there isn't a single TeaBag complaining about this colossal waste of money.
Humpty
1 / 5 (5) Aug 29, 2011
I thought it was a SCRAM jet.... - thus how can an empty tin can fly for three minutes at M 20 - without no engine?
KingDWS
not rated yet Aug 29, 2011
This is interesting but the one thing I've yet to hear is just how are they proposing to get larger vehicles up to speed? Or is this just a steerable reentry vehicle and nothing more? The bit about aggressive manoeuvring and previous posters mentioning kinetic impact warheads makes you wonder what the end use actually is. A manoeuvrable kinetic warhead would definitely make it on the annoying side if you were about to receive. Can't think of too many abm systems that would be even worth trying to shoot at it.
GSwift7
3 / 5 (4) Aug 29, 2011
1)how are they proposing to get larger vehicles up to speed?
2)Or is this just a steerable reentry vehicle and nothing more?
3)The bit about aggressive manoeuvring and previous posters mentioning kinetic impact warheads makes you wonder what the end use actually is.


1)The final vehicle will be relatively small, but big enough to do its job.
2)Yes, that's essentially what it is. It allows you to hit a precision target anywhere on the planet with almost zero warning from existing air defense systems.
3)DARPA describes the mission goal as a "reusable bomber". So I assume you'll have some kind of GPS guided bombs in a bomb bay, and/or reconnaisance gear. The launch system was originally designed to carry up to 10 MIRV's wich are each about the size and wieght of a 1000 lb bomb. The glider might be able to deploy several sub-munitions, steering from one target to the next. At such high speed, there's no need for an engine; It can glide home.
GSwift7
3.4 / 5 (5) Aug 29, 2011
To clear the confusion about scramjets versus hypersonic aerodynamic flight:

They are two entirely seperate areas of study. The above project has nothing to do with scramjets. The scramjet tests which are currently being done by other groups, are not controlled aircraft. They are merely self-propelled ballistic projectile at this time. The project shown above is a non-powered re-entry vehicle. The aim of the above project is to figure out how to steer a craft at hypersonic speed. At some future time, the scramjet project and the above project might be combined to create a steerable hypersonic scramjet, but for now, those are two completely seperate engineering problems. DARPA is correctly attempting to solve each problem on its own, in completely independent test programs. The above project completely circumvents the need for a scramjet, using old fashioned rockets to achieve rapid global response times.
tadchem
5 / 5 (2) Aug 29, 2011
The hardware cost was chump change. The expensive part was figuring out how to build something that would fly at Mach 20.
As a repairman one said, "Kicking your machine was free. The $200 service charge covers the time I spent learning just *how* to kick it."
GSwift7
3.4 / 5 (5) Aug 29, 2011
For people who don't understand what the big deal is about steering something at mach 20, I'll give a short layman's explaination:

There are several issues. First is material. You must find materials that can take the heat for a long enough period of time. Once you get past that, you are faced with a balance problem. Any aircraft faces the problem of balancing stability against maneuverability. On a conventional aircraft you can make the tail fin large to give added stability. The tradeoff is that this makes the aircraft harder to turn. On the flip side, you can make the aircraft highly maneuverable, but then it tends to want to flip around and fly backwards if you aren't carefull. The P-51 Mustang, F4 Corsair and F14 Tomcat are all known to be excellent dogfighters, but also prone to spin. The F117 stealth fighter is so instable that it requires a computer to keep it under control. In the extreme case of mach 20, the knife edge of control is razor slim.
bluehigh
1 / 5 (3) Aug 30, 2011
You must find materials that can take the heat for a long enough period of time.


No big deal. Theres a range of ablative and other materials available.

In the extreme case of mach 20, the knife edge of control is razor slim.


No big deal. I expect you are correct but do you have a reference that reports experimental data at Mach 20 to prove it? If thats all it requires then using fast PLC avionics as you say is demonstrated with the F117.

Its a dangerous escalation of the arms race.
Thats the big deal.

Ricochet
5 / 5 (1) Aug 30, 2011
No big deal. I expect you are correct but do you have a reference that reports experimental data at Mach 20 to prove it?

No big deal, though it seems to me that we'll have to wait until DARPA makes the test data public... if they make it public...

Its a dangerous escalation of the arms race.
Thats the big deal.

No big deal. Many countries have the nukes these days, and they're all afraid to use them.
GSwift7
3 / 5 (6) Aug 30, 2011
No big deal. Theres a range of ablative and other materials available


It's a little more complicated than that. An ablative heat shield works for the leading edge of the fuselage, but I don't think you would want your control surfaces and their seals, fasteners, lubricants, expansion joints, etc. to be ablative.

No big deal. I expect you are correct but do you have a reference that reports experimental data at Mach 20 to prove it?


That's the whole point. There is no such data. Nobody knows just how much force to tell the computer to apply to correct the flight path and keep the aircraft flying in the direction you want, or how fast it's possible to turn, if at all. You're fighting against a whole hoste of fluid dynamics problems that change characteristics as the speed and air pressure change. The F117 controls are specifically tailored to that aircraft. They tested it in a wind tunnel. Can't do that here. No wind tunnel is fast enough for a long enough time.
Javinator
5 / 5 (2) Aug 30, 2011
No big deal.


From an engineering perspective, those are pretty big deals bluehigh.

Theres a range of ablative and other materials available.


Dynamically changing the geometry of the leading edge of the glider would affect the aerodynamics of the glider and make it more difficult to control. There may be some that work, but I don't suspect there are a wide range that actually applicable.

I expect you are correct but do you have a reference that reports experimental data at Mach 20 to prove it?


The purpose of these test flights is to gather experimental data at Mach 20.

If thats all it requires then using fast PLC avionics as you say is demonstrated with the F117.


Except Mach 20 is significantly faster than the F117 goes and it would require a significantly faster control system.
GSwift7
2.6 / 5 (5) Aug 30, 2011
Dynamically changing the geometry of the leading edge of the glider would affect the aerodynamics of the glider and make it more difficult to control


exactly. The size and shape of the control surfaces and fuselage will change constantly.

Except Mach 20 is significantly faster than the F117 goes and it would require a significantly faster control system


correct again. Even at the relatively slow speeds of the f117, the computer needs to be proactive rather than reactive. If the computer doesn't know what to do before it needs to be doing it, then it's over before you can say "oops". The controls need to be predictive. That's the point of these experiments. We have a total of about 18 minutes of data? Probably need a bit more. lol.

Its a dangerous escalation of the arms race.
Thats the big deal.


The ability to deliver a couple 1000 lb bombs at short notice isn't going to give us the ability to take over China. It's a precision spec-ops weapon.
GSwift7
2.6 / 5 (5) Aug 30, 2011
I'm sure the bean-counters have worked this all out already, but this could actually result in a cost savings in the long run.

We already have the ability to hit targets in far-away parts of the globe at short notice. It requires us to keep fleets of aircraft carriers and submarines on station at flash-points 24/7 though. A weapon system like this could be cheaper and more versatile than keeping multiple aircraft carrier battle groups on station, just waiting to see if they are needed. You could keep the aircraft carrier closer to home, use this weapon for initial high-priority strikes, while you move the aircraft carrier and/or B2's into position. I wouldn't call this an escalation of the arms race. It's more like being able to do the same thing we already do, but do it faster and cheaper in the long run. It allows us to only place expensive and vulnerable aircraft carriers out when we really NEED to.
antialias_physorg
5 / 5 (1) Aug 30, 2011
We already have the ability to hit targets in far-away parts of the globe at short notice.

And the question always is: what for?

Has the US ever been under threat? Has there ever been a power of a certain size that had a military that was geared towards offensive purposes? (Russia's and China's armies, aircraft - and especially their navies - are only really effective for defensive purposes)

Sure the US HAS that ability to strike others. But no one ever asks whether that isn't just a way of (artificially) keeping makers of military hardware in business rather than a real need.
bluehigh
1 / 5 (3) Aug 30, 2011
In the extreme case of mach 20, the knife edge of control is razor slim.


How do you know this when there is no prior data? Perhaps the new data will confirm your opinion but until then you are guessing.

That's the point of these experiments.


It's a precision spec-ops weapon.


Since when is a very large energetic impact perhaps equivlent to a small atomic strike in any way - precision?

Dynamically changing the geometry of the leading edge of the glider would affect the aerodynamics of the glider and make it more difficult to control.


Another speculation. They dont know what geometry changes might be required, leading edge or otherwise, until they run the tests and assess the data.

Its the perception of threat that raises the level of fear and thats a big deal.

bluehigh
1 / 5 (3) Aug 30, 2011
.. of course it could be justified by double speak that characterizes this new weaponry as defensive. My guess is that if you find a new bigger stick and start waving it around then others will go looking for an even bigger stick - all over again. Madness.

Javinator
5 / 5 (2) Aug 30, 2011
Another speculation. They dont know what geometry changes might be required, leading edge or otherwise, until they run the tests and assess the data.


An ablative material is a material that chips or breaks away in pieces when heated or stressed. This means that, if an ablative material is used as you advocated above, the geometry of the leading edge of the wing would change during flight (ie. dynamically). Dynamically changing the geometry of the leading edge changes the aerodynamics of the leading edge of the glider. That's not speculation, that's basic fluid dynamics.

The rate of change of ablation would be due to a number of factors which also wouldn't remain exactly constant (speed, temperature, surface area, humidity, etc). What you end up with is a large amount of rapidly changing variables that the control system has to deal with quickly which makes control very difficult.

Javinator
not rated yet Aug 30, 2011
In the extreme case of mach 20, the knife edge of control is razor slim.


How do you know this when there is no prior data? Perhaps the new data will confirm your opinion but until then you are guessing.


It's well known that control becomes more difficult as speed increases when travelling through a fluid. At a higher speed, more fluid particles come in contact with the control surface per unit time meaning small corrections (ie. small changes in surface area) make for larger course corrections the faster the vehicle is travelling.

This can be confirmed by sticking your arm out the window when driving and seeing how wind resistance changes at different arm angles at different speeds.

You can also check jet boat crash videos on youtube. See what happens when they try to turn or hit slight turbulence because they're going so fast.
GSwift7
2.6 / 5 (5) Aug 30, 2011
How do you know this when there is no prior data? Perhaps the new data will confirm your opinion but until then you are guessing


Oh my. You need to read up a bit. We have some knowledge of hypersonic flight dynamics, but all previous examples have been uncontrolled (ballistic) aircraft. German V2 rockets were capable of hypersonic flight way back in the 1940's. I not guessing here. I studied aerospace engineering at Auburn, and my brother did the same at Embry Riddel and Old Dominion. Just because you haven't read much about it, don't assume that I haven't. I don't have the time or inclination to explain it to you if you aren't willing to at least google it on your own.

Another speculation. They dont know what geometry changes might be required


You mis-understood what I was saying. As the aircraft heats up and cools down, the vehicle will expand and contract. It will actually get longer and wider when it heats up. You must account for that in the control system.
GSwift7
2.6 / 5 (5) Aug 30, 2011
An ablative material is a material that chips or breaks away in pieces when heated or stressed. This means that, if an ablative material is used as you advocated above, the geometry of the leading edge of the wing would change during flight (ie. dynamically).


They are using materials now that don't change shape like that. The state of the art in ablative heat shields is more like a sponge filled with a coolant. The sponge will remain, and the coolant will be leached out. In this case the sponge is usually some kind of ceramic composite, and the coolant is something like solid copper. It works something like placing a sponge soaked with water onto a hot stove. The sponge won't burn until you evaporate out some of the water, but the structure of the sponge remains intact until you reach the failure point. Kinda cool actually.
Javinator
5 / 5 (2) Aug 30, 2011
That is very cool. Do you have a link for this? It would still change the weight distribution slightly, but it wouldn't affect the aerodynamics as much as surface changes. I wouldn't mind reading a paper/seeing a more detailed explanation of how they work.

Of course I could just google it, but you seem to know so I was wondering if you had a good source.
bluehigh
1 / 5 (3) Aug 30, 2011
@Javinator

If all these factors are known in well known basic fluid dynamics then why are these tests being conducted? Just run a computer model simulation and hey presto design done.

I suggested materials are available that can be used for the purpose of heat protection. If I follow your reasoning on heat resistant materials, then the Space Shuttle would have never been controllable. Build the thing from molded space shuttle tiles maybe. Finding appropriate materials is not a big deal.

Its the evil intent that is the big deal.
GSwift7
2.6 / 5 (5) Aug 30, 2011
What you end up with is a large amount of rapidly changing variables that the control system has to deal with quickly which makes control very difficult.


Another major engineering problem is phase change. The air undergoes rapid and violent phase changes at these speeds. If you try to extend some kind of control surface you can trigger an unexpected phase change which is equivelant to an explosion or implosion, or even a rapid series of implosions and explosions. That's worse than "crossing the beams" for the aircraft in question. lol.

I'll see if I can find a link to the ablation stories. I know there have been several here on physorg in the past year.
bluehigh
1 / 5 (3) Aug 30, 2011
@GSwift

I didn't know that hypersonic flight dynamics was an area of study generally available at Auburn. Does DARPA know? We should get you to DARPA quickly as you seem to know all about hypersonic flight. Drop into the CSIRO at Lindfield some time and I'll teach you a thing or two about fluid dynamics in gasses (like air).

Javinator
5 / 5 (1) Aug 30, 2011
If all these factors are known in well known basic fluid dynamics then why are these tests being conducted?


The existence of these factors are known and their behavior is known at lower speeds, but how to control them or how much each factor affects the flight at Mach 20 is not well known. As GSwift just mentioned, phase changes of the air is a different factor that is not a concern at lower speeds.

I suggested materials are available that can be used for the purpose of heat protection. If I follow your reasoning on heat resistant materials, then the Space Shuttle would have never been controllable. Build the thing from molded space shuttle tiles maybe. Finding appropriate materials is not a big deal.


Apples and oranges. The space shuttle doesn't need to be controlled at Mach 20. It needs to be controlled during descent and landing. We're talking about control at Mach 20.
bluehigh
1 / 5 (3) Aug 30, 2011
Hypersonic Apples and Oranges - now thats food for thought!
GSwift7
3 / 5 (6) Aug 30, 2011
That is very cool. Do you have a link for this? It would still change the weight distribution slightly, but it wouldn't affect the aerodynamics as much as surface changes. I wouldn't mind reading a paper/seeing a more detailed explanation of how they work.


I finally found a story about it:

http://www.physor...091.html

Check out the video, around 1 minute in. It shows how the coper regenerates itself from within the matrix. Cool stuff.

I didn't know that hypersonic flight dynamics was an area of study generally available at Auburn


No need to be an ass. Of course they didn't teach that. I do like to keep up on things though. You keep questioning me on things that should be basic common knowledge, so I assume that you are not knowledgeable in regard to flight dynamics. They do teach flight dynamics at Auburn. The basic principles apply accross a wide range of flight domains. Hypersonic is a special case but many of the basics remain. Go figure.
GSwift7
2.6 / 5 (5) Aug 30, 2011
If all these factors are known in well known basic fluid dynamics then why are these tests being conducted


The basic theory makes it possible to predict some aspects, but you're always limited to a certain level of detail. As you try to get down to smaller intervals of time and space the models get ambiguous. For example, I did a model of turbulence on a helicopter carrier deck once. It wasn't anything fancy. Just two dimensional vectors up to 10 feet off the deck with about a 10 meter grid spacing (I had help from smarter people than me). It could tell us general things like where there was likely to be turbulence and at what speeds, and a general idea of the magnitude of the turbulence. That allows you to know where to place your instruments so that you can get detailed measurements if you do a field test. It can at least let you know where you might want to place an extra hand rail.
pauljpease
5 / 5 (1) Aug 30, 2011
They're probably advertising this Mach 20 failure so nobody thinks to consider the Mach 16 success. With this much money in play, it would be easy to be funding multiple projects. How else can the military/government keep large projects secret. Remember the movie "Contact"? The first rule of government spending, why buy one when you can buy two for twice the price!

Obviously this is not a totally serious statement, more like a hope since a hyper-mach aircraft would just be pretty awesome.
GSwift7
2 / 5 (4) Aug 30, 2011
They're probably advertising this Mach 20 failure so nobody thinks to consider the Mach 16 success.


There are parts which are still secret, and other parts that are somewhat open. DARPA tends to put out a public request for a plan first. Then there may be several groups who respond with a plan. They might fund one or more of the plans to procede to the next step, which might be a technology demonstration or simply a feasability study. So, you might get more than one group working on parallel projects. Then DARPA might decide to take the best parts from one or more of the groups and combine them to take it to the next step, which might be a prototype or just a computer model or maybe even just a design proposal. At any point in the process they can take the whole thing off the public radar screens. Hypersonic tests have been going on since the 40's so it's hardly a secret that people have been trying. Giving out detials is another story. lol.
Javinator
5 / 5 (2) Aug 30, 2011
I finally found a story about it:


Hey thanks for finding that for me. It was said before, but that is seriously cool stuff. Looks like they're just looking at going up to Mach 8 with that research. Hopefully something similar can apply at Mach 20.
GSwift7
2.3 / 5 (3) Aug 31, 2011
Yeah, they were working on scramjets in that project, so it's way slower speed than the glider project above. Notice how the scramjet exhaust is actually hotter than the leading edges? I wonder what the speed of the scramjet exhaust is? It would need to be a lot faster than mach 8, in order to get the aircraft up to mach 8.
Ricochet
5 / 5 (2) Aug 31, 2011
Hypersonic is a special case but many of the basics remain. Go figure.

Very true... it's a matter of materials that can withstand the heat/cold, pressures, etc, as well as being able to control the craft well enough at those speeds in the sparse atmosphere to keep it stable and, ultimately, pointed in the correct direction. Otherwise, it's the same-ole same-ole with surfaces that control lift, pitch, roll, etc.
Burnerjack
1 / 5 (1) Sep 05, 2011
@ Tadchem: Brilliant! That "kicking" saying is going on my toolbox! LOL!!
To all the rest trying to figure out what this craft is good for, just remember the X series craft also had no practical value. Without them, our Jet fighter fleet would not have been possible.
What goes faster than this craft? Defense secrets to the Chinese.

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