Mach 6 Test Aircraft Set For Trials

coondoggie writes "The aspiration that jets may someday fly at over six times the speed of sound took a very real step toward reality recently, as the US Air Force said it successfully married the test aircraft, known as the X-51A WaveRider, to a B-52 in preparation for a Dec. 2 flight test. The X-51A flight tests are intended to demonstrate that the engines can achieve their desired speed without disintegrating. While the X-51 looks like a large rocket now, its applications could change the way aircraft or spaceships are designed, fly into space, support reconnaissance missions and handle long-distance flight operations. At the heart of the test is the aircraft's air-breathing hypersonic scramjet system."

Comments

Hmmm...

[voss]

Engines reaching desired speed without disintegrating....thats a GOOD feature to have.

Re:Hmmm...

[Cormophyte]

Only if you want the chimp to survive. Some stories unfold when man and ape work in close quarters that just shouldn't be allowed to be told.

Re:Hmmm...

[KangKong]

Nice to be the test pilot. "Increase the speed to mach 6, we're just gonna check that the engines don't disintegrate."

Re:Hmmm...

[Z00L00K]

The biggest problem for general use is to achieve speeds above about Mach 3.5.

This was roughly the maximum speed for the SR-71 and the problem was the friction heat from the air. And the SR-71 had a hull of Titanium. The Concorde did achieve about Mach 2 and had a hull from Aluminum. So for commercial use it's probably not practical to exceed the speed of the Concorde. What has to be done for commercial use is to get a more economic version and a version that has a less annoying sound bang.

But there is a use for faster vessels and that is to decrease the amount of fuel needed for putting a vessel into orbit by using the air in the atmosphere. And other uses are of course military use allowing for rapid strikes from long distance.

Re:Hmmm...

[oldhack]

Engines reaching desired speed without disintegrating....thats a GOOD feature to have.

Kids these days. Back in my days ... never mind.

With lube strip

[imashination]

Mach 6, how blades is that?

Re:With lube strip

[Shadow of Eternity]

Fuck everything, we're doing 10 blades.

Re:With lube strip

[Eudial]

Obligatory extrapolation

Re:With lube strip

[BigFootApe]

http://www.youtube.com/watch?v=4F7TMlrDXtw

Re:With lube strip

[mjwx]

16 blade razor

"the aircraft's air-breathing hypersonic scramjet"

[MRe_nl]

WHOOOSH!

(ducks)

Rockets vs Scramjets

[sanman2]

Rocket supporters say that it's better to clear the atmosphere asap, and accelerate cleanly in a frictionless environment. Scramjet supporters say it's better to accelerate inside the atmosphere as much as possible to exploit its available oxygen, rather than carrying it as extra weight.

Which costs more energy - carrying the extra O2, or overcoming the friction from having to accelerate in an atmosphere? Which imposes more design compromises?

Which would be more economical in the long run? Bear in mind that there are 2 kinds of people that need to achieve very high velocities -- astronauts trying to make orbit and intercontinental travelers trying to get to the other side of the world.

Re:Rockets vs Scramjets

[CrimsonAvenger]

Which would be more economical in the long run?

Depends almost entirely on how fast you can get on scramjets. I don't think Mach six is enough to make it worth the bother. But I'm pretty sure Mach twelve would be enough to make it worthwhile.

Re:Rockets vs Scramjets

[TheLink]

For short trips e.g. New York to London it's not worth it whether it's Mach 6 or Mach 12 - the gains you have would be overshadowed by the hours you spend getting to/fro the airport and getting through the airport to/fro the plane. For longer trips yes - e.g. New York to Singapore, or London to Auckland. On the bright side maybe if your luggage ends up on the wrong flight (to Hawaii?) it won't take as long for them to get it back to you.

Seriously though, when you talk about economical - you have to ask how much fuel it uses. Whether scramjet or rocket, if both use way too much fuel, there won't be an "Economy Class" ticket ;).

Re:Rockets vs Scramjets

[DynaSoar]

You start to answer your own question with the "two kinds of people" statement. Rocket supporters and scramjet supporters, whatever those are, might take up the cause of a particular vehicle. But the point is not to use a particular vehicle, it's to get something done using the most effective and efficient vehicle available.

You start with your goal, develop flight profiles for the available vehicles, add in ground support and maintenance costs, and calculate your costs/benefits.

There are more than "2 kinds of people" -- actually goals to accomplish and flight profiles that can be used. Suborbitals: rapid deployment air to ground, air to air and air to space weapons platform; critical cargo delivery; recon. Orbital: supply, including immediate need repair supply, to orbital craft/stations; debris sweeping ahead of a sensitive craft or mission. Extra-orbital: lunar insertion; placement of probes such as solar weather into Earth/Sun LaGrange points; interplanetary delivery. All of these can be expanded greatly.

All other things being equal, a reusable booster with a delivery system fired from high speed and altitude would probably end up being very, if not most, economical in most cases. That would make 'both' a good answer.

For the most part, 'people' will have little to do with it. It'll be a long time before there's a human rated scramjet vehicle, and then it'll probably be of the two stage nature mentioned. The energy necessary for a given velocity/trajectory grows faster than the vehicle cross section. Something big enough to carry passengers would require more fuel than it could carry.

Re:Rockets vs Scramjets

[sirrunsalot]

Which costs more energy - carrying the extra O2, or overcoming the friction from having to accelerate in an atmosphere? Which imposes more design compromises?

Seems the best answer is likely somewhere between the two. I mean the idea behind scramjets is only to get you through part of the journey anyway. You'll still need a running start, and you'll still need to carry oxygen to get you up into space.

Which would be more economical in the long run? Bear in mind that there are 2 kinds of people that need to achieve very high velocities -- astronauts trying to make orbit and intercontinental travelers trying to get to the other side of the world.

What about people trying to get a few kilometers downrange and get blown to smithereens the other end? Missiles are people too, y'know.

Re:Rockets vs Scramjets

[wisdom_brewing]

How do you define "economy"?

Isn't it all relative?

Compare a bus ticket, to a plane ticket, to a cruise ticket...

Re:Rockets vs Scramjets

[HiThere]

It's worth remembering that Mach numbers are dependent on the current speed of sound.

If a scramjet can reach over 7 miles/second in the very upper stratosphere, then the scramjet would clearly win....at least if it didn't need the same G forces as the rocket. And particularly if it could carry a sizable cargo. (I.e., anything better than an Apollo capsule, but the larger the better.)

A scramjet might make an admirable second stage for a rocket, but then you need a first stage to get it up to speed. Note that these first two stages are airplanes, and are expected to be built to be re-useable.

There's a bit of a question as to how feasible this is, however, given that this little test plane requires a B-52 to launch it.

Re:Rockets vs Scramjets

[cheesybagel]

The problem with using scramjets is that you need another engine for liftoff, and yet another engine for space travel (scramjets are made for travelling inside the atmosphere at only startup at a certain Mach number). With a rocket engine you only need *one* engine to go for zero velocity to space. In other summary, scramjets make no sense for space travel.

Scramjets would be nice for a high speed reconaissance platform or bomber though.

Re:Rockets vs Scramjets

[cheesybagel]

Yet, for some unfathomable reason, none of the commercial geostationary satellites are launched in this fashion. SpaceShipOne and Pegasus are the only things launched in this fashion and they have miserable payload. Good luck developing your three stage to orbit vehicle using scramjets.

Re:Rockets vs Scramjets

[Kagura]

He's making fun of you because it sounds like you just came up with the idea for multi-stage rockets and you act like scientists never considered them.

Re:Rockets vs Scramjets

[daver00]

You fail. Current rocket designs use multiple stages to get into orbit, that means multiple engines, plus whatever the payload is it will have its own engine as well. The thing is that rockets are incredibly simple engines, they simply throw their mass away to achieve thrust, thus the amount of mass you can move is a function of the fuel you can carry and vice versa. With scramjets you can take mass from the atmosphere, raise its energy and then throw it away, thus a portion of your fuel is collected along the way, an you will have a higher payload to fuel ratio as a result.

We already have multiple engines in our rockets, it makes sense to use a more efficient one where it is possible to do so.

Re:Rockets vs Scramjets

[cheesybagel]

No, it is you who don't understand. A scramjet has a low thrust-to-weight ratio, which means to get up to speed takes a lot longer than a rocket. It also only works in the atmosphere. At those speeds you will need cooling for the entire skin of the vehicle. Which means you will lose a lot of payload just for that cooling system which wouldn't be necessary if you had a rocket where you want to get out of the atmosphere as soon as possible.

Scramjets are useless for space vehicles.

Re:Rockets vs Scramjets

[cenc]

"Which would be more economical in the long run? Bear in mind that there are 2 kinds of people that need to achieve very high velocities -- astronauts trying to make orbit and intercontinental travelers trying to get to the other side of the world."

I would add, bombers getting to their target and home for dinner.

Re:Rockets vs Scramjets

[Jarnin]

In the television series StarGate SG-1 and StarGate Atlantis they have a top secret alien-human tech derived aerospace fighter called the F-302. It uses 3 forms of propulsion in order to do what it needs to do:

2x regular air-breathing jet engines for low altitude operations.
2x scramjets for high altitude operations.
1x Rocket booster to get into orbit.

Re:Rockets vs Scramjets

[daver00]

I wasn't claiming that scramjets are without problems, I merely pointed out that current rockets already have multiple engines, which you kind of claimed they do not.

Re:Rockets vs Scramjets

[c4ffeine]

Take a look at the SABRE engine sometime. It's a hybrid rocket/turbojet/ramjet engine designed specifically to solve the problem you're referring to. I'll admit that it still needs a lot of further development, but it's the approach that I think is most likely to be practical.

Fortunately, Wiki seems to have a moderately accurate overview of the project:
http://en.wikipedia.org/wiki/Reaction_Engines_SABRE

Re:Rockets vs Scramjets

[Guysmiley777]

In the television series StarGate SG-1 and StarGate Atlantis

Erm... In the television series Star Trek they have matter/anti-matter reactors and warp drives capable of traveling faster than the speed of light.

It's a cruise missle

[wigaloo]

This appears to be more about the development of a hypersonic cruise missile than an actual aircraft.

Not for aircraft.

[Stan Vassilev]

While the X-51 looks like a large rocket now, its applications could change the way aircraft or spaceships are designed, fly into space, support reconnaissance missions and handle long-distance flight operations.

The Concorde flew at 2.2 Mach and in order to achieve this, it ended up too expensive to create, manufacture and maintain. It would be awkward to see airlines adopt airplanes which are more expensive to fly than current models. The trend is towards less fuel usage, and cheaper flight, in fact, at the expense of speed at times. On the other hand I'm happy to see that US is working heavily on creating a replacement for F-22, an insanely expensive jet with a nearly 30 year history that was barely ever used for something at all, before being discontinued :P...

Re:Not for aircraft.

[maeka]

When calling the Concorde (or any other aircraft) "too expensive to create, manufacture, and maintain." on needs to take into account the ticket price the market will bear.
Since the Concorde was not designed with a range suitable for flying the Pacific routes, it was forced to try to make up it's high costs on the much tighter margins of the Atlantic routes. Had it been able to fly the higher margin Pacific routes it is quite possible it would not have been too expensive to be sustainable - even at the same (or slightly higher) cost basis.

Re:Not for aircraft.

[moosesocks]

The concorde was profitable in its last years (not extremely profitable, but it made money, which is more than most airlines can currently say).

In the end, its operators decided it wasn't worth maintaining/refurbishing the planes, scrapped the program, and wouldn't let competitors purchase the unused aircraft. Richard Branson allegedly made several serious offers for the planes, all of which were rejected. Numerous allegations have been made that the grounding of the Concorde fleet was a result of a conspiracy between Airbus and the airlines (unsubstantiated, but certainly plausible, especially in light of their refusal to sell the craft to other carriers at a time when the company was losing money)

In short, we got lazy and stupid.

Re:Not for aircraft.

[DerekLyons]

When calling the Concorde (or any other aircraft) "too expensive to create, manufacture, and maintain." on needs to take into account the ticket price the market will bear.

And on that issue - the market has spoken loudly and clearly. "It ain't worth it".
 
Yeah, I know the Concorde made a paper 'profit' towards the end - but the proof is in the amount of money the airlines were willing to spend to keep this 'profitable' airliner in operation, which coincidentally is equal to the number of Concorde's still in service...
 
Zero.
 
I you can't make enough money to pay your own maintenance bills, then making a 'profit' is pretty much meaningless.

Re:Not for aircraft.

[maeka]

And on that issue - the market has spoken loudly and clearly. "It ain't worth it".

I assume it was unintentional that you missed the rest of my post, but let's be clear - the Atlantic market has spoken, not the market as a whole.
The Concorde could not fly the profitable Pacific routes due to limited range, and it could not fly supersonic over mainland USA or Europe due to noise regulations. This greatly limited the market segment it participated in.
This need not be the case (well, the noise issue likely does) with a future supersonic passenger aircraft.

Re:Not for aircraft.

[Myrcutio]

The F-22 wasn't created for our time, it's intended use is to aid our future brethren in overthrowing their tyrannical alien overlords. See the documentary here.

Re:Not for aircraft.

[ahankinson]

I think you need to refine your stance. "The Market" has not spoken loudly and clearly; "A Market" at a specific place and time has spoken. Supersonic trans-atlantic flight has been shown, in hindsight, not to work in a very specific place and time in history. That's all. It has not proven that it can never be done.

Analyzing failures are helpful for gaining insight into processes, but the failure of one instance shouldn't be taken as a broad indication that the idea itself is a failure. It may simply be the execution.

Re:Not for aircraft.

[smoker2]

Utter shite. No amount of money would have kept the manufacturers in the business of maintaining the airframes. They have too much else to do. The airlines didn't shut it down, the manufacturers did. Without a place to go for regular maintenance, you don't keep your airworthiness certificate. This means you don't fly. And the airlines did indeed spend a lot of money to try and mitigate the mechanical circumstances of the Paris crash, which wasn't even their fault. Crap on the runway is crap on the runway, no matter who or what runs over it. If that incident had not happened, I'm willing to bet Concorde would still be flying, even in the current climate.
But Airbus is the new darling, so they've distanced themselves from Concorde and concentrated on their own designs. With recent advances in engine design and composite technology, a new supersonic plane would not consume so much fuel and would doubtless get longer range, given it's only a matter of initial design choice.

It fucking annoys me - one accident (not even self inflicted) in 30 years and people turn round saying "I told you so".

Re:Not for aircraft.

[greyhueofdoubt]

The f-22 didn't take much longer than other 5th generation aircraft. Oh wait, the F-22 is the ONLY 5th gen fighter in the world. And it only just went into service. And frankly, I don't want us to ever *need* it- Needing an f-22 would require an enemy with excellent air power, which would mean that we were fighting a major power such as china, india, or russia.

Do you complain that our nukes don't get used often enough?

-b

Re:Not for aircraft.

[DerekLyons]

Utter shite. No amount of money would have kept the manufacturers in the business of maintaining the airframes. They have too much else to do.

Horseshit. If there was money to be made in it, they'd have still been in it.
 
 

With recent advances in engine design and composite technology, a new supersonic plane would not consume so much fuel and would doubtless get longer range, given it's only a matter of initial design choice.

Weight isn't the problem for supersonic aircraft - you could cut the weight of Concorde by 80% and give the most fuel efficient engines available, and it still wouldn't get across the Pacific. Drag is the dominant problem, and nobody has solved that one yet.

Re:Not for aircraft.

[wagnerrp]

This need not be the case (well, the noise issue likely does) with a future supersonic passenger aircraft.

There is no regulation against flying supersonic over the continent. The regulations are for maximum decibel levels generated over populated areas. You can fly high enough that the pressure waves have dissipated by the time they hit the ground, although this has been found to have limited effect. You can design your fuselage and wing such that the pressure wave is spread out over a longer area, and directed laterally, so it never spikes above the limits. There is been a lot of work in that area over the past few years with the intent of bringing back SSTs.

Re:Not for aircraft.

[maeka]

There is no regulation against flying supersonic over the continent.

I never suggested there was.

The regulations are for maximum decibel levels generated over populated areas.

Which is what I said.

You can fly high enough that the pressure waves have dissipated by the time they hit the ground

That has proven to be awfully high.

although this has been found to have limited effect

Though you appear to know that.

You can design your fuselage and wing such that the pressure wave is spread out over a longer area, and directed laterally, so it never spikes above the limits.

In theory - but nothing really juicy has come to fruition yet.

There is been a lot of work in that area over the past few years with the intent of bringing back SSTs.

And little has come of it.

I had already qualified my statement, didn't really need it read back to me.

Re:Not for aircraft.

[Patch86]

Lets please try to remember that the Concorde was originally designed and built 40 years ago, That's -4-0- years. Despite the fact they obviously would have refined and upgraded wherever possiblle in those 40 years, it's still a 40 year old vehicle.

Please find for me, if you can, any other aircraft which first flew on or before 1969 which is still being used, profitably, for trans-continental passenger services today.

Technology marches on. Concorde being withdrawn from service after 27 years in action proves nothing about the feasibility of a modern supersonic airliner designed and built today.

Titanium may well get cheaper

[PeterM from Berkeley]

Recent advances in the production of titanium may bring this metal into wide use in airframes. And everything else.

Re:Titanium may well get cheaper

[modecx]

How much titanium is there, laying around, if the demand would suddenly start to rise?

How much of that titanium is locked up by China, who has seen for some time that strategic metals will become a growth limiter in the not-so-distant future?

A lot. It's pretty abundant, actually. It's just that with current processes, it's goddamn expensive to produce, uses large amounts of chlorine and energy, etc... That's the only practical reason for its rarity as a structural material.

AFAIK, China doesn't produce a significant amount of the requisite ores, or finished metal product for that matter. Most of the ore, by the way, gets processed into titanium dioxide, a very common white pigment which is used in Everything.

Re:Titanium may well get cheaper

[dpilot]

I thought about white pigment a few minutes after posting.

As for China, I said "locking up", because they're investing heavily in Africa, for instance. The stuff they want may not be on their territory, but they're very present in places where those things are.

Now that I actually take a look, Titanium is 22 and Iron is 26, and the contentious Lanthanoids are 57-71. (No doubt higher stuff will be scarcer.)

Re:Titanium may well get cheaper

[modecx]

They're present alright, but even discounting the whole continent of Africa, there's almost cerianly enough to keep the rest of the free world humping along, elsewhere. Oil or copper will be much more immediately contentious of a resource, all other things considered.

When or if it becomes more economically viable (profitable), Ti mines will certainly start up.

Re:Titanium may well get cheaper

[greyhueofdoubt]

Ti is the 9th most abundant element in the crust (7th most abundant metal).

The wiki page answers all your questions.

http://en.wikipedia.org/wiki/Titanium

Ti is abundant enough that we use it in toothpaste and toilet cleaner; I don't think you need to worry about it going anywhere.

-b

Re:Titanium may well get cheaper

[cheesybagel]

There is a lot of titanium. Titanium oxide is used as the pigment for white paint. If you ever tried buying paint, you probably realized white paint is usually cheapest. So there.

The issue is how do you turn titanium oxide into pure titanium. This process seems somewhat similar to the Fray-Farthing-Chen process. Then again I remember that used to be a hot topic at the time, but it never got to production.

Re:Titanium may well get cheaper

[WindBourne]

Actually, China is trying hard to lock up LOADS of resources all over the world, but the biggies are Rare Earth minerals as well as Uranium. This last week, they quit exports of a select group of REMs that they have control of, and others that they do not have total control of, they dropped the possible exports. At this very moment, Australia is deciding whether to sell them several of their mines. Hopefully they do not as they are REM mines and will be needed by the entire rest of the world. These minerals are concerned with making permanent magnet motors that are going into Electric Cars as well as are used in nearly all electronics.

.. and in further news... from 1967

[meglon]

http://www.hq.nasa.gov/office/pao/History/hyperrev-x15/ch-0.html

perhaps one of the tags should have been "been there, done that"

Re:.. and in further news... from 1967

[jklmuk]

http://www.nasa.gov/missions/research/x43-main.html

nasa have already achieved mach 9.6. Mach 6 should be a walk in the park

Re:.. and in further news... from 1967

[jnik]

The X-15 used rocket engines (carried its own oxidizer). This is a jet, using oxygen from the air.

Re:.. and in further news... from 1967

[wagnerrp]

They ran the engine for 10 seconds. With that limited duration, a bit of ablative material on the skin, and you're fine. Running for 5 minutes and 350 miles is considerably more difficult.

Re:.. and in further news... from 1967

[PachmanP]

The key is sustaining power. The x43 engines where basically big copper heatsinks. The goal was to demonstrate demonstrate supersonic combustion before the engine melted. I believe the goal for this one is to be able to run an engine that doesn't melt.

Re:.. and in further news... from 1967

[jklmuk]

where are you getting the 5 minutes from? the article talks about 60s which is such a great achievement when you are going 50% slower. Meaning the temperatures that the plane/missile experience will be significantly lower.

Real step?

[SlayerofGods]

The X-43 already did mach 9.68.
This is actually a bigger step towards making a mach 6 missile rather then a mach 6 plane....

Where's my credit card?

[wessto]

For some reason at first glance I read "Mach 6 Test Aircraft for sale" and I reached for my wallet...

Re:Where's my credit card?

[witherstaff]

You can buy one for $39.99 right now. Of course you'll have to learn scottish to make some of the things work.

Re:Where's my credit card?

[skyride]

Damn you all Slashdot! I am scottish, however the link has been slashdot'd so I am unable to fulfill my dreams! Damn you all!

Re:Where's my credit card?

[clem]

Of course you'll have to learn scottish to make some of the things work.

I have Tourette Syndrome. Does that count?

Cool but...

[Brad1138]

What ever happened to the Aurora?

Re:Cool but...

[DerekLyons]

Nothing can happen to something that doesn't exist.

Re:Cool but...

[Steven_Lunn]

Interesting. I'm fascinated by secret aircraft stories. I guess I just like hearing about future tech, in whatever form that takes. There is a lot of disinformation and fiction regarding this subject but at least some of it has to be true.

That's fine for the Air Force, but ...

[PPH]

... they could save me more travel time by not making me take my shoes off and stand in endless, pointless security lines.

Re:That's fine for the Air Force, but ...

[D Ninja]

I so wish I had mod points.

What's great is that, even given today's security measures, 9/11 would have still happened. Nothing that those terrorists did on 9/11 would have broken today's laws.

Re:That's fine for the Air Force, but ...

[D Ninja]

Hmmm...I'm reading my post, and I don't mean to say that it would be great 9/11 would still happen. Don't get me wrong - 9/11 sucked and I would never want that to happen again. But, when I say "what's great" is the fact that nobody seemed to stop and think about how pointless many/most of the security measures actually are. (AKA, I was attempting sarcasm and it definitely did not come through...my apologies.)

Re:That's fine for the Air Force, but ...

[PPH]

They didn't kick in the cockpit door. They killed a few passengers/cabin crew and the pilots let them in. SOP at the time was: cooperate. Let them hijack the plane. The worst that will happen is a trip to Havana.

Not any more. Cockpit door, box cutters or not, odds are that the passengers will kill the hijackers. All the pilots have to do is land the plane fast.

Re:That's fine for the Air Force, but ...

[TheTurtlesMoves]

I was looking at flying to a meeting in Germany from Austria. However even a 5 hour train ride works out quicker than the 1 hour flight with all the extras (including traveling to and from the airports).

Re:That's fine for the Air Force, but ...

[TheTurtlesMoves]

My friends children were invited into the cockpit by the pilots in jan 2002. Reinforcing cockpit doors did nothing.

Gat Marriage?

[Crock23A]

Since most vehicles, including aircraft, are named after girls, would this be considered a gay marriage?

Re:Gat Marriage?

[sirrunsalot]

Since most vehicles, including aircraft, are named after girls, would this be considered a gay marriage?

No. Apparently it's gat.

Re:Gat Marriage?

[Trepidity]

Presumably gat marriage is the gangsta equivalent of the traditional shotgun wedding.

Re:Unanswered question

[sirrunsalot]

But will this development be recognized outside of states like California and Massachusetts?

Don't ask, don't tell.

it sorta works...we have to admit to it

[speedlaw]

At some point, some of the Black projects bear fruit. We now need to admit that this can happen, now that we want to go big with it. Sorta like stealth, we had it for a while but at some point needed to go "white" with it. If it is ready for prime time, cool. You didn't think the SR 71 wasn't replaced, did you ?

Mach 6

[rombertw]

Is that somewhere around Warp 2?

It's no concorde

[Errol backfiring]

It's no Concorde in any sense. The Concorde was created to make an efficient aircraft, not a fast one. This is the history I learned in college:

Jet engines are more economical the faster you get. Too bad the air friction (drag) gets worse the faster you get. For subsonic aircraft with single flow engines, the optimum lies just a bit below the speed of sound. As there were only single-flow jet engines at that time, the Concorde was created to try to shift the optimum to above the speed of sound. They succeeded in that.

But then, the multi-flow jet engine was invented. Instead of blowing the air out even faster, a more powerful jet engine could now mount an extra turbine that drove an extra flow of air, thereby spreading the power over more air, that was accelerated less. Bummer. Now the Concorde was just a fancy fast-flying airliner.

Worthless

[ShooterNeo]

Scramjet tech is worthless. It's not a very good weapon - a scramjet is going to have one heck of a heat signature and probably can't be very stealthy. Not just from the exhaust...at Mach 6 the entire aircraft/missile is going to be glowing red from heat. Also, air to air missiles (like the Patriot) that use rockets already go that fast.

Second, it's worthless for getting stuff into orbit. The reason is simple - the reason a rocket costs so darn much has nothing to do with fuel. It has to do with complexity - it's very expensive to make something as complicated as a rocket work under all the stresses of a launch. A scramjet just worsens the problem. It's not the fuel or the size of the tankage that makes the rockets that SpaceX builds cost so much. It has to do with building the rocket well enough that it makes it and doesn't fail (again). A scramjet engine is evidently incredibly complex to make work, and is just another pork barrel project of the air force.

Re:Worthless

[WindBourne]

Scramjet is one of the easiest engines to build. In fact, they will be a great deal less expensive for maintenance. It is just difficult to get it correct. It will also be difficult to get it up to the speed. Right now, we are using a rocket to get there. But down the road, we will likely use a ramjet which will be inefficient taking off (probably will use an electronic runway launcher to get going), all the way to the mach 5.

Re:Worthless

[pohl]

You sound very sure. I'm curious, how would a Patriot (traveling at its top speed of Mach 5) overtake and intercept something traveling at the same (or greater) speed given that the latter has a rage of 600 nautical miles and the former has a range of 99 miles?

Are you sure that stealth is a priority given the X-51's intended mission?

Re:Worthless

[rcw-home]

The reason is simple - the reason a rocket costs so darn much has nothing to do with fuel. It has to do with complexity - it's very expensive to make something as complicated as a rocket work under all the stresses of a launch.

All of that complexity in turn stems from the insanely high mass ratios that chemical rockets require to achieve orbital velocity (93.5% of the Shuttle's weight is fuel/tank/boosters). That, in turn, means the rocket itself must be made as lightly as possible; you cannot merely overengineer things like you would a car (or to a lesser extent, a plane) and hope that you'll still get off the ground with them. And if your calculations are wrong, the part fails and perhaps takes the rocket with it.

Since a scramjet gets its oxygen from the air, you can potentially carry up a lot more mass. Some of this could be payload, some of it could be a heavier-duty structure with a better safety margin.

Also, most of the complexity of a scramjet is in the design of the shape. This test vehicle has only one moving part, the fuel pump.

Re:Worthless

[cheesybagel]

Fine. Use a Russian S-300 PMU then. Or if you are from the USA an Aegis using RIM-161 Standard Missile 3. If you can only get Israeli, an Arrow missile. If you need more range you just require a larger missile.

Re:Worthless

[cheesybagel]

Also, most of the complexity of a scramjet is in the design of the shape. This test vehicle has only one moving part, the fuel pump.

A rocket engine's most complex part is also the fuel pump... Unless you use pressure-fed engines, in which case you don't even need a pump at all!

You cannot reach space using just a scramjet anyway. You need rockets. There is no air in space.

Re:Worthless

[pohl]

None of those have the range necessary to overtake something at that speed. These are all anti-ballistic missiles, and the X-51 isn't a ballistic missile. At best, one would need one of these near the target site in order to get lucky. Given the purpose of the X-51, this seems unlikely.

Re:Worthless

[4D6963]

Scramjet tech is worthless. It's not a very good weapon - a scramjet is going to have one heck of a heat signature and probably can't be very stealthy. Not just from the exhaust...at Mach 6 the entire aircraft/missile is going to be glowing red from heat. Also, air to air missiles (like the Patriot) that use rockets already go that fast.

It's a moot point. You can't intercept something that fast, even if it's easy to see. It's hard enough to intercept a missile that doesn't go that fast..

By the way, isn't a scramjet basically just about dumping fuel in the wind and igniting it? I doubt you get the issues that rockets get with that, like the pogo effect.

Re:Worthless

[A beautiful mind]

Second, it's worthless for getting stuff into orbit. The reason is simple - the reason a rocket costs so darn much has nothing to do with fuel. It has to do with complexity - it's very expensive to make something as complicated as a rocket work under all the stresses of a launch. A scramjet just worsens the problem. It's not the fuel or the size of the tankage that makes the rockets that SpaceX builds cost so much. It has to do with building the rocket well enough that it makes it and doesn't fail (again). A scramjet engine is evidently incredibly complex to make work, and is just another pork barrel project of the air force.

The reason a rocket costs so darn much has everything to do with fuel. According to Richard A. Mueller's book I've read recently, the mass of fuel used is usually 25-50 times larger than the payload it helps to put into orbit. For the space shuttle, it's 68 tons of payload vs. 1931 tons for the boosters and fuel weight.

For useful orbits the most important thing is to reach a high enough speed to stay in orbit. The required speed for practical orbiting is about 5 miles per second, so about mach 18.

You see airplanes are a lot more efficient than rockets for two reasons: first, they don't have to carry any oxidizer (air is available) and second: they are pushing against air itself, not against their own exhaust. Now, we can't reach mach 18 yet, so a purely aircraft driven approach to reach orbital velocities is not yet possible. However, it is possible to use a hybrid approach: use an aircraft to lift up the rocket to as high and as fast as technology allows and launch the rocket from there. This approach is currently commercially done by Orbital Sciences Corporation and they have already launched over 30 satellites this way.

The better scramjet designs become, the less expensive it becomes to put something in orbit, so scramjet tech is not worthless, on the contrary. It is possibly the cheapest way to put something in orbit barring a space elevator, but the good thing about the approach that this allows incremental improvements to the technology. A space elevator either works (but then it works very well) or it doesn't.

Re:it sorta works...we have to admit to it

[greyhueofdoubt]

You didn't think the SR 71 wasn't replaced, did you ?

Um... Yeah, it was replaced... With *satellites*.

And just a word of wisdom from someone who works for 'the dark side': Supersonic aircraft are not stealthy--http://en.wikipedia.org/wiki/Sonic_boom

http://www.pbs.org/wgbh/nova/xplanes/stea-flash.html

-b

Re:Sigh

[cheesybagel]

... not again. Dude, you need Mach 25 to get into orbit. Also a scramjet, or any -jet engine, cannot work in space because there is no atmosphere to scoop oxygen from. A scramjet also needs something to push it up to speed before it can start. In short: it is useless for spaceships.

Re:it sorta works...we have to admit to it

[cheesybagel]

The SR-71 was replaced. By spy satellites. Ever used Google Maps? That uses satellites photos. Now imagine something higher resolution and with dynamic updates.

Re:"the aircraft's air-breathing hypersonic scramj

[Kreigaffe]

Actually I've heard that they're supposed to be more resilient than jet engines, because they don't have all those tiny little rapidly-spinning compressor blades. The compression is accomplished just from the pressure of the incoming air, the shape of the scramjet, and the combustion of the fuel (and doesnt it combust due to the high pressure / hence heat?)

I dunno. I've not looked into them for a while now and I'm not an experimental-propulsion-systems-making-dude, so I may be a bit off, but it's my understanding that ram and scramjets should be less vulnerable to ducks.

Re:Sigh

[cheesybagel]

The X-51 gets to Mach 7+. NASP (X-30) would get to higher speeds by employing a vapourware airframe cooling system which no one ever got to work. Also notice NASP was supposed to use a composite LH2 tank (using even cooler slush LH2 no less!) while for X-33, done years later, noone could manufacture such a tank. NASP was a collection of vapourware items. You couldn't get it to work on schedule for all the money in the world.

Re:it sorta works...we have to admit to it

[speedlaw]

Yes, but the problem with sats is that everyone knows when they go by. A fast plane is not predictable. Mach five with stealth, even minimal stealth, will be in and out before the enemy can do anything.

Re:"the aircraft's air-breathing hypersonic scramj

[frosty_tsm]

If hit just the right way, I think it will result in a duck being flung into space.

The demon lived at Mach 6 on the meter...

[endernet]

Hey, Ridley, ya got any Beeman's?

Re:it sorta works...we have to admit to it

[toolie]

Yes, but the problem with sats is that everyone knows when they go by. A fast plane is not predictable. Mach five with stealth, even minimal stealth, will be in and out before the enemy can do anything.

And miss most things of any tactical value in that time. There is a place for fast places, in strategic recon, which happens to be a lot harder to hide from satellites. We are going toward slower (I prefer the term lumbering) platforms with awesome endurance for tactical recon, staring is better than glimpsing in that case.

I like this one better

[Phoghat]

The Falcon is a DARPA vehicle that looks a lot more practical.

Re:Sigh

[cheesybagel]

No they did not. Obviously you are confusing it with the composite liquid oxygen which they did manage to do. But the temperature of liquid oxygen is way higher, and hence easier to handle, than liquid hydrogen.

NASP was vapourware.