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Scramjets...have they had their day?

Posted by: shogunmike - Tue Apr 03, 2007 10:36 pm
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Scramjets...have they had their day? 
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Post Scramjets...have they had their day?   Posted on: Tue Apr 03, 2007 10:36 pm
Hi,

I'm a researcher working on scramjet intakes/inlets and I guess my head is usually too far into my work to stop and look at the big picture. My work is 100% computational, but a few of my colleagues are doing some more fundamental experimental work.

It seems to me that there are very few scramjet programs actually being carried out around the world. I understand this is primarily due to cost and lack of good available composites, but why isn't the funding there? Surely the benefits of a more straightforward path to LEO would be more than enough reward for the initial outlay?

Any thoughts?

Mike.

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Post    Posted on: Tue Apr 03, 2007 11:26 pm
You would know better than I would if a scramjet is really capable of reaching orbit, or of really being a cost effective first stage of a two stage orbital vehicle. It seems to me like it would be impossible to make it go all the way to orbital speed while still low enough in the atmosphere to have enough air to operate. It would have to be lower than the shuttle during reentry I would think, where the drag and heating would be fierce!


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Post    Posted on: Wed Apr 04, 2007 1:29 am
I donno, maybe if there were some way to make them work from ground level in some kind of air breathing rocket type assembly. Like how the SR-71 was a turbojet/ramjet, you would have a turbojet/ramjet/scramjet/rocket engine... so far that seems unlikely... while I think most people would think that nigh impossible, I think it would only be really difficult.


Atm it seems to me the easiest way to reach orbit would be something along the lines of what armadillo is doing. Something that really only needs to be refuelled between flights and requires not much in the way of exotic matterials to build and opperate.


Now I have heard all about extra weight/useless appendages/ect... in space, but if all you need to do is refuel and fly back to space I don't see why there is a problem with attaching a 747 to the butt of your space craft if it works better that way, meaning it is 100% recoverable, yet is as safe as flying Alaska Airlines... I think a big part of the problem is many engineers like to "over engineer" things. No offense meant to any of the many engineers... really. :D


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Post    Posted on: Wed Apr 04, 2007 5:09 am
Like NASA bailled on the Sea Dragon program because big, pressure fed, LOX /RP-1 engines, "weren't technically interesting"?


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Post    Posted on: Wed Apr 04, 2007 7:26 am
The sea dragon is a good example, not elegant enough...


What is the expected speed needed for a scarmjet to orbit vehicle? Isn't something like mach 25?. I would think it is a factor in funding, to a 60 year old congressman that sounds outlandish.

The X-15 I think still holds the record at mach 5, the SR-72 is still the fastest jet plane at mach 3. Now scramjets are going to bust those numbers sure, but the number you are aiming for is not mach 6 or 7 or even 10... but mach 25(or whatever it is) it seems like a very big leap.

Keep in mind getting to orbit is something we can already do. Heavy lift to orbit is something the government/governments are interested in, soon private industry will be able to do it smaller and cheaper. While I love the idea of Scramjet tech, it kinda sounds like a darkhorse in the orbital vehicle department anytime soon.


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Post High speed yes, technically feasible...maybe!   Posted on: Thu Apr 05, 2007 11:25 am
Well, it is true that a high Mach number is required, but this has implications more for the materials and the combustion phase than anything else. The real bottlenecks are materials and getting a good specific impulse.

I think it's realistic to expect it to be the second stage of a two/three-stage to orbit vehicle. Any saving is a good saving.

However...is it cost effective?

Mike.

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Post    Posted on: Tue Oct 23, 2007 8:32 am
Right now you need jet/ ramjet/ scramjet/ rocket assembly. lol wtf an aircraft with four engines? Expecially since thrust to weight ratio of atmo breathers is not all that good. Now if you combine jet/ramjet/scramjet into one engine you'll be getting somewhere. Untill you can do that you might just as well forget about it. Ofcourse if you were to design such an engine it will be cassified for reasons of national security. To answer your question, there is a lot of reseach in that area but I'd say most of it is classified as it has significant military application (suborbital bomber anyone?).

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Post    Posted on: Fri Oct 26, 2007 4:28 pm
Horus wrote:
Right now you need jet/ ramjet/ scramjet/ rocket assembly. lol wtf an aircraft with four engines? Expecially since thrust to weight ratio of atmo breathers is not all that good. Now if you combine jet/ramjet/scramjet into one engine you'll be getting somewhere. Untill you can do that you might just as well forget about it. Ofcourse if you were to design such an engine it will be cassified for reasons of national security. To answer your question, there is a lot of reseach in that area but I'd say most of it is classified as it has significant military application (suborbital bomber anyone?).

Would a two-stage approach help things here? Or would building a super- or hypersonic launcher aircraft (the first stage) be overkill?

I agree it has lots of military applications. Bombing is one. Recon is another.

Cheers,
ErikM :twisted:


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Post    Posted on: Thu Nov 08, 2007 12:57 am
If all you want is a suborbital bomber, you can get away with chemical atmo breather. But if you want to go to orbit on chemical power alone two stages are pretty much a requirement. You can do it in one stage if you use a nuke powered atmo breather, but that ain't happening any time soon, at least not publicly. So the big question is how do you combine a jet, a ramjet and a scramjet into one engine? The obvious answer is to construct an engine that reconstructs itself for different modes of operation. To turn a jet into a ramjet you need a retractable turbofan, to turn a ramjet into scramjet you need a retractable ram. That sounds exceedingly complex, expensive and unreliable. But it could be done in theory and probably has been done already, since the idea of airbreather has been kicking around since 1960'es.

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Post    Posted on: Fri Nov 09, 2007 4:26 pm
WannabeSpaceCadet wrote:
Like NASA bailled on the Sea Dragon program because big, pressure fed, LOX /RP-1 engines, "weren't technically interesting"?


Disgusting.

Scramjets are sexy and are doubtless being funded in the black--for missiles of course. I seem to remember a letter to the editor of a science magazine that was critical of scramjets when ballistic projectiles from rockets like Skybolt were so much simpler.

As far as Sea Dragon is concerned--the Mythbuster episode with the water-heater/rocket is all the proof you need that pressure-feds work.

And that was without combustion--and it flew about as high as their dedicated rocket. Imagine if they had heated fuel and oxidizer, and had one metal plate designed to fail and release the pressure of both propellant tanks at once, as a gas cannon launches the vehicle upward.

Home-made Sprint.


Quest magazine is going to have a story on Truax in the near future. look for it.


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