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Two methods can be used to achieve the Vulcan hypersonic engine

DARPA held an industry day where it outlined some of its plans for hypersonic aircraft of the future. The program being shown off at the industry day was the DARPA Vulcan project. The project centers around developing an aircraft that uses a constant volume combustion (CVC) engine capable of flight at speeds from a standstill to Mach 4 and over.

Aviation Week’s Ares blog reports that the first part of the program was an introduction to the problem the program faces -- how exactly to accelerate an aircraft from a stop to speeds fast enough to activate a supersonic-combustion ramjet.

The program has some interesting slides and information (PDF) from the famed Lockheed Skunk Works HTV-3X flight demonstration vehicle that was conceived as part of the DARPA Falcon program. One of the slides gives an idea of the size of the HTV-3X vehicle by comparing it to the Have Blue aircraft that ended up being about 60% of the F-117 stealth fighter.

The Lockheed HTV-3X vehicle itself has been superseded by the DARPA Blackswift hypersonic program DailyTech has covered before. The engine that DARPA envisions for the Vulcan project is a CVC and turbojet combination.

According to Ares two methods can be used to achieve this type of engine. In one method a common air inlet would be used for both the turbojet engine that is to carry the aircraft from a stop to Mach 4 and higher speeds and the CVC that would take over at propel the aircraft to Mach 6 and over. This method is called turbine-based combined cycle.

The second method to achieve the engine needed is called an annular approach and would embed a turbojet inside a CVC ramjet engine. The big challenge here is that the turbojet would have to be cocooned when the CVC is active to protect it from the high heat produced inside the Vulcan engine over Mach 2.

Because a turbojet capable of propelling a aircraft over Mach 4 would be large and expensive to develop, DARPA instead wants to take a conventional Mach 2 turbojet and combine it with a CVC to get an engine capable of high Mach speeds, but at much cheaper development costs.

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Better idea
By FITCamaro on 6/26/2008 1:39:49 PM , Rating: 3
Start working on those warp engines. We can already go fast enough on this planet. We need the ability to get to Mars in a few days. Not a few months.

RE: Better idea
By nosfe on 6/26/2008 1:41:31 PM , Rating: 4
and what would we do there? have a picnic with Marvin?

RE: Better idea
By Mitch101 on 6/26/2008 1:47:58 PM , Rating: 5
How about we activate the martian air generators.

RE: Better idea
By ajfink on 6/26/08, Rating: -1
RE: Better idea
By Screwballl on 6/26/2008 2:35:56 PM , Rating: 5
Google this: movie Total Recall

Kuato demands it

RE: Better idea
By gyranthir on 6/26/2008 2:00:24 PM , Rating: 2
Arnold Shwarzenegger called he wants his plot back.

RE: Better idea
By G2cool on 6/26/2008 2:55:50 PM , Rating: 5
Umm... I don't believe Arnold Shwarzenegger has ever been involved with any sort of plot.

RE: Better idea
By RjBass on 6/26/2008 11:35:13 PM , Rating: 2
Thats a 6 right there. ^^^

RE: Better idea
By althaz on 6/27/2008 3:42:39 AM , Rating: 2
Everybody was thinking that, kudos to you for saying it :).

RE: Better idea
By m1ldslide1 on 6/26/2008 1:56:06 PM , Rating: 2
I would guess that we'd start developing a martian military industrial complex.

RE: Better idea
By djc208 on 6/27/2008 2:06:17 PM , Rating: 2
Right, need to start taking over those hostile asteroids, I hear they may be considered weapons of mass destruction.

RE: Better idea
By HighWing on 6/27/2008 4:00:33 PM , Rating: 2
Well for starters we would need a faster way to move supplies there before we could even do anything in the first place. So "getting" there in a reasonable amount of time IS the first big step to any kind of project involving another planet.

RE: Better idea
By kattanna on 6/26/2008 1:57:41 PM , Rating: 5
We can already go fast enough on this planet

i beg to differ. When i can pop over from los angeles to say.. paris for dinner and then be back for bed, then.. we might be going fast enough on this planet.

RE: Better idea
By FITCamaro on 6/26/08, Rating: 0
RE: Better idea
By DukeN on 6/26/2008 2:17:31 PM , Rating: 5
Doesn't Paris live in LA? Shouldn't be too difficult.

RE: Better idea
By Spuke on 6/26/2008 3:09:08 PM , Rating: 2
Doesn't Paris live in LA? Shouldn't be too difficult.
Oh God. Please, just stop. LOL!

RE: Better idea
By HrilL on 6/26/2008 6:22:17 PM , Rating: 1
In that case he would probably want to spend the night there ;)

RE: Better idea
By Gul Westfale on 6/26/2008 7:41:33 PM , Rating: 5
well if a pretentious airhead whose body looks like she spent time in auschwitz and who has a face like the boy from the home alone movies is his thing... but she probably has a helluva lot of STDs.

RE: Better idea
By Reclaimer77 on 6/26/2008 4:59:29 PM , Rating: 3
Yeah it was called the Concorde, and now it doesn't fly anymore.

I guess high speed travel isn't that important to us after all.

RE: Better idea
By EricMartello on 6/26/2008 5:36:51 PM , Rating: 2
The Concorde was loved by those who used it (rich people), and it was shut down primarily due to the noise levels it generated when flying at super-sonic speeds near populated areas. A sonic boom from a large object, like a passenger jet, is "OH SHIT it's the end of the world" loud, with earth-shaking vibrations and all to boot.

RE: Better idea
By FITCamaro on 6/26/2008 7:24:24 PM , Rating: 2
Funny. I slept through plenty in Florida. It might shake the walls a tiny bit, but it by no means freaks anyone out once they're used to it.

RE: Better idea
By Calin on 6/27/2008 2:50:59 AM , Rating: 2
I guess high speed travel isn't that important to us after all.

I should rephrase that:
I guess European high speed travel isn't that important to US after all

RE: Better idea
By Seemonkeyscanfly on 6/26/2008 4:12:56 PM , Rating: 2
well dam, if they have all this figured out what am I going to do with my supplies:
3 gals. mountain dew
1/2 gal 5 hour energy
2 Viagra
1 lbs coffee
6 red bull
7 Mexican jumping beans
4 bottle rockets and one non-safety match.\
1 set of safety goggles
and a superman decal.
Thought for sure I make something with a little kick....

RE: Better idea
By DASQ on 6/27/2008 12:06:48 AM , Rating: 2

RE: Better idea
By James Wood Carter on 6/26/2008 6:03:41 PM , Rating: 3
There is a limitation to speed, humans can't get to mars quick enough isn't because of its engines lacking speed ... engines will never be fast enough. Besides humans can't go at speed of light, this means they wil never be able to reach far end of solar system. what they need is to find ability to fold space.

RE: Better idea
By lagitup on 6/26/2008 8:10:07 PM , Rating: 2
so challenge the common wisdom (we dont understand most of what Einstein said anyway...) and come up with something new that allows for faster than light travel? If you don't get what I'm talking about go read some Sci-Fi.

RE: Better idea
By Indianapolis on 6/26/2008 10:51:13 PM , Rating: 3
So what we really need is spice.

RE: Better idea
By BarkHumbug on 6/27/2008 4:28:07 AM , Rating: 3
Besides humans can't go at speed of light, this means they will never be able to reach far end of solar system. what they need is to find ability to fold space.

Ford Prefect, is that you? :)

RE: Better idea
By JimmyC on 6/30/2008 7:53:12 PM , Rating: 2
Actually I peg him for a Biiavian or possibly Screed, uhhhhhh...

RE: Better idea
By rebturtle on 6/28/2008 2:03:48 AM , Rating: 2
At one point in time, people believed that humans couldn't survive at speeds over about 35MPH (the first trains). There was less science in the fear then, but we tend to find ways of accomplishing things that were previously accepted as "impossible."

RE: Better idea
By James Wood Carter on 6/28/2008 6:02:38 PM , Rating: 2
But it has been proven that nothing can move at the speed of light, as speed increases so do their mass. They can never exceed the speed of light with an engine.

RE: Better idea
By kkwst2 on 6/29/2008 11:14:25 PM , Rating: 2
Probably best to say that Newtonian physics break down as you approach the speed of light. It does seem to be true that more and more (approaching infinite) force is required to accelerate a particle as it approaches the speed of light, but to interpret this as an increase in mass is not really correct.

People talk about relative mass, but I do not believe this is strictly correct. A particle's mass is constant. It's the F=ma part that breaks down at light speed.

Is that fast enough to reach orbit?
By sparkuss on 6/26/2008 1:56:29 PM , Rating: 2
Just wondering, would this lead to powered orbital flight? Not for transport of materials, like the Shuttle, but at least to get personnel up and back to the Space Station?

By sparkuss on 6/26/2008 2:04:32 PM , Rating: 2
The slides kinda say so, but one seems to show that this can't be used beyond the air-breathing envelope, but the other says the utility is space access.

RE: Is that fast enough to reach orbit?
By FITCamaro on 6/26/2008 2:15:55 PM , Rating: 3
Pretty hard to combust air that doesn't exist.

RE: Is that fast enough to reach orbit?
By Mojo the Monkey on 6/26/2008 2:45:59 PM , Rating: 2
No, but it might be the most effective delivery system to take you to the place where air doesnt exist. Once there, like and initial thrust engine, a space propulsion thruster could do the job with MUCH less fuel than it would need if it were air/space dual purpose.

RE: Is that fast enough to reach orbit?
By phazers on 6/27/2008 1:01:20 PM , Rating: 2
Exactly so. IIRC, it was Arthur C. Clarke, the recently-deceased SF author, who first published the idea of a hybrid space-plane (he also first published the idea of telecomm satellites). As I recall, his idea was to mount a rocket-powered plane on the back of an air-breathing lift vehicle which would get above the troposphere where 90% of the atmosphere lies. The end speed of the air-breathing lift vehicle doesn't really matter - it's the air resistance encounted during conventional rocket launch that requires the bulk of the fuel. And by launching west-to-east near the equator, you already gain ~1000 mph due to Earth's rotation. Also, you save the weight of the oxidizer and added propulsion system components such as tanks, plumbing and pumps, needed for a rocket engine.

Unfortunately Werner Von Braun, who favored giant rockets, left his legacy at NASA which is likely why the space shuttle is launched using a huge external fuel tank and SRBs. The entire system has to be strong (& heavy) enough to stand up to the acceleration and pressure encountered at the 'max Q' or transition to supersonic flight.

In contrast, the Bell X1 and later X15 rocketplanes were launched from underneath the wings of bomber aircraft. So what I would imagine for the next-gen shuttle Orion lift vehicle would be something like an upscaled B1 with additional (sc)ramjet engines to kick the final launch velocity up to mach 4 or beyond.

By US56 on 6/30/2008 3:03:18 AM , Rating: 2
In fact, Von Braun was in favor of using a "flyback booster" for the Shuttle. One favored proposal was to use the flight controls, wings, engines, nacelles, and other key components of the Lockheed C-5 and build what would have effectively been a huge flat-bed flying truck. The use of the 747 to launch the Shuttle Enterprise for flight testing evolved from the concept. The design of the tail modification to the 747 Shuttle carrier was borrowed from the twin vertical stabilizer configuration of the proposed flyback booster. The original design of the Shuttle itself was about the same overall size and weight and had the same general apearance as the current Shuttle but the main engine liquid propellant tanks were internal. No throwaway external tank. The SRB's were to have been much smaller so a segmented design would not have been necessary. The SRB's would have been mounted something like the launch configuration of the X-15 for the last series of high-speed tests. The SRB's could have been made recoverable so the entire system would have been reusable. The Shuttle payload bay would have been less than half the size of the current Shuttle, only large enough for one typical communications satellite of the day. The name Shuttle came from the main purpose of the system which would have been to shuttle space station crews or deep space manned mission crews to and from orbit. It also would have performed on orbit maintenance and repair such as has been done for Hubble as well as missions such as refueling KH series satellites which was the original mission of the X-20, conceptually the forerunner to the Shuttle system for which the USAF did not receive funding. The payback from that activity in itself might have paid for the whole Shuttle program since the KH's even then cost $1B or so to build and get into orbit and have a relatively short service life if heavily used without refueling. A separate heavy launch system, most likely the Saturn IB would have been funded. The reason that Shuttle system was not built was Congress did not want to fund the flyback boosters projected to cost $100M for two examples nor the separate heavy launcher at a time before Project Apollo had met its goal and during one of the costliest years of the Vietnam War. Von Braun was so upset about the decision he set his retirement date as a result and never had the same degree of influence within NASA. When I first saw the artist's conception of the current Shuttle launch configuration I thought it was about the most awkward looking vehicle imaginable. The current idiom is, "What were they thinking?" The large, segmented SRB's and foam insulated external tank turned out to be the Achille's Heel of the Shuttle program. Had the original Shuttle system been built, it could have undergone a more evolutionaary development since the major components would not have been so interdependent. Conceivably, we could now be flying a second or third generation Shuttle using the original flyback boosters which should have had an indefinite service life like a B-52H or KC-135R.

RE: Is that fast enough to reach orbit?
By RabidDog on 6/26/2008 2:27:05 PM , Rating: 2
Nope. At Mach 4, you are still about 10,000mph short to reaching orbit. To orbit you must go about 17,500mph.

RE: Is that fast enough to reach orbit?
By Mojo the Monkey on 6/26/2008 2:52:01 PM , Rating: 2
well wouldn't it depend on the specific orbit speed of the space station vs the atmospheric entry point of the second ship? Is the space station geo-sync'd? -just curious

By Curelom on 6/26/2008 3:29:05 PM , Rating: 2
It would depend on the speed of the space station, which is orbiting, thus going at or faster than the 17,500 specified in the previous post.
The space station is not ge-sync'd. Occasionally you can see it fly across the sky.

By masher2 on 6/26/2008 5:04:17 PM , Rating: 3
> "At Mach 4, you are still about 10,000mph short to reaching orbit"

Mach 4 is the minimum ignition speed for the ramjet, not the maximum velocity. We've had test Scramjets that broke Mach 30, IIRC.

By James Wood Carter on 6/26/2008 6:09:10 PM , Rating: 2
Nope these engines are jet like engines ... they absolutely require compressed air.

Get your facts straight
By Mclendo06 on 6/26/2008 3:37:36 PM , Rating: 3
The second method to achieve the engine needed is called an annular approach and would embed a turbojet inside a CVC ramjet engine.

Little problem here:

A there is no such thing as a CVC ramjet. By definition a ramjet works on the Brayton cycle, which is constant pressure combustion, not constant volume combustion. A CVC engine would work on the Humphrey cycle, but these are generally (by necessity, to retain the constant volume during combustion) pulse combustion engines which are still in development AFAIK. Here's how it works:

In a ramjet, the pressure of the air remains about the same as it is combusted, but its volume increases which is how you get power out of the cycle.

In a CVC engine, the volume in the combustion chamber is held constant (by sealing it off somehow, which is why there is a "pulse" as the chamber is sealed and unsealed) and the pressure increases as the air is "detonated" instead of just burned. This results in a larger amount of energy being obtained from the cycle which is why DARPA is interested in this sort of an engine.

Aurora Bomber, here we come...

RE: Get your facts straight
By Master Kenobi on 6/26/2008 6:05:43 PM , Rating: 3
Aurora in flight!

RE: Get your facts straight
By phaxmohdem on 6/26/2008 8:39:20 PM , Rating: 2
Best not send that towards my Strategy Center, or I'll send my Burton over to knife ur d00ds :)

RE: Get your facts straight
By Cullinaire on 6/27/2008 1:32:04 AM , Rating: 2
Not if the pathfinders have anything to say about that.

RE: Get your facts straight
By ikkeman2 on 6/27/2008 2:52:16 AM , Rating: 2
V1 (WWII) was powered by PD.

By introducing a shut-off plate in the front section of your (SC)ram-jet, you can use it as a CVC. A ram-jet is nothing more than a shaped tube with a burner in it. As you approach the speed that the RAM starts to work, you can just keep the plate in the open position.

Combined cycle here we come

RE: Get your facts straight
By Mclendo06 on 6/27/2008 6:55:49 PM , Rating: 2
True, it is possible to create an engine that is capable of behaving two different ways (the J58s on the SR-71 come to mind). I was just pointing out that the way the article is worded, it comes across as a ramjet that utilizes constant volume combustion, which is not currently conceivable. Once you start CVC, you aren't operating a ramjet anymore. You can have one or the other, but not both at the same time.

There are some interesting Wiki articles about Pulse Jet Engines, Ramjets, and the V1 (which used a PD engine, not a ramjet). Pretty straight forward and worth a read, and accurate as far as my aerospace engineering BS degree can tell.

What no Pulse Detonation Engines
By mkruer on 6/27/2008 2:45:38 AM , Rating: 2
Interesting that this is coming out now, when they could have built the same type of multi stage engine back 20yrs ago. Perhaps is because there was a successful demonstration of PDE powered flight in January of this year and has the potential to replace all the existing designs.

By Solandri on 6/27/2008 1:09:20 PM , Rating: 2
The first public demonstration was this year. People have been seeing contrails from some sort of PDE powered aircraft near USAF bases since the 1990s. At least one sighting was in the UK, which would seem to suggest that whatever aircraft is generating them is beyond the R&D phase and is actually in service.

RE: What no Pulse Detonation Engines
By US56 on 7/1/2008 5:22:20 AM , Rating: 2
After looking through the slides referenced in the article it seems as if the Vulcan may primarily be a jobs program for government employees and contractors. If there is/was no Aurora then there hasn't been any significant improvement on the 50 year old J58 design. What have they been doing all those years and why the big deal now? If Aurora exists then the Vulcan and some of the other programs cited may be disinformation or covers for classified advanced propulsion technology programs.

It should be possible to do something much more sophisticated with current technology than siamese a conventional turbojet with a CVC or ramjet engine. Above Mach 2 the turbojet would be dead weight. That wastes a lot of fuel when efficiency seems to be a major goal and works against using that approach for a low-cost orbital launch system. Based on some personal experience, it should be possible to build a single multi-mode engine which can transition smoothly from pulse to pulse detonation or continuous detonation mode or alternately pulse to ramjet operation. It would rely heavily on the kind of digital processing capability available now which wasn't even imagined when the J58 was designed in order to automate fuel management, inlet and exhaust nozzle variable geometries, and possibly combustion aids specific to each operational mode. That would seem to be the kind of technology investment which would be a worthy successor to the J58.

By callmeroy on 6/27/2008 9:36:58 AM , Rating: 1
I can't not post this anymore it bugs me too much. I can't stand when layman (myself included) on a subject in an Internet forum always have such snide comments to say against some ongoing advancement, recent research or new discovery.

While there is always this small 1% (or less) chance that the person posting such remarks can really be highly knowledgable, with an impressive history of accolades and credentials in the given field being discussed - its highly unlikely on most "common folk" Internet forums.

People that read some 50 page PDF story on a subject, or watch a few sci-fi films come to a forum story about going to mars, the moon or jet engine technology and they are instant experts slamming the technology, we should have done this already, Nasa is stupid...etc. etc.

I mean come on guys...who are you fooling?

By InsaneGain on 6/27/2008 12:03:32 PM , Rating: 2
Haha you're right of course, but let us have our fun.

"People Don't Respect Confidentiality in This Industry" -- Sony Computer Entertainment of America President and CEO Jack Tretton
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