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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The Lockheed HTV-3X vehicle itself has been superseded by the DARPA Blackswift hypersonic program DailyTech has covered before.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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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.


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