Mach 3+ Powerplant.


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28 January 2007
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I've been reading this forum for a couple weeks now, and I must say I've really enjoyed all of it. And now I was wondering if some people smarter then me might be able to answer a few questions. I've been toying with a story of mine on and off for years, and when I hope to introduce a 'scratch design' aircraft, I try to make the design as realistic as possible. Recently I began considering a Mach 4+ Reconnaissance and/or Strike Platform. Somewhat of a cross between a SR-71 replacement and Lockheeds Mach 4 future strike platform they recentled showed a few images on. I understand quite a bit about Aircraft design and such, but I'm curious as to what sort of proplusion system a aircraft of that class would use.

I've been over the engine choices for concepts and aircraft built during the Cold War ((IE: XB-70, SR-71, F-108 etc.)) but I've been able to find little information related to present technology, I'm sure a lot of its classifed but there should be enough basic knowledge to help get me where I want to be. I've seen the YJ102R Turbjet jet designed by the Rolls-Royce Liberty works, which is rather fasinating.. yet i've only found two articles on it sadly. I know that turbofans were problematic at higher mach numbers due to the high temperatures but I read somewhere that with more advanced materials it'd be possible to build turbofan engines that'd be able to cope with the stress. So, what would be the best option? A modern turbo-ramjet design? Something like the YJ102R? Or maybe even specially built turbofan engines? I'm really curious as to what something like Lockeeds proposed.. might feature as far as a powerplant, again I know there is little hard information but speculation is always appreciated.

I figured after researching for weeks, months I'd find the answer I was looking for, Or I could run it by some of the people here. If you can help, I'd appreciate it, if not? I still apprecaite it.

Thanks Kindly.
I'm fascinated by Reusable Launch Vehicles and their engines. I've made a website on the subject (my error was I wrote in French! :'()

To cruise between below mach 3, you have a wide variety of engines... all fall on the TBCC category

TBCC mean "Turbin based combined cycle". These engines are all based on air breathing engine and fans.
RBCCs are based of Rocket...

No way of using a turbofan at such speed : the fan just can't resist to the high speed airflow...
First solution is improving the J-58. I vaguely remember that NASA had a program for a mach 4+ engine of this kind (sadly I didn't downloaded the article at the time).
you have to mask the fan at high speed, and use the afterbuner section as a ramjet. Air enter the engine by special intakes, avoiding the fan (bypass).

There's another engine, the supercharged ejector ramjet or SERJ. Marquardt studied the engine in the late 60's for the X-15

In brief, TBCC include all combinations between turbofan and ramjet...

Hope this help !!!
Actually, that helps confirm what I already had in mind. lol I know that some believed the J-58 was capable of Mach 4 but the A-12 Airframe was the limiting factor. Those links you provided are truly fasinating though. I do appreciate it. :)

Now I can plot a bit more! ;D
you also might try a guy who goes by the name "turboshaft" on the Key Publishing forum. I'm fairly certain he's actually involved in the YJ102 program in one way or another and he may be able to give you some help. (Obviously he couldn't tell you EVERYTHING but I'm sure he knows what is/isn't public I'd think ;) )
I remember that the cancelled Blackswift was to use a combo turbofan ramjet powerplant, with the turbofan operating at speeds less than Mach 3, and the ramjet taking over operations beyond Mach 3.

The X-51 used a Mach 3+ scramjet, and therefore, only combined cycle jet and scramjets will work beyond Mach 3, as well as turboramjets.
I'll have to check but I recall an aircraft that used a turbofan to get up to speed and which had a machine closed door to divert the air intake to a ramjet, leaving the turbofan idle. It is possible.
XF-103 was designed to use an Americanized Olympus turbojet, with a ramjet first supplementing, at high speed completely taking over propulsion. Ramps would close the turbojet intake.

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