Solid state propulsion: a ramjet aircraft WI

Blair152

Banned
The theory behind the ramjet dates from the early years of powered flight, when French engineer René Lorin first thought of applying the compression-combustion-expansion thermodynamic cycle to aircraft propulsion in 1908. The problem was that such a jet engine required a minimum speed to kick in that was unattainable at the time, and the idea was shelved until its rediscovery by another Frenchman, René Leduc, in 1935.

Ramjet_operation.png


Leduc was a firm believer in the potential of ramjet propulsion for fighter aircraft, and proceeded to develop prototypes. The first one, the Leduc 0.10, finally flew in 1949. Further prototypes were assembled in the following years, the 0.16, 0.21 and finally the 0.22, which used a dual propulsion system--a classic turbojet engine to reach the required speed threshold, and the ramjet itself. Some 30 test flights took place, but in 1956 the cash-strapped French government stopped funding the project.

But what if the ramjet concept had generated more interest both in France and abroad? Could it have successfully competed against the classic turbojet concept for fighter aircraft? Would it have found a niche, perhaps for interceptors?

Here's what the 0.22 looked like. Note the cockpit located in the inner wedge.

leduc_022.jpg


leduc_022_1.jpg
The ramjet's been around since 1910. It's also a very hot engine. A ramjet, or scramjet, engine, was tested by an SR-71 Blackbird sometime
in the 1990s, or 2000s.
 
Republic XF-103, a competitor in the US Air Force "1954 interceptor" competition. Forward visibility was to be achieved by means of a periscope, take-off and flight up to Mach 2 was to be under turbojet power, after that internal ramps were to be closed that ducted the air to a ramjet. Speeds of Mach 3 and beyond were envisioned. The plane was to be built largely of Titanium. Problems with the engine were so great that development of the plane did not progress much beyond the mock-up stage and the Convair F-102 Delta Dagger and Convair F-106 Delta Dart were built for the interceptor role for which the XF-103 Thunderwarrior was intended.

Ironically, it was not the engine (which was a version of the Bristol Olympus engine, produced under licence) that finished off the XF-103, it was problems with fabricating the titanium airframe, coupled with the fuselage redesign to accomodate the larger AGS-18 fire control system, (which was also considered for the cancelled F-108 Rapier interceptor, as well as the A-12 interceptor version of the SR-71 Blackbird) which replaced the original MA-1 design then used by the Delta Dart ...
At one point, 4 construction techniques were considered for the XF-103, using different materials for the airframe, such as stainless steel, a stainless steel/titanium composite structure consisting of a titanium alloy "skin" covering a stainless steel inner structure, the all titanium airframe eventually chosen, and a reference all aluminium airframe...
The reference aluminium structure was the first to go, as it was the heaviest, & would have restricted the F-103 to a maximum speed of Mach 2.75, followed by the all stainless steel airframe (which was ironically 100 Lbs lighter than the aluminium airframe), & lastly the steel/titanium composite airframe..
 
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It should be remembered that the J-58 engines used in the A-12/YF-12/SR-71 were variable-cycle engines like those proposed for the XF-103. The J-58 was originally designed by Pratt and Whitney for the aborted Lockheed CL-400 Suntan (later Gusto, then Oxcart, which then went on to become the A-12) hydrogen-fueled reconnaissance aircraft.

Ramjet engines, as has been said earlier in the thread, are hideously inefficient. They are, however, simple and cheap which was why they were (and are) used for missiles (like the BOMARC, which used two Marquardt ramjets as cruise propulsion).

Just about every fighter manufacturer looked at them back in the 40s and 50s but what you get is more than offset by what you give up. Unless it's for a one-way trip, you have to be able to land the thing, and having a high-performance aircraft be a glider on final is not something that appealed to pilots and planners alike. Sure they were fast but to have something approaching flexibility you had to have a turbojet for takeoff and landing anyway; why not just ditch the ramjets altogether and go for a bigger turbojet? This was the same thinking that killed off rocket-boost for interceptors -- with the exception of the Mirage III which hardly ever used it operationally.
 

Blair152

Banned
The theory behind the ramjet dates from the early years of powered flight, when French engineer René Lorin first thought of applying the compression-combustion-expansion thermodynamic cycle to aircraft propulsion in 1908. The problem was that such a jet engine required a minimum speed to kick in that was unattainable at the time, and the idea was shelved until its rediscovery by another Frenchman, René Leduc, in 1935.

Ramjet_operation.png


Leduc was a firm believer in the potential of ramjet propulsion for fighter aircraft, and proceeded to develop prototypes. The first one, the Leduc 0.10, finally flew in 1949. Further prototypes were assembled in the following years, the 0.16, 0.21 and finally the 0.22, which used a dual propulsion system--a classic turbojet engine to reach the required speed threshold, and the ramjet itself. Some 30 test flights took place, but in 1956 the cash-strapped French government stopped funding the project.

But what if the ramjet concept had generated more interest both in France and abroad? Could it have successfully competed against the classic turbojet concept for fighter aircraft? Would it have found a niche, perhaps for interceptors?

Here's what the 0.22 looked like. Note the cockpit located in the inner wedge.

leduc_022.jpg


leduc_022_1.jpg
I was considering this for an airplane in an alternate history novel of my own that I'm writing. I gave it up because John G. Cramer, the Alternate View columnist of Analog, said that ramjets tended to burn a little too hot.
 
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