Mixed, but no match

In the early 1950s, the biggest military threat to Western nations seemed to be a few Soviet bombers dropping atomic bombs from high altitude on major cities. For countries in Europe close to the Soviet Union, this meant a requirement for a fast climbing, high speed interceptor to shoot down the bombers before they dropped their weapon. Range, in the form of fuel weight, was sacrificed for this high performance, and these aircraft were known as point defense inceptors.

At this time, ordinary turbojet engines did not provide enough power for such performance, and mixed powered inceptors seemed to be the only way to get the required speed and rate of climb.

There were two approaches to mixed power. One, especially common in the United Kingdom, was to combine a turbojet engine with a rocket engine – the rocket being used for takeoff, climb and acceleration to the target to supplement the turbojet. Another approach was to combine the turbojet with a ram jet, an approach favored by the French who had been experimenting with ram jets since 1949 with René Leduc’s Leduc 021 and 022 (see the June 27, 2008, Kaiserslautern American, “A French Revolution”).

While the Leduc ramjet’s high drag fuselage kept the aircraft’s performance low, the ramjet engine showed considerable promise for high speed flight, and the French state-owned aircraft manufacturer Nord Aviation began to work on a turbojet-ramjet combination for a French air force fighter. The turbojet was necessary since a ramjet does not have a compressor and cannot produce thrust at zero airspeed. It must use the turbojet engine’s forward motion to compress incoming air, and ramjets only become really effective at about 600 mph. This was, of course, ideal for a high altitude interceptor.

Nord used a delta wing configuration from its Nord 1402 research aircraft, the first European aircraft to exceed the speed of sound in level flight, and produced an aircraft that could be converted easily into an interceptor – the Nord 1500 Griffon.
The Griffon was a fairly conventional delta with 60 degree of sweepback on the leading edge, elevons for control in pitch and roll and a swept vertical tail. It did, however, have several unusual features that made it quite radical looking: fixed canard foreplanes just below the cockpit and a huge engine mounted under the cockpit.

The Griffon 01 first flew on Sept. 20, 1955, but was powered only by a turbojet while Nord worked on a combination turbojet/ramjet engine. However, even with just an afterburning turbojet, the Griffin 01 reached 1.17 Mach in level flight, more than enough to power the ramjet.

At the completion of initial airframe testing, the Griffin was modified to accept the combined Nord turbojet/ramjet with a 5,000 pounds of thrust Atar 101E3 turbojet located just forward of the ramjet burners. The aircraft, redesignated N 1500-02 Griffon II, first flew on Jan. 23, 1957, and quickly showed a high turn of speed. It set a new international record of 1,643 kph over a closed 100 kilometer course, achieved Mach 1.85 during climb and reached a top speed of Mach 2.19 (about 1,450 mph) in 1958 with only 80 percent power.

While the high speeds proved the basic soundness of both the airframe and turbojet/ramjet combination, there were problems. The very high speed caused a major increase in airframe heating and since the aircraft was made of conventional materials, not material such as titanium, its speed was limited to a little over Mach 2, though the engine could have pushed it much faster.

Additionally, the ramjet had much the same problem as a rocket engine, an inability to be controlled by a throttle to increase or decrease thrust incrementally – they were “all or nothing” propulsion systems. While Nord tried to solve the problem, surface to air missiles (SAMs) began to become part of air defense networks. SAMs ended the era of the high flying bomber and reduced the need for point defense inceptors.

Meanwhile, turbojet engines were improving and Dassault Aviation was working on a fighter with a single afterburning turbojet with about 14,000 pounds of thrust and a small rocket motor in the tail. The rocket motor was eliminated when it showed a disturbing tendency to set the tail on fire and, at the insistence of Dassault’s first overseas customer, the Israeli Air Force, replaced with two 30 millimeter cannon in the nose, and the fighter became the immortal Dassault Mirage III.

The Nord Griffin 02 ended its test program at the end of 1960 and is now on display in the French Air and Space Museum at Le Bourget airfield near Paris. The museum is a simple Metro/bus ride from Paris and is highly recommended.


(For questions or comments, contact Dr. Michel at marshall.michel@ramstein.af.mil.)