>>4047
The first prototype of the Mystere-Delta, without afterburning engine or rocket motor and with an unusually large vertical tailfin[1], flew on 25 June 1955. After some redesign, reduction of the tailfin to more rational size, installation of afterburners and rocket motor, and renaming to Mirage I, in late 1955, the prototype attained Mach 1.3 in level flight without rocket assist, and Mach 1.6 with the rocket.
However, the small size of the Mirage I restricted its armament to a single air-to-air missile, and even before this time it had been prudently decided the aircraft was simply too tiny to carry a useful warload. After trials, the Mirage I prototype was eventually scrapped.
Dassault then considered a somewhat bigger version, the Mirage II, with a pair of Turbomeca Gabizo turbojets, but no aircraft of this configuration was ever built. The Mirage II was bypassed for a much more ambitious design that was 30% heavier than the Mirage I and was powered by the new SNECMA Atar afterburning turbojet with thrust of 43.2 kN (9,700 lbf). The Atar was an axial flow turbojet, derived from the German World War II BMW 003 design.
The new fighter design was named the Mirage III. It incorporated the new area ruling concept, where changes to the cross section of an aircraft were made as gradual as possible, resulting in the famous "wasp waist" configuration of many supersonic fighters. Like the Mirage I, the Mirage III had provision for a SEPR rocket engine.
The prototype Mirage III flew on 17 November 1956, and attained a speed of Mach 1.52 on its seventh flight. The prototype was then fitted with the SEPR rocket engine and with manually-operated intake half-cone shock diffusers, known as souris ("mice"), which were moved forward as speed increased to reduce inlet turbulence. The Mirage III attained a speed of Mach 1.8 in September 1957.