Basically, Mirage G is a swing wing version of the Mirage F2.
In the 1960s, the variable-sweep wing was one of the most attractive designs in military aviation. In 1964, the French defense requested the development of such an aircraft for use on land and on aircraft carriers. Dassault received an order for a prototype. The result was a variable sweep prototype was made known as the original Mirage G with 2 seats. Despite putting up several records over the time including the highest speed ever for an aircraft in western europe with Mach 2.34 at 42,000ft which still stood in 1995 it was too expensive and therefore never fully adapted for the airforce.
Basically, Mirage G is a swing wing version of the Mirage F2. The wings were swept at 22 degrees when fully forward and 70 degrees when fully aft and featured full-span double-slotted trailing edge flaps and two-position leading edge flaps. Initial version powered by a single Pratt & Whitney engine in its fuselage with the propulsion unit aspirated through a split intake duct arrangement, this made up of two semi-circle openings along the sides of the cockpit walls.
Flight trials were successful, but production orders did not follow. The Mirage G program was cancelled in 1968. Flying with the Mirage G continued however until 13 January 1971 when the sole prototype was lost in an accident. The French preferred to develop an aircraft with a French engine, rather than a U.S. engine.
The type was further developed into the twin-engine Mirage G4 and G8 variants as a multi-role jet fighter capable of both interception and nuclear strike missions. These aircraft were intended to be powered by two SNECMA Atar 9K50 afterburning turbojet engines, with 49 kN dry thrust each, and 70 kN with afterburner. While the aircraft were under construction the requirements changed and the French military requested that the design be converted into a dedicated interceptor, the Mirage G8.
The Mirage G8 had a length of 18.8 m, a wingspan of 15.4 m, a height of 5.35 m, an empty weight of 14.74 tons, and a maximum take-off weight of 23.8 tons. The Mirage G8 could reach a top speed of Mach 2.34, a range of 3,850 km, and a service ceiling of 18,500 m.
The G8 variants were equipped with Thomson-CSF radar and a low-altitude navigational-attack system based on that used in the SEPECAT Jaguar and Dassault Milan. As no funding was included for the Mirage G8 in the 1971-1976 French defence budget the aircraft did not enter production. The two Mirage G8-01 and 02 prototypes had their first flights in 1971 and 1972, respectively, but this initiative also failed and the Mirage G series disappeared from French aviation history.