Graphite-Epoxy Motor - Variants

Variants

Alliant Techsystems manufactures GEMs for Boeing's Delta II, III, and IV launch vehicles in the following sizes:

• GEM-40, 40-inch-diameter (1,000 mm) solid motor used on Delta II beginning in 1990. Delta II vehicles can use three, four, or nine GEM-40s. A special version of the GEM-40, the GEM-40VN (Vectorable Nozzle), is used as the first stage in the United States' Missile Defense System interceptor vehicle, for destroying nuclear warheads.
• GEM-46 (GEM-LDXL), lengthened 46-inch-diameter (1,200 mm) solid motor developed for Delta III. This solid motor variant also includes Thrust Vector Control (TVC), which helps to steer the vehicle by changing (or vectoring) the direction of the thrust. With the discontinuation of the Delta III, the GEM-46 motors (without TVC) are also used on Delta II vehicles to boost payload capacity further. A Delta II with GEM-46 motors is considered a "Heavy" variant. Both Delta III and Delta II-Heavy use nine GEM-46s.
• GEM-60, 60-inch-diameter (1,500 mm) solid motor used on the Delta IV family of launch vehicles. These motors are available with and without TVC. A Delta IV can have two or four GEM-60s, and a Delta IV with these motors is classified as a Delta IV Medium+ launch vehicle.

Aerojet also manufactures strap-on solid rocket boosters for the Atlas V, although they do not use the "GEM" name. They refer to them simply as the Atlas V's Solid Rocket Boosters.