

Antares 2 (X-259) was an American solid-fueled rocket stage built by Hercules/ABL/Thiokol that used a cast, aluminized, double-base solid propellant containing nitrocellulose. It was used from the mid-1960s to 1995, in the Scout and Strypi family of rockets, and on the Project FIRE Velocity Packages, and was used about 96 times.
Basic details of the X-259 stage:
There were various variants: