The Algol family of solid-fuel rocket stages and boosters built by Aerojet (now Aerojet Rocketdyne) and used on a variety of launch vehicles.It was developed by Aerojet from the earlier Jupiter Senior and the Navy Polaris programs.Upgrades to the Algol motor occurred from 1960 till the retirement of the Scout launch vehicle in 1994. They were initially developed as the first-stage motor of the Scout rocket. The design was based on the UGM-27 Polaris, a sea-to-air missile developed for the United States Navy at the Jet Propulsion Laboratory.