The Minotaur I, or just Minotaur is an American expendable launch system derived from the Minuteman II missile.^[1] It is used to launch small satellites for the US Government, and is a member of the Minotaur family of rockets produced by Orbital Sciences Corporation (now Northrop Grumman).^[2]

The Minotaur I is the follow-on to the Orbital Sciences' Taurus (later re-named the "Minotaur-C"^[3]) launch vehicle, combining the original Taurus's booster stage with a second stage from a Minuteman missile.^[4]

Minotaur I rockets consist of the M55A1 first stage and SR19 second stage of a decommissioned Minuteman missile.^[1] The Orion 50XL and Orion 38, from the Pegasus rocket, are used as third and fourth stages. A HAPS (Hydrazine Auxiliary Propulsion System) upper stage can also be flown if greater precision is needed, or the rocket needs to be able to manoeuvre to deploy multiple payloads.^[5] It can place up to 580 kilograms (1,280 lb) of payload into a 185-kilometer (115 mi) low Earth orbit at 28.5 degrees of inclination.^[1]

The Minotaur I is 69 feet tall and 5 feet wide.^[6]

Initially Minotaur I launches are conducted from Space Launch Complex 8 at the Vandenberg Air Force Base. Starting with the launch of TacSat-2 in December 2006, launches have also been conducted from Pad 0B at the Mid-Atlantic Regional Spaceport on Wallops Island.^[5]

There have been twelve launches of the Minotaur I, all successful.

• Comparison of orbital launchers families
• Comparison of orbital launch systems