Pegasus II (rocket)

Pegasus II was an air-launched orbital rocket under development in 2012–2015 by Orbital Sciences Corporation for use by Stratolaunch Systems.

The vehicle was to be carried by the Stratolaunch aircraft, developed by Scaled Composites, which is the world's largest aircraft by wingspan. Originally designed with solid lower stages and a cryogenic upper stage, the Pegasus II design was subsequently modified in 2014 to exclusively use solid rocket motors.

However, the failure of the design to meet the economic cost and revenue targets led to the design being "shelved" by Stratolaunch in May 2015. At the time, Stratolaunch "reopened the design plan and [was] evaluating over 70 different launch vehicle variants" for use on the Scaled Composites Stratolaunch.

Stratolaunch Systems announced plans for its air-launched orbital rocket system in December 2011. Funding would be provided by Vulcan, an investment company created and chaired by Microsoft co-founder Paul G. Allen. The launch system would consist of three primary components: a carrier aircraft, contracted to Scaled Composites; a launch vehicle, originally contracted to SpaceX as a derivative of the Falcon 9—later contracted to Orbital Sciences as the Pegasus II; and a mating and integration system to enable the aircraft to safely interface with, carry, and release the booster, contracted to Dynetics.

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