Pegasus II (rocket)

Pegasus II, also known as Thunderbolt, was an air-launched orbital rocket under development in 2012–2015 by Orbital Sciences Corporation for use by Stratolaunch Systems.[1]

The vehicle was to be carried by the Stratolaunch aircraft, developed by Scaled Composites, which is the world's largest aircraft by wingspan.[2][1] 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.[3]

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.[4] In the end, no good economic case ever closed and Stratolaunch halted all work on their own family of air-launched rockets in January 2019.

History

Stratolaunch Systems announced plans for its air-launched orbital rocket system in December 2011.[5] Funding would be provided by Vulcan, an investment company created and chaired by Microsoft co-founder Paul G. Allen.[6] 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[7]—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.[8]

Design

The Stratolaunch carrier aircraft was planned to be able to take-off from airfields with a runway at least 3700 m in length and travel up to 2200 km before releasing the Pegasus II at an altitude of 9100 m.[5] The system will be the largest aircraft ever built in terms of wingspan; with the first test flight of the carrier aircraft originally expected in 2015 from Scaled Composites' facilities in Mojave, California,[15] and the first test launch of the rocket not expected before 2016.[16]

The first two stages of the Pegasus II were to have had the same outside diameter as the Space Shuttle Solid Rocket Booster, but intended to be constructed using much lighter carbon-composite cases and contain a more energetic propellant mix.[1] To provide guidance while in the atmosphere, the first stage was to have two wings and a V-tail, both with control surfaces. Both the first and second stage solid rocket motors intended to use a thrust vector control (TVC) system for attitude control in the thin upper atmosphere.

See also

• Pegasus (rocket)

External links

• Revised Video – Animation of Stratolaunch with Orbital Pegasus II launch vehicle, June 2013.