Pegasus II (rocket)

Pegasus II is an air-launched orbital rocket being developed for Stratolaunch Systems by Orbital Sciences Corporation.[1] The vehicle will be carried by the Stratolaunch aircraft, developed by Scaled Composites, which will be the world's largest aircraft by wingspan when complete.[2][1] Originally designed with solid lower stages and a cryogenic upper stage, Pegasus II will now use solid rocket motors exclusively.[3]

History

Stratolaunch Systems announced plans for its air-launched orbital rocket system in December 2011.[4] Funding would be provided by Vulcan, an investment company created and chaired by Microsoft co-founder Paul G. Allen.[5] 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[6]—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.[7]

The Falcon 9 Air was to be powered by four Merlin 1D engines in its first stage,[8] and would deliver up to 6,100 kg (13,400 pounds) into low Earth orbit (LEO) or 2,300 kg (5,100 pounds) to geosynchronous transfer orbit (GTO).[9] As development progressed, the scope of alterations to the Falcon 9, including significant structural modifications to the first stage for aerodynamic surfaces,[10] and the disruption to manufacturing processes these modifications would have required,[9] led Stratolaunch and SpaceX to part ways and cease development of the Falcon 9 Air.

Stratolaunch then engaged Orbital Sciences Corporation (Orbital) to develop the Pegasus II.[10] Orbital received a study contract in November 2012, and a full vehicle development contract in 2013. The rocket consists of two solid stages produced by Alliant Techsystems (ATK)[11] and, as originally designed, a cryogenic third stage. In 2014, the cryogenic stage was replaced by two additional solid rocket stages.[3]

In April 2014, Orbital Sciences announced plans to merge with ATK to create Orbital ATK Inc.[12]

In April 2015, Stratolaunch announced that they are considering options for multiple launch vehicle options to be used with Stratolaunch over a range of satellite sizes, and that some development work on the Orbital launch vehicle has been slowed down.[13]

Design

The Stratolaunch carrier aircraft will be able to take-off from airfields with a runway at least 3,700 m (12,100 feet) in length and will be able to travel up to 2,200 km (1,200 nautical miles) before releasing the Pegasus II at an altitude of 9,100 m (30,000 feet).[4] The system will be the largest aircraft ever built in terms of wingspan; with the first test flight of the carrier aircraft expected in 2015 from Scaled Composites' facilities in Mojave, California,[14] and the first test launch of the rocket not expected before 2016.[15]

The first two stages of the Pegasus II will have the same outside diameter as the Space Shuttle Solid Rocket Booster, but will 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 will be equipped with two wings and a V-tail, both with control surfaces. Additionally, both the first and second stage motors will use a thrust vector control (TVC) system for attitude control in the thin upper atmosphere.[1]

The third stage was originally intended to be a restartable cryogenic stage burning liquid hydrogen and liquid oxygen. Missions to LEO would have featured a 5 m (16 ft)-diameter payload fairing and two Aerojet Rocketdyne RL10 engines, with a payload capacity of 6,120 kg (13,500 lb).[1] GTO missions would have used a 4 m (13 ft) meter fairing and a single RL10 engine, with a payload capacity of approximately 2,000 kilograms (4,500 lb).[1] This vehicle would have had a gross weight of about 211,000 kg (465,000 pounds).[2]

Development of the cryogenic third stage was halted in 2014, and ATK was asked to evaluate a replacement consisting of two solid stages.[16] In November of that year, Stratolaunch confirmed that Pegasus II would be an all-solid vehicle.[3]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Bergin, Chris (2013-05-25). "Stratolaunch and Orbital – The Height of Air Launch". NASA SpaceFlight. Retrieved 2013-05-24.
  2. ↑ 2.0 2.1 Norris, Guy (2013-11-04). "Stratolaunch quietly making progress". Aviation Week. Retrieved 2013-10-04.
  3. ↑ 3.0 3.1 3.2 "Stratolaunch Drops Liquid Stage From Rocket System". aerosmart.com.
  4. ↑ 4.0 4.1 Bergin, Chris (2011-12-13). "Stratolaunch introduce Rutan designed air-launched system for Falcon rockets". NASAspaceflightnow.com. Archived from the original on 2011-12-14. Retrieved 2011-12-14.
  5. ↑ Paur, Jason (2011-12-13). "Microsoft Billionaire Paul Allen Launches New Space Venture". Wired (New York). Archived from the original on 2011-12-14. Retrieved 2011-11-14.
  6. ↑ "The Stratolaunch Team". Stratolaunch Systems. 2011. Archived from the original on 2012-02-17. Retrieved 2011-12-20. ... integrate the SpaceX Falcon 9 Air with the Scaled Composites mothership.
  7. ↑ "Stratolaunch Systems: A Paul G. Allen Project" (PDF). Stratolaunch.com. Archived from the original (PDF) on February 21, 2013.
  8. ↑ Belfiore, Michael (2012-01-05). "Stratolaunch: world’s biggest airplane to launch spaceships". Retrieved 2014-11-19. The Falcon 4 will be powered by 4 SpaceX Merlin IB engines.*corrected by author to Merlin 1D in comments
  9. ↑ 9.0 9.1 "Orbital Sciences Replaces SpaceX on Stratolaunch Project". Space.com. Retrieved November 22, 2014.
  10. ↑ 10.0 10.1 Rosenberg, Zach (2012-11-27). "Stratolaunch and SpaceX part ways". Flight Global. Retrieved 2012-11-29.
  11. ↑ Messier, Doug (2013-08-12). "ATK Gets Contract for Stratolaunch Propulsion System". Parabolic Arc. Retrieved 2013-08-14.
  12. ↑ Bergin, Chris (2014-04-29). "Orbital and ATK form space flight super group". NASAspaceflight.com. Retrieved 2014-04-30.
  13. ↑ Foust, Jeff (2015-04-15). "Stratolaunch Considering Using Multiple Launch". Space News. Retrieved 25 April 2015.
  14. ↑ Mecham, Michael (2011-12-14). "Stratolaunch Aims to Break Affordability Barrier". Aviation Week (New York). Retrieved 2011-12-14. The first test flight of the carrier aircraft is planned in 2015 from Scaled Composites’ home in Mojave, Calif.
  15. ↑ Chow, Denise (2011-12-13). "Microsoft Co-Founder Paul Allen Unveils Giant Plane for Private Space Launches". Space.com (New York). Archived from the original on 2011-12-14. Retrieved 2011-12-14.
  16. ↑ Bergin, Chris. "Dream Chaser eyes rides on under review Stratolaunch system". NASASpaceflight.com. Retrieved 2014-11-18.

External links