The first Pegasus launch to use Stargazer was conducted on 27 June 1994 as the maiden flight of the Pegasus-XL. Previous launches used the NASA-operated BoeingB-52 nicknamed "Balls 8," which was also used for four subsequent launches, as the original Pegasus could not be launched from Stargazer due to clearance issues. A modified version, the Pegasus-H, was introduced to rectify this.
Stargazer was also used for captive tests and transportation of the X-34 hypersonic research aircraft; however, the drop tests used Balls 8.
Orbital Sciences also offer the aircraft for research flights.[6] It is capable of carrying a 23,000 kilograms (51,000 lb) payload to an altitude of 12,800 metres (42,000 ft).[7]
In 2010, Stargazer was reengined with 50,000 lbf (220 kN)-thrust Rolls-Royce RB211-524B4 turbofans to replace its original 42,000 lbf (190 kN)-thrust RB211-22Bs.[8]
In 2015, Stargazer was repainted to reflect Orbital Sciences' merger with Alliant Techsystems.[9]
On 15 December 2016, Stargazer successfully launched CYGNSS on behalf of NASA on its second attempt. The first attempt on 12 December was scrubbed due to issues with the hydraulic system responsible for separating the Pegasus rocket from the launch aircraft.[10]
Stargazer appeared in Northrop Grumman livery in 2018 following the acquisition of Orbital ATK.[11] Stargazer launched the Ionospheric Connection Explorer on 11 October 2019. The launch was originally scheduled for June 2017 but was scrubbed when an anomalous piece of vehicle data was observed during a ferry flight. The data was related to the rudder position of the Pegasus XL rocket and was observed during a routine in-flight vehicle health check.[12] The launch was delayed multiple times from 2017 to 2019, finally occurring October 11, 2019.[4]
Background
The Lockheed L-1011 TriStar carrier aircraft first flew in February 1974, and was delivered to Air Canada as C-FTNJ the following month. In May 1992 Orbital Sciences acquired the plane and had Marshall Aerospace in the UK implement accommodations for the Pegasus system. It was renamed for use as carrier aircraft for the Pegasus launch system.[12] The company also considered other aircraft including the Boeing B-52G Stratofortress, Boeing 747, and DC-10, taking into account altitude and speed performance, range, modification complexity, and acquisition and operational costs.[13]