Pegasus is an air-launched multistage rocket developed by Orbital Sciences Corporation (OSC) and later built and launched by Northrop Grumman.

[2][3] Capable of carrying small payloads of up to 443 kg (977 lb) into low Earth orbit, Pegasus first flew in 1990 and remained active as of 2021[update].

Pegasus is released from its carrier aircraft at approximately 12,000 m (39,000 ft) using a first stage wing and a tail to provide lift and altitude control while in the atmosphere.

[5] The Pegasus's three Orion solid motors were developed by Hercules Aerospace (later Alliant Techsystems) specifically for the Pegasus launcher but using advanced carbon fiber, propellant formulation and case insulation technologies originally developed for the terminated USAF Small ICBM program.

[7] NASA did provide the use of the B-52 carrier aircraft on a cost-reimbursable basis during the development (captive carry tests) and the first few flights.

Two Orbital internal projects, the Orbcomm communications constellation and the OrbView observation satellites, served as anchor customers to help justify the private funding.

[10] The first partial failure on 17 July 1991 caused the seven USAF microsatellites to be delivered to a lower than planned orbit, significantly reducing the mission lifetime.

The last mission failure on 4 November 1996 resulted in the loss of gamma-burst identifying satellite HETE (High Energy Transient Explorer).

For their work in developing the rocket, the Pegasus team led by Antonio Elias was awarded the 1991 National Medal of Technology by U.S. President George H. W. Bush.

The initial launch price offered was US$6 million, without options or a HAPS (Hydrazine Auxiliary Propulsion System) maneuvering stage.

In July 2019, it was announced that Northrop Grumman had lost the launch contract of the Imaging X-ray Polarimetry Explorer (IXPE) satellite to SpaceX.

The future (under construction as of 2019) NASA Explorer program mission Polarimeter to Unify the Corona and Heliosphere (PUNCH) was planned to be launched by Pegasus XL; but then NASA decided to merge the launches of PUNCH and another Explorer mission, Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) (also under construction as of 2019).

[16] In August 2022 NASA announced that the 4 microsatellites of the PUNCH constellation will be launched as rideshare payloads together with SPHEREx in April 2025 on a SpaceX Falcon 9 rocket.

Such locations have included Kennedy Space Center / Cape Canaveral Air Force Station, Florida; Vandenberg Air Force Base and Dryden Flight Research Center, California; Wallops Flight Facility, Virginia; Kwajalein Range in the Pacific Ocean, and the Canary Islands in the Atlantic Ocean.

The 45-degree delta wing (of carbon composite construction and double-wedge airfoil) aids pitch-up and provides some lift.

Upon burnout of the second-stage motor, the stack coasts until reaching a suitable point in its trajectory, depending on mission.

[citation needed] The carrier aircraft (initially a NASA B-52, now an L-1011 owned by Northrop Grumman) serves as a booster to increase payloads at reduced cost.