The Pegasus integrates three Orion solid rocket motors, developed by Hercules Aerospace, with a composite delta wing to create the world's only air-launched commercial rocket.  The vehicle, which is 57 feet long and weights approximately 52,000 lb at ignition, is carried aloft by Orbital's L-1011 carrier craft to 40,000 feet.  A final systems check is performed and the Pegasus vehicle is released.  After a few seconds of free fall, the Pegasus Orion 50S XL first stage motor is ignited and the vehicle accelerates out of the Earth's atmosphere.   Two additional Orion solid motors are used to place the satellite into its desired orbit.

The Pegasus launch vehicle was developed in the late 1980's to serve both as a small launcher for US Governmental agencies and to launch Orbital's ORBCOMM satellites.  Since its initial flight April 5th, 1990, the Pegasus and Pegasus XL rockets have flown a total of 27 missions (as of May 1999).  It's unique air-launch system provides a tremendous amount of operational flexibility, allowing the Pegasus to efficiently service any inclination as well as launch from a diverse range of launch sites.  In 1991, to increase payload performance, OSC initiated the Pegasus XL program that used stretched first and second stages.   Structural and avionics upgrades were also incorporated.  Since its entry into service, the majority of flights have been Pegasus XL missions.