Pegasus XL Pegasus Standard

Work began in the spring of 1987, paid for by Orbital Sciences and Hercules Aerospace, with no government money behind the development itself. Antonio Elias led the team; Burt Rutan and Scaled Composites drew and built the delta wing and tail fins, and Hercules Aerospace produced the three Orion solid motors using carbon fibre, propellant and case-insulation work inherited from the cancelled USAF Small ICBM programme.

There were no test launches. The first flight, on 5 April 1990, was operational from the outset, with astronaut and test pilot Gordon Fullerton commanding the carrier aircraft. The rocket dropped for five seconds before lighting the first stage, and since the Orion 50S motor had no steerable nozzle, everything in the atmosphere depended on the 45-degree wing and the tail fins. Pegsat and NavySat rode that first mission.

Four flights used the plain standard configuration between 1990 and 1994 — Pegsat/NavySat, SCD-1, ALEXIS and APEX — and two more added the HAPS fourth stage. The February 1993 mission also left a lesson in launch discipline: NASA's range safety officer called an abort in the final minute, the operator's test conductor restarted the count without coordinating with the other participants, and although the flight went well, the investigation blamed fatigue and unclear command and communication roles.

Once the stretched Pegasus XL appeared in 1994 the standard version had no commercial room left: it carried less for much the same price. The configuration was discontinued, and the programme carried on with the XL and with the hybrid Pegasus H, which kept the standard airframe but took the XL's canted fins so it could hang under the new carrier aircraft.