Pegasus XL Pegasus XL

The XL appeared in 1994 for a plain reason: science satellites were growing and the standard Pegasus could no longer carry them. The two lower stages were stretched into the Orion 50SXL and Orion 50XL, the wing was strengthened a little for the extra weight, and the third stage and flight operations were left alone. Prices rose above the six million dollars quoted in the first catalogue, but the rocket could now put 443 kg into low Earth orbit.

The maiden flight on 27 June 1994, carrying STEP-1, lost control 35 seconds in and range safety terminated it at 39 seconds; the likely cause was faulty aerodynamic modelling of the longer vehicle. The second, in June 1995, was lost when the interstage ring between the first and second stages failed to separate and jammed the nozzle. After that the version strung together thirty consecutive successes.

The XL became the standard ride for NASA's smaller observatories: FAST, TRACE, WIRE, RHESSI, SORCE, GALEX, AIM, IBEX, NuSTAR, IRIS and the CYGNSS constellation. It flew from Vandenberg, Cape Canaveral, Wallops, Kwajalein and the Canary Islands, the last of these carrying Spain's Minisat 01 in April 1997.

By the late 2010s the small-satellite market had moved to rideshare slots on big launchers, far cheaper per kilogram. Between 2016 and 2026 the XL flew just three times: ICON in October 2019, the Space Force's TacRL-2 in June 2021, and the Swift observatory rescue on 3 July 2026 using the last airframe left in Northrop Grumman's inventory. The company had already lost the IXPE contract to SpaceX in 2019, even though the satellite had been designed to fit inside a Pegasus XL.

Across both configurations the programme flew 46 missions from 1990 onwards, with three outright failures and two partial ones. The XL flew most of them, and for two decades it kept the only genuinely operational air-launch route to orbit open.