Pegasus

Pegasus is a three-stage solid rocket with a winged first stage. It is able to launch 600 pounds into a 250 nautical mile polar orbit or 900 lbs into a 250 nautical mile equatorial orbit. The vehicle itself is 49.2 feet long, with a diameter of 48 inches and a wingspan of 22 feet. It weighs 40,000 pounds at launch and is about the same shape and size as X-15 rocket plane, which was also launched from the B-52. The payload fairing is 46'' diameter by 72'' long. The launch costs are estimated at $8 million per launch, or about $10,000 per pound to orbit. This is unfavorable compared to other launchers on a per pound basis, but the small total cost remains attractive to those not needing large payloads.

Launch is from a B-52 flying at 40,000 feet and Mach 0.8. From here until the separation of the first stage, the craft is controlled by a set of aerodynamic control fins. Five seconds after release, the first stage ignites and the rocket begins a 2.5 g pullup. At about fifty seconds into the flight the craft reaches max-Q (maximum aerodynamic pressure on the rocket), at about 950 pounds per square foot of force. After 81 seconds, the first stage burns out and separates. At this point, the rocket is at 208,000 feet and moving at Mach 8.7. The second stage is controlled by a cold-gas reaction control system which takes over immediately after the first stage separates. At 87 seconds into the flight, the second stage ignites, thrusting at an angle of 26 degrees above the horizon. At this point the craft is at 231,000 feet altitude. At the 120 second mark the payload fairing separates from the craft. At 159 seconds the second stage burns out, with the craft at 552,000 feet and 17,800 feet per second velocity. It is oriented 18.4 degrees above the horizon. The rocket now enters a coast phase, with no activity. When it reaches the 470 second point, the rocket is at 248 nm altitude and 16,300 feet per second velocity, with an angle of 1.9 degrees to the horizon. At this point the third stage ignites, and burns until 533 seconds, at which point the spacecraft is at 250 miles and 25,000 feet per second velocity (orbital velocity). Additional variants have already been proposed; DOD is funding a variant using the first stage of a MX missile to boost the rocket instead of using a B-52 launch. The reasoning is that this would make an excellent quick reaction light satellite launcher. The Pegasus was developed by the Orbital Sciences Corp., located in Fairfax, VA and Hercules, which builds the solid motors.

The first Pegasus successfully completed its first test flight on 04-05-1990. At 1220 PDT, it launched its first payload into space, Pegsat 1. A NASA B-52 carrier aircraft carried Pegasus mounted under its right wing. Pegsat was used to conduct two barium chemical releases over central Canada.