NASA has successfully flown a 12.5m-long, one-tenth scale model of the Lockheed Martin X-33 advanced technology demonstrator on the back of its Lockheed SR-71. The model reached speeds of up to Mach 1.2 over the Dryden Flight Research Center, Edwards AFB, California.

The X-33 model contains an aerospike rocket motor which will be ignited for 2-3s on test flights in 1998. The linear aerospike rocket, built by Boeing North America, differs from conventional rockets in using the surrounding atmosphere itself rather than a traditional bell-mouth as a nozzle. The rocket will be used to power the X-33 demonstrator which will pave the way for a single-stage-to-orbit re-usable launch vehicle.

The Lockheed Martin Linear Aerospike SR-71 Experiment is designed to gather data on the aerospike's exhaust plume as it travels through the transonic region. This initial sortie was the first flight of any aerospike rocket. Initial flights will assess handling qualities and stability and control characteristics of the SR-71 with its 6,490kg payload before beginning assessment of the rocket's performance. These will include firings at a range of speeds and altitudes.

The 30kN (7,000lb)-thrust rocket is about 75% smaller than a conventional rocket which has equivalent thrust.

Source: Flight International