ASSET (Aerothermodynamic Elastic Structural Systems Environmental Tests) were the first part of the United States Air Force START (Spacecraft Technology and Advanced Reentry Test) project on lifting bodies. ASSET test flights took place in 1963–1965 and used surplus Thor missiles, returned from the United Kingdom, for 4,000 meters per second flights and Thor-Delta for 6,000 meters per second flights. A spacecraft known as an aerothermodynamic structural test vehicle (ASV) was flown on a suborbital trajectory to a recovery zone near Ascension Island in the Atlantic to carry out heat shield experiments.