Technical results obtained at the completion of the contract effort are described for the Advanced Cryogenic Rocket Engine Program, Aerospike. This program includes analysis and preliminary design of an advanced rocket engine using an aerospike nozzle and experimental evaluation of critical technology related to the aerospike concept. Component and system features, physical arrangements, design parameters and details, operational characteristics, and performance have been established for an optimum demonstrator engine. Studies were made of application of a flight engine to certain vehicles. Experimental injector performance investigations and experimental cooling investigations on segment chambers were conducted, producing the target combustion performance. Various materials were studied for long life of thrust chamber cooling passages and the target life was demonstrated. Full-scale, cooled thrust chambers were fabricated and tested for overall combustor and nozzle performance demonstrations.