Status: Study 2005.
Andrews Space, Inc., of Seattle, Washington, developed an In-flight Propellant Collection System, the "Alchemist" Air Collection and Enrichment System (ACES), which generated liquid oxygen (LOX) through the separation of atmospheric air. ACES took high-pressure air from turbofan jet engines flying at subsonic speeds and liquefied it by passing the air through a series of heat exchangers cooled by liquid nitrogen, liquid hydrogen, or both. Then, using a fractional distillation process, liquid oxygen was separated into its constituent parts and stored in propellant tanks for use by liquid hydrogen and LOX rocket engines. Alchemist ACES allowed horizontal take-off and landing launch vehicles to leave the ground without oxidizer, dramatically reducing their takeoff weight, increasing payload capability, or both.
The company proposed Alchemist ACES in conjunction with its two-stage-to-orbit RLV design, known as Gryphon, as well as for use in other horizontal take-off launch vehicles. Andrews Space carried out initial studies of the Alchemist ACES technology using internal funds, then under a NASA SBIR contract. Detailed feasibility studies and risk analyses were carried out under a NASA SLI contract. Critical components for the ACES system were in prototype hardware development at Andrews under a DARPA seedling contract. Future work involving design, fabrication, and test of a subscale all-up ACES system on board a flight vehicle was planned. ACES was first demonstrated in the 1960's for the USAF Aerospaceplane program.