The proposed work will enable the design of safe N2O-cooled hybrid rocket motors having truncated aerospike nozzles, which will allow cost effective, reusable, and less expensive rocket designs. The potential non-NASA users of this technology are the U.S. military and companies providing inexpensive access to low Earth orbit. In addition to the business of launching satellites, there is a burgeoning interest in space tourism. Scaled Composites and Virgin Galactic have teamed up to develop SpaceShipTwo specifically to pursue the space tourism market. Likewise, Benson Space Company is developing the Dream Chaser, which is a 4-passenger suborbital or 6-passenger orbital vehicle. Each of these vehicles will use a hybrid rocket motor. Under study in the U.S. is a sewage treatment process that intentionally increases the production of nitrous oxide and methane, and uses the gases to power the treatment plant. In a low-oxygen environment in the treatment plant, where N2O-producing bacteria are favored, while aerobic species die off, the N2O-producing microbes consume relatively small amounts of organic matter, which allows for an increased production of methane. The methane will be used as a fuel, and the N2O will be burned in a hybrid rocket motor, where it will decompose into pure nitrogen and gaseous oxygen, both of which are completely green from a sustainability viewpoint. N2O-cooling could produce rocket nozzles with very long burn times for the use in this process. The proposed work will enable the design of safe N2O-cooled hybrid rocket motors having truncated aerospike nozzles, which will allow cost effective, reusable, and less expensive rocket designs. NASA could use this technology in any single-stage-to-orbit program.