Radiation-cooled, bipropellant thrusters are being considered for the Ascent Module main engine of the Altair Lunar Lander. Currently, iridium-lined rhenium combustion chambers are the state-of-the-art for radiatively cooled thrusters. To increase the performance of radiation-cooled engines, improved chamber materials are being developed that will allow higher operating temperatures, better resistance to oxidation, and reduce mass. In an effort to increase performance, hafnium oxide thermal barrier coatings and improved iridium liners have been developed, and hot-fire tests of rhenium chambers with these improvements have shown higher operating temperatures, i.e., >200o
C increase, are possible. To reduce engine mass, recent efforts have focused on the development of carbon-carbon composites. Replacement of a rhenium structural wall with carbon-carbon could result in a mass savings of >600%. During this effort, an innovative composite thrust chamber will be developed that will incorporate advanced hafnium oxide and iridium liner techniques as well as replacing the expensive, high density rhenium with a low mass carbon-carbon composite. As a result of this investigation, an advanced composite thrust chamber with improved performance capability and reduced mass will be produced. During Phase II, the fabrication methods will be optimized and a full-size Ascent Module chamber will be produced and hot-fire tested.