Hydrocarbon Rocket Engines for Earth-to-Orbit Vehicles

The Space Shuttle has initiated a new era in Earth-to-orbit transportation and studies are now under way to assess the technology requirements for more advanced vehicles. Potential derivatives of the Space Shuttle and completely new vehicles might both benefit from advanced hydrocarbon engines, several versions of which were recently studied. In the present paper, selected single-stage vehicles have been compared using these engines. The results indicate that propane staged-combustion engines are attractive for this application. The potential effects of advanced engine materials are also shown. HE Space Shuttle has initiated a new era in Earth-to-orbit transportation, and the large number of payload reservations indicates that the system will be used to capacity. Many advantages of operating in space with the Shuttle have been hypothesized, such as satellite checkout and repair in orbit. Assembly of large space structures from the Shuttle is also being considered. Beyond the first few years of the Shuttle era, Earth-to-orbit traffic will grow to the point that vehicles beyond the Space Shuttle should be developed for a more efficient transportation system. Advanced orbit-transfer vehicles are being considered in several future systems studies. Even though the Space Shuttle era has just begun, the time to develop the technology for future vehicles is now. Derivatives of the Space Shuttle have been studied in the past,1 and a current study2 will provide additional insight into such derivatives. For the more distant future, completely new, fully reusable vehicles have been proposed as in Refs, 3-6. One of the more promising concepts that have been con- sidered for new vehicles is the single-stage, dual-fuel vehicle. Vertical launch and horizontal landing, which is the operational mode of the Space Shuttle, may provide the lowest risk. One of the most significant design concerns for such a concept is the aft center of gravity. This concern is somewhat alleviated by dual-fuel propulsion, and recent work on control-confi gured design indicates that vehicles can be controlled during return from orbit to the runway with center- of-gravity locations considerably aft of the current Shuttle limits.7 Previous studies have shown that advanced hydrocarbon liquid rocket engines would be beneficial to both Shuttle derivatives and advanced vehicles. Replacing the Shuttle solid rocket boosters with liquid-fueled boosters could reduce environmental concerns and operational costs. Although derivatives of the Space Shuttle Main Engine (SSME) could be used for such liquid-fueled boosters, advanced hydrocarbon engines would reduce operational costs more. Several ad- vanced hydrocarbon engines have been studied in the past for use with hydrogen-fueled engines for new Earth-to-orbit vehicles, and the results have indicated a significant advantage over hydrogen engines alone.l One of the findings that surfaced in previous studies is that