Reusable Launch of Small Satellites Using Scramjets

Reduced scale and improved responsiveness will be the technical and economic drivers of future satellite systems. Based on decades of practical experience with rocket-only expendable launch vehicles, current technology is operated close to theoretical limits. Scramjets have an advantage over rocket propulsion in terms of a significantly higher specific impulse. Other benefits of airbreathing propulsion for access to space are increased launch flexibility and the possibility of reusable aircraftlike operations. This paper describes the use of a three-stage rocket–scramjet–rocket system for transporting payloads of the order of 100 kg to a sun-synchronous orbit. The reusable second stage is based on a winged-cone vehicle and is powered by hydrogen-fueled scramjets. An assessment of the complete three-stage system is conducted here by performing a fully trimmed trajectory simulation of the airbreathing second stage, along with simplified trajectory simulations of the rocket stages. The scramjet-powered second stage accelerates from Mach 5.1 to Mach 9.5 with an average net specific impulse of 933 s, which is more than double that of a rocket. As a result, this partially reusable system shows a payload mass fraction of 1.17% to sun-synchronous orbit, which compares favorably with expendable rocket-based systems of this scale. These results indicate that scramjets should be investigated further for use on the second stage of satellite launch systems.