Tripropellant Engine Option Comparison for Single Stage to Orbit

Recent evaluations of main engine options for the single-stage-to-orbit/reusable launch vehicle mission have considered the use of a tripropellant engine to take advantage of its improved fuel density. A wide range of options has been addressed, including configuration, technology level, and design practices, A study was conducted to evaluate engine configurations on a consistent basis of technology level, design practice, and design ground rules. Engine weight and performance of several cycles and cycle variants were determined and then compared on a vehicle dry weight basis to determine the merit of each, A series of bipropellant configurations was also studied under identical ground rules to evaluate the inherent differences due to propellant selection only. The results showed that the three major variants considered, a single-chamber tripropellant, an annular bell tripropellant, and a bipropellant, were nearly identical in terms of overall vehicle performance.