Analysis of Propellant Density Influence on Microwave Thermal Rocket Vehicle Mass

Abstract

This paper analyzes whether the microwave thermal rocket, with an isp of 900 s, is advantageous to chemical rockets for use in single stage to orbit launch vehicles. The low density of liquid hydrogen, 70 kg=m 3 , increases the structural mass and reduces the potential robustness of the vehicle. A structural reinforcement parameter, , which is the ratio of the payload to the structural mass of the vehicle, is introduced to quantitatively compare the propulsion systems. In this paper, mass estimations for tanks, turbopumps and propulsion systems for both types of propulsion are made to calculate . Conservative mass estimates are made using existing turbopump and tank technologies not optimized for use in a microwave thermal rocket. Additionally, composite tank technology and turbopumps designed for nuclear thermal rockets are used to make optimistic mass estimates. Furthermore two dierent initial accelerations are analyzed for the microwave thermal rocket, 1 and 2 g’s respectively, and chemical rockets are all analyzed at 1 g. With conservative estimations, chemical rockets are shown to have a large with 2 g’s of initial acceleration; however, the microwave thermal rocket has a larger with optimistic estimations. The micro thermal rocket has a larger in all comparisons with 1 g of acceleration.