Y. Ohkami et M. Maita, AIRBREATHING ENGINE SELECTION CRITERIA FOR SSTB PROPULSION SYSTEM, Transactions of the Japan Society for Aeronautical and Space Sciences, 37(118), 1995, pp. 239-247
This paper presents airbreathing engine selection criteria to be appli
ed to the propulsion system of a Single Stage To Orbit (SSTO). To esta
blish the criteria, a relation among three major parameters, i.e., del
ta-V capability, weight penalty and effective specific impulse of the
engine subsystem, is derived as compared to these parameters of the LH
2/LOX rocket engine. The effective specific impulse is a function of t
he engine I-sp and vehicle thrust-to-drag ratio which is approximated
by a function of the vehicle velocity. The weight penalty includes the
engine dry weight, cooling subsystem weight. The delta-V capability i
s defined by the velocity region starting from the minimum operating v
elocity up to the maximum velocity. The vehicle feasibility is investi
gated in terms of the structural and propellant weights, which require
s an iteration process adjusting the system parameters. The system par
ameters are computed by iteration based on the Newton-Raphson method.
It has been concluded that performance in the higher velocity region i
s extremely important so that the airbreathing engines are required to
operate beyond the velocity equivalent to the rocket engine exhaust v
elocity (approximately 4,500 (m/s)).