Microwave Rocket is a beamed energy propulsion system that is expected to reach space at drastically lower cost. This cost reduction is estimated by replacing the first-stage engine and solid rocket boosters of the Japanese H-IIB rocket with Microwave Rocket, using a recently developed thrust model in which thrust is generated through repetitively pulsed microwave detonation with a reed-valve air-breathing system. Results show that Microwave Rocket trajectory, in terms of velocity versus altitude, can be designed similarly to the current H-IIB first stage trajectory. Moreover, the payload ratio can be increased by 450%, resulting in launch-cost reduction of 74%.

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Microwave rocket is an air-breathing Beamed Energy Propulsion (BEP) rocket, which use a gyrotron microwave oscillator as a beam source. Recently a reed valve air-intake was proposed to ensure air-breathing during the atmospheric flight from zero velocity to high flight Mach number. In this paper a conceptual design of the air-breathing microwave rocket is described. Then using an analytical model of the thrust produced by the airbreathing microwave rocket, launch simulations are discussed. As a result "maximal roads" of an altitude and Mach number are obtained. Additionally it is found that the vehicle can be accelerated to a velocity of 4 km/s in the air-breathing flight mode by the altitude of 60 km. NomenclatureA = Thruster transversal area [m 2 ] D air = Air drag [N] D th = Thruster diameter [m] D total = Rocket total diameter [m] E = Emitted energy during one cycle [MJ] g = Earth's gravitational acceleration [m/s 2 ] I n = Impulse generated during step n [Ns] ṁ = Mass flow through a reed valve per unit area [kg/(s m 2 )] L th = Thruster length [m] L total = Rocket total length [m] P = Pressure [Pa] r = Distance from Earth's center [m] S av = Average beam power density 2 T = Temperature [K] U D = MSD propagation velocity [m/s] v = Upward velocity (rotational earth referential) [m/s] W em = Emitted power [MW] α = Angle between thrust direction and position vector direction [rad] α reed = Ratio of opened reed valves area to thruster lateral area γ = Heat capacity ratio of air η = Attenuation coefficient μ = Gravitational constant [m 3 /s 2 ] ρ = Density [kg/m 3 ] Φ Duty = Duty cycle ω = Earth's rotation rate [rad/s] Subscripts ext = Value at outside of the thruster f = Beginning state in the thruster in = Value at the inside thruster near a reed valve w = Value at the thrust wall