Microwave Rocket Research Articles

Experimental Study of Plasma Decay for Enhancing Pulse Repetition Frequency in Microwave Rocket

Experimental Study of Plasma Decay for Enhancing Pulse Repetition Frequency in Microwave Rocket

Toward the Realization of 600 kW Output Power of a 94 GHz Gyrotron for Microwave Rocket Development

Toward the Realization of 600 kW Output Power of a 94 GHz Gyrotron for Microwave Rocket Development

Proposal of the optimum frequency for microwave rocket launch

Proposal of the optimum frequency for microwave rocket launch

Study of Transmission Frequency and Transmission Optics to Minimize Microwave Rocket’s Launch Cost

Study of Transmission Frequency and Transmission Optics to Minimize Microwave Rocket’s Launch Cost

Development of a Long-Distance Millimeter-wave Transmission System for a Low-cost Mas Driver: Microwave Rocket

Development of a Long-Distance Millimeter-wave Transmission System for a Low-cost Mas Driver: Microwave Rocket

Development Policy of a High-Power Millimeter-Wave Oscillator Gyrotron Intended for Microwave Rocket Research

Development Policy of a High-Power Millimeter-Wave Oscillator Gyrotron Intended for Microwave Rocket Research

High-Power Millimeter-Wave Multiplexer for Beam Station of Microwave Rocket

High-Power Millimeter-Wave Multiplexer for Beam Station of Microwave Rocket

Gas propellant dependency of plasma structure and thrust performance of microwave rocket

To identify the characteristics of a suitable gas propellant for a microwave rocket, the discharge physics induced by an intense microwave in nitrogen, hydrogen, and helium was numerically reproduced by coupling a plasma fluid model with an electromagnetic wave propagation model. A discrete plasma structure was induced in nitrogen and hydrogen, because the ionization region was smaller than the incident-beam quarter wavelength. However, a diffusive plasma pattern was generated in helium, because the electron temperature increased and the electron-impact ionization was maintained even in the low-electric-field region. The shock wave propagation inside the rocket nozzle was numerically reproduced to evaluate the thrust performance dependence on the propellant species; this was achieved by solving the two-dimensional axisymmetric Euler equation with an energy source term for the microwave heating. The simple shock-tube theory indicated that the momentum coupling coefficient is proportional to the energy stored inside the rocket nozzle and inversely proportional to the propellant sound speed. The smallest momentum coupling coefficient was obtained for the helium case, although the sound speed in helium is faster than that in hydrogen. This was because insufficient energy was stored inside the rocket nozzle when helium was used, owing to the faster plasma propagation and lower energy absorption rate. The findings of this work indicate that to obtain a large thrust for a microwave rocket, selection of a gas propellant with a high energy absorption rate, small electron diffusion coefficient, low sound speed, and low specific heat ratio are preferable.

Thrust-Performance Maximization of Microwave Rocket Sustained by Resonant Magnetic Field

Thrust-Performance Maximization of Microwave Rocket Sustained by Resonant Magnetic Field

Postural Control for Beam-Riding Flight of a Microwave Rocket Using an External Magnetic Field

Postural Control for Beam-Riding Flight of a Microwave Rocket Using an External Magnetic Field

Development of a Novel Launch System Microwave Rocket Powered by Millimeter-Wave Discharge

This paper presents the state of art of Microwave Rocket development and related researches on atmospheric discharge in a high-power millimeter-wave beam. Its operational mechanisms, thruster design, history of development, and flight path and cost analyses are introduced along with millimeter-wave discharge observations and numerical simulations. A thruster model of 126 g weight with no on-board propellant was launched to 1.2 m altitude using a 1 MW class gyrotron. A flight analysis that shows 77% cost reduction is possible using Microwave Rocket as the first stage of H-IIB heavy. A millimeter-wave discharge with unique plasma structure such as a quarter-wavelength microstructure and a comb-shaped filamentary structure was observed and reproduced by a two-dimensional numerical model.

Gas-species-dependence of microwave plasma propagation under external magnetic field

In this study, the gas-species-dependence of plasma propagation was numerically investigated to maximize the thrust performance of a microwave rocket with a gas propellant tank. An external magnetic field was applied to the breakdown volume inside the rocket nozzle to suppress plasma propagation toward the exit of the nozzle. In the absence of the magnetic field, the speed of plasma propagation in argon was higher than that in nitrogen because of the smaller elastic collision frequency and faster electron diffusion. However, the relationship in terms of the speed of plasma propagation was reversed when the magnetic field was applied to the breakdown volume because of infrequent elastic collisions in argon. The speed of plasma propagation under the external magnetic field was theoretically modeled as 2D⊥νi and decreased with increasing value of the Hall parameter Ω in the region where Ω>1. It is, therefore, better to use a gaseous propellant that incurs a small elastic collision frequency in the microwave rocket supported by an external magnetic field, because a larger value of Ω suppresses plasma propagation and yields a superior thrust performance.

Thrust generation experiments on microwave rocket with a beam concentrator for long distance wireless power feeding

Experiments using a 1 MW-class gyrotron were conducted to examine a beamed energy propulsion rocket, a microwave rocket with a beam concentrator for long-distance wireless power feeding. The incident beam is transmitted from a beam transmission mirror system. The beam transmission mirror system expands the incident beam diameter to 240 mm to extend the Rayleigh length. The beam concentrator receives the beam and guides it into a 56-mm-diameter cylindrical thruster tube. Plasma ignition and ionization front propagation in the thruster were observed through an acrylic window using a fast-framing camera. Atmospheric air was used as a propellant. Thrust generation was achieved with the beam concentrator. The maximum thrust impulse was estimated as 71 mN s/pulse from a pressure history at the thrust wall at the input energy of 638 J/pulse. The corresponding momentum coupling coefficient, Cm was inferred as 204 N/MW.

Consideration on Phased Array Transmission Antenna for Microwave Rocket

Consideration on Phased Array Transmission Antenna for Microwave Rocket

Numerical Calculation on Air-Inlet Design of Microwave Rocket

Air-inlet design and resulting thrust performance of Microwave Rocket at 10km altitude and a flight Mach number of 2 were computed using CFD and the influence of plenum area size was examined. The results showed that, the partial filling rate was found to monotonically increase with the area ratio of plenum to thrust tube, though aerodynamic drag was increased with the ratio. Optimum area ratio was found about 1.0, and 85% of the maximum thrust was obtained when the range was between 0.60 and 2.0.

Open-Front Approach of a Microwave Rocket Sustained by a Resonant Magnetic Field

Shock-wave propagation around a microwave-rocket nozzle was numerically reproduced using a computational fluid dynamics code when an electron cyclotron resonance condition was satisfied by irradiating 25 GHz microwaves onto the rocket nozzle under an external magnetic field. The pulse-duration and nozzle-shape dependence for the thrust performance of the microwave rocket was evaluated by changing the normalized heating length and the normalized nozzle radius. The open-front approach using a butterfly valve was newly proposed to improve the thrust performance by eliminating the negative thrust and removing the stagnation region during the gas-refilling process. The thruster only received the positive pressure of the shock wave by eliminating the contribution of the negative pressure using the open-front approach, which improved the thrust performance. In addition to the thrust improvement, the gas-refilling performance was also improved because the ambient gas flowed from the open front to the nozzle inside without forming the stagnation region. The improvement of the thrust performance and the gas-refilling performance can improve the payload transportation efficiency and further reduce the cost of launch using beamed-energy propulsion.

Asymmetric Shock Wave Generation in a Microwave Rocket Using a Magnetic Field

A plasma pattern is reproduced by coupling simulations between a particle-in- cell with Monte Carlo collisions model and a finite-difference time-domain simulation for an electromagnetic wave propagation when an external magnetic field is applied to the breakdown volume inside a microwave-rocket nozzle. The propagation speed and energy-absorption rate of the plasma are estimated based on the breakdown simulation, and these are utilized to reproduce shock wave propagation, which provides impulsive thrust for the microwave rocket. The shock wave propagation is numerically reproduced by solving the compressible Euler equation with an energy source of the microwave heating. The shock wave is asymmetrically generated inside the nozzle when the electron cyclotron resonance region has a lateral offset, which generates lateral and angular impulses for postural control of the vehicle. It is possible to develop an integrated device to maintain beaming ight of the microwave rocket, achieving both axial thrust improvement and postural control, by controlling the spatial distribution of the external magnetic field.

Development of Plasma Fluid Model for a Microwave Rocket Supported by a Magnetic Field

A fluid model of plasma transport is developed to reproduce a plasma pattern induced by microwave irradiation when an external magnetic field is applied to the breakdown volume. Transport coefficients in the fluid model are evaluated using a fully kinetic simulation under a magnetic field to maintain consistency of electron transport between the particle and fluid models. The electron-density profile and propagation speed of the ionization front obtained by the fluid model agree with those of the particle model. Multidimensional or longer time-scale simulations can be conducted using the fluid model in the case of the application of an external magnetic field, with the simulation reducing computational cost compared to the fully kinetic model.

A study of RF power station for microwave rocket launch system

A study of RF power station for microwave rocket launch system

Plasma filamentation and shock wave enhancement in microwave rockets by combining low-frequency microwaves with external magnetic field

A filamentary plasma is reproduced based on a fully kinetic model of electron and ion transports coupled with electromagnetic wave propagation. The discharge plasma transits from discrete to diffusive patterns at a 110-GHz breakdown, with decrease in the ambient pressure, because of the rapid electron diffusion that occurs during an increase in the propagation speed of the ionization front. A discrete plasma is obtained at low pressures when a low-frequency microwave is irradiated because the ionization process becomes more dominant than the electron diffusion, when the electrons are effectively heated by the low-frequency microwave. The propagation speed of the plasma increases with decrease in the incident microwave frequency because of the higher ionization frequency and faster plasma diffusion resulting from the increase in the energy-absorption rate. An external magnetic field is applied to the breakdown volume, which induces plasma filamentation at lower pressures because the electron diffusion is suppressed by the magnetic field. The thrust performance of a microwave rocket is improved by the magnetic fields corresponding to the electron cyclotron resonance (ECR) and its higher-harmonic heating, because slower propagation of the ionization front and larger energy-absorption rates are obtained at lower pressures. It would be advantageous if the fundamental mode of ECR heating is coupled with a lower frequency microwave instead of combining the higher-harmonic ECR heating with the higher frequency microwave. This can improve the thrust performance with smaller magnetic fields even if the propagation speed increases because of the decrease in the incident microwave frequency.