Reducing the amount of propellant for re-cooling is an important issue for the rocket propulsion system using cryogenic fuel. Immediately after the start of the engine, the liquid fuel boils and becomes two-phase flow. In the state of two-phase flow, the void fraction, which is the gas-liquid ratio, is one of the important value for flow control. For above problem, we are developing void fraction measurement system for the cryogenic fluid. These devices were attached to the S310-43 sounding rocket for the purpose of “measuring two-phase flow behavior and heat transfer characteristics during coasting flight.” These devices withstood the vibration shock test of 40G and succeeded to measure the void fraction of liquid/gas nitrogen two phase flow under vacuumed and microgravity circumstance. This report explains development and experiment results of the void fraction sensor and a capacitance amplifier.
A water-propellant ion thruster was proposed and studied using microwave discharge for a propulsion system of CubeSats aiming for a high delta-V. In this paper, we measured the ion production cost and the microwave reflectivity of the water-propellant ion thruster with a changing discharge chamber height and microwave frequency. As a result, we found lower and upper limitations of the frequencies to sustain the plasma. The lower limitation depended on the discharge chamber height, and the upper one showed no dependency. Microwaves from 4.4 to 5.4GHz were found to sustain the plasma stably for all the heights. In this range, the ion production cost became low as the height was set low. On the other hand, the characteristics of the reflectivity largely differed by the height. Furthermore, the characteristics changed in the experiments using xenon propellant, which implied that the microwave frequency should be optimized depending on the chamber shape and the propellant type.
A new scheme for the polynomial chaos expansion (PCE) is developed and tested to quantify the propagation of the input uncertainty in CFD. The Haar wavelet is used as basis for the PCE instead of globally continuous, orthogonal polynomials to properly represent the strong discontinuity such as a shock wave. We further extended the method to inputs with arbitrary probability distribution functions (PDF), although the natural application of the Haar wavelet is the uniform PDF. A transonic nozzle flow with an uncertainty in the nozzle-exit pressure is simulated. The wavelet basis well reproduces the Monte Carlo simulations at a single execution of the program, unlike the multi-element (ME) PCE developed in the previous report. But the quantitative agreements of the statistics are better obtained by the result using ME-PCE.
Flying cars have been developed as next generation vehicles that enable high speed and flexible door-to-door transportations. A short take-off distance is expected to contribute to increase the possibility that flying cars will be used in our daily life. The purpose of the present study is to investigate to shorten a take-off distance of a flying car by using a wheels' driving force, propeller thrust and lift of main wings. This paper shows that accelerating the car by using wheels is efficient when the velocity is low. On the other hand, using propellers is more efficient when the car approaches to the take-off velocity. As a practical way to shorten the take-off distance, we propose a law to determine the power consumed by propellers and wheels as a function of the velocity of the flying car. Computation results show that the performance of the take-off phase of the flying car can be improved by using a high running ability of the car with wheels.