A new ignition system utilizing discharge plasma for reaction control system (RCS) thrusters with green monopropellant is designed and evaluated experimentally in this study. The discharge plasma ignition system laboratory model (DPI-LM) is designed for one of hydroxyl ammonium nitrate (HAN) based monopropellant, SHP163; moreover, the DPI-LM is in substitution for conventional solid catalyst. Objectives of this study are (1) to design and build of DPI-LM and (2) evaluate basic propellant ignition characteristics in terms of successful and stable propellant ignition conditions, power consumption, and fundamental lifetime estimation. In addition, in order to generate discharge plasma prior to propellant ignition, a noble gas is used. Effect of noble gas type, argon and helium, on propellant ignition characteristics are also evaluated. Argon gas shows better propellant ignition with wide ranges of argon and SHP163 mass flow rates. It is considered that the propellant ignition strongly connects to discharge plasma diffusion condition prior to ignition. The power consumption at an argon mass flow rate of 0.075 g/s and a SHP163 mass flow rate of 0.3 g/s is approximately 270 W. The electrode degradation as a function of accumulated experiment time is evaluated as simplified lifetime estimation. The results of the degradation is only 0.1 % in electrode mass at 2000s , and the stable propellant ignition keeps at an accumulated time of 2000 s. Nomenclature I (t) = instantenous discharge current PW = power consumption t p,i = beginning time of the phase t p,f = end time of the phase V (t) = instantenous discharge voltage Δt p = duration of the phase 1 Graduate Student, Department of Aerospace Engineering, tiizuka@astak3.sd.tmu.ac.jp, Student Member.
A colloidal fluid is found to rotate spontaneously during electrolysis when gravity acts perpendicular to the direction of an applied electric field. An aqueous dispersion containing charged colloidal particles is placed inside an O-ring sandwiched between two parallel ITO electrodes. A clip is used to hold the assembly together to prevent the liquid from leaking out. The assembly is positioned such that the electrodes stand vertically, i.e., the electric field during electrolysis points perpendicular to gravity. When a direct-current voltage is applied to initiate the electrolysis of water, a nonlinear colloidal pattern is formed by electroconvective flow. Moreover, the entire fluid rotates spontaneously about the O-ring center with a constant angular velocity. The rotational dynamics are governed by how strong and where the assembly is clipped relative to the gravitational direction. A new phenomenological relationship between the angular velocity, compression vector, and gravity is derived. Coupling of an electrochemical reduction reaction of the ITO film with electroconvection during electrolysis is proposed as a mechanism for the rotational motion.
New reaction initiation (ignition) system utilizing discharge plasma is proposed for 1N-class reaction control system (RCS) thrusters utilizing green monopropellant; especially for one of hydroxyl ammonium nitrate (HAN) based liquid monopropellants, called SHP163. This reaction initiation system was designed in substitution for conventional catalytic decomposition system. In this study, fundamental reaction initiation characteristics of propellant, based on total amount of energy and propellant mass reduction, were investigated. At the same energy level, higher mass reduction was observed at larger number of discharge attributed from frequency. Additionally, a laboratory model of the reaction initiation system was built, and fundamental characteristics based on power consumption were investigated experimentally. The new reaction initiation system was demonstrated without propellant flow. In order to understand effects of helium mass flow rate and frequency on power consumption and plasma generation characteristics, helium mass flow rate was varied from 3.2 to 27.8 mg/s, while frequency was varied from 100 to 5000 Hz. Power consumption was increased as frequency increased, and the highest power consumption, 34 W, was recorded at 5000 Hz of frequency at 12.9 mg/s of helium mass flow rate. In this study, stable plasma generation was observed at any frequency and helium mass flow rate.
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