Taiichi Nagata

Investigation of Helium Assisted Low Frequency Plasma for Liquid Oxygen and Hydrocarbon Ignition

A low frequency plasma jet as a new ignition procedure for non-hypergolic bipropellant thrusters is proposed. Typical applications include LOX with methane and other hydrocarbon fuels.. Helium is used as a working fluid for plasma jet because of its low breakdown voltage. Preliminary ignition experiments about plasma configuration for gaseous oxygen and methane are performed and indicate that a dielectric barrier discharge plasma is insufficient to ignite the propellant mixtures, and that a thermal plasma should be used instead.. A test setup, suitable for both gaseous and liquid propellants for ignition testing of a 20 N-class thruster, is described. It is applied to ignition characterization of gaseous oxygen and methane at various flow rates and equivalence ratios at atmospheric conditions. Results show reliable ignition with less than 30 ms delay and over a wide range of equivalence ratio, from approximately 0.5 to 2.5.

Statistics of Velocity Field in Laboratory-Simulated Downburst

As a laboratory model of downburst, the statistics of a turbulent velocity field of a vertical gravitational flow is investigated. By mechanically breaking a thin film fixed at the bottom of a cylindrical container, a finite mass of a high-density liquid begins to fall into a stationary low-density liquid, forming a vertical thermal. It impinges onto the horizontal ground and then diverges radially outward. By employing particle image velocimetry, the ensemble-averaged maps of velocity vectors, azimuthal vorticity, and turbulent stresses in a meridian plane are obtained. The statistical characteristics in the downdraft stage, impinging stage and diverging stage are examined. The nature and the role of the circulatory flow are demonstrated. The results show reasonable agreement with the actual downbursts observed in the atmosphere. Based on these results, the windshear hazard index for aircraft encountering a downburst is evaluated.

Feasible Study on Low Frequency Plasma Jet as Ignition System for HAN based Propellant

A low frequency (LF) plasma jet is proposed as an ignition system candidate for hydroxyl ammonium nitrate (HAN) based propellant, especially focused on SHP163, as substitution of conventional hydrazine. Plasma generation capability and power consumption characteristics were investigated as functions of frequency, applied voltage, and distance between high-voltage and ground electrodes. LF plasma jet in itself was generated at 5 Hz of frequency, 5 KV of applied voltage, and 5 mm of electrodes distance; and its power consumption was 16 W. At lower frequency and higher voltage, plasma generation capability was increased. Power consumption was decreased at lower frequency, lower applied voltage, and shorter electrode distance. At same applied voltage, lower power consumption was obtained at lower frequency and shorter electrodes distance. Additionally, LF plasma jet was applied to initiate SHP163. 1.1 × 10 -2 g/s of mass reduction rate was obtained at 5 Hz of frequency and 5 KV of applied voltage, and its power consumption was 30 W. This result indicates that LF plasma jet has excellent possibility to be a good reaction initiation/enhancement system.

Visualization of Propellant Behavior inside Catalyst Thruster Using Neutron Radiography

One of our studies to improve the reliability of propulsion systems is the activity of visualization through which we can directly observe the physical and chemical phenomena that occur inside the catalyst thruster. In this paper, we introduce the visualization test results of the catalyst thruster utilizing Neutron Radiography. Neutron Radiography is a non-destructive imaging technique using thermal neutrons. Contrary to X-rays, neutrons are attenuated by some light materials such as hydrogen, but penetrate heavy materials. Using these neutron properties, we have conducted various visualization tests of the propellant behaviors inside the catalyst thruster elements. This paper includes an overview of Neutron Radiography and the preliminary visualization test results of the catalyst thruster elements obtained with Neutron Radiography.

Hydrazine decomposition phenomena observed by Neutron radiography at a catalyst bed

Most mono-propellant thruster technologies were developed in the 1960s and the basic principles and fundamental structures, such as the catalyst and propellant, have remained in use without major technical innovation. Conversely, much remains to be identified in terms of the concrete mechanisms and quantitative limitations of the phenomena inside the monopropellant thruster. One of our studies to improve the reliability of propulsion systems involved visualization, facilitating direct observation of the physical and chemical phenomena occurring within the catalyst bed of the mono-propellant thruster. In this paper, we introduce the visualization test results of the mono-propellant thruster utilizing Neutron Radiography. We have also succeeded in shooting movies of hydrazine decomposition phenomena using Neutron Radiography at the Kyoto University Research Reactor.

Experimental Study of Low Frequency Plasma for Liquid Oxygen and Methane Ignition

,To achieve reliable, low power ignition source for methane and oxygen thruster, a low frequency plasma is proposed. Helium is used as a working fluid for the plasma jet because it is easier to ionize than oxygen and methane. The heat of helium plasma must then transfer to the mixed gases of oxygen and hydrocarbon, which then ignite. This heat transfer process generates an additional ignition delay. We performed an experiment to estimate this ignition delay by using gaseous methane and oxygen under atmospheric conditions in an thruster configuration. The result shows that ignition delay, estimated by chamber pressure, is 20ms for this configuration. Further studies will be conducted vacuum conditions and ultimately under cryogenic conditions.

Basic Characteristics of Discharge Plasma Ignition System for 1N-class RCS Thruster with Green Monopropellant

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.

Feasibility Study of Low Frequency Plasma for Bipropellant Thruster Ignition

To achieve reliable, low power ignition source for methane and oxygen thruster, a low frequency plasma is proposed. Helium is used as a working fluid for the plasma jet because it is easier to ionize than oxygen and methane. The heat of helium plasma must then be transferred to the mixed gases of oxygen and hydrocarbon, which then ignite. To understand the mechanism of this ignition process, we performed an experiment to visualize with a high speed video camera by using gaseous methane and oxygen under atmospheric conditions in a thruster configuration. Discharges in the propellant mixture were observed prior to ignition which then led to ignition. This experiment reveals, actually, that the helium plasma itself is not the source of ignition in this configuration.

Basic Characteristics of Reaction Initiation System Using Dishcharge Plasma for 1N-class Thruster with Green Propellants

A new reaction initiation (ignition) system using discharge plasma is proposed for 1Nclass reaction control system (RCS) thruster with green monopropellant, especially, one of hydroxyl ammonium nitrate (HAN) based liquid monopropellant, SHP163. This reaction initiation system is designed in substitution for conventional catalytic decomposition system. In this study, fundamental reaction initiation characteristic of SHP163 by discharge plasma, based on total amount of energy applied, were investigated. Better propellant reaction initiation was achieved at larger number of discharge attributed from frequency even though levels of applied energy were same. It became clear that reaction initiation characteristics depend on not only total amount of energy but also number of single discharge. Additionally, a laboratory model of new reaction initiation system was designed and built. Fundamental characteristics based on power consumption were investigated. The new reaction initiation system was demonstrated with 100 to 5000 Hz of frequency and 3.2 to 27.8 mg/s of helium mass flow rate. At any cases in this experiment, stable discharge plasma generation was observed, and highest power consumption was 35 W.

Experimental Results of a Centrifugal Pump Using Hydrazine and MON-3

A performance evaluation test was conducted on a low Ns pump using real liquids of bipropellant liquid rocket engine. The pump’s low efficiency using water had been previously reported and was attributed to the pump’s small size. However, the pump’s performance using real propellants, hydrazine, and MON-3 remained unknown. To test with real propellants, we considered improving the design of the pump seal mechanism and conducting test operation to measure performance with a rig test model. This report discusses the points of improved design, such as the seal system and test operation. It also discusses the results of the real propellant rig test.