A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

Summary

The goal of this protocol is to introduce the design of a 100 kW class applied-field magnetoplasmadynamic thruster and relevant experimental methods.

Abstract

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate plasma to high speed; they have considerable potential for future space applications with the significant advantages of high specific impulse and thrust density. In this paper, we present a series of protocols for designing and manufacturing a 100 kW class of AF-MPD thruster with water-cooling structures, a 130 V maximum discharge voltage, a 800 A maximum discharge current, and a 0.25 T maximum strength of magnetic field. A hollow tantalum tungsten cathode acts as the only propellant inlet to inhibit the radial discharge, and it is positioned axially at the rear of the anode in order to relieve anode starvation. A cylindrical divergent copper anode is employed to decrease anode power deposition, where the length has been reduced to decrease the wall-plasma connecting area. Experiments utilized a vacuum system that can achieve a working vacuum of 0.01 Pa for a total propellant mass flow rate lower than 40 mg/s and a target thrust stand. The thruster tests were carried out to measure the effects of the working parameters such as propellant flow rates, the discharge current, and the strength of applied magnetic field on the performance and to allow appropriate analysis. The thruster could be operated continuously for significant periods of time with little erosion on the hollow cathode surface. The maximum power of the thruster is 100 kW, and the performance of this water-cooled configuration is comparable with that of thrusters reported in the literature.

Introduction

MPD thrusters are well known for a relatively high thrust density and a high specific impulse^1,2,3. However, the typical thrust efficiency¹ of MPD thrusters is relatively low, especially with propellants of noble gases^4,5,6. For most MPD thrusters, a part of the propellant flow is injected into the discharge chamber from a slit between anode and cathode^7,8 , with the result that a radial component is a....

Protocol

1. Preparation for experiment

1. Install the thruster.
   1. Wipe the components of the thruster withnon-dust cloth,soaked with anhydrous alcohol, in a clean room.
   2. Assemble the anode with the insulator.
   3. Bring together the cathode, cathode holder and cathode connector.
   4. Add the cathode part to the anode part.
   5. Install the middle connector into the assemblage and fix them with screws (hexagon socket head screw, M5×16).
   6. Establish the coil seat on experiment platform with forklift.
   7. Place the experiment platform on guide rail of the vacuum chamber.
   8. Install the thrus....

Results

In the experiment, we control discharge current (Id), propellant mass flow rate(m) and applied magnetic field (Ba). In operation, we measure the value of discharge voltage (Vd) and thrust (T), from which base we can get other performance parameters like power (P), specific impulse (Isp) and thrust efficiency (η)¹.

A typical signal of discharge voltage is shown in Figure 6

Discussion

This protocol describes the processes of ignition, operation, and thrust measurement of a 100 kW class applied field MPD thruster. The key point in designing an MPD thruster for optimum performance is choosing the proper configuration according to the specific objective. MPD thrusters with convergent-divergent anode can function steady-state in a large operation range. However, the performance may be lower than the thruster with divergent anode. The hollow cathode, especially the multichannel hollow cathode, is superior .......

Materials

Name	Company	Catalog Number	Comments
Cryogenic Pumps	Brooks Automation		Pumping speed: 10000L/s
Displacement Sensor	Panasonic	HG-C1030	Repetition precision: 10μm Linearity: ±0.1% F.S.
Mass Flow Rate Controller	Brooks Automation		Range: 0-120mg/s
Molecular Pump	Oerlikon		Pumping speed: 2100L/s
Moveable Plantform	Beijing Weina Guangke Automation equipment Co., Ltd.		Range:0-2000mm
Plsatic Water Pipes	Xingye Xingye fluoroplastics (Jiaxing) Co., Ltd.		Ultimate pressure: 4.5MPa
Propellant Argon	Beijing Huanyu Hinghui Gas Technology Co., Ltd.		Purity:99.999%
Refrigerator	Beijing Jiuzhou Tongcheng Technology Co., Ltd.		Refrigeration power:45kW
Water Pumps	Liaocheng vanguard Motor Co., Ltd.; Shanghai people pump industry group Manufacturing Co., Ltd.; Nanfang Pump Limited company		Maximum Output pressure: Centrifugal pump:1MPa Plunger pump:10MPa