Name: a 100 kw class applied-field magnetoplasmadynamic thruster
Uploaded: 2018-12-22T13:00:00
Description: Watch this Scientific Journal Video about A 100 KW Class Applied-field Magnetoplasmadynamic Thruster at JoVE.com

This work was supported by the Fundamental Research Program (No. JCKY2017601C). We appreciate the helping of Thomas M. York, Emeritus Professor at Ohio State University.

1.&#160;Preparation for experiment
<ol>
	<li>Install the thruster.
	<ol>
		<li>Wipe the components of the thruster withnon-dust cloth,soaked with anhydrous alcohol, in a clean room.</li>
		<li>Assemble the anode with the insulator.</li>
		<li>Bring together the cathode, cathode holder and cathode connector.</li>
		<li>Add the cathode part to the anode part.</li>
		<li>Install the middle connector into the assemblage and fix them with screws (hexagon socket head screw, M5&#215;16).</li>
		<li>Establish the coil...

<ol>
	<li>Kodys, A., Choueiri, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Critical+Review+of+the+State-of-the-Art+in+the+Performance+of+Applied-field+Magnetoplasmadynamic+Thrusters.">A Critical Review of the State-of-the-Art in the Performance of Applied-field Magnetoplasmadynamic Thrusters.</a> , (2005).</li><li>Arakawa, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electromagnetic+Effects+in+an+Applied-field+Magnetoplasmadynamic+Thruster.">Electromagnetic Effects in an Applied-field Magnetoplasmadynamic Thruster.</a> Journal of Propulsion &amp; Power. 8 (1), 98-102 (1992).</li><li>Myers, R., Lapointe, M., Mantenieks, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MPD+thruster+Technology.">MPD thruster Technology.</a> , (1991).</li><li>Myers, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applied-field+MPD+thruster+performance+with+hydrogen+and+argon+propellants.">Applied-field MPD thruster performance with hydrogen and argon propellants.</a> Journal of Propulsion &amp; Power. 9 (5), 781-784 (1993).</li><li>Albertoni, R., Rossetti, P., Paganucci, F., Andrenucci, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Study+of+a+100-kW+class+Applied-Field+MPD+Thruster.">Experimental Study of a 100-kW class Applied-Field MPD Thruster.</a> , (2011).</li><li>Lapointe, M., Strzempkowski, E., Pencil, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+Power+MPD+Thruster+Performance+Measurements.">High Power MPD Thruster Performance Measurements.</a> , (2004).</li><li>Tahara, H., Kagaya, Y., Yoshikawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+and+Acceleration+Process+of+Quasisteady+Magnetoplasmadynamic+Arcjets+with+Applied+Magnetic+Fields.">Performance and Acceleration Process of Quasisteady Magnetoplasmadynamic Arcjets with Applied Magnetic Fields.</a> Journal of Propulsion and Power. 13 (5), 651-658 (1997).</li><li>Tahara, H., Kagaya, K., Yoshikawai, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Applied+Magnetic+Fields+on+Performance+of+a+Quasisteady+Magnetoplasmadynamic+Arc.">Effects of Applied Magnetic Fields on Performance of a Quasisteady Magnetoplasmadynamic Arc.</a> Journal of Propulsion and Power. 11 (2), 337-342 (1995).</li><li>Li, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+the+Effective+Voltage+in+Applied-Field+MPD+Thrusters.">Increasing the Effective Voltage in Applied-Field MPD Thrusters.</a> Journal of Physics D Applied Physics. 51, 085201 (2018).</li><li>Myers, R., Mantenieks, M., Sovey, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Geometric+Effects+in+Applied-field+MPD+Thrusters.">Geometric Effects in Applied-field MPD Thrusters.</a> , (1990).</li><li>Myers, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Geometric+Scaling+of+Applied-Field+Magnetoplasmadynamic+Thrusters.">Geometric Scaling of Applied-Field Magnetoplasmadynamic Thrusters.</a> Journal of Propulsion and Power. 11 (2), 343-350 (1995).</li><li>Mikelides, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applied-Field+Magnetoplasmadynamic+Thrusters,+Part+2:+Analytic+Expressions+for+Thrust+and+Voltage.">Applied-Field Magnetoplasmadynamic Thrusters, Part 2: Analytic Expressions for Thrust and Voltage.</a> Journal of Propulsion and Power. 16 (5), 894-901 (2000).</li><li>Nakata, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Study+for+the+Optimal+Electrode+Geometry+in+an+MPD+Thruster.">Experimental Study for the Optimal Electrode Geometry in an MPD Thruster.</a> , (2007).</li><li>Kurtz, H., Auweter-Kurtz, M., Merke, W., Schrade, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+MPD+thruster+investigations.">Experimental MPD thruster investigations.</a> , (1987).</li><li>Blackstock, A. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experiments+Using+a+25-kW+Hollow+Cathode+Lithium+Vapor+MPD+Arcjet.">Experiments Using a 25-kW Hollow Cathode Lithium Vapor MPD Arcjet.</a> AIAA Journal. 8 (5), 886-894 (1970).</li><li>Krulle, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+and+local+analysis+of+MPD+thruster+operation.">Characteristics and local analysis of MPD thruster operation.</a> , (1967).</li><li>Malliaris, A. C., Libby, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Velocities+of+Neutral+and+Ionic+Species+in+a+MPD+Flow.">Velocities of Neutral and Ionic Species in a MPD Flow.</a> , (1969).</li><li>Wang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Target+thrust+measurement+for+applied-field+magnetoplasmadynamic+thruster.">Target thrust measurement for applied-field magnetoplasmadynamic thruster.</a> Measurement Science &amp; Technology. 29, 075302 (2018).</li><li>Tikhonov, V. B., Semenikhin, S. A., Brophy, J. R., Polk, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Experimental Performance of the 100-kW Li MPDT with External Magnetic. , (1995).</li><li>Burkhart, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Low environmental pressure MPD arc tests. , (1967).</li><li>Boxberger, A., Jüstel, P., Herdrich, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+of+100+kW+Steady+State+Applied-Field+MPD+Thruster.">Performance of 100 kW Steady State Applied-Field MPD Thruster.</a> , (2017).</li><li>Malliaris, A. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+of+Quasi-Steady+MPD+Thrusters+at+High+Powers.">Performance of Quasi-Steady MPD Thrusters at High Powers.</a> AIAA Journal. 10 (2), 121-122 (1972).</li><li>Knudsen, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Kinetic Theory of Gases (London:Methuen). , 26-27 (1950).</li><li>Auweter-Kurtz, M., Krulle, G., Kurtz, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Investigation+of+Applied-Field+MPD+Thrusters+on+the+International+Space+Station.">The Investigation of Applied-Field MPD Thrusters on the International Space Station.</a> , (1997).</li><li>Connolly, D., Sovie, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+background+pressure+on+magnetoplasmadynamic+thruster+operation.">Effect of background pressure on magnetoplasmadynamic thruster operation.</a> Journal of Spacecraft and Rockets. 7 (3), 255-258 (1970).</li><li>Esker, D., Kroutil, J., Sedrick, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cathode Studies of a Radiation Cooled MPD Arc Thruster. , (1970).</li><li>Myers, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plume+characteristics+of+MPD+thrusters+-+A+preliminary+examination.">Plume characteristics of MPD thrusters - A preliminary examination.</a> , (1989).</li></ol>

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 ...

MPD thrusters are well known for a relatively high thrust density and a high specific impulse1,2,3. However, the typical thrust efficiency1 of MPD thrusters is relatively low, especially with propellants of noble gases4,5,6. For most MPD thrusters, a part of the propellant flow is injected into the discharge chamber from a slit between anode and cathode7,8 , with the result that a radial component is a significant proportion of the total discharge. However, in order to generate thrust, radial kinetic effects need to be converted into axial kinetic motion with a physical nozzle or a magnetic nozzle. Accordingly, a key feature of the new design MPD thruster is that all propellant is supplied through the cathode, which can act to inhibit radial discharge; in this way, the proportion of axial energy can be increased. There is an added effect in that the Hall parameter in the plasma around the anode can be increased by the decrease of the number density around the anode, which can strengthen the Hall acceleration component9. Since the propellant is close to the inner surface of the cathode where large quantities of initial electrons are emitted in this mode of injection, the propellant ionization rate can be increased greatly. Furthermore, the anode length has been minimized to decrease the wall-plasma connecting area and reduce anode power deposition10,11. As a divergent anode is applied, this will decrease the angle between the anode and magnetic field lines and decrease anode power deposition further12,13.
Despite the advantages noted above to improve performance, complete propellant supply by cathode injection can increase the risk of anode starvation which can result in &#34;onset&#34; phenomena14. To inhibit this behavior, we have retracted the cathode back to the base of anode. The electrons can then diffuse sufficiently in the radial direction before leaving the anode exit, which will act to relieve anode starvation. Further, a multichannel hollow cathode is adopted; compared to the single channel hollow cathode, a multichannel hollow cathode can increase the electron emission area and make the distribution of the propellant more uniform. With this modification, both the lifetime and stability of the thruster can be increased15,16,17.
The designed power of the thruster is 100 kW and a cooling structure is necessary with steady state operation. In the present laboratory experiments, an efficient water-cooling structure is employed. However, to evaluate the performance of the MPD thruster design, it is critical to obtain the thrust. With the application of a high-pressure water system to transfer heat, there will be strong vibration during the operation of such cooling, which can create significant interference if we used traditional thrust measurements. Accordingly, a target thrust stand is employed to measure the thrust.
MPD Thruster
As shown in Figure 1, the MPD thruster consists of anode, cathode and insulator.&#160;The anode is made of copper with a cylindrical divergent nozzle, the minimum inner diameter of which is 60 mm. There is an S-shaped cooling channel around the inner wall of the anode. The inlet and outlet of the channel are on the top of the anode, which are separated by a baffle. A slender copper block is employed to connect the anode and electric cable. The junction is on the outer surface of the anode.
The cathode material is tantalum tungsten, with nine propellant channels. The outer diameter of the cathode is 16 mm. The cooling of the cathode is achieved with a water-cooling holder around the cathode base. There is a ring-shaped channel inside the holder. The cold water is injected into the holder from the bottom and flows out from the top. There is a hollow cathode connector on the left side of the cathode. The propellant flows through the center of the connector and into the hollow cathode chamber; there is a large cavity inside the cathode base connecting with nine narrow cylindrical channels. The cavity acts as a buffer to increase the uniformity of the propellant distribution in nine channels. The cathode is connected to the electric cable with an annular copper block, which is installed around the cathode connector.
In addition to the main body of the thruster, an external magnetic coil is also necessary to generate fields for the mechanisms in the AF-MPD thruster; magnetic fields provide a convergent-divergent magnetic field to accelerate the plasma together with the electric field. The field coil consists of 288 turns of circular copper pipes, which act as the passage for both electric current and cooling water. The inner diameter of the coil is 150 mm, while the outer diameter is 500 mm. The highest field strength in the center is 0.25 T with current of 230 A.
Experiment System
The experiment system includes six subsystems. The schematic diagram of the overall layout of the experimental system is shown in Figure 2; the layout of the thruster inside the vacuum chamber is shown in Figure 3.
First, the vacuum system, which provides the necessary vacuum environment for the thruster operation, consists of one vacuum chamber, two mechanical pumps, one molecular pump and four cryogenic pumps. The diameter of the chamber is 3 m, and the length is 5 m. The environment pressure can be maintained under 0.01 Pa when the flow rate of (argon) propellant is no more than 40 mg/s.
Second, this source system provides a high voltage pulse to ignite the thruster, provides power for the thruster to accelerate the plasma, and provides power for the magnetic field coil to sustain the external magnetic field. The power source system consists of an ignition power source, a thruster power source, a coil power source and cables. The ignition power source can provide 8 kV or 15 kV discharge voltage. The thruster power source provides a direct current up to 1000 A. The coil power source provides a direct current up to 240 A.
Third, the propellant supply system feeds gas propellant for thrusters. The system mainly includes the gas source, the mass flow rate controller and gas supply pipelines.
The fourth sub-system is the water-cooling system, which provides cool high-pressure water to exchange the heat of the thruster, magnetic coil and power sources. As shown in Figure 4, the system consists of pumps group, water tank, refrigerator, water supply pipelines and pumps controllers. The non-conducting pipes inside the vacuum chamber provide a cooling water terminal for the thruster and magnetic coil, and ensures that electrical insulation among the anode, the cathode, and the ground.
The acquisition and control system can record the signals measuring thruster operation conditions and control operation of other systems. It is composed of three computers and corresponding software, data acquisition card and cables.
As shown in Figure 5, the target thrust stand consists of plate target, slender beam, displacement sensor, support frame, axial moveable platform and radial moveable platform. The target can intercept the plasma which pushes the target. The displacement of the target can be measured by a sensor placed behind the target, in this way enabling evaluation of the thrust18.

<table border="0" cellpadding="0" cellspacing="0" style="width:1097px;" width="1097">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Cryogenic Pumps</td>
			<td style="width:454px;">Brooks Automation</td>
			<td style="width:123px;"></td>
			<td style="width:317px;">Pumping speed: 10000L/s</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:205px;">Displacement Sensor</td>
			<td style="width:454px;">Panasonic</td>
			<td style="width:123px;">HG-C1030</td>
			<td style="width:317px;">Repetition precision: 10&#956;m 
			Linearity: &#177;0.1% F.S.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Mass Flow Rate Controller</td>
			<td style="width:454px;">Brooks Automation</td>
			<td style="width:123px;"></td>
			<td>Range: 0-120mg/s</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Molecular Pump</td>
			<td style="width:454px;">Oerlikon</td>
			<td style="width:123px;"></td>
			<td>Pumping speed: 2100L/s</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Moveable Plantform</td>
			<td style="width:454px;">Beijing Weina Guangke Automation equipment Co., Ltd.</td>
			<td style="width:123px;"></td>
			<td>Range:0-2000mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Plsatic Water Pipes</td>
			<td style="width:454px;">Xingye Xingye fluoroplastics (Jiaxing) Co., Ltd.</td>
			<td style="width:123px;"></td>
			<td>Ultimate pressure: 4.5MPa</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Propellant Argon</td>
			<td style="width:454px;">Beijing Huanyu Hinghui Gas Technology Co., Ltd.</td>
			<td style="width:123px;"></td>
			<td>Purity:99.999%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:205px;">Refrigerator</td>
			<td style="width:454px;">Beijing Jiuzhou Tongcheng Technology Co., Ltd.</td>
			<td style="width:123px;"></td>
			<td>Refrigeration power:45kW</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:63px;width:205px;">Water Pumps</td>
			<td style="width:454px;">Liaocheng vanguard Motor Co., Ltd.; 
			Shanghai people pump industry group Manufacturing Co., Ltd.; 
			Nanfang Pump Limited company</td>
			<td style="width:123px;"></td>
			<td style="width:317px;">Maximum Output pressure: 
			Centrifugal pump:1MPa 
			Plunger pump:10MPa</td>
		</tr>
	</tbody>
</table>

a 100 kw class applied-field magnetoplasmadynamic thruster

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.

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 (&#951;)1.
A typical signal of discharge voltage is shown in Figure 6</strong...

Watch this Scientific Journal Video about A 100 KW Class Applied-field Magnetoplasmadynamic Thruster at JoVE.com

A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

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

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate ...

The goal of this protocol is to introduce the design of a 100 kilowatt class applied-field magnetoplasmadynamic thruster and the relative experimented method. Magnetoplasmadynamic thruster, that is MPD thruster, is a typical electric accelerator. It is well known for high specific impulse and a high thruster density, and is treated as primary candidates for our main propulsion in our future high power space missions.In this article, we will introduce a design of a 100-kilowatt class applied-field MPD thruster, the necessary experiment systems to hold a relative thruster experiment and the operation steps to finish this experiment. Thruster designing. The thruster mainly consists of anode, cathode and insulator.The anode is made of copper with a cylinder divergent nozzle, the minimum inner diameter of which is 60 millimeters. The cathode is built of tantalum tungsten with nine propellant channels, the outer diameter of which is 16 millimeters. There is a hollow cathode connector on the left side.The propellant flows through the central of the connector and reach the hollow cathode. There is a large cavity inside the cathode base connecting with nine cylindrical channels. The cavity acts as a buffer to increase the uniformity of the propellant distribution in nine channels.The cathode is connected to the electric cable with an annular copper block, which is installed around the cathode connector. Besides the main body of the thruster, external magnetic coil is also necessary for the working of MPD thruster. The coil consist of 288 turns circle copper pipes which act as the passage for both electric current and cooling water.The inner diameter of the coil is 150 millimeters, while the outer diameter is 500 millimeters. The highest field strength in the central is 0.25 telsa. Experiment system.Experiment system provides necessary conditions for the experiment, which mainly includes six subsystems. Firstly, vacuum system provides the necessary vacuum environment for the thruster. And the diameter of the chamber is three meters, while the length is two meters.The environment pressure can maintain under 0.01 pascal. Secondly, power source system. Power source system consists of ignition power source, thruster power source, coil power source and cables.The ignition power source can provide eight kilovolt or 15 kilovolt discharge voltage. The thruster power source provides a direct current up to 1, 000 ampere. The coil power source provides a direct current up to 240 ampere.The third one is propellant supply system, which feeds gas propellant for thrusters. This system mainly includes gas source, mass flow rate controller and gas supply pipelines. The fourth one is water cooling system, which provides high pressure water to exchange the extra heat of the thruster, magnetic coil and power sources.Then is acquisition and control system, which can record the signals of thruster operation conditions and control other systems. The last one is target thrust measurement system, which can be used to measure the thrust. The target thrust stand mainly consists of plate target, slender beam, displacement sensor, support frame, axial movable platform and radio movable platform.The plasma can be intercepted by the target, and the target will be pushed by the plasma. The displacement of the target can be measured by the sensor placed behind the target. By this way, we can evaluate the thrust.Preparation for experiment. Install the thruster. Wipe the components of the thruster with alcohol in a clean room.Assemble the anode with the insulator. Bring together the cathode, cathode holder and cathode connector. Add the cathode part to the anode part.Install the middle connector into assemblage and fix them with screws. Establish the coil seat on experiment platform with forklift. Place the experiment platform on guide rail of the vacuum chamber.Install the thruster on the coil. Link the anode and cathode with corresponding electric cables. Link the magnetic coil with the coil power source.Join up the water cooling pipes and propellant supply pipe with thruster. Join up the water cooling pipes with the coil. Install the movable platform inside the chamber and fix the main body of thrust stand on it.Adjust the position of the movable platform to make the center line of the thruster and the target concede with each other. Then we collaborate the thrust stand. Firstly, load different weights on the collaboration device and record corresponding output of the thrust stand.Repeat the process for three times at least. Then we can calculate the elastic coefficient of the thrust stand according to the calibration data. Vacuumize the vacuum chamber.Close the door of the chamber. Start the mechanical pumps. Start the molecular pumps when the background pressure in the chamber is lower than five pascal.Start the cryogenic pumps when the background pressure in the chamber is lower than 0.05 pascal. Wait for the pressure to reach 10 to the power of minus four pascal. Ignition and thrust measurement experiment.We need to preheat the thruster if the thruster has been exposed to the air. Start recording the signal. Set the propellant mass flow rate at 40 milligrams and keep supplying for at least 20 minutes.Switch on the cooling water supplying. Set the working frequency of anode and cathode water cooling pumps at 10 hertz. Move the thrust stand to the position far from the thruster.Switch on the coil power source with the coil current of 90 ampere. Switch on the thruster power source with the discharge current of 240 ampere. Switch on the ignition power source.Keep the thruster working for at least five minutes. Switch off the thruster power source and propellant supplying. Stop the recoding.After the preheating, we can perform the thrust measurement. Move the thrust stand to the position 550 millimeters from the thruster. Start recording the signal.Start the propellant supplying. Ignite the thruster with 90 ampere coil current and 240 ampere discharge current. Increase the coil current to 90 ampere.Subsequently, increase the discharge current to 800 ampere. Then increase the coil current to 230 ampere. Switch off the thruster when the output of the thrust stand becomes stable.Stop the propellant supplying. Stop the recoding. Representative results.In the experiments, we control discharge current, propellant mass flow rate and applied magnetic field. Then we measure the value of discharge voltage and thrust based on which we can get other performance parameter like power, specific impulse and thrust efficiency. A typical signal of discharge voltage is shown in this figure.After turning on the power source, a high voltage will be employed on the thruster to break down the neutral propellant. After the ignition, the voltage trends to a constant value and basically keeps constant. Then we can say the ignition is successful.A typical thrust measurement result is shown in this figure. We start record the signal of the thruster stand before the propellant supplying, which is treated as a zero thrust point. There will be a slight thrust after supplying the propellant.After the ignition, there will be a large oscillation. Then the thrust tends to a steady value. There will be a zero drift due to the thermal deformation of the target, the value of which is 50 millinewton.The error caused by the drift is no more than 1%The figure shows the discharge characteristics during half-hour continue work. We confund that the thruster trends to steady state rapidly after ignition, and the voltage is very stable during this period. This figure shows the appearance changes of tantalum tungsten hollow cathode before and after experiments.The total experiment time is more than 10 hours. We can find slight erosion distributing uniformly on the outer surface of the cathode, which means the thruster has the potential to work for a much longer time than 10 hours. After the continue work test, we explored the performance of the thruster in the power range of 50 to 100 kilowatt.The best performance is obtained at 99.5 kilowatt while the thrust is 3, 052 millinewton. Specific impulse is 4, 359 seconds, and thrust efficiency is 67%It is noteworthy that when the thruster reaches the best performance, the background pressure is 0.2 pascal. Measured performance may be higher than the actual value due to the influence of high pressure.The tester is made out of tantalum tungsten and it shows the operation resistance. The gas power is 100 kilowatt with a thrust of 3, 050 millinewton, the specific impulse of 4, 300 seconds, and the efficiency of 67%

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Unit 1

Linear Momentum, Impulse and Collisions

SCIENTISTS IN ACTION

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

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