i

THE STUDY OF ELECTRIC PROPULSION TECHNOLOGY ON

SPACE CRAFT

THESIS PAPER SUBMITTED IN

SCHOOL OF SCIENCE, TECHNOLOGY, ENGINEERING AND MATH

FOR MASTER’S OF SCIENCE IN SPACE STUDIES

BY

Immanuel Gitamo

January 25, 2015

ii

𝜂𝑒 =𝑝𝑏

𝑝𝑇=

𝐼𝑏𝑣𝑏

𝐼𝑏𝑣𝑏 + 𝑝0

-Unknown, 1956-2003

Abstract

iii

Many spacecraft application are now focusing on using electric propulsion

technology, because, electric propulsion technology has not yet only proven its sound

engineering solution but also has proven how cost effective it can be. In recent years

more experiment have been done on the electric propulsion for example; In Chemical

Propulsion Information System, form 1960 to 1997 it was only 100 spacecraft which had

flown 300 electric propulsion. But since 1998 to 2010 which is a short period of time

compared to the previous, more than 150 spacecraft have used I one way or the other

the electric propulsion devices.

Main focus on this paper will be on the technology used in electric propulsion and

providing preliminary evidence for the endeavor of the technology and how much it can

be worked out to help explore deep space while cutting expenses.

Plasma and Ion thruster will be discussed in detail and how it’s being achieved in

electric propulsion. Through diagram, figures, tables and mathematical, all has been

used in order to give a clear picture that the technology is reliable and efficiency to be

used in spacecraft.

Acknowledgements

iv

I would like to start by saying we did it. I do use ‘we’ because from deep in my

heart I know I could have not done all this on my own. First of all, ill like to thank each

and every one and express my deepest gratitude to all have help me to reach this point

in my life. I say thanks to all my professor especially, Professor, Edward Albin,

Professor, Brian Anderson, Professor Lisa Kearney and all others I can’t remember on

top of my head in the American Military University universe for sage of wisdom,

guidance, constant encouragement, expertise and unwavering support you all gave.

My thanks also go to my fellow students whom all we worked together and come

up to this particular point of time. Ill would like just to say apart from being my fellow

students you guy became my friends in-which your companionship I always enjoyed

Extra special thanks to my parents (Dad, Hezekiah Gitamo and Mom, RoseLeah

Gitamo) for their love, support that is invaluable, affection and support during my whole

life and studies. Ill also like to extend my profound appreciation to my true love Eline

Illah for standing with me all through and believing in me. I love you.

Lastly but not least, I owe my sincere appreciation to my brother Moses Gitamo,

my sister Karen Mose and her beloved husband Evans Mose and entire family for

support and encouraging me over and over the years. I especially want to thank Philip

Ammons for coming into my life and playing big role, with his support, prayers and

encouragement I don’t know how much I can repay, I just want to say thank you and

God Blessing you. Finally, to my friends, Mike N. Kingoina, Cliff Nyachae, Duke Mwebi,

Felix A. Lowole and Jobie Oichoe thanks for continuous encouragement. I owe you

guy’s big time.

v

Table of Content

vi

Abstract …….……………………………………………………………………………………iii

Acknowledgements ……………………………………………………………………………IV

Table of Contents …………………………………………………………………………….…v

List of figures ……………………………………………………………………………….…..ix

List of Tables …………………………………………………………………………….….…..x

List of Abbreviations ……………………………………………………………………………………….xi

1 Introduction …………………………………………………………………….…..……1

1.1 Purpose Statement ………………………….…………………………….……… 2

1.2 Thesis Statement …………………………………………………….……….…... 3

1.3 Theoretical Framework ……………………………………………………….….. 3

1.4 Significance of the Study ……………………………………………………...…. 3

1.5 Research Design and Instrumentation …………………………………….…… 4

1.6 Data Analysis …………………………………………………………………..…. 5

1.7 Research Question ……………………………………………………………….. 5

1.8 Background …………………………………………………………………….…..5

(a) 1906 – 1945 ……………………………………………….………………..5

(b) 1946 – 1956 ………………………………………………..…………….…7

(c) 1957 – 1979 ………………………………………………..……………… 8

(d) 1980 – 1992 ……………………………………………….………………. 8

(e) 1993 – Present …………………………………………….……………….9

1.9 Limitation …………………………………………………………………….…… 9

2 Literature Review ……………………………………………………………….…… 11

vii

2.1 Current Status and Capabilities of Rocket Propulsion ……………………… 11

2.2 Current and Future Plans of Electric Propulsion System …………………… 11

2.3 Guidance Set Forth in Space Policy ………………………………………….. 14

2.4 Summary ……………………………………………………………………….….16

3 Research Methodology ………………………………….……………………….…. 17

3.1 Methodology ……………………………………………………………………... 17

3.2 Plasma Thrust Methodology …………………………………………..……….. 17

3.3 Result …………………………………………………………………………….. 18

3.4 Methodology Analysis ………………………………………………………..…. 20

3.5 Summary ……………………………………………………………………..….. 21

4 Electric Propulsion system …………...………………………………………………22

4.1 Plasma ……………………………………………………………………….…… 22

4.1.1 Plasma Thruster Design ……………………………………………… 29

4.2 Thruster ………………………………………………………………………...… 31

(a) Helicon Hall Thruster ……………………………………………….…… 32

(I) Operational Principles ………………………………….…….….. 33

(ii) Hall Thruster Assembly …………………………………………. 35

(b) Plasma Thruster ………………………………………………….……… 36

4.3 Analysis of Electric Propulsion Cost ……………………………………………37

4.4 Survey Analysis …………………………………………………………………..37

4.5 Summary …………………………………………………………………………..39

5 Conclusion Summary and Recommendation ……………………………………. 41

6 Bibliography …………………………………………………………………..………49

viii

LIST OF FIGURES

4.1 Pulsed Plasma Thruster ……………………………………………………………………. 31

ix

4.2 Power processing Unit …………………………………………………………………..….. 32

4.3 Operating Principles of Ion Thruster ………………………………………………….…… 34

4.4 Operating Principle of Hall Thruster …………………………………………………….…. 36

4.5 Hall Thruster Assembly ………………………………………………………………….….. 39

4.6 Trajectory ……………………………………………………………………………….……. 39

5.1 Ion Thruster ……………………………………………………………….………….………. 42

5.2 Liquid Thruster ……………………………………………………………………….………. 43

LIST OF TABLES

x

3.1 Analysis showing calculated measurement of Faraday ………………………………...…19

4.1 Plasma Thruster Design Summary ……………………………………..…………………. 30

5.1 Comparison between Ion thruster and liquid rocket ……………………………….…..… 47

5.2 Comparison of different propulsion in time to Mars ……………………………………….48

LIST OF ABBREVIATIONS

xi

AFOSR Air Force office of Scientific Research

AC- DBD Dielectric Barrier Discharge

COSPAR Committee of Space Research

EPRB Electric propulsion Research Building

EP Electric Propulsion

FEATHER Flight Demonstration of Electric Aircraft Technology for Harmonized

Ecological Revolution

ICSU International Council on Scientific Union

JAXA Japan Aerospace Exploration Agency

NASA National Aeronautics and Space Administration

UN United Nation

VE Visionary Era

NOMENCLATURE

xii

Constants

ⅇ 2.7183, Base of the natural logarithm [-]

𝐹 96485, Faraday constant [C/mol]

𝜀0 8.8542 𝑥 10−12 , Vacuum Permittivity [F/m]

𝜇0 4𝜋 𝑥 10−7, Vacuum Permeability [H/m]

Variables

�⃗� Magnetic field [T]

𝐵𝑧 Axial magnetic field [T]

𝑐 Capacitance [F]

𝐶𝐷 Drag coefficient [-]

�⃗� Electric field [V/m]

𝑓 Circular frequency [1/s]

𝑚 Particle mass [kg]

�̇� Mass flow rate [kg/s]

𝑀 Vehicle mass [kg]

𝑛𝑑 Density of object [𝑚−3]

𝑝 True pressure [Torr]

xiii

𝑝𝑏 Base Pressure [Torr]

𝑝𝑒𝐿𝑒 Electrical power delivered to Thruster [W]

𝑞 Particle charge [C]

𝑟 Faraday probe distance from thruster [m]

𝑠3 Speed ratio [-]

𝑡 Time [s]

𝑣, 𝑣 Velocity [m/s]

𝑣𝐵 Bohm velocity [m/s]

𝜀, 𝜀 Electron energy [F/m or J]

𝜀0 Permittivity of free space while in charge of density [-]

𝑛 Efficiency [-]

𝜆 Wave length [m]

𝜇 Electric mobility [H/m or 𝑚2/V/s]

𝜙3 Normal mass flux [kg/𝑚2/s]

𝛹𝐵 Beam divergence [-]

𝜔 Frequency of angular [rad/s]

𝜔𝑐 Frequency of cyclotron [1/s]

𝜔𝑝 Frequency of plasma [1/s]

xiv

1

CHAPTER 1

Introduction

Unpiloted or piloted spacecraft do employ the propulsion system that is able to

exert force so as to control and maintain on orbit. They are different kinds of propulsion

system that are being used, for example, the one which need no mass reaction from

external is referred as a rocket. Propellant is the stored mass reaction. The propellant

can be either chemical, liquid or solid.

In this paper, the focus will be on electric propulsion that uses electrical energy

to accelerate the propellant to higher velocity. Electric propulsion (EP) is not just a

portion of satellite or spacecraft, but it is combination of whole different system, such as

the mechanical part, the electric part, the power electronic and the thruster which is the

core in whole system.

The concept of electric propulsion and its technology it’s not new application to

the field of engineering. Since the beginning of the first design of spacecraft and other

meaningful conceptual development and maturity. Electric propulsion system has been

tested in three fundamental types namely; Electrostatic, Electro-thermal and

Electromagnetic. However, having this technology been tested and its advantage been

known like; long duration mission which will benefit more on electric propulsion in either

the attitude precision or even the position control, the deep space mission and the travel

to interplanetary whereby, the satellite or spacecraft will have much higher speed that

will be able to overcome from far away on Earth the relative weak gravitational field, the

2

aircraft with electric propulsion can be operated in very extreme condition, can last

longer compared to other propulsion, the models that’s has already been designed cut

the design cost on future because they can be generated, and last but not lease, the

electric propulsion will have to cut the cost of fuel consumption and trip time in a large

proportion. These importance have not yet been given first priority, due to the more

concentration given on solid and liquid propellant propulsion.

In EP there are some of the primary and essential electric propulsion thruster to

be kept in mind such as; the source of energy like nuclear and solar, how the

conversion of the energy happens into proper electrical voltage, delivering way and

metering just to name a few. Therefore, this paper will also focus on the technology

uniqueness and importance of EP giving them much weight.

1.1 Purpose Statement

Rocket propulsion is a subject of high importance whether in short or long

mission. Subsequently the call for low cost of these missions to space has been the key

priorities from public and interested party. Minimizing the cost of fuel during the mission

has become the major concern for both the government and private entities to finance

long mission. Having that on the hook, the electric propulsion system technology may

have the solution on the matter; since the propulsion system uses electric and magnetic

field rather than chemical energy. Because, ambient gasses that exists in the

atmosphere are able to be used as propellant which, it will cut the cost of fuel in a large

amount. Hence, the electric rocket propulsion will not only cut the fuel cost but also

increase the performance and technology on both short and long missions.

3

1.2 Thesis Statement

Increase of the electric propulsion system will increase technology and greatly

decrease the cost of fuel on mission into the space for example, this has been shown to

be true with the ongoing Dawn mission to Vesta and Cares.

1.3 Theoretical Framework

The theory has to be mathematical correct. That’s why the two cases of the

concentration will be; the technology development of electric propulsion with benefits

that will come along with it proven by mathematical way.

In the first case, this study examines the degradation of the technology used on

the electric spacecraft that makes it unique to use from solid and liquid propellant that

has been used before. In this case, it will show how important the technology is to the

application of deep space exploration both in government and private entity cutting the

cost of fuel. In the second case it will examine shortfall and benefit of electric propulsion

system. In this case it will enlighten its significant particular in this the current time frame

and why it is necessary particular in the performance of long mission.

1.4 Significance of the Study

Many researches have been done to configure the electric propulsion system for

example both NASA Glenn Research Center and Electric Propulsion Research Building

(EPRB). Most of the research done have examined fuel cost, design, lifetime of the

rocket propulsion and some even the current technology. And this one will be difference

4

than the others whereby, the different will be it will be showing most aspect of electric

propulsion and also enforcing on the need to have the electric propulsion system on the

future design in-order to protect space exploration from becoming of the past. More-so,

it will continue to show the technology capabilities that is on hand, that is not being used

due to the current situation of the economy. The need to have something done and

maintain the dignity of space exploration is at hand. Therefore, this research will clearly,

show the effectiveness and importance of the new technology on the rocket propulsion.

1.5 Research Design and Instrumentation

In comparing the cost of need to upgrade from liquid/solid propellant to electric

propulsion, or building the new electric propulsion system. Both the research done from

different entities, engineers, field and mathematical formula will be give high priority to

show how it is cost effective than the chemical or solid propellant. Having attention on

the research already done by other engineers, the concentration will be much focused

on the technology that has been adopted. How safe it is and its advantages. Also, when

doing calculation, it will enlighten the cost, compared with the previous one and its

efficiency.

5

1.6 Data Analysis

Using research already done, and math formula show hoe an electric propulsion

system will be the best compared to the current one that uses liquid or solid fuel. In

addition, using of the electric propulsion system it will much cheaper, higher

performance and long lifetime. Each of the analysis will show how it outweighs the

current one and need of replacing the technology is at hand if the current situation of

bad economy will still continue in future.

1.7 Research Questions

How significance will electric propulsion system technology be in the future

mission to space and impacts to the current one?

1.8 Background

Electric propulsion is a moving science. It has been there for almost a century to

date. This means the identification of the time and history is little bit challenging. Hence

the background information is classified into five categories of period of time with the

intent of giving the framework which can be understood and comprehended deeper on

the peculiar history of the electric propulsion.

(a) 1906-1945.

When tackling the background information of the electric propulsion it doesn’t

really mean that the idea of electric propulsion wasn’t there. The ideas were, but the

discernible nature of electric propulsion wasn’t used until recent years. The visionaries

6

era (between 1906 -1945) as it suggests, people heard vision and limited knowledge of

the electric propulsion and even though most of their work was theoretical, the

accomplishment they made can still be traced down to the current era.

To be precise, between 1957-1935 for example, lived a self-taught Konstantin

Tsiolkovsky. During his life he made some major contribution to the field of aerospace.

His rocket equation,

𝛥𝑣 = 𝑣𝑒𝐼𝑛𝑀𝑜

𝑚1 (1.1)

whereby 𝐼𝑛 is natural logarithm, 𝑀1 is final total mass, 𝑀0 is initial total mass, 𝑣𝑒 is the

effective exhaust velocity and 𝛥𝑣 being maximum change of velocity. These formulas

still remain the most major mathematical and fundamental expression in aerospace and

electric propulsion.

In explaining the visionaries’ era (VE) technology. In 1911 Tsiolkovsky in his

article “Albeit Germinal,” he published the ideas on the electric propulsion in which he

talked of how possible it was to produce the large velocity from the electricity straight

from the particle that are being ejected from the rocket device. Further, on the article he

shows how the atoms of thermal energized and velocity electrostatically particle are

bonded which will clearly show the perspective of the electric propulsion of the rocket.

But, when considering the time frame of the writing, the technology wasn’t that

developed. Hence, it was rejected same to idea of ion where the flux electron were

being thought to be great on the rocket propulsion despite of knowing of their small

momentum flux that was being resulted from having the small mass. During the VE,

7

only the electron was known of capable of attaining high velocity. The idea of positive

charge on the ion was still a nightmare.

On the same VE of Tsiolkovsky; lived a young American educated physicist who

was deeply troubled with the electrostatic acceleration of electron equation despite

having full knowledge of the canal ray. Goddard addressed a research problem of

production of electron in a moving velocity, having, and being knowledgeable on

cathode ray he wasn’t able to answer his own question of what could happen if the

electrons reach the speed of light. The knowledge he heard showed how Walter

Kaufmann’s measurement was highly taken into account giving room for expression of

thrust-to-power ratio.

(b) 1946- 1956

Between the year of 1946 thru 1956. This time it was just a step on previous

continuation era of what the VE pioneers heard done. Just to name a few; the

publication of the EP which contained Tsiolkoky’s equation and other material that was

done in 1954 by Ernst Stulinger who was a physicist. Publication on the paper of electric

propulsion having more benefits. Stuhlinger publication on the paper concerning the

trajectory launch

Even though speculation were there, Ernst Stuhlinger was having great idea on

the scientist standards which he was helped by another physicist Herman Oberth. They

both worked hand in hand even though no experiment were being conducted on that

period due to luck of technology but mostly were documented. Which made this period

more important because a lot of scientific ideas were published.

8

Some challenges and opposition was still there and not all aspect of publication

was accepted because, during that period of time the technology was still young

therefore, most of the things were done not in the aspect of the device but rather on the

feasibility for example the problem of how human being were going to pilot on space

which was not going to be answered unless experiment was done.

(c) 1957-1979.

From 1957 -1979 is a period which is mostly known as diversification period. This

period is where first man walked on the moon. A period which ushered diversification of

Ideas and more experiment were done. During these period completion for space

exploration occurred and it was seen as another era of scientific maturity.

Formation of law, governmental agency and other non-governmental sprung up.

The world was on a race towards the technology. States come together to have

harmonious law to govern use of space in which many treaties were formed and signed

in law. This is a period where EP was tested for the first time and accepted through

engineering.

(d) 1980-1992.

Civil engineer Sylvie from the University of Toulouse and his colleague from

Boeing, Jordan Charles have come openly describing how Einstein’s theory of special

relativity wasn’t accepted before which brought to the earlier ideas felling short. For

example, they heard to compare more than hundred different model of aircraft collecting

their performance and dimensions and after plotting the figures they found common

relationship that was before predicted on the law of physics and constructed law that

9

was for the prediction of aircraft flow system but not for the data mining experiments.

These accounted on geophysics, technology and the design evolution in 1990.

(e) 1993- Present

This is a period of application era, where the technology has been put to work.

The air vehicle together with the land vehicle has evolved becoming more efficient on

transportation of mass to and fro in which the history confirms the trend.

Technology has emerged that has opened windows of what flows especially into

space which was unavailable before. Human being are today moving through morph

design which it is understandable well, the flow of design has changed which is useful

and made huge changes to happen in terms of knowledge. Because the knowledge

always flows through the territory naturally. These is short meant means that less

knowledgeable people are able to accept technology evolution and gain knowledge

through interacting with more knowledgeable people and implementing what works on

the architectural flow technology.

1.9 Limitation

This thesis major limitation is encountered whereby there have not been many

experimental research into the topic on the technology of the electric propulsion in long

mission due to politics, luck of technology at the time and more-so luck of funds. And,

the few experimental research mission conducted especially on the air breathing space

craft on electric propulsion system, different researcher have not agreed in one

conclusion but conflicted and have diversion opinion. Hence, coming up with the

10

conclusion has been, heard task because of rely-lying to the research that has been

done before and luck of fast hand experience.

11

Chapter 2

LITERATURE REVIEW

2.1 Current Status and Capabilities of the Electric Propulsion

Centuries now, EP has being considered as the technology of the future in the

application of space. Being 21st century, its being understandable that the future is at

our hand and the application of the electric propulsion is spread in a wide range of

mission. For instance; the new mission especially the one for deep space probe or to

the interplanetary travel will greatly benefit from the electric propulsion, mission that

require position control or precision attitude are the best candidates for the EP, mission

that may be able to require the increase of vehicle velocity and at the same time

overcoming the weak gravitational from far distance from the earth will be the best

application of the electric propulsion and, lastly but not limited to this, mission of

geosynchronous that rely on the rotational perturbations and overcoming translational.

This application of the electric propulsion is being viewed as so, beneficiary when

compared to the chemical rocket. In a quick illustration, considering any

geosynchronous satellite. Take an example of the communication which has a lifetime

of fifteen years with 5732 pounds mass. In annual basis, the satellite will need an

increase in velocity for about 50 m/s, which means 1,654 pounds, that is much heavier

than a quarter of satellite mass of the chemical propellant that will be needed for its

lifetime. These is contrary with the electric propulsion which is capable of increasing the

specific impulse higher, nine times (2,800 sec) than the chemical propellant. Therefore,

12

the mass in the electric propulsion for satellite has been saved for about 1,213 pounds

which is roughly 18%. This is all contribution from reducing the propellant mass,

deleting the inert mass of chemical system and adding the electric thruster and power

supply. Also, it will be big potential advantages for tax payer money, because it will be a

big saving during the time of launch as delivering 1 kg to space cost $ 10,000.

2.2 Current and Future Plans of Electric Propulsion System.

In mid of 90’s researchers in United States step up to realization when engineers

from Russia published article called Ajax that simply described how plasma, mixture of

free electrons and electrically charged electron can be produced on the vehicle that

could will help to weaken the shock waves that is produced dung the hypersonic flight.

The authors based their technique on the knowledge of how the shock is

weakened due to the effect of heating with the experiments that was done on wind

tunnel earlier and it was deliberately ignored due to luck of science concept behind it.

Team of researchers from Air Force Office of Scientific Research (AFOSR) took the

matter to test whereby, they quickly create the electrodes through controlling plasma

which with other devices and magnet they attached on aircraft fuselage.

The result was positive in which the team was able to examine and see the airfoil

onset, therefore, they used stall which uses hot film sensor that turned automatic

actuator and increase lift. They were joined by the team of international researchers

mostly from Europe who came in for the collaboration. They forwarded to the design

13

engineers and recommended it to be added on the conceptual stage of the aircraft

because it could greatly be helpful in the reduction of aerodynamic stall vulnerability.

In the realization of how plasma could dump shock wave, researcher learned

also during the process the air flow on wings and around the vehicle also could be

impacted. They went ahead and contact universities and aviation companies like

Lockheed and Boeing to do some experiment on subsonic and hypersonic flight having

the plasma device with aim of getting knowledge of safest way of producing plasma on

air flow and how to generate plasma from the wings.

By late 90’s, the experiment done yield positive result that build greater

confidence of alternating current, dielectric barrier discharge (AC-DBD) or plasma

actuators generating more vorticity which will be able to keep the flow of air from

separating with the wing, that could end up causing loss of stall and lift. Even though the

technology is not yet 100%; for instance, the technology on which the currents are

forced through ionized air is capable of producing heat on the combination and

relaxation of molecule which the technology is still being explored, despite that, it stand

at its best and positive feedback from the experiments continue to yield hope on the

growing technology in the right direction.

They are many way of generating plasma and the AC-DBD is one just among.

And they are some of the experiment going on, in generating plasma such as sparks

discharge, radio frequency, high voltage coronas, microwave and electrical arcs. The

main reason of focusing on the plasma actuators is due to the reason that, it’s easy to

use, it has high amplitude, it positively offer possibility of low weight, has rapid response

14

compare to others and wide band width, it’s energy efficiency, scalability, it is durable

and they don’t have moving parts.

The electronic devices flushed with no any moving part has been experimented

and seen offering more rapid response in times of low profiling. Not only experiment

done on controlling shock on transonic shock mitigation and supersonic shows that but

also experiment that were done in the interaction of shock of boundary layer, controlling

of shock, getting rid of any transient phenomena during the off design condition, the

ways reducing drag and boosting lift.

The negative side of the experiment is seen on the re-entry flight. This is

because, during the re-entry, plasma can be manipulated due to the process whereby

plasma that is being generated in aerodynamic heating, can cause heat transfer

mitigation through the magnet on board for the controlling the flight and on generation of

electrical power (Anderson, 2010).

2.3 Guidance Set Forth in the Space Policy.

Before, man entered space, Vladimir Mandl heard already written first law of

monographic on study of space. But it was never published until when Wolf Heinrich in

1953 presented his doctoral thesis that was entitled; Air Law and Space, at university of

Gottingen then in 1958 it was published (Verpaetse, 1960).

Since that time to now, many policy and law concerning space has been passed

and published that is necessary to govern man’s consequential matters and activities in

the outer space. Even though there are different kind of arguments and debates that

have been brought forward to oppose the law of jurisdiction ( Vassile, 1985), Freedom

15

and even sovereignty (Diedericks-Verschoor) concerning space such in Universal

Declaration of Human Right Article 19 about freedom of speech and Antarctic Treaty of

1959 that talk of the disparities of space law. The guidance that was set still rules and

govern the space. This doesn’t mean the sovereignty and jurisdiction argument is

completely irrelevant (Vasilevskaya, 1960).

There is generally four types of law that apply to space, law that apply to

activities that is being performed in the outer space; law that is concerned and apply to

only outer space; law that is apply to the function that is being done on Earth as the

result of activities that will be performed during the outer space exploration and lastly,

the law that apply solely to the environment on the airspace and Earth (John, 2009).

The major point to bear is even though there are arguments and debate from

non-governmental institution like COSPAR (Committee on Space Research) and ICSU

(International Council of Space Law) and intergovernmental organization like UN (united

nation) and many more organization. They both have shown need of exploring the

space. That’s, why until now, article 21 of 1979 is till used and agreement on the

activities that governs states on celestial bodies and moon still applying. Hence,

therefore, the guidance set forth in space policy still apply but recommendation need to

be made so that, the space environment shall be protected from emission. This gives

electric propulsion a better chance of developing its technology.

16

2.4 Summary

Major big step have been made in EP system. Significant advances are

continuing to happen each day, for example the underway test of HK36TTC-ECO

Diamond by the Japan Aerospace Exploration Agency (JAXA) through a project of

Flight Demonstration of Electric Aircraft Technology for Harmonized Ecological

Revolution (FEATHER) through their own build electric powered propulsion system. In

this the JAXA flight test, it was able to bring academia from different institution, NASA,

EP enthusiasts and different industries for a discussion on electric propulsion future and

its advances.

In conclusion, the advancement of electric propulsion technology was given high

priority than negative side of EP moving forward on the technology was constrained

budget. Constrained budget being stumbling block towards testing and advancing the

new technology. Cooperation of companies, organizations and countries was concluded

to be able to conduct research together on same aspect in order to minimize budget

issues (Batishchev, 2009).

17

Chapter 3

RESEARCH METHODOLOGY

3.1 Methodology

Mixed method of methodology has been used in getting to know the efficiency of

technology of the electric propulsion both in the Hall thruster and the Plasma. As seen

from the earlier chapters, both heard shown good performance converting the beams of

ion from the helicon plasma and having the thrust increased rapidly. Therefore, the

methodology that will be described below examines probe to diagnose emanating

plasma from the thruster. Choosing this method was due to it being the most reliable

and active but still under analysis by the researchers from different department of

engineering.

3.2 Plasma Thruster Methodology

The plasma thruster methodology can be divided into three sections: (1) Velocity

of the exhaust ions, (2) divergence effectiveness of the beam and (3) flow rate of ion on

the exhaust. All this will show how efficiency the thruster is when put to work on the long

mission. It’s clearly by now, the knowledge on the reaction of the ion that generates the

thrust (Anderson, 2010). And getting the result on this is through the measuring of

plasma according to the equation 3.1

𝐹𝑖 = �̇�𝑖𝑣𝑖 cos𝑂𝑑𝑖𝑣 = (𝐼𝑏𝑒𝑎𝑚𝑚𝑖

𝑞) (

2𝑞𝑣𝑖

𝑚𝑖) 1

2⁄ (𝐼𝑎𝑥𝑖𝑎𝑙

𝐼𝑏𝑒𝑎𝑚) (3.1)

𝑣𝑖 𝑖𝑠 𝑡ℎⅇ ⅇ𝑓𝑓ⅇ𝑐𝑡𝑖𝑣ⅇ 𝑎𝑐𝑐ⅇ𝑙ⅇ𝑟𝑎𝑡𝑖𝑜𝑛. 𝐼 𝑎𝑥𝑖𝑎𝑙 𝑖𝑠 𝑎𝑥𝑖𝑎𝑙 𝑐𝑜𝑚𝑝𝑜𝑛ⅇ𝑡. 𝐹𝑖 𝑖𝑠 𝑡𝑟𝑢𝑠𝑡 𝑝𝑟𝑜𝑑𝑢𝑐ⅇ𝑑 𝑏𝑦 𝑖𝑜𝑛. �̇�𝑖 𝑖𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡ⅇ 𝑜𝑓

𝑜𝑓 𝑖𝑜𝑛. 𝐶𝑜𝑠0 𝑑𝑖𝑣 𝑖𝑠 ⅇ𝑓𝑓ⅇ𝑐𝑡𝑖𝑣ⅇ 𝑑𝑖𝑣ⅇ𝑟𝑔ⅇ𝑛𝑐ⅇ

18

Therefore, when getting the thrust efficiency of thruster in total, the total power

that is supplied (electrical) is dived through the kinetic power which is contained on the

ion that is produced on thrust. In addition, the thrust efficiency can be still broken further

on its physical component in which telemetry (Brown, 2009) can be able to determine

according to equation 3.2.

𝑛𝑅𝐹 = 𝜙𝑃𝑛𝐵𝑝𝛹𝐵 = [𝐼𝑏ⅇ𝑎𝑚𝑀𝑖 /𝑞�̇�] [𝐼𝑏𝑒𝑎𝑚𝑣𝑖

𝑝𝑅𝑓] [

𝐼𝑎𝑥𝑖𝑎𝑙

𝐼𝑏𝑒𝑎𝑚] (3.2)

𝜙𝑝 𝑖𝑠 ⅇ𝑓𝑓𝑖𝑐𝑖ⅇ𝑛𝑐𝑦 𝑜𝑓 𝑝𝑟𝑜𝑝ⅇ𝑙𝑙𝑎𝑛𝑡 𝑢𝑡𝑖𝑙𝑖𝑧𝑎𝑡𝑖𝑜𝑛.𝛹𝐵 𝑖𝑠 𝑐𝑜𝑠𝑖𝑛ⅇ 𝑑𝑖𝑣ⅇ𝑟𝑔ⅇ𝑛𝑐ⅇ 𝑎𝑛𝑑 𝜂𝐵𝑝 𝑖𝑠 ⅇ𝑓𝑓𝑖𝑐𝑖ⅇ𝑛𝑐𝑦 𝑜𝑓 𝑝𝑜𝑤ⅇ𝑟

3.3 Results

The electric plasma thruster efficiency was calculated and measure on Faraday

probe which showed the effectiveness (Brown, 2009) of the acceleration voltage in table

3.1 which concur with the equation 3.3

𝑣𝑖 = (𝑒

2𝑚𝑖)(

𝐹𝑅𝐹

𝐼 𝑎𝑥𝑖𝑎𝑙) (3.3)

19

Table 3.1 Analysis showing calculated measurement on Faraday

𝜃 �̇� 𝛹𝐵 𝜙 𝑛𝑅𝐹 𝑝𝑅𝐹 𝑣𝑖 𝑣𝑚𝑝 𝐵𝑧 𝐹𝑅𝐹

deg Mg/s % % % W V V G mN

48 2.4 45 14 0.34 1080 33.7 68.4 550 4.15

49 4.7 42 6.5 0.11 1210 30.9 75.0 470 3.47

46 4.7 48 7.8 0.16 1068 26.2 62.3 550 3.98

48 7.6 44 4.9 0.16 961 40.9 55.5 550 4.86

Table 3.1 has shown the probable measurements which provide kinetic energy

that explain the thrust. Also the result shows the kinetic energy is used to provide the

thrust rather than only to the Vmp (Yano, 2006). But, this is not be the only source of

thrust. Because there is need to increase the performance on the propulsion which will

require the increase of power too.

The two scenario come to play when considering increasing power to the

propulsion. The first scenario is whereby, knowing that the velocity exit of the isentropic

or supersonic can be known only through the constant temperature (Cohen, 2003), it is

assumed, therefore, the specific heat ratio and the area ratio of the nozzle to be same.

This will bring forth the charge exchange which will result on the effective increase of

temperature on the propellant and its effectiveness.

The second scenario is whereby; the gas has strong influence on the

performance of the propulsion. This is more explained later on the next chapter in

equation 4.15, the Maxwellian distribution in which thermalization (Lias, 2005) of the

20

free molecular is used for the acceleration of the neutrals of argon. Therefore, this

scenario closes out other experiment that show pumping of neutral that has been

demonstrated out by other authors on the same.

3.4 Methodology Analysis

From the work done previously with scholars, researchers and engineers on

efficiency methodology of EP thruster. They have put much weight on two probe;

Langmuir probe and Faraday probe. Faraday probe had more advantage in this

experiment over Langmuir because of showing the consistently on the total efficiency

which is always power of electric that is being consumed, 𝑝𝑒𝐿𝑒𝑐 dividing the trust kinetic

power, 𝑝𝐽𝑒𝑡, according to equation 3.4 below.

𝑛𝑡 =𝑝𝐽𝑒𝑡

𝑝𝑒𝐿𝑒𝑐=

1

2�̇�𝑣𝑒𝑥

2

𝑃𝑑+𝑝𝑚𝑎𝑔

(3.4)

𝑝𝑚𝑎𝑔 Is for power supplied while 𝑃𝑑 is power discharged.

Longmier and his colleague wrote in Journal of Propulsion and Power which was

featured in 2011 suggesting how to adapt the scalable technology and low cost in order

to increase the robustness, and in there methodology they used Faraday. Admitting

both can be used but depending on different stages.

21

Therefore, result from the Faraday probe and Langmuir probe has greatly helped

to show how the efficiency of the thruster, determining the ion required for the thrust,

acceleration effectiveness and diagnosing the internal parameter on plasma.

3.5 Summary

Using mixed methodology in this paper. Cross designing, validating and resolving

some discrepancies have been the key. Even though there is a little guideline given

that, emphasis has been put here for the transformative framework in order to get the

accurate result through calculation and observation comparing to the experiments that

has already been done so to eradicate any era in the technology.

22

Chapter 4

ELECTRIC PROPULSION SYSTEMS

4.1 Plasma

Ionized gas that are collectively reacting from the external magnetic and electric

field when applied on them or simply the gas that are electrical charged are known as

plasma. In Lorentz force through the equation 4.1 show that, the electric charge is the

one manifest the interaction (Yano, 2006).

𝑡 𝑖𝑠 𝑡𝑖𝑚ⅇ,𝑚 𝑖𝑠 𝑝𝑎𝑟𝑡𝑖𝑐𝑙ⅇ 𝑚𝑎𝑠𝑠, 𝑞 𝑖𝑠 𝑝𝑎𝑟𝑖𝑐𝑙ⅇ 𝑐ℎ𝑎𝑟𝑔ⅇ, 𝜈 𝑖𝑠 𝑡ℎⅇ 𝑝𝑎𝑟𝑡𝑖𝑐𝑙ⅇ 𝑣ⅇ𝑙𝑜𝑐𝑖𝑡𝑦, 𝜀 𝑖𝑠 𝑡ℎⅇ ⅇ𝑙ⅇ𝑐𝑡𝑖𝑟𝑐 𝑓𝑖ⅇ𝑙𝑑,

and �⃗� 𝑏ⅇ𝑖𝑛𝑔 𝑡ℎⅇ 𝑚𝑎𝑔𝑛ⅇ𝑡𝑖𝑐 𝑓𝑖ⅇ𝑙𝑑.

𝑚𝑑�⃗�

𝑑𝑡= 𝑞(𝜀 + 𝜈 𝑥�⃗� ) (4.1)

The equation 4.1 above just shows how the forces that are acting on the particle

which are charged are functional of the velocity, mass and charge. Also taking a look at

Young Mills equation of buddle curvature can be applied for a better understanding of

both strong and weak forces on the interaction of particles. But, the problem will occur

because it will be therefore forced to put a side and ignore the mass completely which

will be introduced later through Higgs field.

Implementing of plasma technology is so important in successful of electric

propulsion. Just to be caution when plasma becomes time dependent due to variety of

time scales that is associated with frequencies that are different is physics. For

23

instance, where is on the faster time on scale will automatically correspond with the

frequency characteristics. This may end up becoming more complicated. Therefore, by

the definition of plasma, the charge of the whole plasma is approximately zero as both

the negative and positive are nearer to be equals (Brown, 2009). That is being referred

as quasineutrality in which can be expressed by the following equation 4.2

𝑞𝑛𝑖 ≈ ⅇ𝑛𝑒. (4.2)

Even though plasma is being quasineutral, both of the electron and ions create

net charge density due to the capabilities of them to move parallel to each other, in

which it makes it possible to determine the electric field that created on the separation

of the charge. Therefore, in order to determine the electric field Poisson’s equation 4.3

is used:

𝛻 ∖ �⃗� =𝜌𝑞

𝜀𝑜 (4.3)

𝜀0 𝑖𝑠 𝑝ⅇ𝑟𝑚𝑖𝑡𝑡𝑖𝑣𝑖𝑡𝑦 𝑜𝑓 𝑓𝑟ⅇⅇ 𝑠𝑝𝑎𝑐ⅇ 𝑤ℎ𝑖𝑙ⅇ is cherge density.

The force that is being exerted to the charged particles, 𝐹𝑒⃗⃗ ⃗𝐿 , through, the electric

field causes the acceleration that is determined with the equation 4.4

24

𝐹𝑒⃗⃗ ⃗𝐿 = 𝑞�⃗� (4.4)

Therefore, because of electrons is being lighter in weight than ions, the force

from the electric field will on act to change the electrons velocity according to the

equation 4.5

𝑚𝑒𝑑𝑣𝑒⃗⃗⃗⃗

𝑑𝑡 = −ⅇ�⃗� (4.5)

𝑣 𝑒 𝑖𝑠 𝑣ⅇ𝑙𝑜𝑐𝑖𝑡𝑦 𝑜𝑓 ⅇ𝑙ⅇ𝑐𝑡𝑟𝑜𝑛, ⅇ 𝑖𝑠 𝑡ℎⅇ 𝑐ℎ𝑎𝑟𝑔ⅇ 𝑜𝑓 ⅇ𝑙ⅇ𝑚ⅇ𝑛𝑡𝑎𝑟𝑦 𝑎𝑛𝑑 𝑚𝑒 𝑏ⅇ𝑖𝑛𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 ⅇ𝑙ⅇ𝑐𝑡𝑟𝑜𝑛𝑠

To make it a well understandable and simpler, the analysis of the behavioral of

the plasma can be looked in a one dimension according to the following equations 4.6-

4.8.

𝑑𝐸

𝑑𝑥=

𝜌𝑞

𝜀0 (4.6)

𝑑𝐸

𝑑𝑡=

𝑑𝐸

𝑑𝑥

𝑑𝑥

𝑑𝑡= 𝑣𝑒

𝑒𝑛𝑒

𝜀𝑜 (4.7)

𝑑𝑣𝑒

2

𝑑𝑡2 =𝑒

𝑚𝑒

𝑑𝐸

𝑑𝑡= 𝑣𝑒 (

𝑒𝑛𝑒2

𝑚𝑒𝜀𝑂) (4.8)

𝑛𝑒 𝑖𝑠 𝑡ℎⅇ 𝑛𝑢𝑚𝑏ⅇ𝑟 𝑜𝑓 ⅇ𝑙ⅇ𝑐𝑡𝑟𝑜𝑛 𝑑ⅇ𝑛𝑠𝑖𝑡𝑦 𝑎𝑛𝑑 𝑥 𝑏ⅇ𝑖𝑛𝑔 𝑠𝑝𝑎𝑡𝑖𝑎𝑙 𝑑𝑖𝑚ⅇ𝑛𝑠𝑖𝑜𝑛.

25

In plasma, the oscillatory behavior that is described on the equation will only

mean the sloshing of electrons about the ion, whereby the frequency of electron plasma

characteristics is being described in the following equation 4.9

𝑤𝑝 𝑖𝑠 𝑡ℎⅇ 𝑓𝑟ⅇ𝑞𝑢ⅇ𝑛𝑐𝑦 𝑜𝑓 ⅇ𝑙ⅇ𝑐𝑡𝑟𝑜𝑛 𝑝𝑙𝑎𝑠𝑚𝑎.

𝑤𝑝 = √𝑞2𝑛𝑒

𝑚𝑒𝜀0 (4.9)

There are things which are important to note. In obtaining the plasma

frequency from the analyzing ion, the natural arising of charged particle from the

thermal motion due to the oscillatory behavior of the plasma is one illustration on the

nature of plasma physics time dependent. This is rather different from quasineutral

plasma as the following equation 4.10 implies. The electron plasma frequency is much

heavier than that of the ion plasma frequency.

𝑤𝑃𝑖 𝑖𝑠 𝑖𝑜𝑛 𝑝𝑙𝑎𝑠𝑚𝑎 𝑓𝑟ⅇ𝑞𝑢ⅇ𝑛𝑐𝑦 𝑎𝑛𝑑 𝜔𝑝𝑒

𝑠𝑡𝑎𝑛𝑑𝑠 𝑓𝑜𝑟 ⅇ𝑙ⅇ𝑐𝑡𝑟𝑜𝑛 𝑝𝑙𝑎𝑠𝑚𝑎 𝑓𝑟ⅇ𝑞𝑢ⅇ𝑛𝑐𝑦

𝑤𝑃𝑒𝑤𝑝𝑖

⁄ ≈ √𝑚𝑖 𝑀𝑒⁄ . (4.10)

26

Plasma do shield the bulk population from electric field that comes from external.

These characteristics of plasma enable it to re-arrange charges collectively in a process

called Debye length 𝜆𝐷 as the equation 4.11 shows.

𝜆𝐷 = √𝑘𝐵𝑇𝑒

𝑛𝑒𝑒2 (4.11)

𝑇𝑒 𝑖𝑠 𝑡ⅇ𝑚𝑝ⅇ𝑟𝑎𝑡𝑢𝑟ⅇ 𝑜𝑓 ⅇ𝑙ⅇ𝑐𝑡𝑟𝑜𝑛 𝑎𝑛𝑑 𝑘𝐵𝑖𝑠 𝐵𝑜𝑙𝑡𝑧𝑎𝑚𝑎𝑛𝑛 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡.

On the process of shielding out the electric from external sources for a period of

time especially if it is large plasma, according to Debye lengths, spontaneous electric

field will be developing forming a sheath on the surface which the thickness is few

Debye lengths. Note that the sheath is not quasineutral and the Debye length both

function of the density and the electron temperature. Therefore, in order to get the

characteristics of the plasma speed, whereby the speed here means am bipolar speed,

the multiplication of Debye length and the frequency of ion plasma will be the solution

according to the following equation 4.12.

𝑣𝐵 = √𝑘𝐵𝑇𝑒

𝑚𝑖 (4.12)

𝑚𝑖 𝑖𝑠 𝑖𝑜𝑛 𝑚𝑎𝑠𝑠

27

The ion acoustic speed or the Bohm speed is also known as the am bipolar

speed. The am bipolar speed will only represent the speed of both electron and ion that

propagate on a free surface when the material surface was not bonded with the plasma.

And, the plasma that is mostly used on the propulsion on the space system are mostly

operated in a low pressure.

Plasma are not in a thermodynamic equilibrium because electrostatic propulsion

system are non-thermal and uses plasma with low temperature. This low temperature

plasma gives an advantage on the distribution of ion energy which is lower than room

temperature. These plasma of lower temperature and non- thermal have the weak

ionization characteristics. Therefore, the uncharged gas (neutrals) of the plasma have

strong behavioral properties effects on the plasma. This is because, on plasma, the

neutrals will interact only with other neutrals, ion and electron which means that, they

can’t be either influenced by the magnetic field nor the electric.

Mean free path is the length scale, which is relevant to the neutral behavior that

averages the distance of the gas particles that will travel before colliding into another

particle of the gas. The gas particle will not be likely to collide into each other if the

mean free path is bigger than the unbounded particles of the gas system length scale

until after leaving the system. Equation 4.13 show how the gas particles are molded like

a hard- sphere in a mean of the neutral ideal gas, homogeneous and single species.

𝜆𝑚𝑓𝑝=

1

𝑛𝑔𝑣𝑚 (4.13)

28

𝜎𝑚 𝑖𝑠 𝑐𝑟𝑜𝑠𝑠 − 𝑠ⅇ𝑐𝑡𝑖𝑜𝑛 𝑓𝑜𝑟 𝑚𝑜𝑚ⅇ𝑛𝑡𝑢𝑚 ⅇ𝑥𝑐ℎ𝑎𝑛𝑔ⅇ 𝑐𝑜𝑙𝑙𝑖𝑡𝑖𝑜𝑛

𝑛𝑔 𝑖𝑠 𝑛ⅇ𝑢𝑡𝑟𝑎𝑙 𝑔𝑎𝑠 𝑑ⅇ𝑛𝑠𝑖𝑡𝑦.

Therefore, the characteristics of the time scale of neutral gas are determined

through the time that elapses between neutral gas collisions. And it is being expressed

as collision frequency, 𝑣𝑀. Collision frequency is function to relative velocity the particle

that interact, gas density,𝑛𝑔 and the cross- sectional area of the colliding particles of the

hard-sphere, 𝜎𝑚 as expressed in equation 4.14.

𝑣𝑚 = 𝑣

𝜆𝑚𝑓𝑝= 𝑛𝑔 < 𝜎𝑚𝑉 > (4.14)

According to the equation 4.15, the mean speed of the neutral is being defined on

gas temperature because, the neutral gas in Maxwellian distribution velocity is assumed

to be typically isotropic.

𝑣𝑡ℎ =√8𝑘𝐵𝑇𝑔

𝜋𝑚𝑔 (4.15)

𝑣𝑡ℎ 𝑖𝑠 𝑡ℎⅇ𝑟𝑚𝑎𝑙 𝑣ⅇ𝑙𝑜𝑐𝑖𝑡𝑦, 𝑇𝑔 𝑖𝑠 𝑔𝑎𝑠 𝑡ⅇ𝑚𝑝ⅇ𝑟𝑎𝑡𝑢𝑟ⅇ,𝑚𝑔 𝑖𝑠 𝑝𝑎𝑟𝑡𝑖𝑐𝑙ⅇ 𝑚𝑎𝑠𝑠.

When dealing with the Maxwellian energy distribution, the other thing to note is if

its assumed the gas is in ambient, the ratio of speed will be so critical in the determining

29

the asymptotic solution as shown in both the equation 4.16 and 4.17 which are incident

mass flux on Boltzmann relation respectively to the momentum flux.

𝛷3 =1

4𝑚𝑛(

8𝑘𝐵𝑔𝑇

𝜋𝑚) 1

2⁄ [exp(−𝑠32) + √𝜋𝑠3{ⅇ𝑟𝑓(𝑠3) + 1)] (4.16)

𝑝3 = 𝑛𝑘𝐵𝑇𝑔 [𝑠3

√𝜋ⅇ𝑥𝑝(−𝑠3

2) + (1 2⁄ + 𝑠32)(1 + ⅇ𝑟(𝑆3))] (4.17)

𝑠3 𝑖𝑠 𝑠𝑝ⅇⅇ𝑑 𝑟𝑎𝑡𝑖𝑜, 𝑝3𝑖𝑠 𝑓𝑙𝑎𝑡ⅇ 𝑝𝑙𝑎𝑡ⅇ 𝑤ℎ𝑖𝑙ⅇ 𝛷 𝑖𝑠 𝐵𝑜𝑙𝑡𝑧𝑚𝑎𝑛𝑛 𝑟ⅇ𝑙𝑎𝑡𝑖𝑜𝑛 𝑓𝑜𝑟 𝑖𝑛𝑐𝑖𝑑ⅇ𝑛𝑡4

4.1.1 Plasma Thruster Design

The design of plasma is to show in the experiment how helicon plasma will be of

the advantage in the effectiveness of the thruster to sustain it to live long on the

spacecraft. Using experiment done on a research on a spacecraft which is a square

meter with circular orbit. The laboratory pressure was approximately 1 millitorr because

most pressure in the laboratories operate in that. The equation 4.18 below was used

𝜆𝑧[𝑚] = 0.83 √𝐵𝑧[𝑇] (4.18)

𝐵𝑍 Is axial magnetic field strength while 𝜆𝑧 is helicon wavelength

Due to 10% temperature being higher on the fractional ionization according to the

formula. It is still not accepted according to the measurement of Langmuir probe of

helicon plasma whereby, still the densities of plasma can be achieved on same helicon

wavelength. This is because previous research and studies has shown it may have still

higher coupling efficiency and still works. The result are as in the table 4.1 below

30

Plasma Thruster Design

SummaryProperty Value

Altitude h = 170- 230 km

Mass Flow rate mpr = 1 -7 mg/s

Inlet A inlet = 1 m

Helicon wavelength 26 cm

Operating Pressure 1 m Torr

Table 4.1 Plasma thruster design table.

31

Figure 4.1 showing pulsed plasma thruster (courtesy of Hughes aircraft co.)

4.2. Thruster

Design project of the electric propulsion has been projected to have been started

in 1960s. And the concept on the electric propulsion as seen from previous chapter is

that, it mainly uses the ionizing gas instead of the chemical propellant that helps the

space craft to propel. In that circumstances, the spacecraft is ionized and then

electrically accelerated; but before then, when the energy has been converted to

electricity either through heat engine, rectenna or photovoltaic cell. The electricity will go

into the power processing unit, where the condition for use will happen according to the

following figure 4.1 below.

32

Figure 4.2. (Courtesy of NASA)

The engineering part of the electric propulsion is now used in wide range

whereby, air breathing electric propulsion has been pointed to be the best in mission.

For example a deep space mission and the geosynchronous satellite like METEOSAT.

The main reason for this is the lifelong survival of the propulsion on the space while

having the source of the electricity and also, the high specific impulse that is associated

with it. Rapid growth of technology in design of electric propulsion and its application will

be the main focus. And on this particular place, the concentration will be in two

thrusters, the Helicon Hall which is a two stage thruster and the Plasma Thruster which

is basically using the scaling on the helicon plasma, (Lias, 2005)

(a) Helicon Hall Thruster.

It was on 1970s that hall thrusters were first employed in space but it took more

than 20 years for more major development to occur on it. Primarily, the research has

shown that, major activity that is done in the hall thruster is increasing the lifetime of it

(Batishchev, 2009), because of avoiding using the xenon. Therefore, the current

research shows that current thruster which are versatile in technology and robust its

performance is extendable and there further more increase on the thrust density and

power.

33

The limitation that we know with hall thrusters is of the erosion material which

limits its lifetime. But many research done with the xenon gas has shown that, the hall

thruster can be operated in a way, that, the erosion part is being reduced (Yano, 2006),

hence, increasing its lifetime. The same principles used with hall thruster on the xenon

gas, can be still be applied on other gasses like oxygen or nitrogen making the hall

thruster viable propulsion for spacecraft that’s uses air breathing mechanism.

As mentioned above, the design part of the hall thruster was designed when

using the xenon it has to have high thrust to power in which is synonymous with the

operation of low voltage. For example, when the spacecraft is in lower altitude the

voltage on acceleration will have compensation for drag. Therefore, this makes the

parameter of the electric propulsion Hall thruster design to function and operate well

than the other (Sutton, 2010).

(i) Operational Principles

Characteristics performance of the Hall thruster, which operates with gas has been

well researched due to the stage of ionization that determine the increase of thrust and

power. In addition of being designed a two stage in the utilization of mechanism of

acceleration and ionization sources from helicon plasma (Cohen, 2003). Helicon

thruster has the wave modes that excite the annular helicon from the plasma upstream.

These has come up with more advantages in the controlling of thrust build up ad

controlling the engine start up compared to the other propellant. For instance, research

done on rocket engine showed most engine during stopping especially and starting, the

mixture ratio considerably varied. The variation came from not having same propellant

34

flow of hydraulic resistance which ends up causing instability. The figure 4.3 below

summarizes operating principle of ion thruster.

Figure 4.3 showing operating principles of ion thruster (courtesy of NASA)

35

(ii) Hall Thruster Assembly

The Hall thruster was assembled and designed in the partner of the Aero jet and

Electro-Dynamic Application whereby, it was purposely meant on using the hollow

cathode from external and the electrodes as shown in figure 4.3 show its operating

principle and figure 4.4 after assembly.

Figure 4.3 Operating principle of Hall Thruster (courtesy of Space Exploration)

This operating principle of the hall thruster is a Russian technology. The thruster

can be compared with the one of the ion grid but the only difference is that is much

small physically than the thruster from ion grid.

36

Figure 4.4 showing Hall thruster assembly (courtesy of Space Exploration)

(b) Plasma Thruster

Many researcher have done a lot of work which involves using ionization stages

that include helicon although, the focus of the experiment rely much on the argon so as

so it can accelerate other gasses (Batishchev, 2009) and simply physic analysis on

different acceleration of the research of plasma thruster in the electric propulsion. Most

of the result that came out, show the velocity of exhaust, from the helicon plasma is up

to the standard range that is being desired for the propulsion system that is air-

breathing (Slough, 2009).

Therefore, the preliminary investigation to show if the use helicon on a plasma

thruster will be better idea was conducted in the plasma-dynamic and electric propulsion

library whereby, measurement were taken which were created with argon because most

37

of the experiment done on helicon operates with Argon, which is commonly known by its

appearance of blue core.

4.3 Analysis of electric propulsion cost

Glenn Research center in NASA analyzed the EP cost from the design to the end

of mission in a study done on the exploration and aerial vehicle reconnaissance. They

noted that if the use of the powered core on the engine which was able to extract

hydrogen and helium three and four from the atmosphere will be so advantageous and

will be able to cut the cost of fuel.

The EP weight and size has contributed for the cost of fuel to be low. In addition,

the design of the EP has been able to cut the volume and mass dramatically. And this

has been concurred with NASA who have already put four spacecraft on space and said

the cost has been cut for about 65%.

4.4 Survey Analysis.

They compared with other data and experiment that was done in more than 30

years on the turbulent combustion because is a center that determines operability of the

engine and also, it remains the major process where the energy is being converted in

mostly propulsion engines such like of rockets, engines of the jet and in scramjets.

They took a keenly interest at these engines, because the combustion of oxidizer

and fuel are done there on a high turbulent condition whereby, mechanical energy is

38

converted from chemical energy for propulsion. They still found it’s of more

advantageous approach using the EP from the design, operational and mission wise.

In a different part, the Propulsion Research Laboratory in the State of Utah tested

EP compared with the acrylonitrile butadiene styrene as being new fuel for the hybrid

rocket. The analysis cost was compared from the design of the prototype, building and

testing.

The key note while analyzing the EP will be on the mass and the power in which

power is equal to force multiply by velocity. But in this case of moving aircraft the power

will be termed as power available, 𝑝𝐴 in which it can be represented as for equation

4.19 below.

𝑝𝐴 = 𝑇𝑣∞ (4.19)

T is thrust while 𝑣∞ is velocity.

Simply, the power supply and the energy source input must be in high voltage

than the power output. Hence, for every engine design configuration module the specific

power has to be defined. And when talking of specific power, it mean independent total

mass which will be expelled in the proportion of the power of engine.

39

4.5 Summary

The ion thruster generally can be divided in five part. The ion thruster, power

processing unit, control computer, power source and propellant management system.

This ion thruster has become the most researchable propulsion with the current

engineers as described by Barrett in interviewed on NASA television. Barrett works in

NASA Glenn Research Center. He describes how there is no any other top speed

rocket in the current generation that can move faster and for long distance rather than

the one of ion thruster (Brown, 2009).

Even though it produces low thrust density it is efficiency and cheaper, and also

EP have a characteristic of having trajectories that are spiral because of low thrust and

long thrusting time (Sutton, 2010) as the figure 4.5 shown below, taken from Rocket

Propulsion Elements 8th Edition page 629.

Figure 4.5 Trajectory diagram

40

Lastly, thrusters play a major role in EP. And be in of non-thermal electrical or

electro-thermal the most important aspect is the optimum performance of the flight. And

due to budget constrained not much study has been contacted on its efficiency, specific

power and other most things which is still underway.

41

Chapter 5

Conclusions

In this paper, the EP technology was the major focused and given the priority,

these is because the advantages such as it is much safer, easier to control, easy to

maintain, it can be reused, its environmental friendly, easy to operate, it can last longer,

good geometric constraints and communication attenuation among others.

Therefore as explored, the electric propulsion system on the air-breathing

spacecraft. It’s clearly known how in a wide range on theoretically perspective how it’s

possible for the electric propulsion system to be able to operate (Sutton, 2010). Plasma

and Helicon thruster emerged whereby, the reported measurement concurred with the

requirement of the needed specific impulse for the air breathing spacecraft to

accomplish the mission for long period of time. Figure 5.1.and 5.2 and table 5.1 shows

difference comparison between the ion thruster and liquid.

Electric propulsion technology has three major categories; (a) Electrostatic that

included the microwave, bombardment of ion, colloid ion and many more. (b)

Electromagnetic contained inductive plasma, helicon plasma and other variable specific

impulse plasma just to name a few. (d) Electro-thermal category contains resist-jet and

arc-jet.

In recent years we have seen application of the EP for instance in 1998 the

NSTAR ion engine for deep-space1. In 2003 the Hayabusa spacecraft using ion

propulsion and later on the same year Smart1 having the hall thruster which used the

xenon, and by 2007, the launch of Dawn which was purely using ion propulsion.

42

The principle of electric propulsion general performance can be divided into four

important categories; (a) the thrust which is beam currents which will be proportion to

thrust and acceleration voltage that agrees with the following equation 5.1 and equation

5.2 is the thrust efficiency of the electrical propulsion.

𝑇 =𝑑

𝑑𝑡[𝑚𝑝𝑉𝑒𝑥] =

𝑑𝑚𝑝

𝑑𝑡𝑣𝑒𝑥 = �̇�𝑝𝑣𝑒𝑥

(5.1)

𝑛𝑒 =𝑃𝑏

𝑃𝑇=

𝐼𝑏𝑣𝑏

𝐼𝑏𝑣𝑏+𝑝0 (5.2)

(b) Rocket equation make sense a lot in EP on the utilization of the efficiency of mass

thruster as the equation 5.3 suggest.

𝛥𝑣[𝐼𝑠𝑝𝑔∗ ]𝑙𝑛 [

𝑀𝑑+𝑀𝑝

𝑚𝑑] (5.3)

(c) Force transfer is just simply the one for instance ion to the thruster. And in this case

the electric field will be equal to the net forces on the grid as equation 5.4 explains;

43

𝑑𝐸(𝑥)

𝑑𝑥=

𝑃(𝑥)

𝜀0=

𝑞𝑛𝑖(𝑥)

𝜀0 (5.4)

(d) Specific impulse. There are two important equation in the specific impulse in EP that

need to be put in mind for the thrust mass utilization. Equation 5.5 and 5.6

𝐼𝑠𝑝 =𝑣𝑖

𝑔

�̇�𝑖

�̇�𝑝 (5.5)

𝑛𝑀 =𝑚𝑖

�̇�𝑝=

𝐼𝑏

𝑒

𝑚

�̇�𝑝 (5.6)

44

Figure 5.1 Ion thruster (courtesy of NASA)

45

Figure 5.2 Liquid thruster (courtesy of NASA)

I

Ion

Rocket Liquid Rocket

ue 30,000 m/s 4,500 m/s

Thrust 0.1 N 2,000,000 N

Energy 1,000 GJ 100 GJ

Power 1 kW 300 MW

Isp 3,000 s 450 s

Table 5.1 summarizes comparison between ion thruster

and liquid rocket

46

Recommendation

There are still more research needed to be done in the pursuing of the electric

propulsion; for example the use of fuel cell in spacecraft which is powered by electric

propulsion. There is no measurement of thrust that is published which agrees with each

other, because, of the high energy density on the space craft. Therefore, the physics

student and other interested parties which are responsible on the production of thrust

have to come up with a more guideline on the acceptable way to go with the process

(Sutton, 2010).

Due to some budget constrain and many politics about space exploration. The

need of using available resources at hand is more essential. For instance the idea of

fusion powered electric propulsion. This has been given deaf ear for long and need to

be put in practice and research need to be done on them as more advantages are

known than disadvantage. Therefore, in short electric propulsion need to be

experimented and worked on for the best future space exploration.

Lastly, but not least, more practically on using the thruster for experiment should

be established for knowledge gain. Let them not be in big facility only such as NASA

and big name of schools, accessing it should not be limited and hard to access but open

to space ambition student and easily to access.

47

Summary

EP technology is advancing rapidly, being an active field with different

development stages for instance, from 1906 with Robert Goddard then Konstantin E.

Tsiolkovkiy from the year 1911, then came in 1929 Herman Oberth with his

advancement. After period of time, in 1964 Earnst Stuhlinger came and geared the ion

EP for space flight and up to now the EP is still being tested for different spacecraft

application.

Electric propulsion spacecraft that have already been used have already solved

some problem such the cost of launching, therefore, cutting the cost because of light

mass. They are much safer and environmental friendly especially the one of nuclear.

Using EP on thrust mission will save time compared to the solid or liquid propellant just

to name a few. Therefore, using EP technology is much more dependable and

efficiency. The graph below 5.2 is just an example of comparison of time between

chemical and other electric propulsion to mars.

48

Table 5.2 Showing comparison of time to Mars in different propulsion system

Solid Chemical

Ion

Nuclear

Mars

0

50

100

150

200

250

Tra

ns

it t

ime

(d

ays

)

Propulsion Systems

49

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