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Electric PropulsionThrusterThruster

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Electric PropulsionA set of component arranged to convert electrical power from theSpacecraft(S/C) power system into the kinetic energy of the propellant jet.

Major components PPU(Power Processor Unit)

BatteriesPropellant

S/C computer

Thruster

Plumbing

Valves, Heaters

The Heart of systemThe Heart of system ThrusterThruster

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Thruster is not the upmost critical components even though it may seems to be

The PPU and Valves system is the most complex and challenging

EP components. - PPU : Control Unit

- Valves : Usually no detail is shown.

ChallengeChallenge FlowFlow handledhandled isis veryvery small(precisesmall(precise flowflow control)control)

operationoperation forfor prolongedprolonged periodperiod ofof time(months)time(months)

leakleak freefree valvevalve Besides PPU and Plumbing, Thruster is the main concern

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1) Electrothermal

(Resisto, Arcjet) . (Arcjet)

(Resistjet).

Hydrazine , moderate thrust,

relatively low specific impulse(500-1200)

potential candidate : Well established physics

(Actually in use for NSSK : North South Station Keeping, EWSK, orbit raising)

2

) Electrostatic

.

(ion thruster,

Hall Thruster) . Intermediate impulse(1500-2500),

Xenon , Higher thrust

3) Electromagnetic ,

(MPD thruster) .

(MagnetoPlasmaDynamic) (How much do w e know about Plasma Physics ?)

Eachtypetailoredtoitsspecificneed :

Usually they are all for station-keeping, orbit raising(Low Earth orbit)

and on-orbit maneuvering as well as drag compensation

Main Objective : Toward a primary propulsion system

Thruster

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Table. 1 Operating range of electric-propulsion thrusters Fig. 3 Operating ranges of electric-propulsion thrusters

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ProsPros large exhaust velocity, low consumption of propellant

Applicability for Deep space main propulsion unit(MPD, Ion)

For Ion, Hall : high Isp, high efficiency, broad regime of application

ForArcjet : Still competent in Geo-stationary application

ForArcjet : Occupies an intermediate place in the Isp

ConsCons Low thrust of order of 0.1N

Insufficient onboard electric power

Adequate Vacuum facilities are essential to conduct research in EP

(Especially for MPD)

ForMPD, and ion type thrustercomplex S/C integration problem,

plume interaction

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Table. 2 Typical Electric thruster features

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OurOur concernsconcerns :

too many types and derivatives of EP as well as propellant choice for

the feasibility study

Selection of Low risk EP thruster ? If chosen, what would be the Application range & tailored type of EP

that would match with Korea satellite development program ?

Existence of Sufficient Market for us to penetrate ?

Alternative : Joint work with Russia(Rich Experience on EP system)

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CommentsComments

For Hall, Ion, MPD type

Too away behind US, Japan, EC

Complexity(S/C integration, heavy PPU than electrothermal PPU,

Plume angle problem.)

Can we support those plasma related technology??

( ) too risky

For resistojet, Arcjet

Feasible thruster relative to MPD, Hall type

Conventional technology already available, and operational

Low impulse Hydrazine arcjet and resistojet has still penetrable market

(Increase of commercial LEO and GEO satellite)

A Place for us in this niche market(US, Asia, EC, Japan) ?

Competency would require joint international work (e.g., Russia)

(Technology and Cost) Low risk

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proposed EP ThrusterHydrogenHydrogen ArcjetArcjet

Electrothermal family (Still competent thruster type)

Well Established physics (Affordable time to catch up)

Unlike Hydrazine, performance gain of order 1500s or more Isp

with hydrogen Broad range of application (from low to high Isp)

increased efficiency(thruster performance) achievable by regenerative

cooling (& nozzle coating). Current available device: HIPARC-R

Yet the inherent storage problem of hydrogen exist(cryogenic nature)

However, this is everybodys concerns for all hydrogen fed propulsion

device. (Alternative fuel: Ammonia, 800 Isp)

Even for Solar & nuclear thrusters(with hydrogen) Isp limited to 800 s