Electric Propulsion Thruster 한국항공대학교 항공우주 및 기계공학부 문 희 장 한국항공대학교

The Heart of system ⇒ Thruster Electric Propulsion ☞ A set of component arranged to convert electrical power from the Spacecraft(S/C) power system into the kinetic energy of the propellant jet. Major components ⇒ PPU(Power Processor Unit) Batteries Propellant S/C computer Thruster Plumbing Valves, Heaters … The Heart of system ⇒ Thruster 한국항공대학교

◈ The PPU and Valves system is the most complex and challenging ◈ 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. ◈ Challenge ⇒ Flow handled is very small(precise flow control) operation for prolonged period of time(months) leak free valve ◈ Besides PPU and Plumbing, Thruster is the main concern 한국항공대학교

한국항공대학교

Thruster ※ Each type tailored to its specific need : 1) Electrothermal ⇒ 로켓내부에 저장된 추진제를 전력으로 가열하여 고온의 가스로 전환시킨 후 노즐을 통해서 (Resisto, Arcjet) 분사하여 추력 발생. 추진제를 가열하는 데는 방전에 의한 방전제트(Arcjet)와 전기코일 등의 가열표면으로 가열하는 저항제트(Resistjet)가 있음. 통상 Hydrazine 이용, 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 ⇒ 추진제를 가열하여 증기상태로 만든 후 방전으로 이온화. 이온에서 전자를 모두 제거하고 (ion thruster, 스크린과 가속전극 사이의 전기장이 이온을 가속시키며 스크린의 많은 작은 구멍을 통해서 Hall Thruster) 가속전극을 향해 끌어들여 분사하여 추력 획득. Intermediate impulse(1500-2500), Xenon 이용, Higher thrust 3) Electromagnetic ⇒ 추진제 가스가 이온화되어 플라즈마가 형성, 이 플라즈마를 전기장이나 자기장에 (MPD thruster) 보내 가속을 시킨 후 분사하여 추력발생. (MagnetoPlasmaDynamic) (How much do we know about Plasma Physics ?) ※ Each type tailored to its specific need : 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 한국항공대학교

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

Pro’s Con’s ▶ 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 ▶ For Arcjet : Still competent in Geo-stationary application ▶ For Arcjet : Occupies an intermediate place in the Isp   Con’s ▶ Low thrust of order of 0.1N ▶ Insufficient onboard electric power ▶ Adequate Vacuum facilities are essential to conduct research in EP (Especially for MPD) ▶ For MPD, and ion type thruster complex S/C integration problem, plume interaction 한국항공대학교

Table. 2 Typical Electric thruster features 한국항공대학교

▶ Selection of Low risk EP thruster ? Our concerns : ▶ 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) 한국항공대학교

Comments ▶ 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?? 우주탐사용(우리에겐 먼 이야기) ⇒ 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 한국항공대학교

Hydrogen Arcjet proposed EP Thruster ▶ 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 everybody’s concerns for all hydrogen fed propulsion device. (Alternative fuel: Ammonia, 800 Isp) ▶ Even for Solar & nuclear thrusters(with hydrogen) Isp limited to 800 s 한국항공대학교