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DECIGO スラスタ – 小型マイクロ波イオンエンジン –

DECIGO スラスタ – 小型マイクロ波イオンエンジン –. 小泉　宏之 國中　均 （ ISAS-JAXA ）. Propulsion; Requirements. Purpose: Drag-free control. Thrust range: 1 – 100 μ N. to compensate the solar pressure. Thrust noise: > 0.1 μN/√Hz. not to disturb the measurement. Quick response & control : > 10 Hz.

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DECIGO スラスタ – 小型マイクロ波イオンエンジン –

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  1. DECIGOスラスタ– 小型マイクロ波イオンエンジン – 小泉　宏之 國中　均 （ISAS-JAXA）

  2. Propulsion; Requirements Purpose: Drag-free control Thrust range: 1 – 100 μN to compensate the solar pressure Thrust noise: > 0.1 μN/√Hz not to disturb the measurement Quick response & control : > 10 Hz to perform feed-back control Very unique requirements

  3. Propulsion; Requirements DECIGO thruster requires the thrust capabilities completely different from usual thrusters. DECIGO (drag-free) Usual (conventional) propul. Thrust noise Response speed Specific impulse Thrust to power ratio Usually, these parameters are not considered There has been no studies except for recent studies relating to LISA

  4. About “usual” requirements Thrust to power ratio Allowed power for propul. = 50 W Thruster (10 μN/W)with 100 μN x 5 sufficient Specific impulse Total impulse = 10 kNs （<< S/C mass） 10kg even if Isp: 100 s thruster Weight＆Volume DECIGO volume: 5 m3 10% for thruster ? Soft requirements of conventional propulsive capabilities

  5. Challenging issues We have to develop… thrusters satisfying DECIGO requirements µ-Ion thruster using microwave discharge instruments to evaluate (measure) these parameters

  6. What is (μ-wave) ion thrusters ? Neutral Plasma production Neutralized ion beam Ion acceleration Ion Electron Gas Microwave Electron emission & Neutralization Potential

  7. µ-Ion thruster using µ-wave discharge Ion thruster Thrust is electrically controlled Acceleration voltage particle velocity Microwave power amount of particle easily & quickly controllable Microwave discharge Simple structure suitable for compact plasma source Electron bombardment type Electron emitter is necessary in plasma source

  8. Developed μ-Ion thruster: μ1 Grid system Side wall Back yoke 10 mm Gas inlet 20 Microwave Outer ring magnet Antenna Inner ring magnet Ignition

  9. Novel μ-Ion Engine System Identical plasma sources Electron emission Ion beam Vsc Vsc Vac Vac Electron emission Ion beam Vneut Vneut Switching by electrical connection Utilization of a plasma source as both ion beam source and neutralizing electron source

  10. Switching Operation What is the benefit of switching operation ? Switching operation A lot of motions Multi-function Translation Y-axis rotation Z-axis rotation z x y Neutralizer mode Ion engine mode Z-axis rotation (also, inverse rot.) Y-axis rotation (also, inverse rot.) Translation

  11. Up-to-date results Electron extraction from ion engine Twin operation & switching operation Low power & High performance plasma source Microwave power per head: 1 W Thrust to power ratio: > 20 µN/W Total dry weight and power would be < 10 kg & 30 W with 10 thruster heads (4 at a time) including gas system & PPU

  12. Voltage vs. Ion beam current Ion beam current can be adjusted by thegrid voltage Simultaneous control of Vsc & Vac is necessary (not so difficult) Potential

  13. μ-wave Power vs. Ion beam current Ion beam current can be adjusted by themicrowave power Microwave source Solid state power amplifier Careful to plasma quenching near 0 W

  14. How About Thrust Noise ? Measurement method We have never measured the thrust noise Power spectrum of thrust between 0.01 Hz – 100 Hz not so difficult quite difficult Thrust measurement of 10 µN thrust with 10 Hz is difficult. Ion thruster Ion beam current = Thrust easily measured there would be no study verified this “equal” under 100 Hz Beam(thrust) noise evaluation

  15. How About Thrust Noise ? ? Noise of ion thruster Feed-back control would reduce the noise Acceleration voltage or Microwave power Beam current High voltage breakdown would generate impulsive noise Between grids Typically 0.1 – 1 times in a hour During recycling sequences, no thrust.

  16. Summery We have developed a novel ion thruster system: µ1 forDrag-free control & micro-spacecraft Our current state is Small ion engine of 20 mm diameter Thrust range: 10 – 250 µN (not yet about minimum thrust) Thrust is adjustable by voltage & µ-wave power (not yet about accuracy)

  17. Example of thrust noise Thrust noise of FEEP for GOCE JOURNAL OF PROPULSION AND POWER Vol. 20, No. 2, March–April 2004

  18. μ-wave Power vs. Ion beam current

  19. Appendix; Competitive thrusters？ Chemical thrusters Noise by valve ? Cold gas thruster 10 Hz valve response ? mono/bi-propellant engine & solid rocket quite difficult to control gas flow or combustion reaction with 10 Hz response μ-Ion thruster FEEP Colloid thruster μ-arc jet PPT Laser ablation Electric propulsion 10 Hz response is easy for electrical control

  20. Appendix; FEEP & CT 現在、LISAのDrag-free制御の有望株 FEEP ＆ Colloid thruster 要求される性能については、既に結果を出してきている FEEP ・高電圧(10 kV)が悪影響をおよぼしそうだが？ ・最大の特徴である高 Isp(>5000s)は全く活かされない 　（無駄に高電圧） ・セシウムという推進剤も不安（窓へのコンタミ） Colloid thruster ・FEEPに比べると、スラストノイズに不安 ・低比推力は問題にならない （データが少ない）

  21. Appendix; μ-Arc jet, PPT, Laser ablation μアークジェット ・放電電流でどこまで推力制御できるか？ ・ノズルの耐久性は？ ・パルスの推力発生が大きな短所 ・1 kHz動作＆ダンパ搭載で擬似定常推力は可能、 　しかし、イグナイタ電力および寿命が懸念される PPT レーザーアブレーション ・推進剤の送り機構が”静か”にできるならば、可能性はある

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