Download - DECIGO スラスタ – 小型マイクロ波イオンエンジン –
DECIGODECIGO スラスタスラスタ– – 小型マイクロ波イオンエンジン 小型マイクロ波イオンエンジン ––
小泉 宏之國中 均( ISAS-JAXA )
Propulsion; RequirementsPropulsion; Requirements
22/30/30
Purpose: Drag-free control
to compensate the solar pressureThrust range: 1 – 100 μN
Quick response & control : > 10 Hzto perform feed-back control
Thrust noise: > 0.1 μN/√Hz not to disturb the measurement
Very unique requirements
Propulsion; RequirementsPropulsion; Requirements
33/30/30
Usual (conventional) propul.
Thrust noise
Response speed
except for recent studies relating to LISA
DECIGO thruster requires the thrust capabilities completely different from usual thrusters.
Specific impulse
Thrust to power ratio
DECIGO (drag-free)
Usually, these parameters are not considered
There has been no studies
44/30/30
About “usual” requirementsAbout “usual” requirements
Allowed power for propul. = 50 WThruster (10 μN/W) with 100 μN x 5 sufficient
Total impulse = 10 kNs
10kg even if Isp: 100 s thruster ( << S/C mass )
Thrust to power ratio
Specific impulse
DECIGO volume: 5 m3 10% for thruster ?Weight & Volume
Soft requirements of conventional propulsive capabilities
Challenging issuesChallenging issues
55/30/30
We have to develop…
instruments to evaluate (measure) these parameters
thrusters satisfying DECIGO requirements
µ-Ion thruster using microwave discharge
What is (What is (μμ-wave) ion thrusters ?-wave) ion thrusters ?
66/30/30
Plasma production
Neutralizedion beam
Ionacceleration
Electron emission & Neutralization
Po
ten
tial
Gas
Microwave
Ion
Electron
Neutral
Gas
Electronemitter
µ-Ion thrusterµ-Ion thruster using using µ-wave dischargeµ-wave discharge
77/30/30
Microwave discharge
Simple structure
Ion thruster Thrust is electrically controlled
Acceleration voltage
easily & quickly controllable
suitable for compact plasma source
Microwave power
particle velocity
amount of particle
Electron bombardment typeElectron emitter is necessary in plasma source
Microwave
Outer ring magnet
Inner ring magnetAntenna
Side wallGrid system
10
mm
Back yoke
Gas inlet
Microwave
Ignition
Developed Developed μμ-Ion t-Ion thruster: hruster: μμ11
Vneut
Vac
Vsc
Vneut
Vac
Vsc
Identical plasma sources
Electron emission
Ion beam Electron emission
Ion beam
Switching by electrical connection
Utilization of a plasma source as both ion beam source and neutralizing electron source
Novel Novel μ-μ-Ion Engine SystemIon Engine System
Translation Y-axis rotation(also, inverse rot.)
Z-axis rotation(also, inverse rot.)
Ion engine modeNeutralizer mode
x
y
z
Switching operationTranslation Y-axis rotationZ-axis rotation
What is the benefit of switching operation ?
A lot of motions Multi-function
Switching OperationSwitching Operation
Up-to-date resultsUp-to-date results
1111/30/30
Twin operation & switching operation
Electron extraction from ion engine
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
Voltage vs. Ion beam currentVoltage vs. Ion beam current
1212/30/30
0.0
1.0
2.0
3.0
4.0
5.0
0.0 0.5 1.0 1.5
Ion
beam
curr
ent (
mA
)
Screen voltage (kV)
Vac = -506 VVac = -400 VVac = -303 VVac = -202 VVac = -101 VVac = -30 V
Po
ten
tial
Ion beam current can be adjusted by the grid voltage
Simultaneous controlof Vsc & Vac isnecessary (not so difficult)
μμ-wave -wave Power vs. Ion beam currentPower vs. Ion beam current
1313/30/30
0.0
2.0
4.0
6.0
8.0
0.0 2.0 4.0 6.0 8.0
Ion
beam
curr
ent (
mA
)
Input microwave power (W)
0.25 sccm; Down0.2 sccm; Down0.15 sccm; Down0.1 sccm; Down
Ion beam current can be adjusted by the microwave power
Microwave sourceSolid state power amplifier
Careful to plasma quenching near 0 W
How About Thrust Noise ?How About Thrust Noise ?
1414/30/30
We have never measured the thrust noise
Thrust measurement of 10 µN thrust with 10 Hz is difficult.
Ion thruster
Ion beam current = Thrust
Power spectrum of thrust between 0.01 Hz – 100 Hz
not so difficult quite difficult
easily measured there would be no study verified this “equal”under 100 HzBeam(thrust) noise evaluation
How About Thrust Noise ?How About Thrust Noise ?
1515/30/30
?Feed-back control would reduce the noise
Beam current Acceleration voltageor Microwave power
High voltage breakdown would generate impulsive noise
Typically 0.1 – 1 times in a hourBetween grids
During recycling sequences, no thrust.
1616/30/30
SummerySummery
Our current state is
We have developed a novel ion thruster system: µ1for Drag-free control & micro-spacecraft
Small ion engine of 20 mm diameter
Thrust range: 10 – 250 µN
Thrust is adjustable by voltage & µ-wave power
(not yet about minimum thrust)
(not yet about accuracy)
1717/30/30
1818/30/30
Example of thrust noiseExample of thrust noise
JOURNAL OF PROPULSION AND POWERVol. 20, No. 2, March–April 2004
Thrust noise of FEEP for GOCE
μμ-wave -wave Power vs. Ion beam currentPower vs. Ion beam current
1919/30/30
0
200
400
600
800
1000
0.0 0.2 0.4 0.6 0.8 1.0
Ion
prod
uctio
n co
st (W
/A)
Propellant utillization efficiency
0.25 sccm; Down0.2 sccm; Down0.15 sccm; Down0.1 sccm; Down0.05 sccm; Down
2020/30/30
Appendix; Competitive thrustersAppendix; Competitive thrusters ??
Noise by valve ?Cold gas thruster
10 Hz valve response ?
mono/bi-propellant engine & solid rocket
Chemical thrustersChemical thrusters
Electric Electric propulsionpropulsion
μ-Ion thrusterFEEPColloid thrusterμ-arc jetPPTLaser ablation
quite difficult to control gas flow or combustion reaction with 10 Hz response
10 Hz response is easy for electrical control
2121/30/30
Appendix; FEEP & CTAppendix; FEEP & CT
FEEP&Colloidthruster
現在、 LISA の Drag-free 制御の有望株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)
2222/30/30
Appendix; μ-Arc jet, PPT, Laser ablationAppendix; 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?
PPT ・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
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