Miniaturisation of solid propellant thrusters for space

Outline
• Introduction – MicroPyros project
Miniaturisation of Solid Propellant Thrusters
for Space Application
D. Briand, P. Q. Pham, C. Rossi*, N. F. de Rooij
Sensors, Actuators and Microsystems Laboratory (SAMLAB)
Institute of Microtechnology
University of Neuchâtel
Switzerland
*LAAS-CNRS, Toulouse, France
• MicroPyros demonstrator
– Millimeter-scale DEMO
• Microscale device
– Design, fabrication, assembling
– Characterisation
• Conclusion & outlook
2
Introduction
Introduction
• MicroPyros project objectives (2000-2003)
• Solid propellant technology
– Integration of energetic material, MEMS device and
– Combustion : large quantity of energy from small volume
electronics to realise new performing PowerMEMS
– Application of Micropyrosystems to propulsion
– Solid fuel : no leakage, stability in time
• Nanosatellite: micropropulsion for station keeping
– No moving parts, eliminating frictional force and making
• Solid propellant concept
– Combustion of a solid material stored
in a micromachined chamber
technological fabrication easier
nozzle
igniter
– The chamber is not pressurised, the reservoir does not
need to be massive
chamber
3
Introduction
4
Introduction
Solid propulsion
Monoliquid
Cold gas
Cold Gas
Minimum Specific impulse
Biliquid
Solid
Thrust
From B. Larangot, Conception, fabrication, caractérisation de matrices de micropropulseurs
pyrotechniques sur silicium, Thesis, LAAS/CNRS, 2004
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From B. Larangot, Conception, fabrication, caractérisation de matrices de micropropulseurs
pyrotechniques sur silicium, Thesis, LAAS/CNRS, 2004
6
1
Microthrusters : mm-scale DEMO
Challenges
• Single shot microthruster
• Compromises between the reduction of the dimensional
► Array of 4 x 4 microthrusters (16 thrusters)
features and combustion process considerations
• Management in a very small volume of high temperature
and pressure that could lead to mechanical failure
• Limits of silicon and the introduction of best appropriate
materials implying to bond different materials together
Nozzles
• Compatibility of processing and assembling with the
Igniters
propellant
Chambers
Glass seal
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8
DEMO Design
DEMO Fabrication Technology
Ø 250, 500 µm
~10°
Nozzle (IMT)
Material Technology
250 µm
50 µm
Si
Diverging angle : conic DRIE
Cavity : KOH
(LAAS)
Si,
polySi
RIE, DRIE
Chamber
Si
DRIE
(IMT)
Foturan
HF10%
Nozzle
(IMT)
Igniter (LAAS)
Chamber (IMT)
350 µm
Igniter
1500 µm
500 µm
1 mm
Seal (LAAS)
2 mm
– Array of 4 x 4 microthrusters
– Chip size : 14.65 mm x 14.65 mm
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10
DEMO Assembling
DEMO: Tests
• Set-up
• Filling of the parts with propellant
– Source I, measure V(t) => power, energy calculated
– Thrust balance : thrust force measurement (LAAS)
– Igniter
– Sealed chamber
• Ignition tests (GAP / GAP)
– Ignition power : 100–150 mW
– Ignition time : 20–130 ms
– Combustion time : ~ 320 ms
• Assembling
– Anodic bonding
– Thermal gluing (epoxy glue)
•
Ignition tests (ZPP / GAP)
– Ignition power 150–200 mW
– Ignition time : 80–130 ms
– Combustion time : ~ 270 ms
igniter
GAP
GAP
igniter
ZPP
intermediate
chamber
intermediate
chamber
GAP
chamber
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chamber
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2
DEMO: Thrust Force
DEMO: Thrust Force
– Force with nozzle (Ø500 µm)
– Force without nozzle :
• ZPP : 13.5 mN
• GAP : 2.3 mN
• ZPP : 1.2 mN
• GAP : 0.28 mN
with nozzle
without nozzle
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Microscale Device
Microscale Device Design
• Objective
– Investigation of the limit of integration
– Miniaturisation
– Reduction of the number of parts
Nozzle
Igniter
Chamber
• Microthruster dimensions
Seal
– MicroPyros DEMO (macro-scale device)
´ 1500 µm x 1500 µm
– Microscale device
´ 1040 µm x 1040 µm and 500 µm x 500 µm
(275 µm x 275 µm)
– Igniter on membrane
(Design 1)
• Same design than
MicroPyros with smaller
dimensions
– « Free standing » igniter
(Design 2)
• New design
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16
Igniters
Nozzles
• Throat diameters
• Heaters characteristics:
Area
1 mm
500 µm
180 x 180 µm2 1020 Ω
830 Ω
390 x 390 µm2 1975 Ω
1730 Ω
720 x 720 µm2 3340 Ω
–
1 mm
500 µm
275 µm
–
X
375 µm
X
X
500 µm
X
–
Diameter
• Silicon bulk micromachining: DRIE and KOH
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3
Chamber Fabrication
Assembling
• Technology developped for the mm scale design
– DRIE of silicon wafers
– Wet etching of Foturan glass wafers
Si: 500 µm chambers
50 µm grooves
Si: 500 µm chambers
250 µm grooves
Foturan: 500 µm chambers
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Ignition and Combustion
Ignition and Combustion
• Ignition time: 27 to 37 ms
• Constant current of 7.0 to 7.75 mA
• Ignition energy: 4.9 to 7.9 mJ
1 mm
500 µm
180 x 180 µm2
60-90 mW
65 to 105 mW
390 x 390 µm2
130-200 mW
125-200 mW
720 x 720 µm2
200-375 mW
–
Area
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Ignition and Combustion
Chamber = 1mm, Nozzle = 500 µm
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Thrust (mN)
Thrust (mN)
25
15
10
5
0
-5
0
10
20
Time (ms)
Igniter
Chamber
Solid
propellant
10
30
Thrust (mN)
• Thrust force: 12 to 23 mN
15
20
25
30
35
40
45
Φc
∆
275-500 µm
50
Time (ms)
Chamber = 500 µm, Nozzle = 275 µm
15
• Combustion time: 10 to 15 ms
Igniter - nozzle
25
20
15
10
5
0
-5
-10
500 µm
Chamber = 1mm, Nozzle = 500 µm
Microscale Device: Compact design
Φc
[µm]
500
10
5
275
0
∆
[µm]
groove
[µm]
250
50
500
200
225
50
475
175
nozzle diameter
[µm]
180- 240
100 - 130
-5
30
35
40
45
Time (ms)
23
50
55
60
– Array of 4 x 4 microthrusters, chip dimension of 8 x 8 mm2
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4
SOI Igniters Fabrication
SOI Igniters
• SOI igniters
heaters
-
nozzle
SOI
Si doping
Si DRIE
LPCVD Si3N4
conic DRIE
release : HF 50%
Al contacts
Without pn junctions
heaters
nozzles
With pn junctions
Nozzle
Si suspended resistors
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SOI Igniter Characterisation
Assembled SOI Thrusters
– Maximum electrical power controlled by
a limitation on the current delivered
• One step filling procedure
• One bonding step (epoxy gluing)
I (V)
P (V)
1400
1200
80
1000
60
800
40
600
400
20
power [mW]
current Ir [mA]
100
200
0
0
0
2.5
5
7.5
voltage [V]
10
400 µm
12.5
• Heater: 200 to 400 ohms
2 x 1 or 2 x 2 beams
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Ignition SOI Thrusters
Conclusion
Constant Current of 10 to 24 mA / beam
• Micrometer scale device
• Ignition time: 6 to 24 ms
• Ignition power: 225 to 400 mW
• Ignition energy: 1.6 to 11.8 mJ
– Design and specification of a micrometer scale device
– Processing development to fabricate smaller igniters
with integrated nozzles
– Successful ignition of ZPP stored in sub-mm cavities
– Key points:
• reproducibility of the propellant filling
• Development of propellant, igniters, filling and assembling are
strongly linked
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Outlook
MicroPyros
– Complete the characterisation of the ignition and
combustion in smaller dimensions
– Optimised designs and fabrication processes
• Project funded by the
European Commission
• Involved partners:
• Nozzles
• Igniters
• Assembling
¾ Validation of the technology in a space mission
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