A silicon based MEMS resistojet for propelling cubesats
1. A silicon-based MEMS resistojet for propelling cubesats Tittu V. Mathew, B.T.C. Zandbergen, M. Mihailovic, J.F. Creemer, P.M. Sarro. IAC – 11.C4.3.2.
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3. Delft University of Technology Challenge the future Introduction & thesis objective (5/6) Fabrication using MEMS technology (4/4) Introduction (1/2) T3 μ PS – cold gas micro-propulsion system developed at TUDelft Delfi-n3Xt – Student designed 3-unit cubesat to be launched in 2012
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5. Design of the thruster (1/2) Channel width : 50 μ m Channel height : 150 μ m Fin width : 100 μ m Nozzle throat width : 10 (/5) μ m Single channel design Delft University of Technology Challenge the future Design of the thruster (6/6) Fabrication using MEMS technology (4/4)
6. Design of the thruster (2/2) Fabrication using MEMS technology (4/4) Delft University of Technology Challenge the future
7. Thrust vs. chamber pressure (Prediction using ideal rocket motor theory) 10 μ m nozzle Chamber pressure [bar] Thrust [mN] 5 μ m nozzle Delft University of Technology Challenge the future Fabrication using MEMS technology (4/4)
8. PECVD SiO 2 at both surfaces Delft University of Technology Challenge the future Fabrication using MEMS technology (1/4) Fabrication using MEMS technology (1/2) Thermal oxidation of silicon at both surfaces Aluminium deposition and patterning First DRIE step from wafer backside Fabrication using MEMS technology (4/4)
9. Patterning the inlet (2 nd DRIE step) Patterning the channel and nozzle (3 rd DRIE step) Removing SiO 2 from the bonding surface; Sealing of the channels by anodic Si-glass wafer bonding Delft University of Technology Challenge the future Fabrication using MEMS technology (2/4) Inlet manifold Fabrication using MEMS technology (4/4)
10. Delft University of Technology Challenge the future Design of a MEMS micro-resistojet SEM image Silicon Single channel Nozzle throat Fabrication using MEMS technology (3/4) Fabrication using MEMS technology (4/4)
11. Delft University of Technology Challenge the future Fabrication using MEMS technology (4/4) Silicon Pyrex Inlet Nozzle exit Packaged device Needle glues into the inlet manifold Needle PCB Aluminium heater Nozzle outlet
12. Delft University of Technology Challenge the future Test results without propellant heating (1/3) Test setup Fabrication using MEMS technology (4/4)
13. Test results (1/4) Delft University of Technology Challenge the future Design of a MEMS micro-resistojet 5 μ m nozzle 10 μ m nozzle Cold gas test results and discussion (2/4) Test results without propellant heating (2/3) Fabrication using MEMS technology (4/4)
14. Test results (2/4) Delft University of Technology Challenge the future Design of a MEMS micro-resistojet Cold gas test results and discussion (4/4) Throat Reynolds number [-] Discharge coefficient of the nozzle, C d [-] Test results without propellant heating (3/3) Fabrication using MEMS technology (4/4) 5 μ m nozzle 10 μ m nozzle
15. Test results (3/4) Delft University of Technology Challenge the future Design of a MEMS micro-resistojet Hot gas test results and discussion (4/6) Heater temperature [C] Measured pressure [bar] Test results with propellant heating (4/6) Fabrication using MEMS technology (4/4) 5 μ m nozzle 10 μ m nozzle
16. Challenge the future Design of a MEMS micro-resistojet Test results (4/4) Delft University of Technology Hot gas test results and discussion (5/6) Test results with propellant heating (5/6) Propellant heating efficiency : < 13% @ mass flow rate of 1 mg/s Fabrication using MEMS technology (4/4) Heater temperature [C] Electric input power [W]
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18. Delft University of Technology Challenge the future Fabrication using MEMS technology (4/4) Thank you for attention Questions ??
Editor's Notes
Propulsion for micro-satellites is already ready with the development of T2 micropropulsion system Problem of low Isp for cold gas propulsion systems -> need to carry lot of propellant on-board -> leads to large volume or high mss which is unacceptable for high delta-V missions for cubesats.
Aiming for thrust levels of less than or equal to 1 mN Maximum chamber temperature of less than 600 K Electric input power of 1 W Using nitrogen gas as the propellant
5 bars due to cubesat constraints. 1 bar set as the lower limit to prevent any flow seperation in the nozzle.
Chamber temperature - could not be measured; it was assumed to be the same as the measured temperature inside the vacuum chamber The chamber pressure just before the nozzle inlet could not be measured directly due to small geometric features; hence it was decided to measure this just before the inlet of the micro-thruster chip.
Without propellant heating
Discharge coefficient is defined as the ratio of the ideal to calculated chamber pressure.
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