MEMS IN AEROSPACE APPLICATIONS A DEVELOPING TECHNOLOGY PRESENTED BY ARAVIND.B M.SIDDARTH

CONTENTS INTRODUTION BACKGROUND MEMS IN AEROSPACE DIGITAL MICROPROPULSION - Introduction - Fabrication - Testing REDUCTION OF VISCOUS DRAG IN AIRPLANES - Flow theory - Experimental Analysis FUTURE OF MEMS CONCLUSION

MEMS – Micro Electro Mechanical Systems INTRODUCTION MEMS – Micro Electro Mechanical Systems Microstructures Microelectronics Micro Sensors Micro Actuators

SIGNIFICANCE OF MEMS Size & Weight Power consumption Faster Cheaper Reliable Accurate

MEMS IN AEROSPACE TURBULENCE CONTROL MICROPROPULSION MAV & UAV MICRO-JET ENGINES MICRO NOZZLES

DIGITAL MICROPROPULSION

INTRODUCTION Digital Micro-propulsion is used in small spacecrafts. This method produce small impulse for altitude control and station-keeping of small spacecrafts. (m<1 kg) Micro Spacecraft Array

CONFIGURATION LAYOUT Top Die (Rupture diaphragms) Middle Die (Thrust chambers, nozzles) Bottom Die (ignitors, Micro- resistor)

TOP LAYER Contains array of thin diaphragm ( 0.5 micron thick) made of silicon nitride . Material - Silicon Nitride Length - 390 micro meters Thickness - 0.5 micro meters Burst pressure – 10 Atm.

MIDDLE LAYER Main Thrust chambers Contains array of through holes which is 150 micron thick and have various diameter holes of 300,500 and 700 microns. This layer is loaded with propellant. Material - Glass Diameter - 700 micrometer Height - 1500 micrometer

BOTTOM LAYER Consists of array of Poly Silicon Resistors. These resistors are fabricated on top of a 3 micron metre SiO2 insulating layer. Material -polysilicon Resistance - 210 ohms Voltage - 100 volt Time - 50 micro seconds Power - 50W

FABRICATION The bottom two layers are bonded together using Cyanoacrylate. Then the chambers are filled with propellant. The top layer is also bonded using Cyanoacrylate to complete the assembly. With a series of different sizes of plenum holes, diaphragms, and resistors ,90 different configurations of micro-thrusters can be assembled.

TESTING

ADVANTAGES No moving parts. No valves or lines or external tank. The propulsion function can be combined with the satellite structure.

REDUCTION OF VISCOUS DRAG IN AIRPLANES

COMPARISON MEMS CONVENTIONAL METHOD Previously viscous drag are reduced by wall motion, heating ,cooling or by injecting mass (macro scale). MEMS provide good spatial resolution and high operational frequency with low power consumption.

Viscous drag is due to high speed fluid streaks moving along the wall. FLOW THEORY Viscous drag is due to high speed fluid streaks moving along the wall. Vortex pair occurs in high speed flows which contribute to high viscous drag . Fluid flow should be generated to counter the downward motion will reduce the viscous wall drag.

MICRO FLAPS This flaps produce an upward velocity against the streaks there by reducing viscous drag (due to skin friction). Since it is magnetically driven , it has low working frequency and need high power Out-of-plane actuation add form drag which is due to physical presence of an object obstructing the flow.

It is 100 times smaller than magnetically operated micro flaps. MICRO ACTUATOR Micro actuator can be used to generate local flow field which will reduce viscous drag Since it operates in the in- plane direction it does not contribute to additional form drag. Since it is electro statically driven it has high operational frequency and require less power. It is 100 times smaller than magnetically operated micro flaps.

DESIGN The induced flow velocity must be large enough to interfere with the down flow of the incoming high speed fluid. This determine that the actuators need to operate at high frequency. The actuator should produce large enough plate displacement in order to affect the streaks. Actuators are electro statically driven using angled electrodes

TESTING HOT WIRE ANEMOMETER - to verify whether the actuator is capable of generating local flow . FLOW VISUALISATION - to verify whether the amount of induced flow does cancel the velocity due to vortex pair.

TESTING Hot wire anemometer is placed above the micro actuator. Hot wire is turned on and signal is recorded before and after the actuating the actuator.

FLOW VISUALISATION The flow visualization technique allowed for the visual verification of the induced flow. Smoke is introduced into an array of actuators. A laser sheet is placed on top of the actuators. The entire experiment is enclosed in a controlled environment that allows for stagnant fluid. When the actuators are turned on, the smoke is seen to displace upwards and diffuse away.

FUTURE OF MEMS Micro actuator for jet engine emission, micro sensors and actuators for reconfigurable wing geometry CHALLENGES : modeling and simulation tools lack of quality control investment non standardized package

CONCLUSION The application of MEMS in aerospace applications like digital thruster and drag reduction are analyzed theoretically and practically almost infinite number of radial applications are possible. These advantages make the MEMS as the indispensable factor for the advance technology…

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