1. Erik Mueller Michael White

2. Introduction Problem Solution Load-cell Paddle-sensors Testing Q&A Sources

3. Background  New type of small satellite  Common subtypes are Cubesats and nano-satellites  Traditional thrusters designed to have high power to weight ratio  Minaturized thrusters replace compressed gas attitude systems

4. Background  Microthrusters: Produce <1N of thrust (mN range)  Various propulsion systems (fuel/oxidant, monopropellant, ion drive)

5. The Problem  Thruster and forces involved are minute  Must be rugged and durable  Modular design preferable

6. Our Solution  Two methods of thrust measurement  Direct – load cell  Indirect – capacitive plates  Importance of two – better results, redundancy

8. System Overview Load Cell Amplifier Circuit DAQ NI USB-6008 Lab View Software FM Modulator Circuit Fire Control Indirect Thrust Plume Pendulum Sensor Excel Data File Excel Data File

9. Direct vs. Indirect

10.  Direct Measurement of the net forces acting on thruster and any attached devices.  Indirect Measures only reactive forces from the thrust plume.

12. Construction  Aluminum thruster bracket mounted directly to load cell  Mounting Chassis Load cell will be mounted directly to an aluminum chassis to provide a stable platform free of mechanical vibration Load cell mounted vertically to reduce the effect of gravity on the test.

13. Direct Force Measurement  Load Cell  Strain Gauge  Signal Amplification Gain = 1000

14. Mechanical Design

16. Indirect Thrust Measurement  Capacitive Plate System  Exhaust plume exerts force on a plate  Deflection corresponds to a change in capacitance Induced Force Thruster

17. Capacitive Pendulum  Uses electronic principle of capacitance  Two plates, moving and reference  Needle point fulcrums mechanically isolate

18. Capacitive Pendulum  Using an FM generator, plates are a capacitor  Compare frequency shifts to determine deflection.  Advantage – more resistant to noise and distortion, very accurate  Disadvantage –more complex

19. Calculations  Given a distance of 1cm between plates  C = A ε/d = 8.86pF  A Frequency-Modulated system system is sensitive enough at this range

20. Electrical Concept  Phase-locked loop is used to produce a discrete voltage signal, which is read by the DAQ.  Signal varies in amplitude, directly proportional to plate movement. Phase Detector Low-Pass Filter VCO f IN (t)  IN (t) Error signal v e (t) Error voltage v DC f OUT (t)  OUT (t) Primary Oscillator DAQ Sensor

21. Schematic Sensor Input To PLL Primary OscillatorPhase-Locked Loop From Primary Oscillator To signal processing Signal Processing To DAQ Difference amp From PLL

23. Software  The NI USB-6008 DAQ will tie into a computer, along with the rocket ignition circuitry.  Both subsystems will be integrated into a single user- controlled program, using Labview

24. Software

27. Testing  One rocket test has been performed to gauge ignition methods & rocket plume.  A calibration test was performed to verify strain subsystem linearity and determine transfer function.  A subsequent test was performed evaluate the strain subsystem.  Currently testing and revising software with the strain subsystem.

28. Transfer Function Calculation  y = 0.001x – 0.629 (x = Force in grams)  x = (y + 0.629/0.001) x 9.81 mN/g  x = y + 0.629 x 9810 (x = Force in newtons)

29. Testing

31. Testing – Rocket Test #2

33. Work Breakdown Structure  Week 5-6 Subsystem and structure prototype  Week 6-7 Electrical circuit schematics  Week 5-9 Software composition and test  Week 7-10 Revision, second subsystem test  Week 9-12 Assembly, testing, revisions if needed  More details on website

34. Timeline NovDecJanFebMarAprilMay BrainstormingXX ResearchXXXX Concept & Development XXX Sub-system Assembly XXX Sub-system Test XX Full system Test XX Version 2.0X

35. Budget ItemCost($) Estes rocket motors50 DAQ150 Metal stock40 Strain gauges40 Electronic components100 Paddle Sensors100 Misc fund50 Total530

36. Questions?

37. Works Cited http://www.grc.nasa.gov http://images.machinedesign.com www.answers.com/topic/piezoelectricity http://www.boeing.com/defense-space/space/bss/factsheets/xips/xips.html Traceable calibration of the 3-axis thrust vector in the millinewton range, EB Hughes and S Oldfield, National Physical Laboratory Direct Thrust Measurement of In-FEEP Clusters, IEPC-2005-235, K. Marhold and M. Tajmar, ARC Seibersdorf research GmbH Rocket Thrust Measurement For an Estes B6-2 Model Rocket Engine, Peter Hyatt, Jeremy LeFevre, Russell Dibb, Bringham Young University Thrust stand for ground tests of solid propellant microthrusters, S. Orieux and C. Rossi and D. Esteve, Review of Scientific Instruments, Volume73, Number 7, July 2002 A Ground Test Rocket Thrust Measurement System, Mary Fran Desrochers, Gary W. Olsen, M. K. Hudson, Department of Applied Science and the Graduate Institute of Technology, University of Arkansas MilliNewton Thrust Stand Calibration Using Electrostatic Fins, Allen H. Yan, Bradley C. Appel, Jacob G. Gedrimas, Purdue University