Drexel University 2010-2011 RockSat-C Critical Design Review

1. Drexel University2010-2011 RockSat-CCritical Design Review Joe Mozloom Eric Marz Linda McLaughlin Swati Maini Swapnil Mengawade Advisor: Jin Kang, PhD Drexel University Rock-Sat

2. Mission Overview - Objective • Drexel's RockSat payload will incorporate a platform rotating opposite the spin-stabilization of the Terrier-Orion sounding rocket during ascent, resulting in a rotationally static platform from an outside reference frame. Drexel University Rock-Sat

3. Mission Overview - Purpose • Experimentally determine the feasibility of a despun platform under high acceleration and turbulence, driven by a low power system. • Provide a stable platform with respect to the exterior environment to accommodate experiments requiring constant frame of reference in an ascending object. Drexel University Rock-Sat

4. Team Overview Drexel University Rock-Sat

5. Concept of Operations • There are several flight points which are of interest to our experiment (Seen on next slide) • Rotation measurements of despun platform during following time periods: • Terrier Burnout • Orion Burnout • Remaining Ascent • Descent Drexel University Rock-Sat

6. Concept of Operations Drexel University Rock-Sat

7. Expected Results Drexel University Rock-Sat

8. De-Scope • Initial Goal to provide a rotationally stable platform and perform experiment on our despun platform. • De-Scoped to be a feasibility study for our despun platform design. • Reasoning • If despun platform failed, experiment on platform would produce no useful results. Drexel University Rock-Sat

9. Off Ramps • Polycarbonate Plate -> Acrylic Plate • Polycarbonate is more difficult to machine, if we are unable to CNC a usable geared platform and pinion then Acrylic will be cut via laser cutter. • Digital to Analog Converter (DAC) • Initially designed to be created out of a resistor ladder. If precision cannot be easily obtained through this, an aftermarket DAC could be used. • Closed Loop Algorithm -> Open Loop Algorithm • Can simplify algorithm to not take into account despun platform sensor if there are difficulties. Drexel University Rock-Sat

10. Mechanical Design Elements Drexel University Rock-Sat

11. Mechanical Design Drexel University Rock-Sat

12. Labeled Diagram Microcontroller board 1 Unit: Inches Accelerometer 1.2 V AAA Battery 2.0 G-switch 5.0 9.3 1.0 Upper platform Gear 1.25 Drexel University Rock-Sat

13. Labeled Diagram Unit: Inches 4.75 Slip ring holder Slip ring 2.75 Motor holder Motor DAC Drexel University Rock-Sat

14. Manufacturing Plan • Gear • Polycarbonate • CNC Milled • Pinion • Polycarbonate • CNC Milled • Slip Ring Holder • ABS • 3D Printed • Motor Mount • ABS • 3D Printed • Platforms (2X) • Polycarbonate • CNC Milled Drexel University Rock-Sat

15. Procurement Plan • Slip Ring (Received) • Motor (Received) • Polycarbonate sheets • 12”x12”x 0.5” • 12”x24”x0.25” • Standoffs • 8-32 x ¼” x 4” • Bolts (8-32, 0-80, M3) Drexel University Rock-Sat

16. Current Position • All parts have been ordered • Slip Ring and Motor have arrived • 1st Iteration of prototyping is completed • Main objective: Sizing/Fit verification • Slip Ring Holder • Motor Mount • Gear • Pinion • 2nd Iteration of prototyping has begun • Altering design for better fit, wire accommodation, etc Drexel University Rock-Sat

17. Changes Since PDR • Slip Ring Holder and Motor Mount defined • The 5x 9V batteries are replaced by 10x 1.2V AAA batteries • The components on fixed platform defined to adjust COG Drexel University Rock-Sat

18. Electrical Design Elements Drexel University Rock-Sat

19. Electronics Schematic Power Supply Stationary Accelerometer Microcontroller Digital to Analog Converter Motor Despun Accelerometer Slip Ring Drexel University Rock-Sat

20. Manufacturing /Procurement Plan • Manufactured • DAC • Soldered • Sensors • Small electronics • Resistors, capacitors, diodes • Procured • Microcontroller purchased with integrated Control Board • Hi G and Low G Accelerometers • 10 NiMH rechargeable AAA Batteries • G-Switch Drexel University Rock-Sat

21. ATmega32 Control Board Microcontroller and Power Connections Microcontroller Communications Microcontroller External Ports Reset and Power LED "Mini AVR ATmega32 Board Schematic." Micro4You. Web. 1 Dec. 2010. <http://www.micro4you.com/store/mini-AVR-ATmega32-Board/prod_155.html> Drexel University Rock-Sat

22. DAC Design 8-Bit(Subject to Off-Ramp and Improvement) Out to Motor Control Drexel University Rock-Sat

23. DAC Design • 8-Bit DAC • Initial Design • Allows for 0.148 Hz Steps (Taking into account our motor specifications and gear ratio) • 10-Bit DAC • Plan if more precision needed after initial testing • Allows for 0.037 Hz Steps • More difficult to control through our microcontroller’s 8-bit ports. • Simple Modification from 8-bit design. Drexel University Rock-Sat

24. Software Design Elements Drexel University Rock-Sat

25. Software UML Diagram Drexel University Rock-Sat

26. Software FlowMajor Code Blocks • Fixed Platform Sensor Data Read • 10 Times per second sample fixed platform sensor data and calculate rocket rotation. • Despun Platform Sensor Data Read • 10 Times per second sample despun platform sensor data and calculate platform rotation. • Data Storage • 10 Times per second store both Fixed Platform and Despun Platform sensor data with timestamps. • Motor Control • When either fixed platform sensor or despun platform sensor values are above threshold, adjust motor RPM through DAC. Drexel University Rock-Sat

27. Analysis & Prototyping • FEA Analysis (Stress/Deformation) • Tooth Loading, Gear/Pinion • Vertical Loading, Gear/Pinion • Vertical Loading, Motor Mount • Electronic Simulation • DAC Simulation in PSPICE • Physical Prototyping • Gear • Pinion • Slip Ring Mount (top / bottom) • Motor Mount Drexel University Rock-Sat

28. Gear/Pinion Tooth FEA • 10 N Horizontal Load Applied to Single Tooth Face • Theoretical load calculation = 1.26 N • Based on Moment of Inertia of gears and elevated frictional forces in bearings at 25 G • Fixed at 2x 0-80 Set Screw Holes Drexel University Rock-Sat

29. Gear/Pinion Tooth FEA Results Drexel University Rock-Sat

30. Vertical Loading FEA • Loading based on mass of component and multiply by 25G • Loading distributed across top face of component • Tested for Max Stress and Vertical Deflection Drexel University Rock-Sat

31. Vertical Loading FEA Results Drexel University Rock-Sat

32. Prototyping Results • Slip Ring Holder (Top and Bottom) • Prototyped with Fuse Deposition Rapid Prototyping Machine • Verifies fit and sizing and integration of design • Motor Mount • Prototyped with Fuse Deposition Rapid Prototyping Machine • Verify fit and sizing and integration of design Drexel University Rock-Sat

33. Prototyping Results • Gear • Laser Cut from .2” Acrylic • Verifies tooth design mating with pinion • Pinion • Laser Cut from .45” Acrylic • Verifies tooth design mating with gear Drexel University Rock-Sat

34. Center of Gravity Center of Gravity: ( inches ) X = 0.20 Y = -0.88 Z = 0.96 Drexel University Rock-Sat

35. Mass Budget Drexel University Rock-Sat

36. Power Budget Drexel University Rock-Sat

37. Testing Plan Mechanical Testing Data Testing System Testing Electrical Testing Sensor Testing Drexel University Rock-Sat

38. System Level Testing Drexel University Rock-Sat

39. Mechanical Testing • All components will be individually measured for mass • Masses will be summed to verify compliance • Vibration Testing at 2x Flight Conditions (50 G) • Each Subsystem tested • Final Assembly tested • Motor Mount to have vertical loading destructive testing to verify flight readiness Drexel University Rock-Sat

40. Electrical Testing • Battery Testing • Battery will be tested using the battery voltage method with a digital D.C. Voltmeter • Battery is fully charged before testing Drexel University Rock-Sat

41. Sensor Testing • ST pin test : the typical change in output should be 750mV(750mg) • ST pin test allows to verify if the accelerometer is functional • ST pin should never be exposed to a voltage Vs+0.3 V • If Vs=3V is used, the output sensitivity is 560mV • Vs= 4.75 V to 5.25 V, sensitivity is 186 mV/g to 215 mV/g. Drexel University Rock-Sat

42. Sensor Testing • Self Test response in g: • However if Vs≠5V, self test response in volts is roughly proportional to the cube of the supply voltage. • Thus, at Vs=3V, self test response will be approximately equivalent to 150mV(270mg) • Supply current decreases as the voltage supply decreases. Typical consumption at VDD=3V is 450uA. Drexel University Rock-Sat

43. DAC Testing • Differential non-Linearity Test(DNL) • DNL is generally more critical when outputting small signals • To test the linearity of a DAC, we will generate the digital stimulus and capture the analog response. • DAC is swept from 000…0 to 111...1 DNL will show up as a change between each successive digital error output • Comparison between PSPICE simulations with real simulations will make improvements on DAC Drexel University Rock-Sat

44. Risks Drexel University Rock-Sat

45. DP - Risk Walkdown • DP.RSK.1 • Sensor will not function • DP.RSK.2 • Teeth on gear will break due to elevated torque levels from acceleration • DP.RSK.3 • Vibrations will cause loss of contact in Slip Ring Terminals • DP.RSK.4 • High Gs will cause slip ring bearings to seize • DP.RSK.5 • High Load causes gear to distort, losing contact with pinion • Walkdown • FEA Analysis verifies distortion due to vertical loading will be minimal Drexel University Rock-Sat

46. MS - Risk Walkdown Drexel University Rock-Sat • MS.RSK.1 • Motor-Battery Communication Failure • MS.RSK.2 • Motor gear head and platform may lose contact under 25G • MS.RSK.3 • Battery unable to sustain variable rpm requirements • MS.RSK.4 • Motor may not respond to the micro-controller signals correctly.

47. DS - Risk Walkdown • DS.RSK.1 • Microcontroller Power Failure • DS.RSK.2 • Despun Accelerometer Communication Failure • DS.RSK.3 • Microcontroller can’t survive launch conditions • Walk-Down • Microcontroller with previous launch experience selected to limit DS.RSK.5 • Secure housing for slip ring designed to protect data transmission Drexel University Rock-Sat

48. New Risks Drexel University Rock-Sat • New.RSK.1 • Bolts become loose during launch • New.RSK.2 • Components come in contact with the vibrating canister wall • New.RSK.3 • Motor or Sensor communication Failure with Microcontroller • Walk-Down • Caps could be used on bolts • Minimizing placement of components near canister wall • Using hard Soldering for connections

49. User Guide Compliance • G-Switch will be used for system activation • No ports will be required • No plans for high voltage Drexel University Rock-Sat

50. Shared Can Logistics • Sharing ½ can with Temple University • Drexel on bottom half, Temple on top half • Temple University will be measuring gamma and x-rays, up to 100keV, through the use of a scintillator and photomultiplier-tube. They will use visible solar light as a directional z-axis reference point to characterize the high energy particles as solar or cosmic rays. • Both experiments to be separated via two individual platforms (top and bottom) Drexel University Rock-Sat