Drexel University 2010-2011 RockSat-C Preliminary Design Review

1. Drexel University 2010-2011 RockSat-CPreliminary Design Review Joe Mozloom Eric Marz Linda McLaughlin Swati Maini Swapnil Mengawade Advisor: Jin Kang, PhD

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.

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.

4. Mission Overview - Theory • Angular Velocity • ω = dθ / dt • At 5.6 Hz ω = 35.18 rad/sec • Radial Acceleration • ar = ω2 r • At 35.18 rad/sec • With 0.0635 meter Radius ar = 78.62 m/s2 = 8 g ω ar at

5. Expected Results Workbench Flight Meet all NASA / WFF requirements Counter-rotating platform engaged when canister is spinning Platform able to rotate under harsh flight conditions Data is reliably collected and is usable • Meet all NASA / WFF requirements • Counter-rotating platform effective from 0.5 Hz - 10 Hz • Maximum platform spin-rate 10% of current canister spin-rate • Data is reliably collected and is usable

6. Preliminary Design

7. 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

8. Concept of Operations

9. Subsystem Definitions Despun Platform (DP) Data Systems (DS) Motor Systems (MS) Power Systems (PS) • Slip Ring • Despun Gear • Microcontroller • Memory • Accelerometers • Algorithms • DC Micro-motor • Pinion • Batteries • Voltage Regulators • G-Switch

10. Despun Platform Subsystem

11. Despun Platform Definition • System Components • Through-Bore Slip Ring • Slip Ring Fastener • Undefined until Slip Ring is selected • May be unnecessary if mounting holes can be drilled into slip ring • Despun Plate/Cog • 2-axis, High-G Accelerometer

12. DP - Subsystem Description • 4:1 Gear Ratio between platform and motor pinion • Reduces torque needed by motor • Despun gear nominal dimension of 5” (127 mm) • Gear to be CNC cut from ¼” (6.35 mm) polycarbonate • Fabricated In-House

13. DP - Subsystem Requirements

14. DP - Slip Ring Trade Study

15. DP - Selected Slip Ring • Aeroflex Airflyte CAY 1847 • Max RPM: 500 • Through-Bore Diameter: 3/8” =9.525 mm • Length: 1.3” = 33.03 mm • Stator Diameter: 1.25” = 31.75 mm • # of Circuits: 18 • Max Voltage: 210 V • Max Current: 2A/Circuit • Cost; $400

16. DP - Risk Matrix • 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

17. Data Subsystem Power Supply Stationary Accelerometer Microcontroller Digital to Analog Converter Motor Despun Accelerometer Slip Ring

18. DS - Accelerometer vs. Gyroscope

19. Data Systems Definition • Microcontroller • ATMEL 8-bit AVR Microcontroller • Motorola M68HC12 Microcontroller • Accelerometer • Analog Devices ADXL278 MEMS Accelerometer • Colibrys MS8000.D MEMS Accelerometer • External Resistor Ladder for 8-bit/16-bit Digital to Analog Conversion

20. DS - Software Schematic

21. DS - MEM Accelerometers • ADXL103/ADXL203 • Size: 5mm x 5mm x 2mm • Resolution: 1mg at 60Hz • Bandwidth: 0.5 Hz – 2.5 kHz • Sensitivity: 960-1040 mV/g • Supply Voltage: 3.0-6.0 V • Supply Current: 1.1 mA • 3500g Shock survival

22. Accelerometers Trade Study

23. DS - Accelerometers Testing • ADXL203 tested and specified at Vs = 5.0 V • Radiometric output • Vs = 3.0 V output sensitivity ≈ 560 mV/g • Noise density decreases as the supply voltage increases. • Vs = 3.0 V, Noise Density = 190 μg/√Hz • When ratiometricity of sensitivity is factored in with supply voltage, self test response is roughly proportional to the cube of power supply voltage. • Vs = 3.0 V, Self Response ≈ 150 mV

24. DS - Analog to Digital Conversion • Requirement for our electronic system: to convert signals from digital to analog forms • Analog to digital convertor (DAC)needed

25. DS - Risk Matrix • DS.RSK.1 • Microcontroller Power Failure • DS.RSK.2 • Motor Communication Failure • DS.RSK.3 • Stationary Accelerometer Communication Failure • DS.RSK.4 • Despun Accelerometer Communication Failure • DS.RSK.5 • Microcontroller can’t survive launch conditions

26. Motor Subsystem

27. Motor Systems Definition • Required RPM: 600 (without gearing) • 2400 RPM with 1:4 gear ratio • Amperage: < 300 mA • Torque: 80 mNm (without gearing) • 20 mNm with 1:4 gear ratio • Max Length: 3” = 7.62 cm • Max Diameter: 2”= 5.08 cm • Max Mass: 250g • Pinion to be CNC cut from ½” (12.7 mm) polycarbonate • Fabricated In-House

28. MS - Motor Trade Study

29. MS - Brushed vs. Brushless

30. MS - Selected Motor • 3242 SCDC DC Servomotor from Faulhaber. • Selection Criteria • This brushless motor fit all of our design criteria- electronic communication, high speed, data transfer and reception and small size. • Gearing Requirement • Can be provided with the motor (3242 SCDC 012) • 32A-available on request from the supplier.

31. MS - Risk Matrix • MS.RSK.1 • Required Torque exceeds stall torque • MS.RSK.2 • Motor-Battery Communication Failure • MS.RSK.3 • Motor gear head and platform may lose contact under 25G • MS.RSK.4 • Battery unable to sustain variable rpm requirements • MS.RSK.5 • Motor may not respond to the micro-controller signals correctly.

32. Power Subsystem

33. Power System Definition • Rechargeable Battery • 9 V NiMH Powerizer Batteries • Amperage : 170mA • Amount needed : 4 • Weight:125g • Voltage Regulator • ±3.3 V Linear regulator for flash memory and accelerometers • ± 5.0 V Linear regulator for microcontroller • Parallel and Series connection to achieve requirements of motor and electronic devices

34. PS - Power Flow

35. PS - Battery Trade Study

36. Critical Interfaces

37. PS - G-Switch Definition • TBD – Specified by WFF • Activate/deactivate at Wallops command • Light switch form • Current flow can be inhibited by Wallops via Relay • No latch activation • Able to allow Wallops to have full control of activation/deactivation

38. Shared Can Logistics • Sharing ½ can with Temple University • 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. • No Ports needed for experiment • Drexel and Temple have been communicating regularly thus far • Close geographic proximity allows for the teams to meet face to face and will aid in future collaboration

39. Preliminary Mass Estimates Design for 2 Kg, Leaving minimum margin of 760 grams

40. Center of Gravity Estimate • The center of gravity for our Design will be confined within a 1inch cube from the center of the canister. • This will be obtained by placing the large components in such a way that their resulting moment will be within the center of gravity envelope.

41. Prototyping Plans • Gearing • Physical prototypes of gears to verify gear ration/ teeth size • Digital to Analog Converter • Created with resistor ladder and Op-Amp • Motor control algorithm • Slip Ring fastener • Interface stator section of slip ring to fixed platform

42. Budget

43. Timeline

44. Team Overview

45. Future Work • Finalize design for slip ring holder • Choose number of teeth/ tooth design for gearing system • Determine interfacing between motor and fixed platform • Continue to become comfortable with Solidworks