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S T U F F

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S T U F F

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  1. STUFF a t e l l i t e e s t b e d f o r n t e t h e r e d o r m a t i o n l y i n g

  2. Trade Analysis & Requirements Review The STUFF 16.684 Experimental CDIO Capstone Course February 25, 1999

  3. Presentation Outline • Program Objective and Motivations • Subsystems • Propulsion • Power and Avionics • Metrology • Communications and Software • Structures • Design Concept Presentation • Conclusions GPB, AC, JAW

  4. Program Objective To develop a testbed that demonstrates formation flying algorithms between multiple autonomous satellites with six degrees of freedom, in a microgravity environment GPB, AC, JAW

  5. Motivation • Demand for spacecraft to perform autonomous formation flying missions is increasing • Smaller • Simpler • Cheaper • Current testbeds do not allow full modeling of dynamics related to formation flying GPB, AC, JAW

  6. Justification for Flight GPB, AC, JAW

  7. Specific Science Objectives 1. Develop a set of multiple distinct satellites that interact to maintain commanded position, orientation, and direction 2. Allow for the interchange of control algorithms, data acquisition and analysis, and a truth measure 3. Demonstrate key formation flying maneuvers 4. Demonstrate autonomy and status reporting 5. Ensure the implementation of control algorithms is adaptable to future formation flying missions 6. Allow for testbed operation on KC-135, Shuttle middeck, and ISS GPB, AC, DRF

  8. Propulsion Dan Feller Presenter

  9. Safety Non-toxic byproducts Temperatures not to exceed range (TBD) Non-touch hazard Propellant Propellant supply sufficient to last at least 20 seconds. Control System must provide for 6 DOF System must provide constant performance throughout flight duration. Thrust Large ISP (TBD) Propulsion Requirements GPB, DRF, BMP

  10. Propulsion Options • Station Keeping / Attitude • Compressed Gas • Highly Traceable, Cost Effective, Off-the-Shelf Components • Fans/Propellers • Simple, Cost Effective but ... • Micro Engines and Rockets • Technology not yet operational • Attitude Control • Reaction Wheels • large, heavy, large size • Control Moment Gyros (CMGs) • large size • Magnetic Torquers • large size, long time to develop, large power demand GPB, DRF, BMP

  11. Safety: Toxicity Thermal Hazard Touch Hazard Fracture Hazard Impulse Bit (Smallest quanta of thrust) Traceability Cost Efficiency ISP, Mass ratio ISP, Volume ratio Power Consumption Ease of Replacement Time to Develop Propulsion Metrics GPB, DRF, BMP

  12. Propulsion Downselect GPB, DRF, BMP

  13. Compressed Gas Options • CO2 (Liquid or Gas) • Readily Available, Easy Containment, Adequate Thrust, Toxic • N2 / Air (Liquid or Gas) • High Thrust, Non-Toxic, Difficult Containment • Onboard Compressor • Heavy, High Power Consumption, Low Thrust GPB, DRF, BMP

  14. Compressed Gas Downselect GPB, DRF, BMP

  15. Propulsion Budget • Sub-system demands: • Power: 2W • Volume: 1.5 liter • Mass: 3 kg • Cost: $3000 • Sub-system provides: • Thrust: TBD GPB, DRF, BMP

  16. Structures Dan Feller Presenter

  17. Structures Requirements • Structural integrity • Must survive Shuttle launch and landing loads • Must survive a drop of 4 feet in 2-g • Satisfaction of mass and volume constraints • Container requirement • Mass: 60lbs = 27kg • Dimensions: Max. 9 in. = 22 cm diameter (middeck locker) • Single satellite should be less than 7 kg • Structure should be ~10% of total satellite mass (0.7 kg) • Structure should provide easy accessibility to internal components • Must be manufacturable and safe under crew handling DAC, AC, DRF, JES

  18. Structures Options • Materials • Alloys and metals • Composites • Plastics and polycarbonates • Shape • Cube • Sphere • Polyhedron • Assembly • Truss • Shell (no internal truss) • Hybrid (a truss structure with paneling) DAC, DRF, JES

  19. Structures Criteria • Integrity • Internal and external load carriage • Safety • Fracture toughness (structure cannot shatter) • Sharp edges & corners • Feasibility • Manufacturing • Internal accessibility • Cost DAC, DRF, JES

  20. Shape Downselect DAC, DRF, JES

  21. Assembly Downselect DAC, DRF, JES

  22. Materials Downselect DAC, DRF, JES

  23. Structures Budget • Mass • TBD, pending estimates of other sub-systems • Volume • TBD, but must fit within a STS mid-deck locker, i.e. greatest dimension < 9 in. • Cost • TBD, pending allowance notification DAC, DRF, JES

  24. Power and Avionics Chad Brodel Presenter

  25. Power and Avionics Requirements • Total power should be approximately 18 W • Total Volts and Amps TBD • All hardware must be contained in individual satellite • Data storage must be adequate • Components must be compatible with KC-135, Shuttle, and ISS environments • System should be traceable to existing satellites JAW, SEC

  26. Power Distribution JAW, SEC

  27. Power Options • Battery Power • Non-rechargeable batteries • Alkaline • Carbon Zinc • Lithium • Silver Oxide • Zinc Air • Silver Zinc • Rechargeable • Nickel Cadmium • Nickel Metal Hydride • Solar Cells JAW, SEC

  28. Power Criteria • Number of Batteries for 12V • Operating Temperature Range • Capacity • Approximate Lifetime • Energy Density • By mass • By volume • Size • Weight • Volume • Cost • Safety JAW, SEC

  29. Power Downselect JAW, SEC

  30. Power Recommendations • Batteries • Non-rechargeable: Lithium • Lifetime approximately 40 minutes • Rechargeable: NiMH • Lifetime approximately 30 minutes • Solar cells should be considered JAW, SEC

  31. Power Budget • Sub-system demands: • Weight : 300 g • Volume : 250 cm3 • Cost : TBD • Sub-system provides: • 18 W • Voltage and Amps TBD JAW, SEC

  32. Specific Avionics Requirements • Sufficient data storage capacity • Volume and weight TBD • System must be compatible with communications, propulsion, and metrology • Low power drain JAW, SEC

  33. Avionics Options • Build Custom Processors • Purchase Processors • Commercial Processor Options • Tattletale TFX - 11 • Tattletale 5F/5F - LCD • Spectrum INDY • Crickets JAW, SEC

  34. Communication and Software Chad Brodel Presenter

  35. Satellite to Satellite (STS) Real time Send, receive, and temporarily store data Compatible with KC-135 / Shuttle systems Must be traceable to existing satellite technology Satellite to Ground (STG) Does not have to be real time Data must be recorded for post-flight analysis Must be compatible with KC-135 / Shuttle systems Communication & Software • Communication Requirements: GPB, CSB, SLC

  36. Software Requirements • Software is the interface between input (metrology) and output (propulsion) • Requirements: • Must have common programming language • Must be flexible to allow execution of complex maneuvers • Must develop efficient code compiling techniques GPB, CSB, SLC

  37. Communication Methodology Options • All equal authority • Satellites interact to decide how to execute array maneuver • Master / Slave • One satellite gives commands to all others • Hierarchy / Command Chain • Satellites ranked in authority • Easy command transition in case of failure GPB, CSB, SLC

  38. Communication Methodology Selection • Hierarchy / Command chain ensures no confusion • Satellites numbered 1-3: one control stream • No. 1 Satellite • Receives control algorithm from ground • Determines each satellite’s position in array • Sends commands to other satellites • Sends own health status info to ground • Other Satellites • Communicate position, velocity and acceleration data to No. 1 • Sends own health status data to ground • If No. 1 fails, each satellite will shift up in hierarchy GPB, CSB, SLC

  39. Data Transfer Options • Download Data: • Continuously • Larger power requirement • Uses up bandwidth • Post Flight • Possibility of losing on-board data • Long download time • Larger on-board memory cache required • At regular intervals • Efficient combination of options • Our recommendation GPB, CSB, SLC

  40. Communication Downselect GPB, CSB, SLC

  41. Communication Hardware Selection • Best Option (STS, STG): RF • Excellent range • Low power requirement • Reasonable bandwidth and accuracy • Single sensor • Cost effective • Possibility of interference on KC-135, Shuttle middeck GPB, CSB, SLC

  42. Budgets Constraints • Power • Communications sensors and receivers ~ 2 Watts each (1 RF STG and 1 RF STS per satellite) • Mass • Communication sensors and receivers ~ 8 grams per satellite • Volume • Sensors relatively flat / surface mounted (small) GPB, CSB, SLC

  43. Metrology Fernando Perez Presenter

  44. Metrology Overview • Two subsystems • Navigation metrology • Real-time position and attitude determination • On-board navigation system • Accurate • Truth measure • Verification of position and attitude • Probably some sort of off-board camera or ranging system AC, SYC, SLJ, FP

  45. Real time--10 Hz Accuracy Position to 1 cm (TBR) Attitude to 1º (TBR) Must meet space shuttle and KC-135 interface, interference, & safety requirements Setup in 20 minutes (TBR) Interface with other subsystems Communications Avionics Power Onboard = 2 W (TBR) Off-board = 10 W (TBR) Structures Mass = 0.3 kg (TBR) Volume = 20 mL (TBR) Navigation Metrology Requirements AC, SYC, SLJ, FP

  46. Position IR/Ultrasound Ultrasonic Ranging Gyros/ Accelerometers Synchronized clock/RF/IR Attitude Gyros/ Accelerometers IR/Ultrasound Pure IR Navigation Metrology Options AC, SYC, SLJ, FP

  47. Metrics Complexity Cost Accuracy Constraints Onboard Power Volume Real time Mass Safety Interference Navigation Metrology Criteria AC, SYC, SLJ, FP

  48. Navigation Metrology Downselect Note: Power, Volume, Safety, and Interference were considered on a binary scale and are listed as constraints where the subsystem requirements were not met AC, SYC, SLJ, FP

  49. Accuracy Position to 1 cm (TBR) Attitude to 1º (TBR) Must meet space shuttle and KC-135 interface, interference, & safety requirements Interface with other subsystems (not an onboard system) Off-board requirements Power = 2 W (TBR) Structures Mass = 20 kg (TBR) Volume = 5000 mL (TBR) Truth Measure Metrology Requirements AC, SYC, SLJ, FP

  50. Position External fixed cameras Onboard cameras External tracking cameras Informed tracking cameras with rangefinders Radar ranging Reverse IR/Ultrasound Attitude External fixed cameras Onboard cameras Reverse IR/Ultrasound Truth Measure Metrology Options AC, SYC, SLJ, FP