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The MAGIC Tether Experiment

The MAGIC Tether Experiment

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The MAGIC Tether Experiment

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  1. The MAGIC Tether Experiment A Demonstration of DINO’s MAGIC Boom University of Colorado Friday, April 02, 2004

  2. The MAGIC Tether Experiment • Special Thanks To the KC-135 Team for All of Their Hard Work and Great Contributions • Cook, Evan • Martinez, Mike • McArthur, Grayson • Mohler, Andrew • Parker, Jeff • Seibert, Mike • Stamps, Josh • Worster, Kate Colorado Space Grant Consortium & DINO

  3. Background – DINO • Nadir Pointing • Gravity Gradient Stabilization • Deployable Boom • Primary Satellite • 25 kg • Tip Mass • 5 Kg • MAGIC Tether • Mechanically-Actuated Gravity-Induced Control • Stanley Tape Measure • 6m Long • Lightband • 2 +/- .5 ft/sec • Full deployment after 10 sec Tip Mass Tether DINO Colorado Space Grant Consortium & DINO

  4. Why do This Test • Is this System Even Feasible? • Dynamics of the Semi-Rigid System are Poorly Understood • Experimental Results of Energy Dissipation • Over damping will result in inadequate deployment • Poor gravity gradient stabilization • Science objectives • ADCS power Draw • Under damping would shock the system • Could damage Electronics and Cameras • Could recoil, causing a collision Colorado Space Grant Consortium & DINO

  5. Expected Results • The MAGIC Tether team expects the following things: • Four standard springs will accelerate the relative velocity of the tip mass with respect to the primary satellite to approximately 1.7 ft/s (0.518 m/s). • The tip-off rate of the deployment to be less than 1°/s in each axis. • Given a deployment velocity of 1.7 ft/s, the optimal value of x0to be approximately 0.66” to critically damp the system’s motion as the tether is fully deployed. • The semi-rigid tape to be deployed in a controlled fashion without any recoil at the end of its deployment. Colorado Space Grant Consortium & DINO

  6. Experiment Objectives • To measure the large-scale and small-scale dynamics in the deployment • Linear and angular accelerations • To empirically measure how the energy in the system can be dissipated • Spring force in the slow-down mechanism • Critically damp tip mass’ motion • To demonstrate a successful deployment of DINO’s MAGIC Boom Colorado Space Grant Consortium & DINO

  7. Overview of the Experiment • KC-135 • Heavy Sat • 14.6 kg (32.2 lbs) • Light Sat • 8.1 kg (17.8 lbs) • Tether • Two lengths of Stanley Tape Measure (1.0 in) • 4 ft (1.22 m) • Sensors • 6 Accelerometers • 6 Rate Gyros • Equipment Containment System Light Sat Tether Heavy Sat Safety Straps Colorado Space Grant Consortium & DINO

  8. Structure • The structure on each of the two satellites (Heavy and Light Sat ) is composed of two 1/8” 6061Al plates connected by 4”-tall 1/4" 6061Al box walls. • All sharp edges will be covered with pipe insulation Damping System TAZ Foam Padding Colorado Space Grant Consortium & DINO

  9. Heavy Sat The Heavy Sat will have an overall mass of approximately 14.6 kg and dimensions of 18” x 18” x 6”. • Circular inner plate • Male mating adapter • TAZ • Deployment springs • Data loggers • Dummy loads • Sensors and batteries Containment box • Hand holds • Pipe insulation Data Logger Data Logger Colorado Space Grant Consortium & DINO

  10. Light Sat The Heavy Sat will have an overall mass of approximately 14.6 kg and dimensions of 18” x 18” x 6”. • Circular inner plate • Female mating adapter • Spring Adapters • Data loggers • Dummy loads • Sensors and batteries containment box • Hand holds • Pipe insulation • Braking System Data Logger Data Logger Colorado Space Grant Consortium & DINO

  11. Entire Assembly Colorado Space Grant Consortium & DINO

  12. Push off Springs x 4 • Based on Planetary System’s Lightband springs • K = 22.5 lb/in (Per Spring) • Finitial = 60 lb (Total) Colorado Space Grant Consortium & DINO

  13. Tether Description • The semi rigid tether (SRT) • Two face-to-face Tape Measures • Commercial, off the shelf part Colorado Space Grant Consortium & DINO

  14. Tether Mounting • Deployment / Braking System mounted in Light Sat (Tip Mass) • Boom mounted to Heavy Sat (Main Satellite) with a tether attachment system (TAZ), designed to maintain the rigid natural shape of the tether, while providing a secure attachment. Colorado Space Grant Consortium & DINO

  15. Deployment System Colorado Space Grant Consortium & DINO

  16. Damping System • 42 Teeth per Rotation • 366 Teeth per Full Deployment • 3.1 J Total Energy • .0085 J / Tooth • Two 2.5 inch spools • Geared to counter rotate • Ratchet and Pawl • Pawl Spring Loaded • Adjustable Initial Compression Colorado Space Grant Consortium & DINO

  17. Damping System Colorado Space Grant Consortium & DINO

  18. Mechanical Dial • In Flight Spring Adjustment • .55in - .75in • Linear Transducer Colorado Space Grant Consortium & DINO

  19. Release System • Deployment initiation • Mechanical System • Hand held actuating lever • Bicycle brake • Release cable • Switch • Incorporated into handle • Initiates data collection Colorado Space Grant Consortium & DINO

  20. Testing DAY 1 • Set Spring to maximum compression, .75in (Over Damped) • Position Test Equipment • Deploy • Reset • Decompress spring .05in • Repeat until .55in compression is reached (Under Damped) • DAY 2 • Set Spring to maximum compression in range of interest • Position Test Equipment • Deploy • Reset • Decompress spring desired amount • Repeat until minimum compression in range of interest is reached Colorado Space Grant Consortium & DINO

  21. Data Collection • There will be four sources of data in the MAGIC Tether Experiment: • Qualitative observations by the flyers and by the digital video camera • Quantitative measurements of acceleration by the six single-axis accelerometers • Quantitative measurements of angular velocities by the six single-axis gyroscopes • Quantitative measurements of braking spring compression by the linear transducer Colorado Space Grant Consortium & DINO

  22. Safety • Restraint Straps • Four cinch straps to hold satellite to base plate during Takeoff/landing • Two Velcro straps for satellite securing during flight • Velcro connection between Heavy Sat and base plate during flight • Safety straps • 10’ straps connected from the base plate to each satellite • 6’ strap connecting each satellite • Braided steel rated to 1000 lbs. • Safety pin • Prevent accidental deployment • Padding on all metal edges • Four handholds per satellite • Safety straps attached to all tools • Fuses installed on electrical lines Colorado Space Grant Consortium & DINO

  23. Results • Trends will be extrapolated and scaled to DINO’s full Deployment length and weight. • What will happen to the satellite if the damping system does not perform precisely as planned? • What are the risks to the Satellite? • Does the Tether “explode” violently? • Is the deployment controllable? • Does the damping occur as expected? • Real world experience • Will result in a safer, more reliable system for DINO Colorado Space Grant Consortium & DINO

  24. Appendix Colorado Space Grant Consortium & DINO

  25. FEA for KC-135 Experiment Grayson McArthur

  26. G-Load Specs • Takeoff/landing - Forward 9 g’s - Aft 3 g’s - Down 6 g’s - Lateral 2 g’s - Up 2 g’s • 3 g’s in any direction - Randomly picked 3 configurations to simulate the structure being dropped Colorado Space Grant Consortium & DINO

  27. FEA Setup • Program used for analysis → CosmosWorks • Takeoff/landing - Load acts through the center of gravity - Outer face of the outer panel on the light side restrained as immovable/no translation to simulate attachment to base plate - Global size of nodes set at 0.44469 in. with a tolerance of 0.02223 in. - Yield strength of Al 6061 used as max. load = 145 MPa or 21030.51 psi - Factor of safety set at 2 based on the yield strength Colorado Space Grant Consortium & DINO

  28. FEA Setup Con. • 3 g’s in any direction - Load acts through the center of gravity - Global size of nodes set at 0.44469 in. with a tolerance of 0.02223 in. - Yield strength of Al 6061 used as max. load = 145 MPa or 21030.51 psi - Factor of safety set at 2 based on the yield strength ► Thin edge faces of outer plates set as immovable/no translation to simulate the structure being dropped on those two edges Colorado Space Grant Consortium & DINO

  29. Results • Stress: Von Mises (VON) - Measured in pounds per square inch - VON = (0.5[(P1-P2)2+(P1-P3)2+(P2-P3)2])1/2 - P1,P2,P3 are principle stresses - Measures stress intensity required for a material to start yielding • Strain: Equivalent Strain (ESTRN) • Displacement: Resultant (URES) - Measured in inches - Adds displacement vectors in X,Y,Z direction to get a resultant vector • Design Check - FOS < 2 area shows as red - FOS > 2 area shows as blue Colorado Space Grant Consortium & DINO

  30. Stress Colorado Space Grant Consortium & DINO

  31. Strain Colorado Space Grant Consortium & DINO

  32. Displacement Colorado Space Grant Consortium & DINO

  33. Design Check Colorado Space Grant Consortium & DINO

  34. Conclusions • The structure will be able to withstand all the prescribed loads as indicated in NASA document AOD 33897 Experiment Design Requirements and Guidelines NASA 931 KC135A • Structure will survive a 3 g impact such as being dropped by the flight crew during transition from 0 g to 2 g Colorado Space Grant Consortium & DINO

  35. Issues and Concerns • Mesh resolution was limited due to computer memory and time limitations • Boundary conditions being appropriate for load case Colorado Space Grant Consortium & DINO

  36. Onboard Support EquipmentEquipment Containment System (ECS)

  37. Entire Assembly Colorado Space Grant Consortium & DINO

  38. Base Plate • .125-.25in Al 6061 sheet • Note, Current design requires heavy hand construction… It will not fit within the CNC • 4 Aircraft mounting location • 7 handhold, accommodating up to 4 handlers • Experiment restraint harness • Safety cable attachment Colorado Space Grant Consortium & DINO

  39. Tool Box • Store bought • Plastic and steel construction • Round plastic edges • Lockable Colorado Space Grant Consortium & DINO

  40. Stand Off • Al 6061 • Industrial strength Velcro • Non permanent attachment • Only for stability, not critical for LD/TO Colorado Space Grant Consortium & DINO

  41. Mechanisms Michael Martinez

  42. Mechanisms • Contents: • Tether Description • Deployment System • Braking System Colorado Space Grant Consortium & DINO

  43. Tether Description • The semi rigid tether (SRT) is constructed of 2 COTS spring metal "tape measures", four feet length by 1 in wide, curved along their width. • To be configured ‘face to face’, provides greater stability. Colorado Space Grant Consortium & DINO

  44. Deployment System Colorado Space Grant Consortium & DINO

  45. Deployment System(cont) • The MAGIC Tether deployment system consists of two 2.5 inch spools, geared to counter rotate and unwind the spring metal boom in a controlled manner. Colorado Space Grant Consortium & DINO

  46. Deployment System(cont) • Deployment / Braking System • The stowed SRT will be wound on the two spools such that when deployed the two tape measures will be face to face, forming a rigid structure. • Tape to spool connection recessed to reduce stress at connection Colorado Space Grant Consortium & DINO

  47. Braking System • Velocity control is provided by a 48 tooth, 2.0 inch ratchet and pawl system, with the ratchet shafted to the geared spool, and the pawl spring loaded to provide a loading / braking force against the ratchet. • Initial k for spring ~ 0.245 N/mm Colorado Space Grant Consortium & DINO

  48. Release System • Deployment initiation • Mechanical System • Hand held actuating lever • Bicycle brake • Release cable • Switch • Incorporated into handle • Initiates data collection Colorado Space Grant Consortium & DINO

  49. Tether Reset Device • Tether reset device • Two options • Manual crank • Electric drill • Flexible extension used to reach the drive shaft easily • Attached to the toolbox by a steel cable tether Colorado Space Grant Consortium & DINO

  50. Tether Mounting • Deployment / Braking System mounted in Light Sat (Tip Mass) • Boom mounted to Heavy Sat (Main Satellite) with a tether attachment system (TAZ), designed to maintain the rigid natural shape of the tether, while providing a secure attachment. Colorado Space Grant Consortium & DINO