THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 1 UCB, October 15-16, 2003 EFI Radial Boom EFI Radial Boom Mechanical (SPB Spin Plane Boom) Bill Donakowski Mechanical Engineer Space Sciences Lab University of California Berkeley

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 2 UCB, October 15-16, 2003 Requirements Structure, Testing, Materials Mechanical-Verification-Spec-1c (Swales/THEMIS specific) THEMIS PAIP GEVS A/R (GSFC General Environmental Verification Specification) Thermal Near Exterior Solar Panel, device gets cold Predicts: -17 C Cold; +36 Hot Range for Deploy: 0 to +20 C Magnetic Cleanliness Mass <1881 grams (Currently: 1757) On-Orbit Deployment is Mission Critical Robust Device with adequate margins Proper Handling of Wire –Storage and Handling –Hand Winding during Flight Build and Following Test Deploys

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 3 UCB, October 15-16, 2003 Design Overview 4 x Attach Legs with G10 Spacers for Thermal Isolation Brushless Gearmotor With Bevel Gears Meter Wheel Base (Magnesium) Sphere and Preamp Release Doors (Spring Preloaded) Main Wire Spool Exit Tube

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 4 UCB, October 15-16, 2003 Flight Heritage Radial Boom Design goes back 25+ years Polar Cluster FAST Mature Designs/Vendor Familiarity Many Design Reviews and Test Data from prior Programs Critical Component Vendors for THEMIS (Wire) Test Fixtures and Procedures in-house at SSL Personnel ramping up to take over Wire Boom ‘Gray Beard’ (Dave Pankow) Dr. Pankow to remain as advisor to program

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 5 UCB, October 15-16, 2003 Customization of Design for THEMIS Use Wire Length Increased to 18m Packaging for mounting to THEMIS Probe Structure Attachment Magnesium replaced 6061 Al for weight savings Sphere Coating Titanium Nitride replaced DAG 213 DC Gearmotor Same Motor Manufacturer (Globe Motors) Similar Performance (300 ounce-inches Torque) Brushless Unit Selected over Brushed –Brushless better design in vacuum –Better Thermal Characteristics –Less Stray Magnetic Field –Higher Performance in smaller package New Electronics Drive Package Required –Designed in-house –Prototype up-and-running 3 weeks without problems

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 6 UCB, October 15-16, 2003 Theory of Operation Integration and Launch Stowed and Unpowered Wire Wound about Spool, constrained by pinch wheels Release Doors Closed Sphere/Pre-Amp Constrained by Release Doors Deployment Release Doors Opened via SMA Pin-Puller Spin of S/C puts outward force on Sphere and Preamp Motor Acts as brake to prevent motion; coaxial wire in tension Motor powers rotation of Meter Wheel Sphere and Preamp is payed out Release Doors Close Back Around Wire As Centrifugal Force exceeds 2G at Sphere, Sphere Key Reel Spring force is overcome and Sphere moves away from Preamp Monitoring –Limit Switch on Shaft counting Rotations –Tension Sensor to sense High Tensile Force Science Ops Deployed Booms Configuration Unchanged

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 7 UCB, October 15-16, 2003 Theory of Operation Meter Wheel Preamp Motor Main Wire Spool Pinch Rollers Release Doors Sphere Motor Drive Electronics

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 8 UCB, October 15-16, 2003 Materials and Construction Standard UCB Construction Most Components Machined Aluminum –6061 T6 and 7075 T73 –Alodined and Anodized Machined Plastics –PEEK Machined Magnesium Alloy AZ31B –Chosen for Weight Relief in Structure –Not MSFC-SPEC-522 High Resistance to SCC –Table II ‘Moderate Resistance’ –Requires MUA for use Thermal Treatments Surfaces covered with VDA tape or blankets No Heaters Required Common manufacturing techniques used No Unusually Tight Tolerances No Difficult Fabrications

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 9 UCB, October 15-16, 2003 Long Lead Hardware Multi-Conductor Wire Vendor: Gore Custom to UCB Spec (THM-SPB-M101) 8 single conductors/ 1 coax Lead Time: 6 weeks RFQ in process Spares: 100% Over DC Brushless Gearmotor Vendor: Globe Motors Custom based on OTS Globe Gearmotor –Braycote 601 lubricant –Nickel Plating replaces Cadmium Lead Time: approx. 90 Days RFQ has gone out Spares: 12 units

THEMIS Instrument PDR Bill Donakowski/ EFI Radial Boom 10 UCB, October 15-16, 2003 Issues and Concerns Scientist’s Mantra: “More Wire=More Science” Care must be taken to resist pushing heritage design too far Full Deploy Testing Difficult Mass See above With 20 units on-board at launch, margins are tight Packaging on Probe ongoing Issue Larger Probe Tanks slightly impinging Tighter Packing being worked Random Vibration Test Inputs 14.7 grms inputs are high, increases risk to Instruments On-going discussion with Swales to decrease Handling/Storage/Build/Accounting of Wire and Parts Build and Test of Radial Booms tedious and labor intensive THEMIS ‘mass production’ of instruments mandates strict parts tracking and accounting paperwork