Magnetometer Booms Critical Design Review Dr. Hari Dharan Berkeley Composites Laboratory

1. Magnetometer Booms • Critical Design Review • Dr. Hari Dharan • Berkeley Composites Laboratory • Department of Mechanical Engineering • University of California at Berkeley

2. Overview • Magnetometer Booms • System Overview • Technical Requirements • System Mechanical Design • Updates to Analyses • Design Margins • Mass and Power • Test Plan • Fabrication Plan • Integration Plan • Performance Assurance • Schedule • Parts and Materials Status • Contamination Control • Problem Areas

3. System Overview • Magnetometer Booms • Each probe has two magnetometers – Flux Gate Magnetometer (FGM) and Search Coil Magnetometer (SCM). • The magnetometers are to be magnetically isolated by suspending via booms from probe. • The booms must be stowed to fit the envelope of the probe. • 1.25 in. ID carbon-fiber tubes. • Al hinges and brackets. • FGM is deployed 2.25m from S/C center. • SCM is deployed 1.4m from S/C center

4. System Overview SCM Base Hinge, similar to FGM Base Hinge, with no Frangibolt Carbon Fiber Tubes FGM Elbow Hinge / Deploy Assist Device (DAD) S/C Top Deck Frangibolt Deployment Assist Spring Saloon Door Spring SCM Frangibolt Tower FGM Base Hinge: Saloon Door Mechanism and Frangibolt Actuator SCMSearch Coil Magnetometer FGMFlux Gate Magnetometer

5. System Overview 1) Frangibolts Actuated 2) Elbow DAD Releases 3) Mid-deployment 4) Fully Deployed

6. Mission Requirements

7. Mission Requirements

8. Boom Requirements

9. Mechanical Design - Status • Major design changes since PDR • Harness routed within mag booms. (Nov 03) • Addition of 2 degree cant angle to FGM and SCM booms. (Nov 03) • Change of FGM boom cant angle to 5 degrees, and SCM boom cant angle to 10 degrees, while minimizing stowed profile. (Jan 04) • Modification of base hinge with flexures to reduce thermal strains. (Feb 04) • Status • Drawings completed and ETU sent out for bid for machining on 3/25/04.

10. System Mechanical Design Frangibolts • Frangibolt actuation separates stowed booms from S/C. • TiNi Aerospace’s FC2-16-31SR2. • Reliable. • Low mass & power requirements.

11. System Mechanical Design Frangibolt Implementation V-Shaped Interface: • Isolates the Frangibolt from vibration loads • vertical shear and moments • Allows axial compliance for assembly Frangibolt Cover: • Contains Frangibolt after firing • Shields components per NASA LLS 1360

12. System Mechanical Design • Elbow Latch Deployment Assist Spring Location Hook-Pin Latch Device Kickoff Disk Springs Harness Tie-Down Clip Harness Routing Spool Flexure Feet

13. System Mechanical Design • Base Hinge Design Features Latch Pin Deployment Assist Spring “Saloon Door” Spring Frangibolt(Integrated Shear Support) Flexure Mount Feet

14. System Mechanical Design • Base Hinge, Animated

15. System Mechanical Design • Boom Cant Effects • Booms are “canted” out of the spin plane • Kinematically defined deployed configuration • Eliminate shadowing of solar panels • In the deployed configuration: • SCM cant of 10° • FGM cant of 5 ° • Deployment axis is also tilted out of plane FGM Base Hinge Stowed FGM Base Hinge Deployed

16. System Mechanical Design • Tube Lay-up • [(±45)T300 / 0M55J,4 ]s • T300 = high-strength carbon fiber woven composite (0.005”/ply), M55J = high-modulus carbon fiber unidirectional composite tape (0.0025”/ply) • Matrix = YLA RS3 cyanate ester. • Thickness = 0.03 in. • Inside diameter = 1.25 in. • Effective longitudinal modulus = 30.9 x 106 psi (213 GPa) • Mass per unit length = 3.2 g/in (1.26 g/cm)

17. Dynamic Analysis Update • Dynamic Model Overview • Numerical solution of Kinematics & Rigid Body Dynamics • Includes: • Kickoff spring forces • Deployment assist spring moments • Latching and de-latching events • Updated for • Boom cant effects • Frictional torque

18. Dynamic Analysis Update • Assumptions: • Increase in moment of inertia due to booms deploying will not slow the spacecraft enough to effect deployment  use a constant spacecraft spin rate to simplify analysis • Linear springs • Elastic collisions (conservative assumption) • Constant frictional torques • Booms are rigid links • Deployment is in-plane

19. Dynamic Analysis Update • MATLAB Simulation • Inputs • Satellite spin rates • Initial boom positions • Boom lengths, MOIs, spring constants, values of friction, etc… • Latching locations • Outputs • Deployment animation • Hinge Forces and Moments • Deployment time

20. Dynamic Analysis Update • Boom Cant Effects • Effects due to tilt of deployment axis • Strategy: Plug simulated 2-D values for αz and ωz (which also generates small values of αY and ωY into full 3-D moment equation, observe deviation from 2-D results • Error in predicted αz values ~0.12% • Addition of out-of-plane moments MX and MY • These are nontrivial, producing frictional moments on the same order as sum of all other moments considered • Moments only act during high velocity or acceleration, i.e. during latching  positive effect • 2-D Moment Equation: • Full 3-D Moment Equation

21. Deployment Stress Analysis • Stress/FEM • Latching loads from dynamic analysis • FEM models for hinge analysis • FOS = 1.7 (SCM @ 15rpm)

22. Torque Margin Analysis • Sources of friction considered • Latch pin sliding along ramp : Vespel-3 on aluminum • Clevis on hinge pin: 544 bronze on 303 stainless • Applies for base hinge and elbow • Forces due to 1) deployment spring force reacting through hinge and 2) out-of-plane moment due to boom canting

23. Torque Margin Analysis

24. Thermal Analysis Updates • Tube bending with thermal gradient • minimal effect (~.003° max)

25. Vibration Analysis Update • Frequency Spec • Mag. Boom stowed stiffness shall be greater than 100 Hz • Mag. Boom deployed stiffness shall be greater than 0.75 Hz • Current Design • Stowed frequency is dominated by tube. • Deployed frequency is dominated by torsion spring stiffness at base hinge 1st mode shape of stowed FGM outer boom.

26. Design Margins

27. Mass & Power • Mass • Power • 25W transient for Frangibolt deployment.

28. Fabrication and Assembly • Documentation • All fabrication and assembly processes are developed and documented as Manufacturing Process Instructions. • Any fabrication work and assembly will be logged. • Fabrication • Boom tubes – In-house • Hinges – external machine shops. • Assembly • Bonding boom tubes and end fittings. • Assembling hinges, harness and Frangibolt.

29. Composite Boom Fabrication • In-house capability to manufacture composite tubes using the table rolling process. • Bldg 151,Richmond Field Station (RFS). • In service since March 2004. Prototype boom tubes successfully fabricated. Table Roller Shrink Tape Wrapper Oven Mandrel Puller

30. Integration Plan • Integration of Tube and End Fittings • End fittings will be bonded to the boom tube via bonding fixtures. • Bonding fixture controls component length and clocking between end fittings. • Bldg 151, RFS. FGM BoomBonding Fixture SCM BoomBonding Fixture

31. Assembly Plan • Assembly of hinges • Assemble base hinge, and DAD boxes. Do not assemble elbow hinge can assembled. • Integration of harness • Harness, without connectors, will be threaded through booms before assembling of boom. For the FGM, harness must also be threaded through the elbow before it is assembled. • Assembly of mag boom • Assemble hinges and tubes with end fittings. • Integration of Frangibolts • Frangibolts will be installed after boom is assembled.

32. ETU Testing Plan • ETU Testing Plan • Vibration test for composite boom tubes. • Mechanical characterization of composite materials. • Proof testing of bonded joints subjected to survival temperature limits. • Deployment testing at low and high deployment temperature extremes. • Boom (tube and end-fittings) proof testing. • Deployment testing at ambient conditions.

33. Flight Unit Testing Plan • Flight Unit Testing Plan • Ambient deployment • Vibration • Ambient deployment • Deployment test at deploy cold extreme minus 10C • Deployment test test at deploy hot extreme plus 10C

34. ETU Testing • Boom Vibration • Adjustable mounting on the shaker to test different support lengths for FGM and SCM booms. • Test will take place at Wyle Laboratories, Santa Clara • Sine and random as per THEMIS requirements.

35. ETU Testing • Mechanical Characterization of laminate • A laminate will be constructed and a coupon used for stiffness and strength. • Four point bending test. • Proof testing of bonded joints. • An end fitting will be bonded to short lengths of the magboom and thermal cycled to THEMIS requirements. • A tensile proof test of the bonded joint is carried out after thermal cycling. • Composite boom with end fittings • Tensile proof test after thermal cycling.

36. Deployment Test Plan • Non-Ambient Testing • Thermal vacuum test for hinge operation. • Horizontal deployment at -50°C to 55°C. • Ambient Testing • Spinless Horizontal Deployment • Gravity off-load fixture using air bearings. • Conservative test for torque margin due to lack of spin. • Vertical Gravity-Assisted Deployment • Gravity used to simulate centrifugal force at end of stroke. • Conservative test for latch up load due to large force at end of stroke.

37. Deployment Test Plan • Deployment Test Support Equipment • FGM and SCM tested separately due to boom cant • Compliant masts allow out of plane motion with constant gravity offset • Air bearings provide low friction stable support during motion • Support equipment made of lightweight materials such that dynamics of deployment are not affected Constant force support mast Air bearing

38. Deployment Test Plan • Instrumentation • Encoders at joints • Accelerometers at link CGs • Data capture via NI DAQ and LabVIEW

39. Test Plan • Vibration Test Plan • Assembled boom will be tested at Wyle Laboratories, Santa Clara • Sine and random as per THEMIS requirements. • Thermal Testing

40. Performance Assurance • Procedures • During personnel, all assembly must follow established Manufacturing Process Instructions. • Work performed on each assembly will be logged. • Documentation • Manufacturing Process Instructions for • Tube fabrication • Bonding of hinge and tubes • Assembly of hinge, and harness • Installation of frangibolts

41. Schedule • ETU • Assembly - 6/18/04 • Deployment Testing - 7/2/04 • Flight • Tubes and Hinges - 7/30/04 • Assembly – 8/2/04 to 9/15/04 • Testing – 9/23/04 to 11/11/04

42. Parts and Materials • Requirements • Materials Outgassing: 1% TML, 0.1% VCML • Magnetic cleanliness

43. Contamination Control • Magnetic cleanliness • Comply with Magnetics Cleanliness standard described in the THEMIS Magnetics Control Plan • Use of non-magnetic materials e.g. Al, carbon-fiber for mag boom. • Non-magnetic tools. • Electrostatic cleanliness • Comply with THEMIS Electrostatic Cleanliness Plan • Keep exposed surfaces of the mag boom conductive by minimizing exposed hard anodizing, exposing outer layers by grinding down epoxy.