EFI AXIAL BOOMS (“AXB”) Critical Design Review Rob Duck Mechanical Engineering Department

1. EFI AXIAL BOOMS (“AXB”) • Critical Design Review • Rob Duck • Mechanical Engineering Department • Space Sciences Laboratory • University of California - Berkeley

2. AXB – Overview • THEMIS Axial Boom • AXB – Design • AXB – Double Deploy Assist Device • AXB – Door Release Mechanism • AXB – Frangibolt Actuator • AXB – Sensor • AXB – Open Design Issues • AXB – Electrical Wiring Diagram • AXB – Deployment Testing • AXB – Thermal Vacuum Testing • AXB – Mechanical Vibration Testing • AXB – Fabrication • AXB – Test

3. AXB – Design • AXB Design Review • AXB located along center of THEMIS probe • Two individual booms housed in a single tube • Electrical Connection • 2 - 26 pin connectors (1 per boom) • 1 - 26 pin flight enable pin on top deck • Mass Properties • 4 Kg mass limit for the full boom Safety Cover Axial Boom Composite Tube Upper AXB Upper Deck Mount THEMIS Probe Boom Connectors Flight Enable Connector Housing 1.32 lbs 0.597 kg Upper Boom 3.69 lbs 1.674 kg Lower Boom 3.69 lbs 1.674 kg Total 8.70 lbs 3.945 kg Lower AXB Lower Deck Mount Stowed Axial Boom

4. AXB – Design • Individual Boom Components • Bobbin • Actuator • Cable • Double Deploy Assist Device (“DDAD”) • Door Release Mechanism • Main Stacer • Preamp • Sensor Stacer • Axial Boom Deployed Properties • Tip to tip distance – 302” (7.67m) • Upper main stacer stroke – 91.5” (2.32m) • Lower main stacer stroke – 99” (2.51m) • Sensor stroke – 40” (1.02m) Sensor Preamp Door Release Mechanism Double Deploy Assist Device Main Stacer (Inside Can) Bobbin (Cable & Actuator Inside) Items in blue italics are ETU focus areas

5. AXB – Double Deploy Assist Device • Purpose • Initiate stacer deployment • Provide double cantilever support once deployed • Occupy minimal volume while stowed • Design • Spring actuation extends supports • Rocker guides provide stacer support • Theory of Operation • DDAD spring actuation • Stacer tip piece is released • Spring within rods pull stacer from can • Stacer supports extend and lock into place • Rocker guides • Stacer pushes roller, rotates arm, & separates plates • Spring pulls plates together, maintains rocker force Rocker Guide Rocker Guide Top Plate Stacer Roller Rocker Arm Spring DDAD (Deployed) Bottom Plate Rocker Guide (Section View)

6. AXB – Door Release Mechanism • Purpose • Hold sensor and DDAD in stowed configuration • Provide simultaneous stacer deployment from one actuation event • Design • Lower doors keep DDAD stowed • Stacer tip piece holds lower doors closed • Upper doors keep sensor stowed • DDAD posts hold upper doors closed • Stowed DDAD keeps posts on upper doors • Theory of Operation • Stacer tip piece is released • DDAD deployment starts & pulls stacer • DDAD separation occurs • Upper doors separate from posts • Upper doors open and sensor deploys • Stacer tip piece separates from DDAD • Lower doors open and stacer deploys • Doors remain open, no tube interference Door Release Mechanism (Stowed) Door Release Mechanism (Deployed)

7. AXB – Frangibolt Actuator • Frangibolt Actuator • Developed by Naval Research Labs and NASA • Shape Memory Alloy cylinder elongates to fracture a bolt element • Reusable • Primary and secondary (redundant) heaters • Flight Qualified in 1994 aboard Clementine • Maximum Load: 500 lbs • Operating Voltage: 22-36 Vdc • Frangibolt Actuation Fastener • Material: Titanium • Notched groove localizes break location • Size #8 Fastener • Required Break Force > 1050 lbs • Design Margins • At 100G, Actuator sees 250 lbs • Actuator FOS: 2.0 • Fastener FOS: 4.2 Frangibolt Actuator Actuation Fastener

8. AXB – Frangibolt Actuator • Testing • Actuator • Fastener • 10% of lot is tested, tensile pull test • Min. Fracture = 1050 lbs, 100% pass • Method of Operation • SMA cylinder is compressed • Fastener is assembled • Current is applied & heats actuator • SMA cylinder elongates • Fastener breaks

9. AXB – Sensor • Sensor Stacer • Smallest stacer ever designed • Thickness 0.0015”, width – 1.00” • Forms with less taper than traditional stacers • DAG 213 coating • Difficulties • Bending or arching once deployed (see picture) • Clips didn’t close well • Handling – easy to tear • Solutions • Bending • Chord length matches free length of stacer • Chord termination close to stacer edge • Clip closure • Use eyelets instead of rivets • Spacer between can wall and clip allows closure • Clip shape modified to avoid rivet contact • Handling • Stowing only by qualified person, myself Arched Deploy Straight Deploy

10. AXB – Open Design Issues • Sensor Test Circuit • Once deployed circuit is floating • Solution – add 50 Mohm resistor to chassis ground • Exposed Insulators • Too much exposed area on the sensor test circuit • Solution – Design to contain insulators in cavities • Boom Isolation from Tube • Reduce boom temperatures • Requires specific chassis ground line • Sensor Can Height • Smaller can height reduces can tilting effect

11. AXB – Electrical Wiring Diagram

12. AXB – Deployment Testing • Sensor Deployment • Total deploys: 7 • Repeatability Test • Chord length: 40 1/8 inches • Boom Deployment • Total deploys: 4 • Stiffness: 1.65 Hz • Repeatability • Requires horizontal deploy track • Week of May 17 Deploy Length 1 40 1/4” 2 41 1/4” 3 41 1/4” Sensor is fully deployed before main stacer reaches full deploy length

13. AXB – Thermal Vacuum Testing • ETU Testing • Designed to test actuator and mechanical integrity of boom • Mass dummy used for preamp, no electronics • Ramp and soak profile • Vertical deployment in HiBay Vertical Chamber • FLT Testing • Horizontal deployment • “THEMIS Snout” chamber • Delivery – June 29th • Horizontal Track – May 17 Deployed Boom in Vacuum Chamber HiBay Thermal Vacuum Chamber

14. AXB – Mech. Vibration Test • Mechanical Vibration • ETU Test Date – 9:00 AM, Friday, April 23th • Quanta Labs, Santa Clara, CA • Single Boom • Sine & Random Vibration – 3 axis, Limits TBD by Swales

15. AXB – Fabrication • Flight Deliverables • Stacers – In house, require preparation • Sensors – Week of May 3 • Frangibolt Actuators – In house • Mechanical Parts – Week of June 14 • Fasteners – In house • Composite Tube/Flange – Week of May 31 • Stacer Preparation • Trim, paint, & rivet • Procedure complete • Part Cleaning • Written procedure complete • Assembly & Fabrication • Fabrication procedures - Week of June 7 • Flight assembly begins week of June 14 • Stowing the Boom • Written procedure – Week of June 7

16. AXB – Testing • ETU Testing • Complete week of May 17 • Tests remaining • Mechanical Vibration • Boom Length Repeatability • Boom Run Out Measurement • Flight Testing • Total boom deployments: 4 • Test Sequence • Actuator Deployment • Boom Deployment - Vertical • Run out measurement • Natural frequency measurement • Mechanical Vibration • Boom Deployment - Horizontal • Length measurement • Thermal Vacuum Hot Cycle (2 Cycles, soak & deploy Hot) • Boom Deployment in Chamber • Thermal Vacuum Cold Cycle (2 Cycles, soak & deploy cold) • Boom Deployment in Chamber

17. AXB – Testing