3-4 Sept. 2008 EFW INST+SOC PDR 1

Electric Field and Waves (EFW)

Spin Plane Boom (SPB)

Gregory Dalton

Space Sciences Laboratory

University of California – Berkeley

gdalton@ssl.berkeley.edu

EFW Spin Plane Boom

3-4 Sept. 2008 EFW INST+SOC PDR 2

Overview• Design Requirements/Drivers• Design Overview• Theory of Operation• Flight Heritage• Custom Design for RBSP• Analysis and Testing

Overview

3-4 Sept. 2008 EFW INST+SOC PDR 3

Design Requirements/Drivers

Thermal Interface• Survival: -45 to +60°C• Deployment: -20 to +40°C• Preamp survival: -160 to 80°C• Preamp science range: -55 to +70°C

Mass• NTE 2.42 kg• Currently 1.943 kg with Mounting Feet

Design• Deploy Sensor to 80/100m Tip-to-Tip with 4.7cm resolution• Test/Enable Plug accessible on S/C• Mount at 10° angle to S/C Panel• 7 Conductor Cable to Preamp• Preamp Enclosure designed for ease of assembly• Keyreel designed to unfurl Fine Wire at 10m & 15 RPM

3-4 Sept. 2008 EFW INST+SOC PDR 4

Design Overview – Overall Dims

[cm]inch

SPHERE

PREAMPLIFIERENCLOSURE

COMPOSITECABLE

FINEWIRE

3-4 Sept. 2008 EFW INST+SOC PDR 5

Design Overview - External

ENABLE PLUG/TEST CONNECTION

MOUNTINGFOOT

SPOOLCONNECTION

S/CPANEL

3-4 Sept. 2008 EFW INST+SOC PDR 6

Design Overview - Internal

SPHERECONTACT

DOOR OPENSWITCH

RELEASEPIN

DOOR

RELEASERING

PINPULLER

METERINGWHEEL

DEPLOYMOTOR

SCIENCE/ENGCONNECTORS

END OF WIRESWITCH

SPOOL

SPOOLBRAKE

CABLECONNECTOR

COMPOSITECABLE

SLIPRING

SPOOLSECTION

MOTORSECTION

MAGNETIC/EMI SHIELD

BEVELGEARS

CAM

METERINGWHEEL

3-4 Sept. 2008 EFW INST+SOC PDR 7

Design Overview – Preamp Enclosure

STRAINRELIEF

TANTALUMSHIELD

SCREWFITTING PWB

USHER

FERRULE

CABLEHOLDER

GUARD

PREAMPLIFIERSPRING

CONTACT

PWBASSEMBLY

3-4 Sept. 2008 EFW INST+SOC PDR 8

Theory of Operation

Integration and Launch

• Stowed and Unpowered

• Composite Cable on Spool, held by Brake

• Sphere and Preamp caged by Doors

• Doors held closed by Release Pins

3-4 Sept. 2008 EFW INST+SOC PDR 9

Theory of Operation

Deployment

• Release Ring rotates when Pin Puller Actuated

• Release pins move clear of Doors

• Doors open, indicated

• Motor pulls cable off Spool at ~2cm/s and meters Cable every 4.7cm

• At 10m and 15RPM, Fine Wire Unfurls

• End of Travel switch disables motor power

3-4 Sept. 2008 EFW INST+SOC PDR 10

Flight Heritage

25+ years mature Radial Boom design at SSL

Mature Design/Vendor Familiarity• Previous mission reviews and test data• Critical components from proven vendors• Test fixtures and procedures• Original Dr. Pankow SPB design

3-4 Sept. 2008 EFW INST+SOC PDR 11

Custom Use for RBSP

Gore Cable

• 100m Tip to Tip (~49m per boom)

• No coax

• Kapton vs. PTFE insulation

Simplified Release Mechanism

• Pin Puller

• Secures own Power

• Redundant

Packaged for RBSP

• Completely enclosed

• Panel Mount

Electronics

• Modified Harness

• Door Open Indication

RBSP Composite Cable

3-4 Sept. 2008 EFW INST+SOC PDR 12

Analysis - Damping

y = 6.7389e -0.1279x

-8

-6

-4

-2

0

2

4

6

8

0 1 2 3 4 5 6 7 8 9

time (s)

amplitude (deg)

Pendulum Motion

Max Half Angle

Curve Fit

Cable Damping (J/rad^2)CRRES -0.031

RBSP ETU -0.0153

Energy Dissipated per cycle per boom:

Cable Damping Test•Simple Pendulum test•Tip Mass Simulates Cable Load•Future test to include accurate RBSP tip mass and vacuum environment

3-4 Sept. 2008 EFW INST+SOC PDR 13

Analysis - CTE

Coefficient of Thermal Expansion• Design for low CTE• Test from 20 – 80°C• 12ppm/°C from RBSP

prototype

ConstantForce

Thermal Shroud

CableLoadCell

Interfere-ometer

LaserElectronics

PC/LabView

Displacementcart

Reflector

Thermocouples

ThermalIsolator

ThermalIsolator

3-4 Sept. 2008 EFW INST+SOC PDR 14

Setpoints and Margins

Fine Wire:

• 0.009”ø, 7x7 strands, stress relieved stainless steel Construction

• > 50N breaking strength, tested with end conditions

• > 10:1 pulley to cable diameter ratio, de-rate cable strength to 85% -> 42N

• Predicted load during deployment: 6N

Composite Cable:

• 3200 Denier Kevlar 49 strength member, 600N breaking strength

• Spool pullout force: 13N

• EOT motor power cutout: 45N

• Shear Pin: 135N

• Predicted load during deployment: 8N

Motor Assembly:

• Bevel gear DF: >50

• Motor manufacturer DF: 4x

• Continuous torque: 2120mNm (x2 after Bevel gears)

• Max intermittent: 4240mNm (x2 after Bevel gears)

• Torque to break shear pin: 4050mNm

SPB Structure First Mode – 300hz

3-4 Sept. 2008 EFW INST+SOC PDR 15

Testing

Prior to Environments:• Motor burn-in, startup and running current tests• Pin Puller power profile• Margin Checks

– Torque: Door springs, motor torque– Force: Spool pullout, EOT switch, door release, fine wire

and composite cable proof loads• Fine Wire force/deflection characterization• Electrical Isolation• Mass Properties• Functional deploy – Self Shock• Length Calibration

THEMIS: 18 Month Motor Accelerated Life Test

3-4 Sept. 2008 EFW INST+SOC PDR 16

Testing

Vibration per APL Environmental Test Spec• New Fixtures for RBSP S/C Mounting – Force Limiting• Unpowered Testing• ETU to Qualification Levels, Flight to Acceptance Levels

3-4 Sept. 2008 EFW INST+SOC PDR 17

Testing

Thermal Vacuum

• Survival Temp: -30 to +60°C

• Full Deployment Test: -25 to +55°C

• Modified Test Fixtures for RBSP

– Protect Sphere surfaces

– Lower Keyreel spring force

– Mounting scheme

3-4 Sept. 2008 EFW INST+SOC PDR 18

Backup Slides

Long Lead Items:

• Gore Cable

– Samples in the Mail

– CTE/Damping/Strength Tests

– November Delivery

• Globe Motors

– Order Placed

– 20 wks

• TiNi Pin Pullers

– PO being processed

– 12 wks

• Sliprings

– 12 wks

Ongoing Developments:

• Verify Composite Cable Production Design

• Mounting Foot Analysis

3-4 Sept. 2008 EFW INST+SOC PDR 19

Backup Slides

Standard UCB Construction

• Machined Parts

– 6061T6 Aluminum

– 544 Bronze

– Stainless Steel

– Titanium

– Delrin, PEEK, Vespel

– Vulcanized Elastomer

– Tantalum

• Finshes

– Alodine

– Anodized

– DAG-213

– Gold Plating

Thermal Treatments

No Special Manufacturing Techniques

3-4 Sept. 2008 EFW INST+SOC PDR 20

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