themis instrument pdrrob duck 1 ucb, october 15-16, 2003 efi axial booms (axb) preliminary design...

THEMIS Instrument PDR Rob Duck 1 UCB, October 15-16, 2003

EFI Axial Booms (“AXB”)

Preliminary Design ReviewRob Duck

Mechanical Engineering Department

and Space Sciences Laboratory

Univ. of Calif., Berkeley


Requirements & Specifications

THEMIS Mission Design Requirements• Axial boom designed in accordance with the THEMIS Product

Assurance Implementation Plan (“PAIP”)

• Mechanical design and test environments as outlined in Mechanical-Verification-Spec-1c by Swales Aerospace

• Deployed axial boom shall be repeatable and stable to and L/L = 1%

• Axial boom shall be designed to be deployed between 0 and 25 RPM

• Axial boom deployed stiffness shall be greater than 0.75 Hz

• Axial sensor baseline will be ~10 m, tip to tip


Requirements & Specifications

Mechanical Design Objectives• Axial boom shall be modular and removable from probe with minimal

probe disassembly• Axial boom test and safe plug shall be externally accessible to probe• Each individual boom shall have a single point of actuation• Axial boom design shall be based on heritage designs from previous

launches

Mass• 2 Kg per boom

Deployment execution is critical• Proper stowing of wire cable• One time deployment• Full boom extension


Axial Boom Overview

AXB are integral part of THEMIS probe• Primary probe structure provided by Swales Aerospace• AXB located along center axis of probe• AXB deployment through top and bottom decks of probe.

Test & Safe Plug

Lower Deck Mount

Composite Tube

Antennae Mount (TBD by Swales)

AXB relative to THEMIS Probe Internal View

AXB Assembly

THEMIS Probe

Upper Deck Mount

Upper AXB

Lower AXB

AXB Housing


Design Heritage

AXB Base Design has flown before• POLAR• FAST

UCB Heritage• Test data from previous flights• Design engineers still at UCB• Using the same vendors• Consistent assembly and test procedures

AXB Heritage Design• Double boom deployment• Stacer booms• Double cantilever design• Deploy Assist Device


Axial Boom General Assembly

Whip Canister (Whip Sensor Inside)

Double Deploy Assist Device

(“DDAD”)

Tube Mounting Brackets

Preamp

Cable Bobbin

Stacer Canister (Stacer inside)

INDIVIDUAL BOOM IN STOWED CONFIGURATION

SMA/Ball détente Actuator

Whip Doors

DDAD Doors

STACER

Design Modifications• Stacer length• Double deploy assist device• SMA/Ball détente actuation• Whip sensor

Roller Nozzles

Whip Posts


Theory of Operation

Integration & Loading• Whip Sensor is loaded into whip canister

• Whip canister is locked to the preamp by the whip clamp

• Stacer is loaded into stacer canister, DDAD doors hold the DDAD, and whip doors hold the whip canister

• Removable stacer pin is inserted through stacer tip piece, which locks the stacer, DDAD, and Whip canister to the boom assembly

• Cable is spooled around the cable bobbin

• Ball détente mechanism is clamped to the stacer tip piece

• Stacer pin and whip clamp are removed

• Boom is loaded into housing

Deployment• SMA wire is actuated and ball détente mechanism is engaged

• Stacer tip piece is released

• DDAD extends and initiates stacer deployment

• DDAD separation opens whip doors, initiating whip sensor deployment

Science Ops• Deployed boom configuration unchanged


Whip Sensor

Theory of Operation

Deployed Properties• Whip sensor deployed length: 40 inches • Stacer deployed length: 150 inches• Option to change length

Stacer

Stacer Pin

Ball Détente Mechanism

Cable Bobbin with Cable

DDAD

DDAD Doors

SMA Actuator

Stowed Boom Deployed DDAD

4”

4”

Stacer Cansiter

Stacer Tip Piece

Whip Canister

Whip Doors

Roller Nozzle

Deployed Boom

Deployed Whip Sensor

150”

40”


Goals 1. Initiate Stacer deployment.

2. Provide double cantilever design at deploy.

3. Maintain minimal boom length while stowed.

4. Single locking contact point.

Design1. Two stage nested spring push rod.

2. Roller nozzle for beam support.

3. Double doors to stow Whip and Main Stacer.

Theory of Operation1. Stacer tip piece is released.

2. Double spring extends roller nozzles.

3. Roller nozzle pulls stacer from canister

4. Stacer deploys.

5. Whip doors open as roller nozzles separate.

6. Whip deploys.

7. Roller nozzles maintain contact on stacer.

Double Deploy Assist Mechanism

STOWED DDAD DEPLOYED DDAD DDAD PUSH ROD

ROLLER NOZZLE STOWED

ROLLER NOZZLE DEPLOYED

Roller Nozzle

Locking Contact Face

Whip Doors

DDAD Doors

Stacer direction


Goals 1. Single actuation point.

2. Safe reload operation for testing.

3. Minimal activation stroke.

4. Minimal activation force.

Theory of Operation1. Applied current contracts SMA wire.

2. SMA wire pulls lever up.

3. Lever pulls deploy pin down.

4. Lower ball detent drops into cavity and release spring rod.

5. Spring extends and pulls locking sleeve down.

6. Upper ball detent drops into cavity.

7. Stacer pin is released and stacer deploys.

Axial Boom Deploy Mechanism

STOWED CONFIGURATION

SECTION VIEW

DEPLOYED CONFIGURATION

SECTION VIEW

Stacer Tip Piece

Cable Bobbin

Locking Sleeve

Spring Rod

Lever

Deploy Pin

Upper Ball DetentSMA Wire

Lower Ball Detent


Assembly & Materials

Standard Flight Materials• AL 6061 T6• SST 440• Elgiloy• PEEK• M55J Graphite Composite

Standard Flight Coatings• DAG-213• DAG-154• TYPE 3 Hard Anodize

Long Lead Items• Stacer – Ordered• Multi-conductor wire


Electrical Connections

Boom Connectors• 1 connector per boom• Located at base of boom• SMA actuator cable• Preamp sensor multi-conductor wire

Test & Safe Connector• External to boom, located on top deck of probe• AC test• Safe - Deploy deactivation


Mass & Power

List Mass Target & Actual• MASS

– Target– 2 Kg per Boom including Housing

– ActualHousing 1.70 lbs 0.772 kg

Upper Boom 3.58 lbs 1.625 kg

Lower Boom 3.58 lbs 1.625 kg

Total 8.86 lbs 4.022 kg

• POWER– 1 AMP


Thermal - AXB

Heat Transfer

Power Dissipation

• 80 mW dissipated at preamp, irrelevant to bus temperatures

• Essentially inert hunks of metal after deployment

Conduction

• Top Deck reaches –93 °C in long eclipse

• AXBs are a heat leaks for the bottom deck so they are isolated with 1/8 inch G10 spacers.

Radiation

• All surfaces covered with low ε VDA tape or blankets

• Black body open end of the tube dominates the heat leak


Thermal - AXB

Temperature Limits

• Steady state predictions from UCB based on top and bottom deck temperatures from Swales

• Cold prediction from cold orbit, not long eclipse

• Hot prediction from hottest orbit and attitude

• Will not deploy in extreme cold case

• Better predictions await more complete instrument thermal models

Deployment (°C)

Predictions

(°C)

Margin

(°C)

Cold Hot Cold Hot

0 30 -7 5 -7 25


Thermal - AXB

Temperature Monitoring and Control

• Modified Interface Monitoring

• None required at this time

• Instrument Monitoring

• IDPU will process additional thermistors if needed

• Heaters

• No operational heaters are required

• No survival heaters needed after deployment

• Unlikely to need deployment heaters


Engineering Model Objectives

Engineering test unit designs are critical

• Boom length repeatability

• DDAD stiffness and length

• Actuation reliability

• Boom reloading

• DDAD roller nozzle design


Axial Boom General Assembly

Axial Boom Installation process• Goal to allow easy removal of boom without probe disassembly

• Process1.Lower mount ears aligned with upper deck cutout.

2.Boom inserted through upper deck.

3.Boom rotated to line up bolt pattern.

4.Boom bolted with 8-32 screws

themis instrument pdrrob duck 1 ucb, october 15-16, 2003 efi axial booms (axb) preliminary design...

Documents

whip clamp stacer

whip canister whip canister

stacer tip piece stacer

main stacer

initiate stacer deployment

themis instrument pdrrob

inches stacer deployed

axial boom overview