Challenges and Design of LightSail-1 Boom Deployment Module Chris Biddy, Stellar Exploration Inc.

LightSail-1 Overview LightSail-1 is made up of a 3U CubeSat –10 x 10 x 34 cm, <5kg LightSail-1 will deploy a 32m^2 aluminized Mylar sail via 4m booms LightSail-1 will demonstrate controlled flight by Light LightSail-1 with deployed sail Avionics Module Sail Storage Section Boom Deployer Payload Section

LightSail-1 Sail Blades Z-fold sail quadrant from outside edge to center Z-fold sail from center outward to form wedge shaped fold Folded sail quadrants fit into wedge shaped cavities and restrained by deployable Solar Cell panels Sail Blades are Z-folded in two directions into a wedge shape for storage Z-fold provides a path for gases to escape Verified with vacuum chamber test

LightSail-1 Booms Lightsail-1 will use the AFRL developed TRAC (Triangular Rollable and Collapsible) boom Stainless Steel rigid booms can be collapsed and rolled around a spindle providing a compact storage solution Booms self-deploy due to stored strain energy when wrapped around a spindle –Boom deployment rate control via dc brushless motor coupled with worm drive gear train TRAC boom shown in deployed state

LightSail-1 Boom Deployer Key Requirements –Store and deploy 4m booms –Control deployment rate so as to not damage booms or sail blades Deployer Functions –Provide normal reaction force against booms at all times (required to keep booms pinched) –Provide for smooth deployment (no interference between booms and deployer components) –Guide booms at deployer exit Deployer Features –Bearing supported spindle –Rocker arm tensioner with flexure springs keep booms against spindle –Delrin AF boom guides at deployer exit Deployer Size –Maximum height = 5.5 cm –Maximum width = 10 cm Isometric view of deployer

LightSail-1 Boom Deployer Deployer Mounting Boss Flexure Clamp Top Mounting Plate Flexure Spring Tensioner Boom exit guide

Spindle Design Boom mounting bolts react boom loads Spindle flanges constrain and protect booms Cable clearance through center of spindle (cable pathway from payload section to avionics section) Spindle section view Cable clearance through hole Spindle Flanges

Deployer Rocker arms deflect flexure springs during boom winding Flexures stick out past solar panel plane only at the end of boom deployment (after solar cell panels are deployed) Booms exit at corners Fully deployed state (flexure springs not deflected)Fully stowed state (flexure springs deflected) Boom Exit

Flexure Clamp Flexure Clamp fastened with stainless flat head cap screws Flexure clamp rotationally constrained by square cutouts in top and bottom mounting plates Square recess in top mounting plate also reacts shear loading under vibration 302 Stainless Steel Recessed Square pocket constrains Flexure clamp

Tensioner Tensioner is fastened with and pivots about Stainless shoulder screws Rulon (or Delrin AF) bushings take axial and radial loads –Bushings reduce friction between tensioner and shoulder bolts Roller Shaft and Flexure Contact Pin have tapped ends and held in place with socket head cap screws Roller Shaft and Flexure Spring Contact pin made from 304 SS 6061-T6 Aluminum Roller Flexure Contact Pin Shoulder Screw Delrin AF bushings

Boom Deployer The first engineering model of the boom deployer has been manufactured –Initial testing has confirmed required flexure spring rate Boom deployer with bottom plate removedBoom Deployer with partial boom deployment

Deployer Planned Tests Boom stowed/deployment test –Verify clearance between stowed booms and deployer components –Verify boom deployment without interference or resistance from deployer components Boom with Sail Blade deployment test Full deployment test with deployment rate control

Questions? Montgomery, E. 2008, NanoSail-D, CubeSat Developers Workshop, San Luis Obispo, CA, California Polytechnic State University