ARISSat-1 Critical Design Review Orlando, Feb 15, 2010 Solar Panels & Covers Bob Davis, Lou McFadin,

Feb 15, 2010ARISSat-1 CDR2 Introduction SMEX-Lite modular solar panels provided by NASA GSFC, mounted 1 per satellite face (6 total). Scope –Requirements –Design –Safety Considerations –Verification –Operations –Status

Feb 15, 2010ARISSat-1 CDR3 Requirements Design of satellite shall use these available solar panels Survive launch environment –Vibration frequency –Stresses Survive orbital environment –Low Outgassing –Flammability –UV exposure –Atomic oxygen –Venting Facilitate handling and removal (covers) ► size of panels actually drove size of structure

Feb 15, 2010ARISSat-1 CDR4 Panel Design 19.1 Watts 17.2” x 8.24” x.14” Composite –0.015” graphite facesheets –aluminum core 1 string of 50 single-junction GaAs/Ge solar cells

Feb 15, 2010ARISSat-1 CDR5 Panel Mounting Each face of spacecraft (4 sides, top, bottom) has one SMEX-Lite solar panel. As-received from GSFC, provisions for spacecraft mounting via perimeter bond line (originally to a composite frame). We use with same epoxy on perimeter bond line to aluminum sheetmetal “frame” which then bolts to structure around perimeter.

Feb 15, 2010ARISSat-1 CDR6 Panel Mounting SMEX bonded to 0.062” AL Side Sheet 36x small perimeter screws on Side Sheet All panels & covers are interchangeable No spare SMEX made available Ass’y Front Ass’y Back SMEX Side Sheet

Feb 15, 2010ARISSat-1 CDR7 Covers 3 independent inhibits for Covers –Perimeter Velcro (also venting and filters potential debris) –4x quick-release pins –Velcro straps (like belt thru belt loops) Lexan cover allows visual inspection for damaged solar cells prior to removal Aside from power & thermal considerations, option to leave Covers attached is procedural

Feb 15, 2010ARISSat-1 CDR8 Power Loss if Covers Left On Lexan manufacturer –Recommends XL102UV (UV blocker on both surfaces and extra power loss; typical of terrestrial solar panel cover) –Terrestrial transmissibility of other “clear” Lexan is 83-86% Distributor –Recommends F6000 (expect yellowing in 3 years terrestrially; but have outgassing data) Both data sheets provided to Safety; awaiting feedback Lou & Joe performed test with load not at peak power –1/8” Lexan (similar to F6000) had 25-30% power drop Lou & Dave performed test with short circuit current –1/8” Lexan (similar to F6000) had 10.6% power drop The truth is likely somewhere in the middle

Feb 15, 2010ARISSat-1 CDR9 Power “Budget”

Feb 15, 2010ARISSat-1 CDR10 Power Generation (No Covers) Notes: Izz is 30-40% larger than Ixx or Iyy. It will tend to spin, not tumble. This analysis assumes max eclipse.

Feb 15, 2010ARISSat-1 CDR11 Power (6 Covers of Lexan 10%) Was…

Feb 15, 2010ARISSat-1 CDR12 Power (4 Covers of Lexan 10%) Was…

Feb 15, 2010ARISSat-1 CDR13 Power (6 Covers of Lexan 30%) Was…

Feb 15, 2010ARISSat-1 CDR14 Thermal Loss if Covers Left On Thermal analysis currently does not include Lexan covers over solar panels Everything runs generally cool as-is Double whammy –Less power generated and wasted inside boxes –Less incident heat absorbed by solar panels themselves Spacecraft would run generally colder Magnitude of affect is unknown

Feb 15, 2010ARISSat-1 CDR15 Safety Considerations Panels added to protect fragile solar cells during handling Started as aluminum sheetmetal Now clear Lexan Designed to be removed during EVA Trade space: leave covers attached during mission to simplify EVA, or operate at full power

Feb 15, 2010ARISSat-1 CDR16 Safety Considerations All exposed edges are rounded Quick-release pin was selected to eliminate threaded fastener & tool during EVA T-handle quick-release pin was selected for compatibility with EVA glove Quick-release pin is tethered to Cover If adjacent covers are removed, then Velcro strap can act as tether between Covers

Feb 15, 2010ARISSat-1 CDR17 Panel Verification GSFC apparently contracted SMEX Panels to survive –1 minute of acoustic environment of dB Acceptance, and dB Qualification –At least 10 cycles in vacuum of -80°C to +110°C No planned epoxy bond line coupons or coupon-testing Functional test before/after environmental test at observatory level includes each Panel’s voltage & current –Shipping –Environmental in US/Russia Only flight set available of SMEX; to qualify the spare structure, the solar panels w/ Covers must be transferred! No panel-specific testing planned inside or outside ISS Aliveness test being discussed, but telemetry may not be collected/reviewed for verification of solar panels Assuming Lexan Covers, removal pending visual inspection for solar cell damage

Feb 15, 2010ARISSat-1 CDR18 Cover Verification Ground test will qualitatively characterize Velcro pull force Awaiting NASA feedback for Lexan outgassing & flammability Reference online tabulates two tests for Lexan and Atomic Oxygen; results similar to Kapton, but no mention of potential loss of transmissibility (clouding) Visual inspection planned before/after environmental testing at observatory level –For status of each of 3 independent inhibits

Feb 15, 2010ARISSat-1 CDR19 Operations Steps for Cover removal provided to Energia Energia to provide procedure; training imminent Option for leaving Covers on handled in procedure In operation, each panels’ voltage and current is available in telemetry

Feb 15, 2010ARISSat-1 CDR20 Status Repeat power loss test using Lexan Cover of proper material and with proper load for peak power Cover req’d update to Lexan; Spacer req’d to provide proper gap between Cover and cells so Velcro will “seal” around perimeter; fab Bond SMEX to Side Panels