ARISSat-1Critical Design Review

Orlando, Feb 15, 2010

Solar Panels & CoversBob Davis, KF4KSS@amsat.orgLou McFadin, W5DID@amsat.org

Feb 15, 2010 ARISSat-1 CDR 2

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, 2010 ARISSat-1 CDR 3

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, 2010 ARISSat-1 CDR 4

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, 2010 ARISSat-1 CDR 5

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, 2010 ARISSat-1 CDR 6

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, 2010 ARISSat-1 CDR 7

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, 2010 ARISSat-1 CDR 8

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, 2010 ARISSat-1 CDR 9

Power “Budget”

Feb 15, 2010 ARISSat-1 CDR 10

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, 2010 ARISSat-1 CDR 11

Power (6 Covers of Lexan 10%)

Was…

Feb 15, 2010 ARISSat-1 CDR 12

Power (4 Covers of Lexan 10%)

Was…

Feb 15, 2010 ARISSat-1 CDR 13

Power (6 Covers of Lexan 30%)

Was…

Feb 15, 2010 ARISSat-1 CDR 14

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, 2010 ARISSat-1 CDR 15

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, 2010 ARISSat-1 CDR 16

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, 2010 ARISSat-1 CDR 17

Panel Verification• GSFC apparently contracted SMEX Panels to survive

– 1 minute of acoustic environment of 138.1 dB Acceptance, and 141.1 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, 2010 ARISSat-1 CDR 18

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, 2010 ARISSat-1 CDR 19

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, 2010 ARISSat-1 CDR 20

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