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Structure (STR)

Subsystem Overview

Jonah White – STR Co-Lead

Structure Overview

• Main Satellite Structure Functions– Provide housing for all components– Protect sensitive components from harmful

launch/space conditions– Electrically conductive to prevent plasma

charging

• Component Box Functions– Secures electrical components to main

structure– Provides electrical magnetic interference

(EMI) containment– Allows for better thermal control

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Component Boxes

Battery Box

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Structure Requirements

STR-1 Must fit within allowable static envelope (60 X 60 X 50 cm) M-1 Test Unverified

STR-2 Must have a fundamental frequency above 100 Hz M-1 Analysis/Test Unverified

STR-3 Must be able to withstand 20 g’s of force in all directions M-1 Analysis Unverified

STR-4 Must meet a safety factor of 2.0 yield and 2.6 ultimate M-1 Analysis Unverified

STR-5Must meet an operating torque margin of 1.0(test) and 2.0(analysis) M-1 Analysis/Test Unverified

STR-6Must survive a random vibration test at 0.25 gRMS from 20 to 2000 Hz M-1 Test(ARFL) Unverified

STR-7 Must survive a sine burst test at 1.2 times the limit loads M-1 Test(ARFL) Unverified

STR-8Must survive a shock spectrum max of 1000-10000 Hz and ASD levels of 3500g M-1 Test(ARFL) Unverified

STR-9 Must have a mass not exceeding 50.00 kg M-1 Test Unverified

STR-10Must have a center of gravity of less than 0.635 cm from the NS-5 centerline M-1 Analysis/Test Unverified

STR-11Must have a center of gravity of less than 30.48 cm above the SIP M-1 Analysis/Test Unverified

STR-12 Must provide vent holes in component boxes M-1 Test Unverified

Structure Requirements

STR-13Must provide venting analysis for depressurization and repressurization M-1 Analysis Unverified

STR-14Must not use pressure vessels and pressurized components as defined in NASA-STD-5003 M-1 Test Unverified

STR-15 Must use at least #10 screws for all structurally critical components M-1 Test Unverified

STR-16 Must use at least #8 screws for all component boxes M-1 Test Unverified

STR-17Must provide a lightband interface in accordance with PSC 4000389 Rev A M-1 Test Unverified

STR-18Must use ¼-28 socket head cap screws for lightband interface fastener holes M-1 Test Unverified

STR-19Must use ¼-28 threaded self-locking inserts if locking helicoils are used for backout prevention M-1 Test Unverified

STR-20Must have a test-verified flatness of 0.0005 inches per inch over the NSS envelope at the SIP M-1 Test Unverified

STR-21Must provide thermal analysis to validate adequate thermal protection during all mission phases M-1 Test Unverified

STR-22 Must provide a list of all payload external surface properties M-1 Test Unverified

STR-23 Must provide metal component boxes for Goldeneye’s hardware GS-1 Test Unverified

STR-24Must have an electrically conductive coating on metal component boxes GS-1 Test Unverified

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Design Strategy

• Make sure strategic requirements are fulfilled first– Static envelope (60 x 60 x 50 cm)– Fundamental frequency (greater than 100 Hz)– 20 g’s loading– C.G. (0.635 cm from centerline)– Mass limit (50 Kg)

• Machine-ability– All parts can be machined– Advice from experienced machinists

• Keep it simple!!!– Ease of assembly (~30 min for prototype)– Structural design is not the mission

• Use NASA preferred parts if possible• Stick to what has been proven

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Satellite Structure

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GPS Direct Signal Antennas

Solar Panels

Lightband Interface High Gain Antenna

Satellite Side Panel

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• Each Side Panel Consists Of– Aluminum panel with isogrid pattern– 11 machined brackets

• Attached with #10 socket cap screws

– Torque coil mounts• Attached with #8 socket cap

screws

Torque Coil

Satellite Side Panel

• Assembly– Brackets tapped – Locking helicoils used for back-out

prevention– Torque coil mounts attached using

lock nuts– All pieces assembled to side panel

before panel attached to main structure

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Satellite Side Panel

• Side Panels– Machined aluminum 6061-T6– 0.635 cm thick (1/4 inch)– Alodined – Isogrid pattern

• NASA-CR-124075, Rev. A, Isogrid Design Handbook• Use 60˚ equilateral triangles• 0.2 cm minimum triangle side thickness• Nodes no more than 7 cm apart• Rounds at all corners

– #10 screw holes tapped to incorporate brackets and solar panels

– #8 screw holes to attach component boxes

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Satellite Bracket

• Brackets– Machined aluminum 6061-T6– 90˚ angle– 0.32 cm (~1/8 inch) round – #10 screw holes tapped thru

(1.5 x diameter of screw) • JSC 23642, Rev. D, JSC Fastener

Integrity Testing Program

– Locking helicoils and spring lock washers for backout prevention

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Torque Coil Mounts

• Torque Coil Mounts– Machined aluminum 6061-T6– 2 piece design– Assembled with #8 button head

socket cap screws– Faces are 0.3 cm thick (~1/8in)

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Satellite Top Panel

• Satellite Top Panel Consists of– Aluminum panel with isogrid pattern– Torque coil

• Attached with #8 socket cap screws

– Battery component box• Attached with #8 socket cap

screws

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Satellite Top Panel

• Top Panel Consists of– Machined aluminum 6061-T6– 0.635 cm thick (1/4 inch)– Alodined– Isogrid pattern – #10 screw holes tapped to

incorporate brackets and attach solar panels

– #8 screw holes to attach battery box

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Satellite Bottom Panel

• Bottom Panel– Machined aluminum 6061-T6– 0.635 cm thick (1/4 inch)– Alodined– Minimal isogriding – Hole cut-out to accommodate high

gain antenna mounting– Lightband interface– #10 screw holes tapped to

incorporate brackets

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Battery Box

• Battery Box– 3 piece box machined aluminum

design– Stand-offs to accommodate solar

panel screws– #8 screws for assembly – Utilize viton gasket for EMI

containment

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Battery Box

• Machined aluminum • 0.3 cm (1/8 inch) thick• Coatings

– Outside box alodined– Inside box anodized

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Component Boxes

• Component Boxes– 3 piece box design– Machined aluminum– Stand-offs to accommodate solar

panel screws– #8 screws for assembly– Utilize viton gasket for EMI

containment– Alodined

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Mass Breakdown

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• Total mass– 38.8 Kg

Structures Schedule

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Questions?

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