C osmic R Ay T elescope for the E ffects of R adiation Telescope Mechanical Design Albert Lin The Aerospace Corporation Mechanical Engineer (310) 336-1023

Cosmic RAy Telescope for the Effects of Radiation

Telescope Mechanical Design

Albert Lin

The Aerospace Corporation

Mechanical Engineer

(310) 336-1023

[email protected]

9/28/05


Overview

Design Overview

Instrument Requirements

Mechanical Requirements

Design Details

Next Steps


Design Overview

• Detectors are housed in stiff structure and decoupled from the interface circuit board

• TEP mounts allow for thermal expansion/contraction

• Instrument is shielded and electrically isolated at interface


Overall Dimensions

• Weight = 2.32 lbs

Component Weight (lbs)

Structure 1.150

Circuit Board 0.300

Telescope 0.870

Total 2.320


Overview

Design Overview



Design Details

Next Steps



From Instrument Requirements Document (IRD) 32-01205

Item Requirement

CRaTER-L2-04 TEP components of 27 mm and 54 mm in length

CRaTER-L3-01 Adjacent pairs of 140 micron and 1000 micron thick Si detectors

CRaTER-L3-02 Aluminum shielding 0.06” thick

CRaTER-L3-03 0.030” thick aluminum on both ends of the telescope

CRaTER-L3-04 Telescope stack: S1, D1, D2, A1, D3, D4, A2, D5, D6, S2

CRaTER-L3-06 Zenith field of view from D1D6 at 35 degrees

CRaTER-L3-07 Nadir field of view from D3D6 at 75 degrees

All requirements incorporated into model


Telescope Geometry

All Requirements Met

A-150 TEP of 27 mm and 54 mm in length

Pairs of thin (~140 micron) and thick (~1000 micron) Si detectors used

0.060” nominal aluminum shielding

0.030” thick aluminum on top and bottom apertures

Telescope stack consistent with requirement

35 degree FOV Zenith

75 degree FOV Nadir


Overview

Design Overview



Design Details

Next Steps



• From 431-RQMT-000012, Mechanical System SpecificationsRequirement Description Levels

2.1.2Net CG limit loads•Superceded by Random Vibration

12 g

2.4.2

Sinusoidal Vibration Loads•Superceded by Random Vibration

Frequency: 5-100 Hz

Protoflight/Qual: 8g

Acceptance: 6.4g

2.5Acoustics•Enclosed box without exposed thin surfaces

OASPL Protoflight/Qual: 141.1 dB

OASPL Acceptance: 138.1 dB

2.6.1 Random Vibration See next slide

2.7.2 Shock Environment

40 g at 100 Hz

2665 g at 1165-3000 Hz

No self induced shock

3.1.2.1

3.3

Minimum Fundamental Frequency Minimum > 35 Hz

Recommended > 50 Hz

Will not provide FEM model > 75 Hz


Random Vibration

• Random Vibration will drive most of the analysis

• For resonances in the Random Vibration Spec, Miles’ Equation shows 3 sigma loading on the order of 100-150 g

• Assume Q = 15

Random Vibration Spec

0.01

0.1

1

1 10 100 1000 10000

Frequency (Hz)

Po

wer

Sp

ectr

al D

ensi

ty (

g^2

/Hz)

Protoflight/ Qual

Acceptance

Freq (Hz)

Protoflight/ Qual Acceptance

20 0.026 0.01350 0.16 0.08

800 0.16 0.082000 0.026 0.013


Stress Margins

• Load levels are superceded by random vibration spec

• Factors of Safety used for corresponding material (MEV 5.1)– Metals: 1.25 Yield, 1.4 Ultimate

– Composite: 1.5 Ultimate

• Margin of Safety = (Allowable Stress or Load)/(Applied Stress or Load x FS) – 1

Description MS yield MS ultimate

Bolt Interface Loading +7,291 +14,709

Interface Circuit Board brittle +0.45

Silicon Detector brittle +48.3

All components have positive Margin of Safety


First Fundamental Frequency

• First Fundamental Frequency at 2340 Hz


Overview

Design Overview



Design Details

Next Steps


How to Mount TEP

• Limited Material Properties information on A-150 TEP

• Need to mount TEP to– Minimize deformation of TEP during assembly

– Allow for thermal contraction

– Exert 20 lbs preload to withstand random vibration

Springs exert 20 lbs at hot and cold cases Detectors

TEP Sample

Solution

• Oversized mounting hole to allow for changes in radial dimension

• Spring clamp to hold in TEP with preload at all temperatures


Mounting Details, Purging and Venting

• Detectors mounted using #2-56 fasteners

• Pigtail connector feeds through hole and plugs into the Analog board in the E-box

• Spacers between each pair of detectors for venting

• No enclosed cavities

• Internal purge line from Ebox connects to telescope purge system (not shown)

– Detailed design of purge system pending

Connection


Overview

Design Overview

Telescope Requirements


Design Details

Next Steps


Next Steps

• Finalize interface between telescope assembly and electronics box

• Detail purge design

• Complete drawings for fabrication



Backup Slides


CRaTER-L2-04

• 4.4.1 RequirementBreak the TEP into two components, of 27 mm and 54 mm in length.


6.1 CRaTER-L3-01Thin and thick detector pairs

• 6.1.1 RequirementThe telescope stack will contain adjacent pairs of thin (approximately 140 micron) and thick

(approximately 1000 micron) Si detectors. The thick detectors will be used to characterize energy deposition between approximately 200 keV and 100 MeV. The thin detectors will be used to characterize energy deposits between 2 MeV and 1 GeV.

6.2 CRaTER-L3-02 Nominal instrument shielding

• 6.2.1 RequirementThe shielding due to mechanical housing the CRaTER telescope outside of the zenith and nadir

fields of view shall be no less than 0.06” of aluminum.


6.3 CRaTER-L3-03 Nadir and zenith field of view shielding

• 6.3.1 RequirementThe zenith and nadir sides of the telescope shall have no less than 0.03” of aluminum shielding.

6.4 CRaTER-L3-04 Telescope stack

• 6.4.1 RequirementThe telescope will consist of a stack of components labeled from the nadir side as zenith shield

(S1), the first pair of thin (D1) and thick (D2) detectors, the first TEP absorber (A1), the second pair of thin (D3) and thick (D4) detectors, the second TEP absorber (A2), the third pair of thin (D5) and thick (D6) detectors, and the final nadir shield (S2).


6.6 CRaTER-L3-06 Zenith field of view

• 6.6.1 RequirementThe zenith field of view, defined as D1D6 coincident events incident from deep space, will be 35

degrees full width.

6.7 CRaTER-L3-07 Nadir field of view

• 6.7.1 RequirementThe nadir field of view, defined as D3D6 coincident events incident from the lunar surface, will

be 75 degrees full width.


Bolt Interface Loading

-3.000

0.000

3.000

6.000

9.000

-3.000 0.000 3.000 6.000 9.000

Mechanical Engineering Design, by Shigley

RP-1228 NASA Fastener Design

First fundamental frequency at 2340 Hz, which is off of the random vibe data set

Assume worst-case loading at 2000 Hz

3 sigma load = 105g

A286 CRES Bolts at Interface

Worst Case Bolt

0 lb 18231 lb 4.71 lb

0 lb 9.63 lb1.2 in 7,291

593 lb 14,709 907 lb356 lb

Margin of Safety Ult

Normal Load Worst Case BoltIn-Plane Load X Normal LoadIn-Plane Load Y Shear LoadIn-Plane Load Offset Margin of Safety YieldTensile Yield

Shear YieldTensile Ultimate


Interface Circuit Board Board Resonance

• First Mode: 632 Hz

• Total nodes: 25225

• Total elements: 12901

COSMOSWorks 2005


Detector Board Stress

• Using Miles Equation, assume Q = 15, FS = 1.5

• 3σ g loading = 146 g

• Material = Polyimide-Glass

• Max Stress = 3,663 psi

• MS ultimate = 24,000 psi / (1.5 * 3* 3,663 psi) - 1 = 0.45


Detector Analysis

• Assuming Q = 15

• Detector Material = Silicon

• Fundamental Frequency = 2130 Hz; 2000 Hz yields 3 sigma load of 105g

• Ultimate Margin of Safety = (17,400 psi / (1.4 * 252 psi) – 1 = 48.3


Sensitivity Analysis

• Preceding calculations used a nominal Q of 15

• This table shows how the 3 sigma g-loads vary with Fundamental Frequency and Q

(g's)1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

5 85 81 78 75 72 70 68 66 64 62 6110 121 115 110 106 102 99 96 93 90 88 8615 148 141 135 130 125 121 117 114 111 108 10520 170 163 156 150 144 140 135 131 128 124 12125 191 182 174 168 162 156 151 147 143 139 136

Fundamental Frequency (Hz)

Q F

acto

r

Most structures have Q between 10 and 20


Factors of Safety Used

Table 3.1 from 431-RQMT-000012Type of Hardware Yield UltimateTested Flight Structure - Metallic 1.25 1.4Tested Flgiht Structure - Beryllium 1.4 1.6Tested Flight Structure - Composite N/A 1.5Pressure Loaded Structure 1.25 1.5Pressure Lines and Fittings 1.25 4.0Untestest Flight Structure - Metallic Only 2.0 2.6

Design Factor of Safety


Material Properties

1. MIL-HDBK-5J

2. Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May 1982, pp 420-457

3. www.efunda.com

Material

Density

(lb/in3)

Young's Modulus

(ksi)Tensile

Yield (ksi)

Tensile Ultimate

(ksi)Poisson's

Ratio Where Used

Aluminum 6061-T6 0.098 9,900 35 42 0.33 StructureBeryllium Copper TH02 0.298 18,500 160 185 0.27 TEP SpringA286 AMS 5731 0.287 29,100 85 130 0.31 FastenersSingle Crystal Silicon 0.084 27,557 brittle 17.4 0.19 DetectorsPolyimide-Glass 0.065 2,000 brittle 24 - Circuit Board

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Documents

C osmic R Ay T elescope for the E ffects of R adiation Telescope Mechanical Design Albert Lin The Aerospace Corporation Mechanical Engineer (310) 336-1023