c osmic r ay t elescope for the e ffects of r adiation 6/27/06 telescope mechanical design1 albert...

6/27/06 Telescope Mechanical Design 1

Cosmic RAy Telescope for the Effects of Radiation

Telescope Mechanical Design

Albert Lin

The Aerospace Corporation

(310) 336-1023

[email protected]

6/27/06



Overview

Design Overview

Instrument Requirements

Mechanical Requirements

Analysis

Design Details

Next Steps



Design Overview

• 3 pairs of thin/thick detectors mounted in rigid structure.

• TEP mounts allow for thermal expansion and contraction.

• Instrument is shielded and electrically isolatedat interface.

• Purge runs through channels machined into housing.



Activities since PDR

Programmatic

• Completed Peer Review.

• Fabricated engineering model.

• Completed part drawings.

Design

• Isolated detectors mechanically from TEP mounts.

• Added G-10 gasket interface to electrically isolate telescope.

• Purge system added.

• Performed mechanical properties testing on TEP.



Peer Review Summary

1. Telescope design requires close machining tolerances for success.Action: Modified design to increase robustness.

2. Detectors are not specified for random vibration and shock seen at the interface mount.Action: Plan to test engineering model detectors mounted in assembly.

3. Thin electrical isolation material specified at PDR may be too thin.Action: Use .063” G-10 sheet for isolation.

4. Purge channel cover screws may not be EMI tight.Action: None at this time. Add more screws if EMI emissions are too high.

5. Detectors will give poor measurements if there is light leakage. Action: Working to specify light tight requirements.

6. Force requirements for TEP preload is not toleranced.Action: Added tolerances to spring requirements.



Overall Dimensions and Weight

ComponentWeight (kg)

Weight (lbs)

Structure 0.699 1.54

Circuit Board 0.145 0.32

Telescope 0.430 0.95

Total 1.274 2.81



Overview

Design Overview



Analysis

Design Details

Next Steps



Instrument Requirements – Level 2

From Instrument Requirements Document (IRD) 32-01205

CRaTER-L2-03

Minimum path length through the total amount of TEP in the telescope shall be at least 60 mm.

CRaTER-L2-04

TEP components of 27 mm and 54 mm in length





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

CRaTER-L3-03

Nominal instrument shielding 1524 micron (0.060”) thick aluminum or equivalent

CRaTER-L3-04

No more than 762 micron (0.030”) thick aluminum on zenith and nadir fields of view





CRaTER-L3-05

Telescope stack: S1, D1, D2, A1, D3, D4, A2, D5, D6, S2, where:

S1, S2 are the zenith and nadir shields, respectively

D1, D3, D5 are thin silicon detectors

D2, D4, D6 are thick silicon detectors

A1, A2 are TEP specimens

CRaTER-L3-07

Zenith field of view from D2 to D5 shall be less than 34°

CRaTER-L3-08

Nadir field of view from D4 to D5 shall be less than 70°

Nadir

Zenith



Overview

Design Overview



Analysis

Design Details

Next Steps




• From 431-RQMT-000012, Mechanical System SpecificationsSection Description Levels Verification

3.1.1.2 Net cg limit load 28.9 g* Analysis

3.1.4.2 Sinusoidal Vibration Loads

Protoflight;

Frequency (Hz) Level

5 - 17.7 1.27cm D.A.

17.7 – 50 8 g’s

Analysis, Test

3.1.5 Acoustics Delta IV Medium: 140.0 dB

Atlas V 401: 137.0 dB

Test at LRO level

3.1.6.1 Random Vibration See Random Vibration slide Analysis, Test

3.1.7 Shock environment See Shock Environment slide Test at LRO level

3.1.8 Venting Minimum of .25 in2 of vent area per cubic foot volume

Analysis

* Interpolated from Table 3-1 for CRaTER at 6.4 kg.



Random Vibration Levels

Frequency (Hz)

Protoflight/Qual

(g2/Hz)

Acceptance

(g2/Hz)

20 0.026 0.013

50 0.160 0.080

800 0.160 0.080

2000 0.026 0.013

Overall 14.1 grms 10.0 grms

Random Vibration levels will drive the analysis.



Updated Shock Environment

Frequency Level (Q=10)

100 Hz 20 g

800 Hz 930 g

10,000 Hz 930 g



Overview

Design Overview



Analysis

Design Details

Next Steps



Frequencies and Mass Participations

Frequency

(Hz)Mass

Participation Where

895 0.003 Shield

1,369 0.46 Large TEP Assy

1,564 0.70 Housing

1,680 0.41 Circuit Board

1,688 0.04 Small TEP Assy



Random Vibration Loads

• 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 150-255 g

• Assume Q = 40 for worst case

Frequency (Hz)

Protoflight/Qual

(g2/Hz)

Acceptance

(g2/Hz)

20 0.026 0.013

50 0.16 0.08

800 0.16 0.08

2000 0.026 0.013



Random Vibration Loads

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

– Composite: 1.5 Ultimate

1Safety ofFactor Loador Stress Applied

Loador Stress Allowable Safety ofMargin

Assume Q=40 Freq (Hz) 3σ load (g) Stress (psi) MSyield MSult

Telescope Housing 1,563 207 16,415 0.7 0.8

Detector 2,130 172 411 - 29.3

Shield 895 255 11,259 1.5 1.7

Circuit Board 1,680 187 2,144 - 14.5

TEP 1,563 207 75.4 - 75.1

3σ load (g)Worst Normal/Shear

(lbs) MSyield MSult

Interface Bolts 194 53 / 45 48 174



Overview

Design Overview



Analysis

Design Details

Next Steps



Detector Details

• 39 mm flat-to-flat Silicon detectors mounted on FR4 mounts

• 140 micron and 1000 micron thick both bond to the same mount design

• Micron Semiconductor Limited

– Lancing Sussex, UK

Cable and connector

4 mounting holes



How the TEP is mounted

• TEP mounted in conical seats to prevent misalignment.

• Spring design allows for thermal expansion and contraction

• Large TEP is clamped into holder with 267 N (60 lbs) preload using 4 springs

• Estimated maximum load is 207 g’s during random vibration

• Springs nominally secure TEP up to 400 g’s

• Springs that exert > 52 N (11.6 lbs) will secure TEP with a 1.5 factor of safety



TEP Material Properties

TEP Delrin

Density 1,110 kg/m3 1,411 kg/m3

Tensile Modulus 1,958 MPa 3,100 MPa

Tensile Yield Strength @ 20 ºC

14.4 MPa 89.6 MPa

Compression Strength @ 20 ºC

58.6 MPa 110 MPa

CTE (20 ºC to –30 ºC) 18.9 μm/m-ºC 84.6 μm/m-ºC

• TEP is resilient to clamping with 75.1 MS.

• TEP interface will shrink 0.08 mm as it cools from 20ºC to –30ºC.

• The spring will make up this difference at –30ºC and still exert preload 258 N (58 lbs) preload.



Purging and Venting

• Spacers between each pair of detectors for venting

• No enclosed cavities

• Purge/vent system shown in red

• Internal purge line from Ebox connects to telescope purge system



Overview

Design Overview



Analysis

Design Details

Next Steps



Next Steps

• Finalize MLI attachment near telescope

• Submit flight drawings for fabrication

• Make assembly drawings



Summary

• Design changes since PDR

– Modified detector mounting scheme

– Added vent/purge path

– Added electrical isolation between telescope from Ebox

• Peer review successfully completed

• Further analysis performed

• Tested TEP material properties

• Engineering model completed

• Flight drawings ready to be submitted



Telescope – Mechanical

Albert Lin



Material Properties

1. MIL-HDBK-5J2. Silicon as a Mechanical Material, Proceedings of the IEEE, Vol 70, No. 5, May 1982, pp 420-

4573. Plastics, Edition 8, Ultimate Tensile from Electronic Materials and Properties4. Boedeker Plastics via www.matweb.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 9900 35 42 0.33 StructureA286 AMS 5731 0.287 29100 85 130 0.31 FastenersSingle Crystal Silicon 0.084 27557 brittle 17.4 0.19 DetectorsPolyimide Glass 0.065 2800 - 50 - Circuit BoardG-10 Fiberglass 0.065 2000 28 45 - Isolator Interface

1

1

2

3

4



Bolt Interface AnalysisBolt Inputs

Bolt Type 8

Bolt Material 5Modulus of Elasticity 29,100,000 psiYield Strength 85,000 psiUltimate Strength 130,000 psiTensile Stress Area 0.00909 in^2Head Diameter 0.218 inBolt Diameter 0.138 in

#6-32

Stainless Steel A286

Bolt CalculationsProof Load 76500 psiPreload 522 lbsl = effective grip length 0.367 in

kb = bolt stiffness 720,760 lb/in

Member CalculationsD1 0.419 inD2 0.207 inMiddle Frustrum on Flange

Frustra t d D E Material1 0.06 0.14 0.207 2,700,000 1,322,196 lb/in G-102 0.124 0.14 0.242 10,000,000 4,592,215 lb/in Aluminum3 0.051 0.14 0.283 10,000,000 11,954,988 lb/in Aluminum4 0.063 0.14 0.247 2,700,000 2,002,953 lb/in G-105 0.069 0.14 0.207 10,000,000 4,479,377 lb/in Aluminum

km = member stiffness 676,212 lb/in

Outputs

C = joint constant; ratio of load taken up by bolt 0.52

P = load at joint separation (including preload) 1,077 lbs

P = Ext Tensile Load at Yield 487 lbs

P = Ext Tensile Load at Ultimate 1,077 lbs

k (8.14)



Bolt Interface Loading

Mechanical Engineering Design, by Shigley

RP-1228 NASA Fastener Design

First fundamental frequency at 1564 Hz3 sigma load = 194gA286 CRES #6-32 Bolts at Interface

Inputs Outputs545 lb 24545 lb 53.02 lb545 lb 45.42 lb

1.682 in 48 487 lb 174

1077 lb464 lb

Tensile Yield

Shear YieldTensile Ultimate

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 Yield

c osmic r ay t elescope for the e ffects of r adiation 6/27/06 telescope mechanical design1 albert...

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