Attachment_B,_WFIRST-SPEC-12739-.pdf

Effective Date: March 5, 2019

Expiration Date: March 5, 2024

CHECK https://gddms.gsfc.nasa.gov/Windchill/app/

TO VERIFY THAT THIS IS THE CORRECT VERSION PRIOR TO USE.

National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

WFIRST-SPEC-12739, Revision -

Wide Field Infrared Survey Telescope (WFIRST), Code 448

Instrument Carrier (IC)

Launch Lock and

Vibration Isolation System (LLVIS)

Performance Specification

GSFC WFIRST CMO

March 11, 2019

Released https://gddms.gsfc.nasa.gov/Windchill/app/

Performance Specification, LLVIS WFIRST-SPEC-12739, Revision -ii

Instrument Carrier (IC)

Launch Lock and Vibration Isolation System (LLVIS)

Performance Specification

Review/Signature/Approval Page

Prepared by:

Wes Alexander

Marc DiNardo

Approved by:

David Content

Electronic Approval available on-line at: https://gddms.gsfc.nasa.gov/Windchill/app/ iii

Preface

This document is a Wide Field Infrared Survey Telescope (WFIRST)

Configuration Management (CM)-controlled document. Changes to this document require prior approval of the applicable Configuration Control Board (CCB) Chairperson or designee.

Proposed changes shall be submitted to the WFIRST CM Office (CMO), along with supportive material justifying the proposed change.

In this document, a requirement is identified by “shall,” a good practice by “should,” permission by “may” or “can,” expectation by “will,” and descriptive material by “is.”

Questions or comments concerning this document should be addressed to:

WFIRST Configuration Management Office

Mail Stop 448

Goddard Space Flight Center

Greenbelt, Maryland 20771 iv

Change History Log

Revision Effective Date Description of Changes

Revision - March 5, 2019 Initial release per WFIRST-CIR-09351 v

Table of TBDs/TBRs/TBSs [optional]

Item No. Location Summary Individual/

Organization

Actionee

Due Date

TBD1 2.1.2 Unit WFIRST IDs Design/CM Prior to Unit

CDR

TBR1 2.2.8 Isolator Externally

Applied Load

Design/I&T Prior to Unit

PDR

TBR2 2.3.12 Launch Lock Mission

Time Prior to Actuation

Systems Prior to Unit

PDR

TBR3 2.15.2 Launch Lock Current Electrical/Systems Prior to Unit

PDR

TBR4 2.15.6 Launch Lock Time

Required to Unlock

Electrical/Systems Prior to Unit

PDR

vi

Table of Contents

1 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Related Documentation

1.3.1 Applicable Documents

1.3.2 Reference Documents

1.4 Order of Precedence

2 REQUIREMENTS

2.1 Configuration Definitions

2.1.1 Launch Lock & Vibration Isolation System (LLVIS) Configuration

2.1.2 Unit Definition

2.1.3 Unit Schematic Description

2.1.4 Unit Placement and Allowable Volume

2.1.5 Flexure Stiffness Design Data

2.2 Isolator Performance Requirements

2.2.1 Isolator Transmissibility

2.2.2 Isolator Resonant Mode Frequency

2.2.3 Isolator Resonant Mode Q Value

2.2.4 Isolator Transmissibility Variation within a Set

2.2.5 Isolator Lateral and Local Vibration Modes

2.2.6 Isolator Lateral Mode Damping Design Goal

2.2.7 Isolator Model Correlation

2.2.8 Isolator External Applied Load

2.3 Launch Lock Performance Requirements

2.3.1 Launch Lock Static Design Limit Loads

2.3.2 Launch Lock Locked Axial Stiffness

2.3.3 Launch Lock Locked Bending Stiffness

2.3.4 Launch Lock External Loads during Unlock

2.3.5 Launch Lock Reset/Refurbishment

2.3.6 Visual detection of Launch Lock Locked or Unlocked Position

2.3.7 Electrical Detection of Launch Lock Locked or Unlocked Position

2.3.8 Launch Lock Function without Power

2.3.9 Launch Lock Redundancy

2.3.10 Minimum Number of Launch Lock Cycles

2.3.11 Dimensional Repeatability

2.3.12 Launch Lock Mission Time Prior to Actuation

2.4 Integrated Isolator/ Launch Lock Performance Requirements

2.5 Unit Internal Clearance (“Stroke”) Requirements

2.5.1 Definition of Stroke / Internal Clearance

2.5.2 LLVIS Unit Stroke Requirements

2.6 Physical Requirements

2.6.1 Units of Measure for Interfacing with WFIRST

2.6.2 Interface Documentation

2.6.3 Unit Mass Property Requirements

vii

2.6.3.1 Isolator Mass

2.6.3.2 Launch Lock Mass

2.6.3.3 Integrated Isolator/Launch Lock Mass

2.6.3.4 Center of Mass Location

2.6.3.5 Determination of Moments and Products of Inertia

2.6.4 Mounting Interface Characteristics

2.6.5 Grounding Implementation

2.6.5.1 Through-Unit Conductivity

2.6.5.2 Ground Strap Accommodation & Contact Area

2.6.5.3 Internal Grounding

2.6.5.4 Surface Resistivity

2.7 Reliability

2.8 Maintainability

2.9 Environmental Conditions

2.9.1 Sine Vibration Levels

2.9.2 Random Vibration Levels

2.9.3 Load Cycle Fatigue for both Isolator and Launch Lock

2.9.4 Shock

2.9.4.1 External Shock Applied to Isolator and Launch Lock

2.9.4.2 Shock Susceptibility Assessment

2.9.4.3 Launch Lock Internally Generated Shock Transmitted to Spacecraft

2.9.4.4 Shock Imparted on Isolator by Launch Lock

2.9.4.5 Unit Self-Generated Shock

2.9.5 On-Orbit Dynamic Environment

2.9.6 Thermal Environment

2.9.6.1 Operational Temperature Environment

2.9.6.2 Survival Temperature Environment

2.9.6.3 Thermal Accommodations

2.9.6.4 Allowable Flight Temperature (AFT) Range

2.9.6.5 Analytical Thermal Margin

2.9.6.6 Acceptance and Qualification Test Temperature Range

2.9.6.7 Unit Shipment Temperatures

2.9.7 Vacuum Environment Requirements

2.9.8 Operating Pressure

2.9.9 Venting and Depressurization

2.9.10 Radiation Environment

2.9.10.1 Total Ionizing Dose Requirements

2.9.10.2 Displacement Damage Dose (DDD) Requirements

2.9.10.3 Single Event Effects Requirements

2.10 Ground Environments

2.11 Design Life

2.11.1 Ground Life

2.11.2 Mission Operations

2.12 Design and Construction

2.12.1 Structural Design Criteria

2.12.1.1 General Structural Design Criteria

viii

2.12.1.2 Load Definition

2.12.1.3 Allowables Definition

2.12.1.4 Design Factors of Safety

2.12.2 Demonstrating Positive Margin of Safety

2.12.2.1 Qualification by Analysis

2.13 Materials, Processes and Parts

2.13.1 Material Selection Guidelines

2.13.2 Stress Corrosion Cracking

2.13.3 Dissimilar Materials

2.13.4 Use of Material Property Allowables

2.13.5 CTE of Materials

2.13.6 Analysis of Temperature Effects

2.13.7 Fastener Sizes

2.13.8 Fastener Control Plan

2.13.9 Outgassing

2.13.10 Surface Finishes

2.13.11 Alignment Critical Joints

2.13.12 Design Bolt Edge Distance

2.13.13 Safe-life or Fail Safe Joints

2.13.14 Seal Analysis

2.13.15 Fastened Joint Margin of Safety

2.13.16 Fastener Locking Methods and Torquing

2.13.17 Fracture Control

2.13.18 Flexures Under Cyclic Loading

2.13.19 Thermal Hardware Design Requirements

2.13.19.1 Thermal Hardware Characteristics

2.13.19.2 Thermal Sensor Calibration Data

2.13.19.3 Heater Circuit Redundancy

2.13.19.4 Heater Duty Cycle

2.13.19.5 Heater Overtemperature Provisions

2.13.19.6 Wiring of Thermostats

2.13.19.7 Watt Density of Kapton Heaters

2.14 Mechanism Design

2.14.1 Torque/Force Margins

2.14.2 Clearances

2.14.3 Tolerancing

2.14.4 Lubricant Requirements

2.14.4.1 Lubricant Compatibility

2.14.4.2 Lubricant Life

2.14.4.3 Solid Lubrications

2.14.5 Springs

2.14.6 Viscous Dampers

2.14.6.1 Damper Filling

2.14.6.2 Damper Temperature Compensation

2.14.6.3 Damper Vacuum Testing

2.14.7 Mechanical End of Travel Stops

ix

2.14.8 Position Sensors

2.14.9 Mechanism Installation

2.14.10 Finishes for Sliding Surfaces

2.14.11 Mechanism Verification Requirements

2.14.11.1 Mechanism Functional Testing

2.14.11.2 Mechanism Qualification Testing

2.14.11.3 Mechanism Acceptance Testing

2.14.11.4 Mechanism Life Testing

2.15 Electrical Requirements

2.15.1 Voltage Supplied to Heaters on LLVIS Units

2.15.2 Launch Lock Current

2.15.3 Launch Lock Impedance

2.15.4 Launch Lock Current vs Time Curve

2.15.5 Launch Lock Release Confirmation

2.15.6 Launch Lock Time Required to Unlock

2.15.7 Release Initiation Circuit

2.15.8 Resistance Test Signal and Duration

2.15.9 No Initiation Current

2.15.10 Internal Charging

2.15.11 Ground Isolation

2.15.12 Dielectric Strength

2.15.13 Insulation Resistance

2.15.14 EEE Parts

2.15.15 Wiring Requirements

2.15.15.1 Wire Sizing

2.15.15.2 Wire Materials

2.15.15.3 Wire Labeling

2.15.16 Soldered and Wire Connections

2.15.17 Wiring/Harness Configuration

2.15.18 Harness Connection Provisions

2.16 Assembly Environment

2.17 Cleanliness

2.18 Vacuum Bakeout Requirements for Outgassing Mitigation

2.18.1.1 Vacuum Bakeout Conditions

2.18.1.2 Outgassing Measurement during Vacuum Bakeout

2.19 Design for Cleanability

2.20 Identification

2.21 Workmanship

2.22 Interchangeability

2.23 Standards of Manufacture

3 VERIFICATION AND QUALITY ASSURANCE PROVISIONS

3.1 General

3.2 Responsibility for Verification

3.3 Mission Assurance Requirements

3.4 Philosophy of Test

3.4.1 Verification Methods

x

3.4.1.1 Not Applicable (N/A)

3.4.1.2 Inspection (I)

3.4.1.3 Analysis (A)

3.4.1.4 Demonstration (D)

3.4.1.5 Test (T)

3.4.1.6 Test Verification Categories

3.5 Test Requirements

3.5.1 Test Procedures

3.5.2 Test Types

3.5.3 EDU Unit

3.5.4 Qualification Unit

3.5.5 Life Test Unit

3.5.6 Flight Acceptance Units

3.5.7 Test Definition

3.5.7.1 Test Sequence

3.5.7.2 Performance Tests

3.5.7.3 Functional Tests

3.5.8 Test Readiness Review

3.5.9 Test Flows

3.6 Test Conditions and Tolerances

3.6.1 Structural and Physical Test Tolerances

3.6.2 Structural Test Levels and Tolerances

3.7 Isolator Specific Tests

3.7.1 Transmissibility Test Requirements

3.7.2 Isolator Static Testing

3.7.3 Isolator Stroke Measurement

3.8 Launch Lock Specific Tests

3.8.1 Locked Launch Lock Static Load

3.8.2 Launch Lock Unlock and Electrical Status Indication

3.8.3 Launch Lock Unlock Under Load

3.8.4 Launch Stroke Measurement

3.8.5 Launch Lock Internally Generated Shock

3.9 Integrated Isolator/Launch Lock Specific Tests

3.9.1 Integrated Isolator/Launch Lock Stroke Measurement

3.10 General Environmental Test Requirements

3.10.1 General Test Configuration

3.10.2 Post-Test Inspection

3.10.3 Equipment Calibration

3.10.4 Measurement Accuracy

3.10.5 Facility Capability

3.10.6 Facility Performance

3.11 Vibration Test Requirements

3.11.1 Fixture Stiffness

3.11.2 Vibration Test Configuration

3.11.3 Vibration Test Directions

3.11.4 Fixture, Mounting Method and Setup Evaluation

xi

3.11.5 Accelerometer Instrumentation

3.11.6 Vibration Facility Equalization

3.11.7 Low Level Sine Survey

3.12 Sine Vibration Specific Test Requirements

3.12.1 Applicability of Sine Vibration Test

3.12.2 Low Level Ramping

3.12.3 Sine Vibration Test Notching

3.13 Random Vibration Specific Test Requirements

3.13.1 Random Vibration Fixture Frequency

3.13.2 Random Vibration Fixture Resonances

3.13.3 Random Vibration Test Notching

3.13.4 Random Vibration Force Limiting

3.13.5 Rolloff for Random Vibration Test

3.14 Thermal Vacuum Testing Requirements

3.14.1 Thermal Test Configuration

3.14.2 Verification of Function

3.14.3 Thermal Test Setup Definition

3.14.4 Thermal Test Profile

3.14.5 Thermal Vacuum Chamber Pressure

3.14.6 Thermal Vacuum Chamber Certification

3.14.7 Determination of Test Temperatures

3.14.7.1 Qualification Test Temperatures

3.14.7.2 Acceptance Test Temperatures

3.14.8 Transition Rate Between Plateaus

3.14.9 Dwell Time at Plateaus

3.14.10 Vacuum Bakeout

3.14.11 Thermal Balance Test

3.14.12 Condensation Precautions

3.14.13 Thermal Hardware Control During Test

3.15 Electrical Verification Tests

3.15.1 Interface Grounding and Surface Conductivity

3.15.2 Resistance Test Signal Duration

3.15.3 No Initiation Current

3.15.4 Circuit Properties

3.16 Quality Assurance Verification

3.16.1 Verification Requirements

3.16.2 Verification Cross Reference Index (VCRI)

4 GROUND SUPPORT EQUIPMENT

4.1 GSE Definition

4.2 GSE Cleanliness

5 PREPARATION FOR DELIVERY

5.1 Applicable Standard

5.2 Design of Shipping and Storage Containers

5.3 Bagging Requirements and Sequence

5.4 Data Packages

xii

6 NOTES

7 REQUIREMENTS VERIFICATION MATRICES

APPENDIX A ABBREVIATIONS AND ACRONYMS

List of Figures

Figure 1 Unit Schematic Representations Figure 2 General Arrangement of LLVIS on WFIRST Figure 3 LLVIS Configuration Installed on Spacecraft showing allowable volume required for separate Isolator and Launch Lock as well as integrated assembly Figure 4 Isolator Transmissibility Requirement Figure 5 Schematic Representation of Unit Stroke Components

Figure 6 External Shock from Spacecraft Applied to Unit Figure 7 Shock Response Spectra for Assessing Component Test Requirements Figure 8 Launch Lock Internally Generated Shock Response Limit Figure 9 Total Ionizing Dose Requirement

Figure 10 Conceptual Test Flow for Isolator Figure 11 Conceptual Test Flow for Launch Lock

Figure 12 Test configuration for Isolator axial transmissibility verification

List of Tables

Table 1 Unit Definition and Nomenclature Table 2 WFIRST Provided Flexure Stiffnesses

Table 3 Locked Launch Lock Design Limit Loads

Table 4 Launch Lock External Loads during Unlock Table 5 LLVIS Unit Stroke Requirements Table 6 Sine Vibration Design Limit Levels

Table 7 Random Vibration Design Limit Levels Table 8 On-Orbit Dynamic Loads

Table 9 LLVIS Thermal Environment Temperatures Table 10 Design Factors of Safety Table 11 Minimum Bolt Edge Distance Table 12 Kapton Heater Watt Density Table 13 Factors of Safety for Mechanism Torque and Force

Table 14 Structural and Physical Test Tolerances Table 15 Structural Test Levels and Durations

Table 16 Locked Launch Lock Test Qualification Loads Table 17 Test Methods and Types Table 18 Shipment and Handling Design Limit Loads and Factors of Safety for WFIRST

Shipping/Storage Containers Table 19 Verification Cross Reference Index (VCRI) for Isolator

Table 20 Verification Cross Reference Index (VCRI) for Launch Lock Table 21 Verification Cross Reference Index (VCRI) for Integrated Isolator/Launch Lock

1 INTRODUCTION

1.1 Purpose

This Specification (SPEC) defines those requirements necessary to design, analyze, develop, fabricate, integrate, test, and evaluate the Launch Lock / Vibration Isolation System (LLVIS) units for WFIRST.

1.2 Scope

This document defines the performance requirements for the WFIRST Launch Lock and

Vibration Isolation System (LLVIS) consists of 6 identical Isolators and 6 identical Launch

Locks which will be used to provide structural support and vibration attenuation for the WFIRST

Payload. These Isolators and Launch Locks can be separate items or an Integrated

Isolator/Launch Lock assembly as defined herein. Each component is attached at both ends of each assembly with flexures designed and manufactured by WFIRST. These are then mounted to the Instrument Carrier assembly and to the spacecraft bus.

The scope of this specification is to identify the requirements for the individual Unit. The

WFIRST project is responsible for all the requirements associated with the LLVIS as a system.

1.3 Related Documentation

The latest versions of all documents below should be used. WFIRST documents can be obtained from URL: https://gddms.gsfc.nasa.gov/Windchill/app/.

1.3.1 Applicable Documents

The following documents are referenced within this document and are directly applicable or contain policies or other directive matters that are binding for the contents of this document. In the event of conflicting requirements between this Specification and the Applicable Documents, the Contractor shall immediately notify the GSFC Contracting Officer’s Representative (COR) that there is such a conflict and request direction from the Government as to how to proceed.

Document Number Title

ASTM E595-15 American Society for Testing and Materials, Outgassing Test

Procedure

GSFC 541-PG-8072.1.2 GSFC Fastener Integrity Requirements

GSFC EEE-INST-002 Instructions for EEE Parts Selection, Screening, Qualification, and

Derating

IPC J-STD-001GS Requirements for Soldered Electrical and Electronic Assemblies

IPC/WHMA-A-620C-S Requirements and Acceptance for Cable and Wire Harness

Assemblies

MIL-STD-889C Dissimilar Materials

MMPDS-12 Metallic Materials Properties Development and Standardization

(MMPDS) Handbook

MSFC-STD-3029A Guidelines for the Selection of Metallic Materials for Stress

Corrosion Cracking Resistance in Sodium Chloride Environments

NASA-STD-5019A Fracture Control Requirements for Spaceflight Hardware

NASA-STD-6016A Standard Materials And Processes Requirements For Spacecraft

NASA-STD 8719.24Ch3 NASA Expendable Launch Vehicle Payload Safety Requirements

WFIRST-SOW-13052(-) Instrument Carrier (IC) Launch Lock and Vibration Isolation

System (LLVIS) Statement of Work

WFIRST-LIST-13054(-) Instrument Carrier (IC) Launch Lock and Vibration Isolation

System (LLVIS) Deliverable Items List and Schedule (DILS)

WFIRST-SPEC-05417B WFIRST Math Model Guidelines

WFIRST-RQMT-

05819A

WFIRST Mission Assurance Requirements (MAR)

WFIRST-PLAN-08012

WFIRST Materials and Processes Selection, Control, and

Implementation Plan (MCSCIP)

WFIRST-PLAN-11850

WFIRST Parts Control Plan

1.3.2 Reference Documents

The following documents are referenced herein and amplify or clarify the information presented in this document. These documents are not binding on the content of this document.

IEST-STD-CC1246E Product Cleanliness Levels –Applications, Requirements, and

Determination

MSFC-HDBK-527F Materials Selection List for Space Hardware Systems

MSFC-HDBK-1674/

JSC 08962 Rev V

Compilation of TVS Data for Nonmetallic Materials

WFIRST-REF-06763

WFIRST Radiation Specification

1.4 Order of Precedence

In the event of a conflict, the following order of precedence shall apply:

1) Statement of Work (SOW)

2) This specification

3) Other WFIRST documents

4) Military standards and specs

5) Other government specs and publications

6) Industry association documents

2 REQUIREMENTS

2.1 Configuration Definitions

2.1.1 Launch Lock & Vibration Isolation System (LLVIS) Configuration

The Launch Lock and Vibration Isolation System (LLVIS) consists of 6 identical Isolators and 6 identical Launch Locks, or 6 independent integrated assemblies that perform both functions. The

Isolators include tuned stiffness and internal damping characteristics. The Launch Locks react launch loads and then unlock during the operational mission phase.

The individual Isolators and Launch Locks will incorporate mounting interfaces that will mount to flexures on both ends of the assembly defined by WFIRST.

Mass properties, dimensions and performance of the Isolators and the Launch Locks will include these mounting interfaces. WFIRST assembled struts will be configured as a hexapod that supports the payload for WFIRST.

2.1.2 Unit Definition

This specification defines three distinct types of units:

Table 1 Unit Definition and Nomenclature

Unit Nomenclature Function WFIRST ID

Isolator Provide vibration isolation between mounting interfaces

TBD1

Launch Lock React launch, ground and handling/shipment loads in the locked mode and actuate into the unlocked mode on command at a significant time after launch

TBD1

Integrated

Isolator/Launch Lock

Provide the function of the Isolator and Launch

Lock in a single integrated assembly

TBD1

Requirements defined herein apply to all units in a set of six of each type.

If a requirement does not include a reference to an applicable unit, i.e. Isolator or Launch Lock, or if the requirement refers to “Unit”, it shall apply to all units.

2.1.3 Unit Schematic Description

Figure 1 depicts the LLVIS units in schematic form. These views are intended solely to describe the interfaces and element responsibilities in a simplistic manner, and are not intended to imply any specific design features.

The figure includes schematic depiction of flexures provided by WFIRST. The flexures are identified by “SC Bus End,” indicating the end that attaches to the spacecraft bus, and “IC End,” indicating the end that attaches to the Instrument Carrier (IC) which is the metering structure that supports the WFIRST Payload.

The Unit design may include flexures which are not depicted. Details of the attachment of the

Units to WFIRST will be negotiated between the Contractor and WFIRST. The baseline scope is that WFIRST will provide flexures as identified in Figure 1. The responsibility for the flexures associated with the Isolator may be negotiated.

Figure 2 illustrates the general arrangement of the LLVIS units on the WFIRST spacecraft. Only basic structure items are shown. For the configuration with separate Isolators and Launch Locks, the Units will be in the general locations shown in Figure 2 with the Isolators and Launch Locks in close proximity as shown in Figure 3.

Figure 1 Unit Schematic Representations

Figure 2 General Arrangement of LLVIS on WFIRST

Figure shows the general arrangement of LLVIS locations relative to the SC bus and IC.

For simplicity, the integrated

LLVIS configuration is shown.

Instrument Carrier (IC).

SC Bus

LLVIS

Unit(s)

Typical

2.1.4 Unit Placement and Allowable Volume

Figure 3 and the associated table describe the maximum allowable volume for the Isolator, Launch Lock, and Integrated Launch Lock/Isolator. The units shall not exceed the applicable allowable volume. Allowable volume requirements may be negotiated between the Contractor and WFIRST. Note that these views show separate Isolator and Launch Lock Units. If an

Integrated Isolator/Launch Lock is used, its placement will be consistent with that shown for the

Launch Lock (larger cylindrical volume)

Diameter Length Width Height

Separate Launch Lock and Isolator

(Shown inside of transparent figure)

Large cylindrical volume (Launch Lock) 200mm 300mm - -

Small cylindrical volume (Isolator) 81mm 130mm - -

Integrated Launch Lock and Isolator 200mm 300mm - -

Transparent shape shown for maximum volume (including SC provided flexures) - 535mm 200mm 547mm

Figure 3 LLVIS Configuration Installed on Spacecraft showing allowable volume required for separate Isolator and Launch Lock as well as integrated assembly

2.1.5 Flexure Stiffness Design Data

This section provides information related to the flexures between the Units and the WFIRST SC

Bus and IC as depicted in Figure 1.

The following values are to be used for representation of the WFIRST provided flexures. They are provided due to the relationship between flexure stiffness and internal displacements in the

Units. Flexure stiffness values will be negotiated between the Contractor and WFIRST.

Table 2 WFIRST Provided Flexure Stiffnesses

Flexure Nomenclature Axial Stiffness, N/m

Lateral

Stiffness, N/m

Bending

Stiffness, N-m/rad

Torsional

Stiffness, N-m/rad

SC Bus to Isolator 9.31E+08 1.25E+08 1.50E+05 2.87E+04

IC to Isolator 5.82E+07 4.89E+05 5.87E+02 1.12E+02

SC Bus to Launch Lock 9.31E+08 1.25E+08 1.50E+05 2.87E+04

IC to Launch Lock 9.31E+08 1.25E+08 1.50E+05 2.87E+04

Integrated Bus to

Isolator/Launch Lock 9.31E+08 1.25E+08 1.50E+05 2.87E+04

Integrated Isolator/Launch

Lock to IC 9.31E+08 1.25E+08 1.50E+05 2.87E+04

These values are to be used as follows:

a) Values as stated for analyses of natural frequency, Isolator performance, etc.

b) Values multiplied by 1.50 for analyses of stroke/internal clearance

The values are representative of an axisymmetric flexure, i.e. a member of circular cross section.

Analyses using these values should assume a fixed boundary condition at the ends of the flexures.

2.2 Isolator Performance Requirements

2.2.1 Isolator Transmissibility

The Isolator transmissibility shall be less than the maximum requirement shown in Figure 4

Transmissibility is defined as:

a) Displacement transfer function, i.e. the ratio of output displacement at load mass to input displacement, or

b) Acceleration transfer function, i.e. the ratio of output acceleration at load mass to input acceleration

Note: see Section 3.7.1 for schematic of transmissibility test configuration.

This requirement shall be met over the operating temperature range specified in 2.9.6.1.

Figure 4 Isolator Transmissibility Requirement

2.2.2 Isolator Resonant Mode Frequency

The stiffness and damping properties of the Isolator shall be sized to produce an Isolator resonant frequency of 1.2 Hz +/-0.06 Hz as verified by analysis and the Isolator level axial transmissibility test.

2.2.3 Isolator Resonant Mode Q Value

The maximum Q value of the Isolator’s axial acceleration transfer function at resonant frequency shall be less than 16 as verified by the Isolator’s axial dynamic test and model, over the operating temperature range specified in Section 2.9.6. Refer to

Figure 4.

2.2.4 Isolator Transmissibility Variation within a Set

The variation of Isolator critical parameter values within a flight shipset of Isolators shall not vary from the nominal values by more than the following tolerances over the operational temperature range.

K Spring Constant (s) ±5%

C Damping Coefficient ±7.5%

2.2.5 Isolator Lateral and Local Vibration Modes

All lateral or local mode frequencies of the Isolator shall be above 400 Hz when the ends are fully constrained in translation and rotation at the interface.

2.2.6 Isolator Lateral Mode Damping Design Goal

The Contractor will attempt to maximize the damping of all lateral modes of vibration where practical. This includes internal modes of the Isolator as well as lateral modes of the Isolator-

WFIRST flexures assembly. The internal and lateral mode frequencies of the Isolator and

Isolator-WFIRST flexures assembly, respectively, should not fall between 200 and 400Hz. The nominal LLVIS dynamic model which includes the Isolator-WFIRST flexures assemblies will be used for the system level assessment; the assessment shall be performed by WFIRST.

2.2.7 Isolator Model Correlation

The Contractor shall provide a correlated Isolator finite element model based on measured data from Isolator’s axial dynamics test. The model correlation shall be valid from 0.1 to 400 Hz and over the operational temperature range. The transmissibility characteristics of the correlated

Isolator model shall yield frequencies and resonant peaks to within 5% of the measured frequencies and response amplitudes. The Isolator finite element model shall meet the model requirements specified in WFIRST-SPEC-05417.

2.2.8 Isolator External Applied Load

The Isolator shall withstand an externally applied load of 890 N (200 lbf) axial tension and compression and 11 N-m (100 in-lb) bending moment simultaneously without damage or degradation of performance. (TBR1)

2.3 Launch Lock Performance Requirements

2.3.1 Launch Lock Static Design Limit Loads

The Launch Lock in the locked mode shall be designed to the design limit loads defined in Table

3.

Table 3 Locked Launch Lock Design Limit Loads

Component Load Design Limit Load

Axial Tension 80,170 N (18,203 lbf)

Axial Compression 101,460 N (22,809 lbf)

Transverse Shear 3,100 N (697 lbf)

Bending Moment 520 N-m (384 lbf-ft)

Notes:

Axial, bending, and transverse shear loads are applied simultaneously.

Transverse shear and bending loads are applied in all worst case clocking directions as determined by the Launch Lock design.

The above design limit loads apply over the following temperature range: 12.8 to 28.4 °C

(285.9K-301.56K).

2.3.2 Launch Lock Locked Axial Stiffness

The minimum axial stiffness of the Launch Lock device shall be 5.32 E8 N/m when placed in the locked position. This requirement applies over the full range of load defined in 2.3.1 in both tension and compression.

2.3.3 Launch Lock Locked Bending Stiffness

The Launch Lock device shall have a minimum locked bending stiffness of 2.24 E5 N-m/rad when fixed at the ends. This requirement applies over the full range of load defined in 2.3.1 in both tension and compression.

2.3.4 Launch Lock External Loads during Unlock

The Launch Lock shall unlock and comply with all applicable requirements while experiencing the applied external loads defined in Table 4, combined and applied in all directions, over the operational temperature range.

Table 4 Launch Lock External Loads during Unlock

Component Load Design Level Loads

Axial 4388 N (945 lbf)

Lateral 3319 N (675 lbf)

Torsion (about longitudinal axis) 105 N-m (606 in-lbf)

Bending (perpendicular to longitudinal axis) 596 N-m (4951 in-lbf)

2.3.5 Launch Lock Reset/Refurbishment

The Launch Lock device shall be resettable or refurbishable. “Resettable” indicates that the

Launch Lock can be returned to the locked condition meeting all ICD requirements without disassembly. “Refurbishable” means that the Launch Lock can be returned to the locked condition meeting all ICD requirements with limited disassembly and inspection. It is preferred that the Launch Lock be resettable while installed, but bench top resettable or refurbishable at

GSFC is also acceptable.

2.3.6 Visual detection of Launch Lock Locked or Unlocked Position

The Launch Lock shall include provisions for a positive visual indication of proper locking and a means to easily detect, from several orientations around the Launch Lock, visibly whether the

Launch Lock is in the locked or unlocked state.

2.3.7 Electrical Detection of Launch Lock Locked or Unlocked Position

The Launch Lock shall include provisions for redundant electrical indication of locked or unlocked state with electrical requirements per 2.15.5.

2.3.8 Launch Lock Function without Power

The Launch Lock shall maintain its locked state in the absence of externally applied power.

2.3.9 Launch Lock Redundancy

Electrical elements required to actuate the Launch Lock, including heaters, thermostats, fusible links, and other items as applicable, shall be redundant and redundantly powered.

2.3.10 Minimum Number of Launch Lock Cycles

The Launch Lock shall be capable of a minimum of seven (7) unlock/lock cycles following delivery to GSFC. It shall meet all requirements after this number of cycles.

2.3.11 Dimensional Repeatability

The Launch Lock interface dimensions between interfaces shall not change more than 0.05 mm

(0.002”) in hole location and more than 0.025 mm (.001”) in parallelism as a result of being reset or refurbished.

2.3.12 Launch Lock Mission Time Prior to Actuation

The Launch Lock shall actuate and meet all performance requirements after being in the locked configuration for the ground storage life followed by a minimum of 3 months (TBR2) at the survival temperature.

2.4 Integrated Isolator/ Launch Lock Performance Requirements

The requirements for an Integrated Isolator/Launch Lock assembly are the same as the requirements defined in Section 2.2 for the Isolator portion of the assembly and in Section 2.3 for the Launch Lock portion of the assembly, except as defined in this section.

REMAINDER OF THIS SECTION RESERVED

2.5 Unit Internal Clearance (“Stroke”) Requirements

2.5.1 Definition of Stroke / Internal Clearance

The “stroke” (internal clearance) requirements for the Units are defined in subsequent sections.

In this document, stroke is defined as allowable movement of the interfaces to the SC relative to the neutral (unloaded) condition, a) prior to contact of internal parts of the Unit (including end of travel stops) or b) any motion that would damage or affect the performance of the Unit.

The axial component is defined as the allowable movement along the longitudinal axis of the

Unit. The lateral component is defined as the allowable movement perpendicular in any direction to the longitudinal axis of the Unit. The torsion component is defined as the allowable rotation about the longitudinal axis of the Unit. The bending component is defined as the allowable rotation about an axis perpendicular to the longitudinal axis of the Unit.

Figure 5 provides a graphical representation of the Unit stroke components.

Figure 5 Schematic Representation of Unit Stroke Components

2.5.2 LLVIS Unit Stroke Requirements

The requirements for LLVIS Units are shown in Table 5. The components of stroke are defined in 2.5.1. For the Launch Lock and the Launch Lock portion of the Integrated Isolator/Launch

Lock, the stroke requirements apply in the unlocked mode. The components of stroke shall be applied simultaneously in all combinations.

Table 5 LLVIS Unit Stroke Requirements

Unit:

Isolator, Launch Lock, and

Integrated Isolator/Launch

Lock

Stroke Component, mm (inches)

Axial, mm

(in)

Lateral, mm

(in)

Torsion, milliradians

Bending, milliradians

+/-4.8 (0.189) +/-5.4 (0.212) +/-7 +/-10.1

Note that for evaluation of stroke/internal displacements in the Units, the information provided in

Section 2.1.5 is to be used.

2.6 Physical Requirements

2.6.1 Units of Measure for Interfacing with WFIRST

The Contractor shall use metric (SI) units when interfacing with WFIRST including any drawings, documents, models, except for the following cases:

Heritage Component: Components that has been previously qualified, or of similar design heritage, may be specified in English units where use of metric equivalents would lead to additional cost to the program.

Fasteners: Although bolt patterns will be defined using metric dimensioning, use of English fasteners (with hole dimensioning and tolerancing) is permitted.

Angular Measurement: Angular measurement may be expressed in degree of arc or in an appropriate subdivision of degree of arc such as second of arc (arc-sec) when advantageous to application.

2.6.2 Interface Documentation

The physical configuration, overall size and volume, and interface definition details, mechanical and electrical, shall be described in detail via an Interface Control Drawing (ICD) to be prepared by the Contractor and reviewed and approved by WFIRST. The details of content of the ICD shall be agreed upon between the Contractor and WFIRST.

2.6.3 Unit Mass Property Requirements

2.6.3.1 Isolator Mass

The mass of each Isolator shall not exceed 0.6 kg (1.32 lb) each.

2.6.3.2 Launch Lock Mass

The mass of each Launch Lock shall not exceed 6.0 kg (13.2 lb) each.

2.6.3.3 Integrated Isolator/Launch Lock Mass

The mass of each Integrated Isolator/Launch Lock shall not exceed 6.5 kg (14.3 lb) each.

2.6.3.4 Center of Mass Location

The Contractor shall define the center of mass in the ICD.

2.6.3.5 Determination of Moments and Products of Inertia

The moments and products of inertia of the Unit shall be determined by analysis and defined in the ICD.

2.6.4 Mounting Interface Characteristics

Mounting interface flatness, and co-planarity requirements for the component side of the interface (including brackets, if any, and shims) shall be as defined in the ICD.

2.6.5 Grounding Implementation

2.6.5.1 Through-Unit Conductivity

The unit shall be electrically conductive through the assembly with a resistance of 10 ohms or less. For the Launch Lock, this requirement applies in the locked mode.

2.6.5.2 Ground Strap Accommodation & Contact Area

The unit shall provide an interface for a ground strap at each interface with a minimum contact area of 80 mm2 (0.124 in2), defined on the ICD.

2.6.5.3 Internal Grounding

All conductive surfaces shall be grounded to the grounding interfaces with a resistance less than

5 ohms, either through the use of ground wire(s) or through metal-to-metal mounting contact.

2.6.5.4 Surface Resistivity

All surfaces shall have a surface resistivity less than 107 ohm-cm or of 108 ohms/square.

2.7 Reliability

The probability of success (Ps) for surviving and performing within specification over the period of mission operations defined in 2.11.2 shall be 0.9999 or greater, for each Unit, over the operating temperature range. Reliability analysis for the Unit, including unit failure rate (in

Failures per Million Hours), shall be provided so that WFIRST can integrate the Unit model into a larger system model.

2.8 Maintainability

The Unit shall not require adjustment or maintenance throughout its design life identified in 2.11.

2.9 Environmental Conditions

The Unit shall satisfy all requirements of this specification over the design life after having been exposed to the environmental conditions specified herein.

2.9.1 Sine Vibration Levels

Input limit levels for sine vibration are defined in Table 6. These levels apply in all directions.

Analysis shall be performed in each direction separately. These levels will be updated with system level analysis results when available.

Table 6 Sine Vibration Design Limit Levels

Frequency (Hz) Limit Level

5 to 100 10.0 g

2.9.2 Random Vibration Levels

Input limit levels for random vibration are defined in Table 7. These levels apply in all directions. Analysis shall be performed in each direction separately. These levels will be updated with system level analysis results when available.

Table 7 Random Vibration Design Limit Levels

Frequency (Hz) ASD Limit Level (g2/Hz)

20 0.013

20 - 50 +6 dB/octave

50 - 800 0.08

800 - 2000 -6 dB/octave

2000 0.013

Overall 10.0 grms

2.9.3 Load Cycle Fatigue for both Isolator and Launch Lock

The unit shall be designed to withstand 4000 cycles of the quasi-static design limit loads including applicable factors of safety. This includes a fatigue scatter factor of 4. For the Launch

Lock, this requirement applies in the locked mode.

2.9.4 Shock

2.9.4.1 External Shock Applied to Isolator and Launch Lock

The Isolator and Launch Lock in the locked mode shall meet all performance requirements after being subjected to the shock input from the Spacecraft defined in Figure 6.

Figure 6 External Shock from Spacecraft Applied to Unit

2.9.4.2 Shock Susceptibility Assessment

A shock susceptibility and attenuation assessment shall be performed for the Unit. This assessment shall be reviewed and approved by WFIRST. Based on this assessment, the verification method for SC induced shock shall be agreed to between the Contractor and

WFIRST. For reference, the shock response spectrum shown in Figure 7 is commonly used for assessing shock susceptibility. If the flight shock environment is enveloped by the curve shown in Figure 7, shock testing at the Unit level may not be required. If the flight shock environment is not enveloped by the curve shown in Figure 7, Unit level shock testing for susceptibility to externally applied shock may be required.

Figure 7 Shock Response Spectra for Assessing Component Test Requirements

2.9.4.3 Launch Lock Internally Generated Shock Transmitted to Spacecraft

The mechanical shock generated by the Launch Lock at its interfaces to the IC and SC bus shall not exceed the limits defined in Figure 8. The shock generated by the Launch Lock shall be verified by test for the Qualification Unit. The need for shock testing of Flight Units shall be determined based on evaluation of data from the Qualification Unit.

Note: Limit levels are based on data measured within 10 inches of the source and a shock spectrum analysis with Q = 10.

Figure 8 Launch Lock Internally Generated Shock Response Limit

2.9.4.4 Shock Imparted on Isolator by Launch Lock

The Isolator shall meet all performance requirements after being subjected to the shock input generated by the Launch Lock defined in 2.9.4.3

2.9.4.5 Unit Self-Generated Shock

The unit shall meet all performance requirements after being subjected to its own self-generated shock, as applicable.

2.9.5 On-Orbit Dynamic Environment

The Unit shall withstand the following on-orbit loading (Launch Locks in unlocked mode) over the survival temperature range. The loads are to be applied simultaneously.

Table 8 On-Orbit Dynamic Loads

Component Units Value

Force, axial N (lbf) 112 (25)

Force, lateral N (lbf) 74 (17)

Moment, bending N-m (in-lbf) 0.4 (3.9)

2.9.6 Thermal Environment

2.9.6.1 Operational Temperature Environment

The Unit shall meet all operational performance specifications while exposed to vacuum environment as defined in 2.9.7 and while exposed to the Operational temperatures in Table 9.

2.9.6.2 Survival Temperature Environment

The Unit shall survive, without performance degradation, non-operational exposure to vacuum environment as defined in 2.9.7 and while exposed to the Survival temperatures in Table 9.

Table 9 LLVIS Thermal Environment Temperatures

Component Type of

Environment

Operational Survival

Note Low High Low High

Instrument

Carrier (IC)

End

Conductive -103 °C

(170 °K) -38 °C

(235 °K) -113 °C

(160 °K) +40 °C

(313 °K) 1

Spacecraft

(SC) Bus End

Conductive -38 °C

(235 °K) +37 °C

(310 °K) -48 °C

(225 °K) +42 °C

(315 °K) 1,2

Guidance

Radiative

Environment

Radiative -128 °C

(145 °K) -58 °C

(215 °K) -138 °C (135 °K)

+40 °C (313 °K) -

Notes:

1) See Figure 1 for illustration of SC Bus and IC Ends

2) For Isolator Transmissibility analysis, the Spacecraft Bus End operational range shall be used.

2.9.6.3 Thermal Accommodations

The thermal environment can be modified by the spacecraft by the use of blankets, Isolators at the interface(s), and heaters on the Unit and/or spacecraft. Use of heaters is not preferred. Use of these methods will be negotiated between the Contractor and WFIRST.

2.9.6.4 Allowable Flight Temperature (AFT) Range

The Allowable Flight Temperature (AFT) range is the range of Unit temperatures over which the

Unit will operate within specification. The AFT range should be chosen by the Contractor based on the thermal environment and the limitations of the hardware.

2.9.6.5 Analytical Thermal Margin

The predicted temperature of the Unit shall be at least 5K inside the Contractor determined AFT.

2.9.6.6 Acceptance and Qualification Test Temperature Range

The Acceptance test temperature range shall be 5K beyond the AFT. The Qualification test temperature range shall be 10K beyond the AFT.

2.9.6.7 Unit Shipment Temperatures

The shipment method shall be controlled such that the unit shipment temperatures are within the survival temperature range.

2.9.7 Vacuum Environment Requirements

The unit shall meet all requirements at operational performance and survival temperatures while exposed to a vacuum environment. Vacuum environment is defined as a pressure of 1.3x10-3 Pa

(1x10-5 Torr) or less.

2.9.8 Operating Pressure

The Unit shall operate without performance degradation after exposure to pressures ranging from ambient pressure of 14.7 psi to a vacuum environment after completion of the survival temperature cycle.

2.9.9 Venting and Depressurization

All internal volumes shall have a vent path to the outside environment. Each volume in the Unit shall have a minimum vent area of 4.1 cm2 (0.25 in2) per 28,317 cm3 (1 cubic foot) of volume or shall demonstrate positive margin due to the maximum depressurization rate of 5033 Pa/sec. This does not apply to items which are considered pressure vessels.

2.9.10 Radiation Environment

The Unit shall be designed to operate within specification requirements over the operating life specified in 2.11.2 when subjected to the following radiation environments, which include the appropriate radiation margins of safety.

2.9.10.1 Total Ionizing Dose Requirements

Figure 9 gives the top-level total ionizing dose requirement for WFIRST. The doses are calculated here as a function of aluminum shield thickness in units of krad in silicon. For a nominal 100 mils (2.54 mm) of equivalent aluminum shielding and the 5.25-year mission, the expected dose is 22.3 krad-Si at the 95% confidence level.

Figure 9 Total Ionizing Dose Requirement

2.9.10.2 Displacement Damage Dose (DDD) Requirements

The displacement damage dose or non-ionizing dose is the mean energy deposited in a material that goes into atomic displacements divided by the mass of the material. It is analogous to the ionizing dose except that the energy considered produces displacements in a semiconductor lattice.

Silicon and gallium arsenide EEE parts susceptible to displacement damage degradation shall be able to tolerate a minimum DDD of 5.84 x 108 MeV/g (or a 10 MeV equivalent proton fluence of

7.40×1010 cm-2 ) and 4.81 x 108 MeV/g (or a 10 MeV equivalent proton fluence of 7.30×1010 cm-

2 ), respectively.

This meets the DDD exposure for a 5.25-year mission with orbit about the Sun-Earth second

Lagrange point, L2, at the 95% confidence level and nominal 100 mils of aluminum shielding.

2.9.10.3 Single Event Effects Requirements

All electrical components shall be designed to avoid or tolerate errors due to non-destructive single event upsets (SEUs).

All EEE parts shall have linear energy transfer (LET) thresholds for single event latchup (SEL) greater than 75 (MeV·cm2)/mg for the destructive events. Parts with LET thresholds between 37

MeV-cm2/mg and 75 MeV-cm2/mg could be used if the evaluation of the probability and outcome of the destructive event shows that there would be no mission impact. Reference the

WFIRST Radiation Specification (WFIRST-REF-06763) for more details.

Any EEE parts that do not comply with the WFIRST radiation requirements will be reviewed and approved by the WFIRST EEE parts control board.

2.10 Ground Environments

The Unit shall meet all of its performance requirements during exposure to air temperature between +5 and +30 degrees C and relative humidity between 30% and 70%.

2.11 Design Life

The Unit shall meet the performance requirements of Section 2 over its design life unless otherwise stated. The design life is the sum of ground life, and mission operations.

2.11.1 Ground Life

The Unit shall be designed to have a ground life of up to 7.5 years.

2.11.2 Mission Operations

Mission operations shall encompass 5.25 years (5 years + 3 months commissioning).

2.12 Design and Construction

2.12.1 Structural Design Criteria

2.12.1.1 General Structural Design Criteria

The unit shall follow the design criteria below:

1) The unit shall withstand (limit, no-yield and ultimate) static and dynamic loads and pressures without experiencing detrimental elastic or plastic deformation.

2) The margins of safety shall be positive and shall be determined by analysis and/or test.

3) Structural components that are subject to instability modes of failure shall not collapse under ultimate loads, nor degrade the functioning of any part of the Unit due to elastic buckling deformation under limit loads.

4) Buckling shall not occur in any structural component subject to compressive in-plane stresses, including loads resulting from temperature changes.

5) Design loads for buckling shall be ultimate loads, except that any load component that tends to alleviate buckling shall not be multiplied by the ultimate factor of safety.

2.12.1.2 Load Definition

Structural sizing of all LLVIS component structure, internal components, and pressurized components shall be in compliance with the following load definitions.

Design Consideration Criteria

Flight Loads Limit load = maximum applied load

No-yield load = limit x yield factor of safety in Table 10

Ultimate load = limit x ultimate factor of safety in Table 10

Non-flight Loads Limit load = maximum applied load

Ultimate load = 2.0 x limit load

Thermal Loads Limit load = thermal stresses based on maximum applied temperature

Ultimate load = limit load

Pressure Vessels Proof load = 1.5 x maximum working pressure

Burst load = 2.0 x maximum working pressure

Pressurized lines and fittings, ID< 1.5”

Proof load = 2.0 x maximum working pressure

Burst load = 4.0 x maximum working pressure

Pressurized lines and fittings, ID> 1.5”

Proof load = 1.5 x maximum working pressure

Burst load = 2.0 x maximum working pressure

Combined Loads Limit load = limit flight + temperature + pressure load

2.12.1.3 Allowables Definition

Stresses and material allowables shall be in accordance with the following criteria.

Mechanical stresses Limit stresses are calculated using limit loads

Combined mechanical and thermal stresses

Limit stresses are calculated using limit mechanical stresses plus thermal stresses caused by temperature variance

Allowable strength Limit allowable = lesser of the yield or ultimate strength divided by the appropriate factors of safety specified in Table 10 and then multiplied by the degradation in magnitude caused by temperature variance

Repeated stresses Allowable stresses shall include considerations of any degradation in properties caused by load repetitions.

2.12.1.4 Design Factors of Safety

The factors of safety defined in Table 10 shall be used for unit design.

Table 10 Design Factors of Safety

Type of Hardware Static /Sine Random/Acoustic 3,4

Tested Metallic Yield 1.252 1.6

Tested Metallic Ultimate 1.42 1.8

Stability/Buckling Ultimate 1.4 1.8

Beryllium Yield 1.4 1.8

Beryllium Ultimate 1.6 2.0

Composite Ultimate1 1.5 1.9

Bonded inserts/Joints Ultimate 1.5 1.9

Glass/Ceramic 3.0 3.8

Bond in Glass/Ceramic 1.5 1.9

(1) All composite structures must be tested to 1.25 x limit loads.

(2) For qualification by analysis only, positive margin must be shown with FS of 2.0 and 2.6 for metallic yield and ultimate, respectively.

(3) Factors shown are applied to statistically derived peak response based on limit/acceptance

RMS level. As a minimum, the peak response must be calculated as a 3-sigma value.

(4) Factors shown assume that qualification/prototype testing is performed at 3dB above limit/acceptance limits.

2.12.2 Demonstrating Positive Margin of Safety

Positive Margin of Safety (MS) shall be demonstrated analytically for all flight hardware under all design and environmental conditions using the formula below with the appropriate Factors of

Safety (FS) defined in Table 10 applied to flight limit loads.

MS is defined as follows:

𝑀𝑆 =

𝐴𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 𝐿𝑖𝑚𝑖𝑡 𝐿𝑜𝑎𝑑 𝑜𝑟 𝑆𝑡𝑟𝑒𝑠𝑠

𝐴𝑝𝑝𝑙𝑖𝑒𝑑 𝐿𝑖𝑚𝑖𝑡 𝐿𝑜𝑎𝑑 𝑜𝑟 𝑆𝑡𝑟𝑒𝑠𝑠 ∗ 𝐹𝑆

− 1

Where: Allowable is the maximum permitted for yield, ultimate, etc. as applicable.

2.12.2.1 Qualification by Analysis

For qualification by analysis only, positive margin shall be shown with safety factors of 2.0 and

2.6 for metallic yield and ultimate, respectively.

2.13 Materials, Processes and Parts

All materials and processes shall be in accordance with those submitted and approved prior to use as defined in WFIRST-SOW-13052. The selection, screening, identification, derating and control of all materials, parts and processes used in electrical materials shall conform to the requirements of GSFC EEE-INST-002 or MIL-STD-1547B or approved equivalent.

A Parts, Materials and Processes Plan shall be prepared by the Contractor in accordance with

WFIRST’s Parts, Materials and Processes Control Plan (WFIRST-PLAN-11850 and WFIRST-

PLAN-08012); and will be submitted to WFIRST for review and approval. Maximum use of existing and qualified parts should be implemented.

2.13.1 Material Selection Guidelines

The following materials guidelines will be adhered to:

Cadmium, Zinc, Tin or Selenium shall not be used in any application. Cadmium and Zinc plating and silver brazing alloys containing Cadmium and Zinc shall not be used.

Solder alloys containing Tin are allowed to be used.

Mercury and mercury compounds shall not be utilized.

PVC shall not be utilized for wire insulation.

Materials with known radioactivity, such as uranium, radium, etc. shall not be used.

Castings are prohibited.

Corrosive agents used in resins shall not be used.

Anaerobic thread locking compounds shall not be used.

All Teflon usage shall be reported and documented to WFIRST.

2.13.2 Stress Corrosion Cracking

Metallic materials listed in Table I of MSFC-STD-3029 per NASA-STD-6016 shall be used.

2.13.3 Dissimilar Materials

The selection and use of dissimilar metals in direct contact shall be in accordance with MIL-

STD-889C per NASA-STD-6016.

2.13.4 Use of Material Property Allowables

Mat…