Draft Spec.pdf

Effective Date: <Date> Expiration Date: <Date> [as required]

National Aeronautics and Space Administration

Goddard Space Flight Center Greenbelt, Maryland

RST-PROP-SPEC-0122, Revision -

Roman Space Telescope (RST), Code 448

Delta-V Thruster Specification

DRAFT

June 20, 2020

RST Delta-V Thruster Spec RST-PROP-SPEC-0122, Revision Number – (Draft)

Check FPD BCI Document Management Guidance to verify that this is the correct version prior to use

400-FORM-0002 (4/16/2014)

Delta-V Thruster Specification

Review/Signature/Approval Page

Prepared by:

Alison Rao

Approved by:

Electronic Approval available on-line in the RST CM Tool https://fpdspi.gsfc.nasa.gov/sites/fpdat/BCI/SitePages/Document%20Management%20Guidance file://gs448share/WFIRST/01.0%20Project%20Management/1.4%20Configuration-Data%20Mgmt/Templates/Document%20Templates/TDMS/Templates%20(boilerplates)/Historical/in ii

Preface This document is a Roman Space Telescope (RST) Configuration Management (CM)-controlled document.

Note: Prior to May 20, 2020, the project name was Wide Field Infrared Survey Telescope

(WFIRST).

For the purposes of configuration management, the prefixes “WFIRST” and “RST” are completely interchangeable. For example, RST-MGMT-PROC-0024 is the same as WFIRST-

MGMT-PROC-0024.

Changes to this document require prior approval of the applicable Configuration Control Board (CCB) Chairperson or designee. Proposed changes shall be submitted to the RST 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:

RST Configuration Management Office Mail Stop 448 Goddard Space Flight Center Greenbelt, Maryland 20771 iii

Change History Log

Revision Effective Date Description of Changes (Reference the CCR & CCB/ERB Approval Date)

Revision - TBD Initial Release per RST-CCR-TBD iv

Table of TBDs/TBRs/TBSs

Item No. Location Summary Individual/ Organization

Actionee

Due Date v

Table of Contents

1 INTRODUCTION

1.1 Purpose

1.2 Scope

1.3 Related Documentation

1.3.1 Applicable Documents and Forms

2 CONTRACT DESCRIPTION

2.1 Delta-V Thruster Description

2.2 Ground Support Equipment Description

3 FUNCTIONAL/PERFORMANCE REQUIREMENTS

3.1 Delta-V Thruster Configuration Requirements

3.1.1 Major Components List

3.1.2 Nozzle Configuration

3.1.3 Valve Configuration

3.1.3.1 Redundancy

3.1.3.2 Independent Operation

3.1.3.3 Thruster Valve Fail-Safe

3.1.3.4 Inlet Filter Rating

3.1.4 Interface Tube Location

3.1.5 Valve Heater Configuration

3.1.6 Valve Thermostat Configuration

3.1.7 Valve Thermal Sensor Configuration

3.1.8 Catalyst Bed Heater Configuration

3.1.9 Catalyst Bed Thermal Sensor Configuration

3.2 Delta-V Thruster Functional Requirements

3.2.1 Pressure Requirements

3.2.1.1 Maximum Expected Operating Pressure/Exposure Pressure

3.2.1.2 Proof Pressure

Proof Pressure with Valves Open Proof Pressure with Valves Closed

3.2.1.3 Burst Pressure

Burst Pressure with Valves Open Burst Pressure with Valves Closed

3.2.1.4 Surge Pressure

3.2.1.5 Interface Tube Pressure Requirements

Interface Tube MEOP Interface Tube Proof Pressure Interface Tube Burst Pressure

3.2.2 Leakage Requirements

3.2.2.1 Internal Leakage

3.2.2.2 Internal Leakage during Random Vibration

3.2.2.3 External Leakage

3.3 Delta-V Thruster Performance Requirements

3.3.1 Thrust

vi

3.3.1.1 Beginning-of-Mission Thrust

3.3.1.2 End-of-Mission Thrust

3.3.1.3 Thrust Repeatability

3.3.1.4 Roughness

Spiking Reporting of Thruster Limitations

3.3.1.5 Steady-State Thrust Variability

3.3.1.6 Thrust Degradation

3.3.2 Inlet Pressure

3.3.3 Specific Impulse Requirements

3.3.3.1 Specific Impulse

3.3.3.2 Specific Impulse Repeatability

3.3.4 Steady-State Firing Duration

3.3.5 Pulsed Performance Requirements

3.3.5.1 Duty Cycles

3.3.5.2 Minimum Pulse Duration

3.3.5.3 Minimum Impulse Bit

3.3.5.4 Ibit Repeatability, > 1 Second

3.3.5.5 Ibit Repeatability, < 1 Second

3.3.6 Throughput

3.3.7 Cold Start Capability

3.3.8 Propellant and Pressurant Requirements

3.3.8.1 Propellant Type

3.3.8.2 Pressurant Type

3.3.8.3 Helium-Saturated Propellants

3.3.8.4 Propellant Temperature

3.3.8.5 Gas Ingestion

3.3.9 Thruster Thermal Cycles

3.3.10 Thruster Warm Pulses

3.3.11 Heat Soakback

3.4 Valve-Specific Requirements

3.4.1 Valve Cycles

3.4.2 Valve Inductance

3.4.3 Valve Heater Sizing

3.5 Catalyst Bed Heater-Specific Requirements

3.5.1 Catalyst Bed Heater Duration to Minimum Temperature

3.5.2 Catalyst Bed Heater Cycles

3.6 Power

3.6.1 Power Allocations

3.6.1.1 Power Allocation – Thruster Valve

3.6.1.2 Power Allocation – Catalyst Bed Heater

3.6.2 Primary (Unregulated) Power Input Requirements

3.6.2.1 Operating Voltage Range

3.6.2.2 Abnormal Voltages

3.6.2.3 Sudden Removal of Power

3.6.3 Load Induced Noise Requirements

vii

3.6.3.1 Turn-on Current Transients

3.6.3.2 Operational Current Transients (one time)

3.6.3.3 Low Frequency Repetitive Transients (during nominal operation)

3.7 Electrical Grounding

3.7.1 Primary Power DC Isolation

3.7.2 Mechanical Contact Resistance

3.7.3 Mating Method

4 PHYSICAL REQUIREMENTS

4.1 Use of Metric Units

4.2 Mass Allocation

4.3 Physical Envelope

4.4 Mounting

4.5 Alignment

4.5.1 Angular Alignment

4.5.2 Position Alignment

4.5.3 Alignment GSE Size

4.6 Interface Tube Physical Requirements

4.6.1 Interface Tube Material

4.6.2 Interface Tube Length

4.6.3 Interface Tube Outer Diameter

4.6.4 Interface Tube Wall Thickness

5 ENVIRONMENTAL REQUIREMENTS

5.1 Quasi-Static Acceleration

5.2 Frequency Requirement

5.3 Vibration

5.3.1 Sinusoidal Vibration

5.3.2 Random Vibration

5.4 Shock

5.5 Acoustics

5.6 Pressure

5.6.1 Operating External Pressure Range

5.6.2 Maximum Depressurization Rate

5.7 Ground Environments

5.7.1 Thermal Ground Environment

5.7.2 Humidity Ground Environment

5.8 Thermal Requirements

5.8.1 Flight Interface Design Temperature Limits, Operational

5.8.2 Flight Interface Design Temperature Limits, Qualification

5.8.3 Flight Interface Design Temperature Limits, Survival

6 CLEANLINESS

6.1 Internal Cleanliness

6.2 Surface Contamination

6.2.1 Surface Contamination Levels at Delivery

6.2.1.1 Particulate Contamination

6.2.1.2 Molecular Contamination – Exposed Surfaces

viii

6.2.2 Surface Contamination Generation

6.2.2.1 Particulate Generation

6.2.2.2 Molecular Generation

Material Selection Material Selection - Silicones Assembly Outgassing

6.2.3 Cleanability

6.2.3.1 Cleanability – Sensitive Surfaces

6.2.3.2 Cleanability – Sensitive Surface Cleaning Methods

6.2.4 Transportation Cleanliness

7 DESIGN & CONSTRUCTION REQUIREMENTS

7.1 Parts, Materials & Processes (PMP)

7.1.1 EEE Parts

7.1.2 Materials

7.1.2.1 Material Conductivity

7.1.3 Material Compatibility

7.1.3.1 Fluid Compatibility

7.1.3.2 Passivation of Wetted Materials

7.2 Electrical

7.2.1 Interface Requirements

7.2.2 Wires

7.2.2.1 Wire Specifications

7.2.2.2 Minimum Wire Size

7.2.2.3 Wire Derating

7.2.2.4 Wire Composition

7.2.2.5 Wire Twists

7.2.2.6 Wire Insulation Resistance

7.3 Thermal Design

7.3.1 Thermal Conduction

7.3.2 Thermal Radiation

7.4 Identification and Marking

7.5 Workmanship

7.5.1 Workmanship Standards

7.5.2 Welding

7.6 Reliability and Mission Lifetime

7.6.1 Mission Life

7.6.2 Shelf Life

7.7 GSE Cleanliness

7.8 Interchangeability

8 MECHANICAL DESIGN REQUIREMENTS

8.1 Mechanical Factors of Safety

8.2 Fracture Control Requirements

8.3 Materials

8.3.1 Dissimilar Metals

8.3.2 Stress Corrosion Cracking

8.3.3 Fastened Joints

ix

8.3.3.1 Fastener Locking

8.3.3.2 Fastened Joint Margin of Safety

8.3.3.3 Installation Torque Documentation

8.3.3.4 Seal Analysis

8.3.3.5 Critical Fasteners

8.4 Mechanism Design

8.4.1 Torque Margin Formula

APPENDIX A ABBREVIATIONS AND ACRONYMS

APPENDIX B THRUSTER DRIVING CIRCUIT SCHEMATIC

List of Figures Figure 3-1 Thruster Interface Tube Location

List of Tables

Table 5-1 Thruster Design Limit Loads Table 5-2 Sine Vibration Limit Levels Table 5-3 Random Vibration Limit Levels Table 5-4 Minimum Workmanship ASD Level Table 5-5 Shock Limit Levels Table 5-6 Depressurization Profile Table 5-7 Temperature Limits at Box Mounting Interface Table 8-1 Design Factors of Safety Table 8-2 Torque Margin Calculation Factors of Safety

1 INTRODUCTION

1.1 Purpose

The Roman Space Telescope (RST) is a mission responding to the 2010 National Research Council New Worlds, New Horizons (NWNH) Astronomy and Astrophysics Decadal Survey top priority recommendation in the large space mission category. The science program includes two dedicated investigations to tackle outstanding questions in dark energy research and exoplanet exploration, and includes a substantial General Observer program to enable targeted investigations of astrophysical phenomena to advance other goals from the Decadal Survey. A coronagraph instrument is included in the payload for purposes of advancing the present state of the art of coronagraph technology. This document defines the requirements for the Delta-V thruster design.

1.2 Scope

This specification describes the electrical, mechanical, and environmental requirements for a space-qualified Delta-V thruster for the NASA Goddard Space Flight Center (GSFC) RST Mission.

1.3 Related Documentation

RST documents can be obtained from URL: https://ipdtdms.gsfc.nasa.gov.

1.3.1 Applicable Documents and Forms

The following documents and drawings in effect on the day this specification was signed (except where noted) apply to the fabrication and to the electrical, mechanical, and environmental requirements of the Delta-V thruster to the extent specified herein. In the event of conflict between this specification and any referenced document, this specification will govern, with the exception of the RST Delta-V Thruster Statement of Work (RST-PROP-SOW-0050), in which case the Statement of Work takes precedence.

Document Number Title AMS2243 Tolerances, Corrosion and Heat-Resistant Steel Tubing AMS5569 Steel, Corrosion and Heat Resistant, Seamless and Welded

Hydraulic Tubing 19Cr - 9.5Ni - 0.03C max Cold Drawn, 1/8 Hard Temper

AMS5647 Steel, Corrosion-Resistant, Bars, Wire, Forgings, Tubing, and Rings, 19Cr - 9.5Ni, Solution Heat Treated

ASTM E595 Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment

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

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

JSC SPEC C20 Water, High Purity Specification for MIL-PRF-26536E Propellant, Hydrazine MIL-PRF-27401 Propellant Pressurizing Agent, Nitrogen

Document Number Title MIL-PRF-27407 Propellant Pressurizing Agent, Helium MIL-PRF-27415 Propellant Pressurizing Agent, Argon MIL-STD-889C Dissimilar Metals MSFC-STD-3029 MSFC Technical Standard: Guidelines for the Selection of

Metallic Materials for Stress Corrosion Cracking Resistance in Sodium Chloride Environments

NASA-STD-5019 Fracture Control Requirements for Spaceflight Hardware NASA-STD-5020A, w/ Change 1

Requirements for Threaded Fastening Systems in Spaceflight Hardware

NASA-STD-6012 Corrosion Protection for Space Flight Hardware NASA-STD-8719.24 NASA Expendable Launch Vehicle Payload Safety

Requirements TT-I-735 Isopropyl Alcohol RST-PROP-ANYS-0032 Propulsion Subsystem Filtration Analysis RST-PROP-ANYS-0034 Propulsion Subsystem Bubble Analysis RST-PROP-ANYS-0136 Propulsion Subsystem Surge Analysis RST-PROP-REQ-0039 RST Propulsion Subsystem Requirements Document RST-PROP-SOW-0050 Delta-V Thruster Statement of Work RST-SC-DESC-0009 Spacecraft Master Equipment List RST-SC-DESC-0010 Spacecraft Power Equipment List RST-SYS-PLAN-0051 RST Contamination Control Plan RST-SYS-SPEC-0013 Thermal Systems Specification RST-SYS-SPEC-0033 RST Cleanliness Specification RST-SYS-SPEC-0037 RST Electrical Systems Specification RST-SYS-SPEC-0042 Mechanical System Specification

2 CONTRACT DESCRIPTION

2.1 Delta-V Thruster Description

The Delta-V thruster is a monopropellant hydrazine thruster capable of providing thrust for mid-course correction, orbit insertion, and disposal maneuvers of the RST spacecraft. The spacecraft contains a suite of Delta-V thrusters to provide primary delta-V. Delta-V thrusters may be used in both steady-state and pulsing mode. The flight units will be individual thrusters consisting of flow control valves, catalyst beds for decomposing hydrazine, a nozzle, and thermal hardware for heating and measuring necessary components. The thruster valves are normally closed valves that require power to open the valve and then return to the closed position in the absence of power.

Each thruster design will either have been qualified for space flight or the vendor will designate one (1) unit as protoflight to test at the qualification levels listed in this document. Thruster designs that have been qualified previously will include qualification documentation as described in the Delta-V Thruster Statement of Work (SOW), RST-PROP-SOW-0050.

2.2 Ground Support Equipment Description

The Delta-V thruster procurement includes the following ground support equipment (GSE) to be delivered with the flight hardware.

• Test plugs – This GSE installs into the nozzle and facilitates an AN-type gas connection for ground testing, such as thruster valve leakage tests.

• Alignment hardware – This GSE installs into the thruster nozzle, self-aligning, and facilitates alignment error verification after thruster installation in the higher assembly.

• Nozzle covers – This GSE encompasses the thruster nozzle exit to prevent contamination from entering the nozzle.

RST Delta-V Thruster Spec RST-PROP-SPEC-0122, Revision - (Draft)

3 FUNCTIONAL/PERFORMANCE REQUIREMENTS

This section defines the functional and performance requirements for the Delta-V thruster.

3.1 Delta-V Thruster Configuration Requirements

3.1.1 Major Components List

The thruster shall include the following components that meet the requirements herein.

• Thruster valve with inlet propellant filter

• Thrust chamber

• Nozzle

• Valve heaters

• Valve thermistors

• Thermostats

• Catalyst bed heaters

• Catalyst bed platinum resistance thermistors (PRT)

Rationale: Prop-61 per RST-PROP-REQ-0039.

3.1.2 Nozzle Configuration

The thruster shall contain a straight nozzle with no cant about the thruster’s central axis.

Rationale: Necessary for layout of propulsion subsystem design.

3.1.3 Valve Configuration

3.1.3.1 Redundancy

The thruster shall contain a series-redundant flow control valve.

Rationale: Prop-81 per RST-PROP-REQ-0039.

3.1.3.2 Independent Operation

The upstream and downstream valves shall open and close independently.

Rationale: Prop-81 per RST-PROP-REQ-0039.

3.1.3.3 Thruster Valve Fail-Safe

In the event of a loss of electrical power, the thruster valve shall remain in the closed position if closed and return to the closed position if open.

Rationale: Prop-60 per RST-PROP-REQ-0039.

3.1.3.4 Inlet Filter Rating

The thruster valve shall include an inlet propellant filter with an absolute filtration rating of 30 microns or larger.

Rationale: Align with filtration rating assumed in RST-PROP-ANYS-0032.

3.1.4 Interface Tube Location

The thruster interface tube shall have a centerline along the thruster’s centerline as shown in Figure 3-1. Refer to Section 4.5.3 for interface tube dimensions.

Rationale: Necessary for layout of propulsion subsystem design.

Figure 3-1 Thruster Interface Tube Location

3.1.5 Valve Heater Configuration

The thruster shall contain a dual-element valve heater with redundant heater circuits.

Rationale: Prop-32 per RST-PROP-REQ-0039.

3.1.6 Valve Thermostat Configuration

The valve heater circuits shall employ a series-redundant philosophy with two thermostats wired in series per circuit.

Rationale: TSS-29 per RST-SYS-SPEC-0013.

3.1.7 Valve Thermal Sensor Configuration

The thruster shall contain redundant thermistors for sensing valve temperature.

Rationale: Best practice for single-fault tolerant spacecraft.

3.1.8 Catalyst Bed Heater Configuration

The thruster shall contain a dual-element catalyst bed heater with redundant heater circuits.

Rationale: Prop-32 per RST-PROP-REQ-0039.

3.1.9 Catalyst Bed Thermal Sensor Configuration

The thruster shall contain redundant PRTs for sensing catalyst bed temperature.

Rationale: Prop-61 per RST-PROP-REQ-0039.

3.2 Delta-V Thruster Functional Requirements

3.2.1 Pressure Requirements

3.2.1.1 Maximum Expected Operating Pressure/Exposure Pressure The thruster shall have a Maximum Expected Operating Pressure (MEOP) of 700 psia, where the valve will open when input voltage is applied as described herein.

Rationale: Prop-19 per RST-PROP-REQ-0039. This pressure represents the exposure pressure of the thrusters in the off-nominal case of propellant heating while the upstream latch valves are closed. The exposure pressure is the sum of the maximum feed pressure and the back-pressure relief cracking pressure of two levels of latch valves (up to 150 psid each). Note that upon valve opening at this worst-case exposure pressure, the pressure will immediately drop to the operating pressure range described herein, so the thruster does not need to operate up to this exposure pressure.

3.2.1.2 Proof Pressure

Proof Pressure with Valves Open

The thruster shall have a proof pressure capability of not less than 1,050 psia with valve open.

Rationale: Prop-23 per RST-PROP-REQ-0039. This pressure represents 1.5 x MEOP.

Proof Pressure with Valves Closed The thruster shall have a proof pressure capability of not less than 1,050 psia with valve closed.

Rationale: Prop-23 per RST-PROP-REQ-0039. This pressure represents 1.5 x MEOP.

3.2.1.3 Burst Pressure

Burst Pressure with Valves Open

The thruster shall have a burst pressure of not less than 1,750 psia with valve open.

Rationale: Prop-26 per RST-PROP-REQ-0039. This pressure represents 2.5 x MEOP.

Burst Pressure with Valves Closed The thruster shall have a burst pressure of not less than 1,750 psia with valve closed.

Rationale: Prop-26 per RST-PROP-REQ-0039. This pressure represents 2.5 x MEOP.

3.2.1.4 Surge Pressure

The thruster shall withstand a peak surge (water-hammer) pressure of 1,050 psi at the closed thruster valve.

Rationale: Surge pressure constraint assumed in RST-PROP-ANYS-0136.

3.2.1.5 Interface Tube Pressure Requirements

Interface Tube MEOP

The thruster interface tube shall have a MEOP of not less than 700 psia.

Rationale: Prop-19 per RST-PROP-REQ-0039. This pressure represents the exposure pressure of the thrusters in the off-nominal case of propellant heating while the upstream latch valves are closed. The exposure pressure is the sum of the maximum feed pressure and the back-pressure relief cracking pressure of two levels of latch valves (up to 150 psid each).

Interface Tube Proof Pressure The thruster interface tube shall have a proof pressure capability of not less than 1,050 psia.

Rationale: Prop-23 per RST-PROP-REQ-0039. This pressure represents 1.5 x MEOP.

Interface Tube Burst Pressure The thruster interface tube shall have a burst pressure of not less than 2,800 psia.

Rationale: Prop-27 per RST-PROP-REQ-0039. This pressure represents 4.0 x MEOP.

3.2.2 Leakage Requirements

3.2.2.1 Internal Leakage

Each thruster valve seat shall maintain an internal leakage of less than 5 standard cubic centimeters per hour (scch) of gaseous helium in the closed position with inlet pressures of both 25 psia and MEOP. Valve leakage is defined as leakage through a single closed valve seat and out the nozzle.

Rationale: Best practice gas leakage to prevent liquid leakage during flight.

3.2.2.2 Internal Leakage during Random Vibration

Each thruster valve seat shall maintain an internal leakage of less than 5 scch of gaseous helium in the closed position with an inlet pressure of 25 psia while subjected to the acceptance random vibration environment stated herein. This requirement may be satisfied through similarity if applicable qualification data exist.

Rationale: Best practice gas leakage to prevent liquid leakage during launch.

3.2.2.3 External Leakage

The thruster shall maintain an external leakage of less than 1 x 10^-6 standard cubic centimeters per second (sccs) of gaseous helium at MEOP with both thruster valve seats open and the nozzle plugged.

Rationale: Best practices for external leakage criteria.

3.3 Delta-V Thruster Performance Requirements

3.3.1 Thrust

3.3.1.1 Beginning-of-Mission Thrust

The thruster shall have a minimum thrust of 27 N at an inlet pressure of 340 psia.

Rationale: Prop-48 per RST-PROP-REQ-0039.

3.3.1.2 End-of-Mission Thrust

The thruster shall have a minimum thrust of 10 N at an inlet pressure of 100 psia.

Rationale: Prop-48 per RST-PROP-REQ-0039.

3.3.1.3 Thrust Repeatability

The thruster shall produce thrust that is predictable to within 5% for a given duty cycle, including steady state.

Rationale: Prop-46 per RST-PROP-REQ-0039.

3.3.1.4 Roughness

Chamber pressure oscillations shall not cause any damage to the thruster or performance shortfalls during any steady-state or pulsed mode operation.

Rationale: Requirement mitigates roughness failure modes.

Spiking The thruster shall not exhibit any occurrence of “spiking” (rapid isolated increases of chamber pressure) at any condition of feed pressure, temperature, pulse mode duty cycle or any other condition.

Rationale: Requirement mitigates roughness failure modes.

Reporting of Thruster Limitations If there are limitations on thruster operation with respect to roughness, the contractor shall describe the limitations, the technical basis for the limitations, and the risks associated with thruster operation at the limiting conditions.

Rationale: Requirement mitigates roughness failure modes.

3.3.1.5 Steady-State Thrust Variability

The steady-state thrust shall vary by no more than +/-2% for constant engine inlet conditions after the initial thermal transient.

Rationale: Provide predictable thruster behavior for steady-state maneuvers.

3.3.1.6 Thrust Degradation

The thruster shall maintain steady-state thrust degradation of less than 5% throughout the mission life defined by Section 7.6.1, as compared to beginning of mission steady-state thrust.

Rationale: Provide predictable thruster behavior for steady-state maneuvers through the mission.

3.3.2 Inlet Pressure

The thruster shall operate over an inlet pressure range of 80-400 psia.

Rationale: Prop-57 per RST-PROP-REQ-0039.

3.3.3 Specific Impulse Requirements

3.3.3.1 Specific Impulse

The thruster shall have a minimum steady-state specific impulse of 210 seconds for all operating conditions.

Rationale: Prop-51 per RST-PROP-REQ-0039.

3.3.3.2 Specific Impulse Repeatability

The thruster shall have specific impulse that is predictable to within 5% for a given duty cycle, including steady state.

Rationale: Prop-46 per RST-PROP-REQ-0039.

3.3.4 Steady-State Firing Duration

The thruster shall be capable of continuous steady-state firing durations of up to 60 minutes.

Rationale: Prop-4 per RST-PROP-REQ-0039.

3.3.5 Pulsed Performance Requirements

3.3.5.1 Duty Cycles

The thruster shall not have any duty cycle operation restrictions for on times between the minimum on time in Section 3.3.5.2 and the firing duration defined in Section 3.3.4 at all inlet pressures and thermal environments specified herein.

Rationale: Ensure unrestricted thruster use within mission requirements.

3.3.5.2 Minimum Pulse Duration

The thruster shall be qualified for a minimum firing time of 20 milliseconds.

Rationale: Prop-59 per RST-PROP-REQ-0039.

3.3.5.3 Minimum Impulse Bit

The thruster shall have a minimum impulse bit (Ibit) of less than 0.45 N-s for a pulse of 20 milliseconds for all duty cycles and feed pressures.

Rationale: Prop-54 per RST-PROP-REQ-0039.

3.3.5.4 Ibit Repeatability, > 1 Second

The thruster shall have Ibit performance that is repeatable to +/- 5% for any continuous firing duration of 1 second or greater with similar initial conditions.

Rationale: Maintain repeatable performance for delta-V thruster pulses.

3.3.5.5 Ibit Repeatability, < 1 Second

The thruster shall have Ibit performance that is repeatable to +/- 25% for any firing duration less than 1 second with similar initial conditions.

Rationale: Maintain repeatable performance for delta-V thruster pulses.

3.3.6 Throughput

The thruster shall have a minimum qualified throughput of 104 kg.

Rationale: Based on throughput estimates in April 2020. Requirement includes 2x margin as required by Prop-44 on 5-year mission life per RST-PROP-REQ-0039. Requirement encompasses 1x margin on 10-year extended mission.

3.3.7 Cold Start Capability

The thruster shall be capable of surviving 3 cold starts with no more than 10% total degradation in thrust. A cold start is defined as starting thruster operation with a catalyst bed temperature of 12 deg-C or lower.

Rationale: Prop-58 per RST-PROP-REQ-0039.

3.3.8 Propellant and Pressurant Requirements

3.3.8.1 Propellant Type

The thruster shall use High-Purity Grade hydrazine per MIL-PRF-26536E (with Amendment 1) as the propellant.

Rationale: Prop-12 per RST-PROP-REQ-0039.

3.3.8.2 Pressurant Type

The thruster shall use helium pressurant gas per MIL-PRF-27407, Type I Grade B.

Rationale: Prop-13 per RST-PROP-REQ-0039.

3.3.8.3 Helium-Saturated Propellants

The thruster shall be capable of meeting all the requirements of this specification when the propellant is fully saturated, partially saturated, or not saturated with helium. Testing may be performed using unsaturated propellant with customer approval.

Rationale: Ensure thruster performance independent of helium saturation level.

3.3.8.4 Propellant Temperature

The thruster shall operate at any propellant temperature between 10 and 50 deg-C.

Rationale: Based on engine operational temperature range in Section 5.8.1.

3.3.8.5 Gas Ingestion

The thruster shall be capable of ingesting 0.11 g of gaseous helium at 354 psia at 20 deg-C before operation without any harm to the catalyst bed, the thruster, or any degradation in performance during subsequent normal firings.

Rationale: Bubble size calculated in RST-PROP-ANYS-0034.

3.3.9 Thruster Thermal Cycles

The thruster shall be qualified for 50 thermal cycles. A single thermal cycle is defined as a temperature excursion from below the thruster’s minimum operational start temperature to the maximum thruster operational temperature and back down below the minimum operational start temperature.

Rationale: Based on planned maneuvers with nominal steady-state or high duty cycle operation of delta-V thrusters. Maneuvers include on-orbit checkout, mid-course correction 1, mid-course correction 2, orbit insertion, and end-of-life disposal, each with one thermal cycle for the delta-V thrusters. Includes greater than 2x margin per Prop-56 on 5-year mission life in RST-PROP- REQ-0039. Requirement encompasses 1x margin on 10-year extended mission.

3.3.10 Thruster Warm Pulses

The thruster shall be qualified for 27,000 pulses while at operational temperature.

Rationale: Based on input provided by GNC summing expected pulses during course correction offpulsing plus an estimated 1,250 pulses needed for thruster acceptance testing. Includes 2x margin per Prop-56 on 5-year mission life in RST-PROP-REQ-0039. Requirement encompasses 1x margin on 10-year extended mission.

3.3.11 Heat Soakback

The thruster shall not exceed the maximum allowable temperature of any component in the thruster due to heat soakback for any steady-state or pulse-mode firing.

Rationale: Ensure unrestricted thruster use within mission requirements.

3.4 Valve-Specific Requirements

3.4.1 Valve Cycles

The thruster valve shall be qualified for 27,000 open/close cycles for each valve seat.

Rationale: Based on input provided by GNC summing expected cycles during course correction offpulsing plus an estimated 1,250 cycles needed for thruster acceptance testing and other ground operations. Includes 2x margin per Prop-56 on 5-year mission life in RST-PROP-REQ- 0039. Requirement encompasses 1x margin on 10-year extended mission. Requirement also encompasses 4x margin on ground cycles to satisfy NASA-STD-8719.24 Section 12.5.2.1.

3.4.2 Valve Inductance

The thruster valve shall have a total maximum inductance of 300 mH. This total maximum value is for the flight configuration in which the upstream and downstream valves are wired in parallel (by the customer).

Rationale: Constraint provided by driving electronics.

3.4.3 Valve Heater Sizing

The thruster valve heater shall be sized to maintain allowable valve temperatures with a maximum heater duty cycle of 70% at 30 VDC input voltage under worst-case cold thermal conditions, assuming only one heater circuit is active.

Rationale: TSS-31 per RST-SYS-SPEC-0013.

3.5 Catalyst Bed Heater-Specific Requirements

3.5.1 Catalyst Bed Heater Duration to Minimum Temperature

The catalyst bed heater shall be designed to achieve the minimum operational start temperature within 45 minutes of enabling from the worst-case minimum temperature with only a single catalyst bed heater active.

Rationale: Support pre-maneuver operations.

3.5.2 Catalyst Bed Heater Cycles

The catalyst bed heater shall be qualified to 50 cycles.

Rationale: Based on planned maneuvers with nominal steady-state operation of delta-V thrusters. Maneuvers include on-orbit checkout, mid-course correction 1, mid-course correction 2, orbit insertion, and end-of-life disposal, each with one thermal cycle for the delta-V thrusters. Includes greater than 2x margin per Prop-56 on 5-year mission life in RST-PROP-

REQ-0039.

3.6 Power

3.6.1 Power Allocations

3.6.1.1 Power Allocation – Thruster Valve

The thruster shall have a nominal (continuous) power consumption of less than or equal to

41.6 W across the operating voltage range in section 3.6.2.1 and the protoflight/qualification temperature range in Table 5-7. This power allocation applies when the upstream and downstream valve circuits are wired in parallel.

Rationale: Prop-37 per RST-PROP-REQ-0039; allocation per RST-SC-DESC-0010 corrected to worst-case voltage and temperature.

3.6.1.2 Power Allocation – Catalyst Bed Heater

The catalyst bed heater shall have a nominal (continuous) power consumption of less than or equal to 11.7 W across the operating voltage range in section 3.6.2.1 and the protoflight/qualification temperature range in Table 5-7. This power allocation applies to a single catalyst bed heater circuit.

Rationale: Prop-37 per RST-PROP-REQ-0039; allocation per RST-SC-DESC-0010.

3.6.2 Primary (Unregulated) Power Input Requirements

3.6.2.1 Operating Voltage Range

The thruster components shall be designed to operate over the bus voltage range of +24 to +35 VDC at their primary power inputs during all mission phases and for all expected load conditions (except when turned off).

Rationale: ESS-5201 per RST-SYS-SPEC-0037.

3.6.2.2 Abnormal Voltages

The thruster shall survive without electrical overstress after exposure to an anomalous voltage range of 0 to +40 VDC and input power short or open. This requirement is to be verified by analysis or testing of a non-flight unit.

Rationale: ESS-5204 per RST-SYS-SPEC-0037.

3.6.2.3 Sudden Removal of Power

The thruster shall meet its performance requirements without degradation after exposure to an abrupt, unannounced removal of power.

Rationale: ESS-5207 per RST-SYS-SPEC-0037.

3.6.3 Load Induced Noise Requirements

3.6.3.1 Turn-on Current Transients

The amplitude and duration of in-rush currents, at both initial application of prime power and subsequent component turn-on, shall be per the following:

• <10 microseconds: 10A

• Between 10 microseconds and 10 milliseconds: 3 times of max steady state or 3A whichever is larger

• >10 milliseconds: not to exceed max steady state

The compliance of this requirement can be demonstrated using a solid-state power switch with the similar turn on characteristics as the flight power control switch (optically coupled solid state relay). A schematic of the thruster driving circuit is provided in Appendix B.

Rationale: ESS-5207 per RST-SYS-SPEC-0037.

3.6.3.2 Operational Current Transients (one time)

a. The thruster operational current transients shall be less than or equal to 5A for a period of less than 1 millisecond.

b. The rate of change of the current shall be less than or equal to 20 mA/millisecond.

Rationale: ESS-5210 and ESS-5211 per RST-SYS-SPEC-0037.

3.6.3.3 Low Frequency Repetitive Transients (during nominal operation) Any repetitive current transients, in the frequency range between 1 Hz to 200 Hz, shall not exceed 0.8 A peak-to-peak.

This measurement will be performed with an oscilloscope current probe in time domain.

Rationale: ESS-5212 per RST-SYS-SPEC-0037.

3.7 Electrical Grounding

3.7.1 Primary Power DC Isolation

At the thruster primary power interfaces, primary power and primary power returns shall be isolated from signal grounds and from the component chassis by a DC resistance of greater than or equal to 1 Mohm.

Rationale: ESS-4104 per RST-SYS-SPEC-0037.

3.7.2 Mechanical Contact Resistance

The DC resistance of the mechanical contact between two current-carrying conductive mating surfaces used for electronic components shall be less than or equal to 2.5 milliohm.

Rationale: ESS-4109 per RST-SYS-SPEC-0037.

3.7.3 Mating Method

The mating method for the thruster will use thermal isolating spacers between the thruster mounting plate and the spacecraft structure.

4 PHYSICAL REQUIREMENTS

4.1 Use of Metric Units

The contractor shall use metric units when interfacing with NASA/GSFC including any drawings, documents, models, except for the following cases:

• SI units with parenthetical English units are permitted for engineering and manufacturing drawings.

• Angular measurement may be expressed in degree of arc or in an appropriate subdivision of degree of arc such as minute or second of arc (arc-min or arc-sec).

• Hardware that has been previously built, or new hardware of similar design heritage, may be specified in English units where use of metric equivalents would lead to additional risk and cost to the program, but interfaces with that hardware must use metric with parenthetical English units.

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

Rationale: Prop-42 per RST-PROP-REQ-0039.

4.2 Mass Allocation

The mass of the thruster shall be less than or equal to 0.8 kg.

Rationale: Prop-14 per RST-PROP-REQ-0039; allocation per RST-SC-DESC-0009.

4.3 Physical Envelope

The thruster external dimensions, including mounting provisions, shall be within an envelope of 100mm diameter x 230 mm long, excluding the interface tube.

Rationale: Necessary for layout of propulsion subsystem design.

4.4 Mounting

The thruster shall accommodate being hard-mounted with mechanical fasteners on a single mechanical surface of the spacecraft structure.

Rationale: Necessary for layout of propulsion subsystem design.

4.5 Alignment

4.5.1 Angular Alignment

The centerline of the nozzle shall be perpendicular with respect to the mounting flange to within ± 0.25 degrees.

Rationale: Prop-31 per RST-PROP-REQ-0039; allocation selected based on supplier capabilities.

4.5.2 Position Alignment

The position of the nozzle centerline with respect to the mounting interface centerline shall be within ± 1.5 mm.

Rationale: Prop-30 per RST-PROP-REQ-0039; allocation selected based on supplier capabilities.

4.5.3 Alignment GSE Size

Optical reference surfaces on the alignment GSE shall be at least 1.52 x 1.52 cm.

Rationale: Ensure alignment surfaces are adequate for verification at customer’s facility.

4.6 Interface Tube Physical Requirements

4.6.1 Interface Tube Material

The interface tube shall be 304L stainless steel per AMS5647 and AMS5569.

Rationale: Selected for weldability with subsystem tubing.

4.6.2 Interface Tube Length

The interface tube shall have a length of 1.5 +/- 0.06 inches.

Rationale: Selected to allow for weld repair if needed.

4.6.3 Interface Tube Outer Diameter

The interface tube shall have an outer diameter of 0.25 +/- 0.003 inches along the length in Section 4.6.2.

Rationale: Selected for weldability with subsystem tubing. Tolerance per AMS2243.

4.6.4 Interface Tube Wall Thickness

The interface tube shall have a wall thickness of 0.028 +/- 0.0028 inches along the length in Section 4.6.2.

Rationale: Selected for weldability with subsystem tubing. Tolerance per AMS2243.

5 ENVIRONMENTAL REQUIREMENTS

Environmental design requirements are specified in this section.

The thruster will meet its performance requirements in Section 3 during and after exposure to the environments specified in this section.

5.1 Quasi-Static Acceleration

Quasi-static acceleration represents the combination of steady-state accelerations and the low-frequency, mechanically transmitted dynamic accelerations that occur during launch.

The thruster shall be designed to withstand the quasi-static Design Limit Loads (DLL) defined in the Mass-Acceleration Curve (MAC) shown in Table 5-1 without damage or degradation of performance.

Note:

1. For masses within the breakpoints, linear interpolation is used to determine load.

2. Loads are considered to act in any direction, one axis at a time.

Table 5-1 Thruster Design Limit Loads

Component Mass (kg) Limit Load (g)

0.5 35.9 1 35

Rationale: MSS-107 per RST-SYS-SPEC-0042.

5.2 Frequency Requirement

The thruster shall have a fundamental frequency greater than 100 Hz when hard mounted at its interface. Requirements are met assuming rigid stiffness to restrained Degree of Freedom (DOF).

Rationale: MSS-101 per RST-SYS-SPEC-0042.

5.3 Vibration

5.3.1 Sinusoidal Vibration

The thruster shall withstand the sinusoidal vibration levels defined in Table 5-2.

Note:

1. Levels defined are acceptance levels. Analysis is conducted against acceptance with the safety factors defined in Table 8-1. Testing factors are defined in RST-PROP-SOW- 0050.

2. Peak levels at the low end of the frequency range (5 - 20 Hz) may be ramped up as needed to accommodate table limitations.

3. The sine sweep vibration levels shown in Table 5-2 are defined at the mounting interface of the component.

4. Input levels may be notched to limit the test article’s center of gravity (CG) response to

1.25 times its DLL outlined in Table 5-1.

5. Test verification is required over the range 5 to 50 Hz. Analytical verification is required from 50 to 100 Hz.

6. Components with a first fundamental frequency equal to or greater than 75 Hz can forgo sine vibration testing from 5 to 50 Hz, while verification through analysis of the 50 to 100 Hz is still required.

7. Components with a fundamental frequency equal to or greater than 150 Hz can forgo the sine vibration environment until higher levels of assembly upon approval by the NASA/GSFC Contracting Officer's Representative (COR).

Table 5-2 Sine Vibration Limit Levels

Frequency (Hz) Limit Level (g)

5 to 100 10.0

Rationale: MSS-110 per RST-SYS-SPEC-0042.

5.3.2 Random Vibration

The thruster shall withstand the random vibration environment in Table 5-3 applied at the mounting interface.

The random vibration inputs may be notched to limit the test article’s CG response to 1.25 times DLL. Notched inputs must envelope minimum workmanship levels in order to screen for design or manufacturing flaws.

Levels defined in Table 5-3 are acceptance levels. Analysis is conducted against acceptance with the safety factors defined in Table 8-1. Testing factors are defined in RST-PROP-SOW-0050.

Table 5-4 defines minimum workmanship levels. Random vibration specifications may be updated based on acoustic analysis.

During testing, force limiting control is recommended and the control method must be approved by the NASA/GSFC COR.

Table 5-3 Random Vibration Limit Levels

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

20 0.013 20 – 50 +6 dB/oct

50 – 800 0.08 800 – 2000 -6 dB/oct

2000 0.013 Overall 10.0 grms

Table 5-4 Minimum Workmanship ASD Level

Frequency (Hz) ASD Level (g2/Hz)

20 0.01 20 – 80 +3 dB/oct

80 – 500 0.04 500 – 2000 -3 dB/oct

2000 0.01 Overall 6.8 grms

Rationale: MSS-112 per RST-SYS-SPEC-0042.

5.4 Shock

The thruster shall be designed to meet its performance requirements after being subjected to the shock environment in Table 5-5, applied at the mounting interface to the spacecraft structure.

Levels defined are acceptance levels. Testing factors are defined in RST-PROP-SOW-0050.

Table 5-5 Shock Limit Levels

Frequency (Hz) Limit Load (g)

100 75 100-738 6.5 dB/oct.

738 858 10000 858

Note: A shock susceptibility and attenuation assessment is to be performed on the thruster design.

This assessment can be based on past shock tests or other relevant information.

Rationale: MSS-113 per RST-SYS-SPEC-0042.

5.5 Acoustics

N/A

Rationale: Appendix C per RST-SYS-SPEC-0042.

5.6 Pressure

5.6.1 Operating External Pressure Range

The thruster shall be designed to withstand a pressure range of 1.08 x 105 N/m2 (813 Torr) to

1.3 x 10-12 N/m2 (1 x 10-14 Torr).

Rationale: MSS-121 per RST-SYS-SPEC-0042.

5.6.2 Maximum Depressurization Rate

The thruster shall be designed to meet all performance requirements after exposure to a depressurization profile shown in Table 5-6 during launch and ascent.

Table 5-6 Depressurization Profile

Transonic Late Early Sec psia sec psia sec psia

0.0 14.70 0.0 14.70 0.0 14.70

10.0 14.20 10.0 14.40 10.0 14.00

15.0 13.70 15.0 14.00 15.0 13.40

20.0 12.95 20.0 13.35 20.0 12.55

25.0 11.95 25.0 12.45 25.0 11.45

41.2 7.90 44.8 7.90 28.0 10.64

43.2 7.70 46.8 7.80 30.2 9.75

45.2 6.24 48.8 6.50 32.2 9.00

46.6 5.40 50.4 6.00 33.5 8.50

48.7 4.30 52.1 5.50 35.0 8.00

50.9 3.30 53.8 5.00 36.4 7.50

54.0 2.40 55.3 4.60 37.9 7.00

58.0 1.60 56.8 4.20 39.4 6.50

65.0 1.00 58.4 3.80 41.0 6.00

70.0 0.80 60.0 3.40 42.7 5.50

80.0 0.50 61.4 3.10 44.4 5.00

110.0 0.30 62.8 2.80 46.3 4.50

150.0 5.00 64.2 2.50 48.0 4.05

65.5 2.25 50.0 3.75

66.9 2.00 52.0 2.88

68.0 1.80 57.0 2.00

68.8 1.68 65.0 1.30

75.0 1.10 80.0 0.60

85.0 0.60 110.0 0.30

110.0 0.30 150.0 0.05

150.0 0.05

Rationale: MSS-121 per RST-SYS-SPEC-0042.

5.7 Ground Environments

5.7.1 Thermal Ground Environment

The thruster shall meet all performance requirements after exposure to air temperature between +5 and +30 deg-C.

Rationale: TSS-65 per RST-SYS-SPEC-0013.

5.7.2 Humidity Ground Environment

The thruster shall meet all performance requirements after exposure to relative humidity between 0% and 70%.

Rationale: TSS-65 per RST-SYS-SPEC-0013.

5.8 Thermal Requirements

5.8.1 Flight Interface Design Temperature Limits, Operational The thruster shall meet all performance requirements within the Operational limits shown in Table 5-7.

Rationale: TSS-3 per RST-SYS-SPEC-0013.

5.8.2 Flight Interface Design Temperature Limits, Qualification The thruster shall meet all performance requirements within the Protoflight/Qualification limits shown in Table 5-7.

Rationale: Section 4.2.1.2 per RST-SYS-SPEC-0013.

5.8.3 Flight Interface Design Temperature Limits, Survival

When powered “OFF”, the thruster shall be capable of surviving indefinitely when its temperatures are within the survival limits shown in Table 5-7 without damage or permanent performance degradation.

Rationale: Section 4.2.1.1 per RST-SYS-SPEC-0013.

Table 5-7 Temperature Limits at Box Mounting Interface

Minimum Temperature (deg-C) Maximum Temperature (deg-C) Operational (In Spec) +10 +50 Protoflight/Qualification (In Spec)

+8 +60

Survival (Unpowered) +5 +120

6 CLEANLINESS

The requirements in this section ensure the cleanliness of the thruster at delivery, so as not to adversely affect its own performance, as well as not be a source of contamination to other items, including not generating contaminants following delivery in excess of that permitted below by virtue of its design, materials of construction, or operation.

6.1 Internal Cleanliness

The thrusters shall be cleaned, and verified internally clean, to level 50R1 per IEST-STD- CC1246E (as modified by the following: no metal particles allowed above 25 um) prior to delivery.

Rationale: Align with Appendix A of RST-PROP-ANYS-0032.

6.2 Surface Contamination

6.2.1 Surface Contamination Levels at Delivery

6.2.1.1 Particulate Contamination

The thruster external surfaces shall meet IEST-STD-CC1246E Particulate Cleanliness Level 300, with visual inspection meeting Level VC-0.5-1000 + UV, or equivalent, when inspected with both UV and white light in a darkened room prior to delivery.

Rationale: Prop-39 per RST-PROP-REQ-0039; level per CS4 in RST-SYS-SPEC-0033.

6.2.1.2 Molecular Contamination – Exposed Surfaces

The thruster external surfaces shall meet IEST-STD-CC1246E NVR Cleanliness Level R1, with visual inspection meeting Level VC-0.5-1000 + UV, or equivalent, when inspected with both UV and white light in a darkened room prior to delivery.

Rationale: Prop-39 per RST-PROP-REQ-0039; level per CS4 in RST-SYS-SPEC-0033.

6.2.2 Surface Contamination Generation

6.2.2.1 Particulate Generation

The thruster design shall not employ any of the following particle generating materials or processes without prior approval by the NASA/GSFC COR:

• Paints prone to shedding due to large paint pigment molecules, overspray, poor adhesion, etc.

• Surfaces prone to corrosion or oxides because of a lack of corrosion protection or dissimilar metals in close contact.

• Fabrics with brittle constituents (e.g., composites, graphite or glass).

• Perforated materials when material is highly susceptible to tear propagation (e.g., multi-layer insulation (MLI)).

• Metal oxides (bare [untreated] aluminum and magnesium, iron, non-corrosion resistant steel, etc.).

• Braided metallic or synthetic wires, ropes, slings, etc. unless measures have been taken to contain any broken filaments or fibers (sheathing, sealing with polymers, covering, etc.).

• Woven materials especially cut or unfinished ends (metal braid, EMI shielding, lacing cord, expando sleeving), unless measures have been taken to prevent fraying or generation of particles (cut with a hot knife, seal with polymer, bag, etc.).

• Materials with thin films known to erode or crack or flake when subjected to normal handling (e.g., indium tin oxide [ITO] or other rigid or brittle semiconductor or ceramic coating on flexible substrates, Teflon, MLI, etc.).

• Foams, highly textured materials.

• Trapped debris in holes.

Rationale: Provide list of materials that are unacceptable from a contamination standpoint.

6.2.2.2 Molecular Generation

Material Selection

The thruster materials shall have a total mass loss (TML) less than 1.00% and a collected volatile condensable mass (CVCM) less than 0.10%, when measured in accordance with ASTM E595 unless a materials usage agreement has been generated and approved by the NASA/GSFC

COR.

Rationale: MAR-188 per RST-SMA-REQ-0032.

Material Selection - Silicones Silicones on external surfaces shall not be exposed to the space environment unless approved by the NASA/GSFC COR. Silicones should be avoided or minimized. It is highly recommended that silicones be baked out at a high temperature prior to integration into the system to prevent extended bakeouts of the entire assembly.

Rationale: Section 4.1 per RST-SYS-PLAN-0051.

Assembly Outgassing

a. The thruster outgassing shall be measured in a vacuum of 1E-5 torr at the test article’s maximum hot survival temperature based on Table 5-7. The hot operating temperature plus 5 deg-C may be used with the NASA/GSFC COR’s approval.

Rationale: Section 4.4 per RST-SYS-PLAN-0051.

b. The thruster outgassing measurements shall be measured and recorded for informational purposes based on condensables on a Quartz Crystal Monitor (QCM) that is operated at - 20 deg-C. The measurement will be made in a chamber that has been certified clean (background outgassing rate and free of silicones and other high molecular weight contaminants) and has been modeled by the Contamination Analyst to account for mass sinks (cold fingers, pumps, cold surfaces, etc.) that could influence the source outgassing rate.

Rationale: Prop-39 per RST-PROP-REQ-0039; Section 4 per RST-SYS-SPEC-0033.

c. A cold finger and/or a scavenger plate shall be used in tests for components that will be mounted externally unless approved otherwise by the NASA/GSFC COR.

Rationale: Section 4.4 per RST-SYS-PLAN-0051.

6.2.3 Cleanability

6.2.3.1 Cleanability – Sensitive Surfaces

If any surfaces are not cleanable with Isopropyl alcohol and polyester wipes or light vacuuming, they shall be identified on the MICD.

Rationale: Section 4.3 per RST-SYS-PLAN-0051.

6.2.3.2 Cleanability – Sensitive Surface Cleaning Methods

Alternate cleaning methods shall be identified and appropriate documentation provided for any surfaces that are not cleanable with Isopropyl alcohol.

Rationale: Section 4.3 per RST-SYS-PLAN-0051.

6.2.4 Transportation Cleanliness

Materials and enclosure used for transportation and storage shall not generate molecular or particle contaminants or degrade the surface cleanliness of the item or adjacent items.

Rationale: Prop-39 per RST-PROP-REQ-0039; CS4 in RST-SYS-SPEC-0033.

7 DESIGN & CONSTRUCTION REQUIREMENTS

7.1 Parts, Materials & Processes (PMP)

7.1.1 EEE Parts

The thruster contractor’s Quality Assurance system for EEE parts will be in accordance with the requirements in the SOW, RST-PROP-SOW-0050.

7.1.2 Materials

The thruster will be comprised of materials and processes in accordance with the requirements in the SOW, RST-PROP-SOW-0050.

7.1.2.1 Material Conductivity

All mounting surfaces should be conductive as defined in Section 3.7.

7.1.3 Material Compatibility

7.1.3.1 Fluid Compatibility

The thrusters shall be fabricated with materials that are compatible with all fluids described below:

• Hydrazine per MIL-P-26536E (with amendment 1), High Purity Grade*

• Deionized water per JSC SPEC C20

• Isopropyl alcohol per TT-I-735, Grade A

• Nitrogen per MIL-PRF-27401, Grade B

• Helium per MIL-PRF-27407

• Argon per MIL-PRF-27415 (with amendment 1)

• Xenon, research grade

* Hydrazine compatibility is required for wetted components only.

Rationale: Encompass fluids used during ground operations and during the flight mission.

7.1.3.2 Passivation of Wetted Materials

All material surfaces that are wetted with propellant shall be passivated.

Rationale: Prevent chemical reactions with the hydrazine propellant.

7.2 Electrical

7.2.1 Interface Requirements

The thruster shall be delivered with a one (1) meter minimum flying lead harness length for the entire bundle.

Rationale: Provide necessary harness length for integration to a local electrical interface.

7.2.2 Wires

7.2.2.1 Wire Specifications

All internal wire types shall meet the Wire and Cable Requirements in Section W1 of EEE-

INST-002.

Rationale:…