CTSD-ADV-2241 Advanced Spacesuit Regulator End Item Specification - DRAFT 04222025.pdf

EAR ECCN 9E515

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ADVANCED SPACESUIT REGULATOR

END ITEM SPECIFICATION

for the Exploration Portable Life Support Subsystem (xPLSS)

Engineering Directorate (EA) Crew and Thermal Systems Division (CTSD)

Verify this is the correct version before use.

Date: April 21, 2025

Revision: Basic

CTSD-ADV-2241

National Aeronautics and Space Administration

Lyndon B. Johnson Space Center

Houston, Texas 77058

Contains Export-Controlled Information: EAR ECCN 9E515 ii

CTSD-ADV-2241

Revision: DRAFT

Engineering Directorate

Crew and Thermal Systems Division

National Aeronautics and Space Administration

Lyndon B. Johnson Space Center

Houston, Texas 77058

ADVANCED SPACESUIT REGULATOR

END ITEM SPECIFICATION FOR XPLSS

Approved by:

Thomas Smith / JETS Component Owner/Author

Sean Miller / EC2 Advanced Spacesuit Regulator Lead

David Westheimer / EC5 xPLSS Test Engineering

Robin Hetherington / JETS xPLSS M&P Chief Engineer

Lawrence Barrett / JETS xPLSS Thermal/Fluids Analysis Lead

David Autrey / EC5

DE SE&I

Carly Meginnis / EC5 xPLSS Hardware Lead

Advanced Spacesuit Regulator End Item Specification CTSD-ADV-2241

DRAFT

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REVISIONS

Rev Date Originator Description of Change/CRs Incorporated

Basic 4/21/2025 Thomas Smith Initial Release

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TABLE OF CONTENTS

Section Title Page

1 INTRODUCTION

Scope

Conventions and Notations

1.2.1 Rationale

1.2.2 Designations and Prioritization

1.2.3 “TBR” and “TBD”

1.2.4 “Reserved”

1.2.5 Nomenclature

Responsibility and Change Authority

2 DOCUMENTS

Applicable Documents

Reference Documents

3 ADVANCED SPACESUIT REGULATOR (ASR)

Overview

Functional Requirements [R.ASR.001-099]

3.2.1 Life

3.2.1.1 [R.ASR.001] Operational Life

3.2.1.2 [R.ASR.002] Useful Life

3.2.1.3 [R.ASR.003] Launch/Landing Cycles

3.2.1.4 [R.ASR.004] Mission Quiescence

3.2.2 Operating Fluid

3.2.2.1 [R.ASR.005] Gaseous Nitrogen

3.2.2.2 [R.ASR.006] Gaseous Oxygen

3.2.2.3 [R.ASR.007] Gaseous Heliox

3.2.2.4 [R.ASR.008] Gaseous Helium and Nitrogen

3.2.3 Pressure and Flow

3.2.3.1 Pressure Regulation and Flow

3.2.3.1.1 [R.ASR.009] POR Pressure Regulation and Flow (PRV-113)

3.2.3.1.2 [R.ASR.010] SOR Pressure Regulation and Flow (PRV-213)

3.2.3.2 [R.ASR.011] Pressures Table

3.2.3.3 [R.ASR.012] Fill-Port Back-Flow Prevention

3.2.3.4 [R.ASR.013] Inlet Flow of Fill-Port, Check-Valve, and Filter

3.2.4 [R.ASR.014] Inlet or Supply Temperature

3.2.5 Leakage

3.2.5.1 [R.ASR.015] External Leakage

3.2.5.2 Internal Leakage

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3.2.5.2.1 [R.ASR.016] Shut-Off Feature Open or Disengaged

3.2.5.2.2 [R.ASR.017] Shut-Off Feature Closed or Engaged

3.2.5.2.3 [R.ASR.018] Supply Check Valve Internal Leakage

3.2.6 [R.ASR.019] Mass

3.2.7 Reliablity

3.2.7.1 [R.ASR.020] First Stage Failure

3.2.7.2 [R.ASR.021] Fail Open Maximum Flow Rate

3.2.7.3 [R.ASR.022] Failure Mode: Catastrophic External Leakage

3.2.7.4 [R.ASR.023] Stepper Motor Hard Stop

3.2.7.5 [R.ASR.024] Redundant Seals

3.2.7.6 [R.ASR.025] Hazardous Materials Summary Table (HMST)

3.2.8 Oxygen Compatibility

3.2.8.1 [R.ASR.026] Cleanliness

3.2.8.2 [R.ASR.027] Filtration

3.2.8.3 [R.ASR.028] Contamination Tolerance

Interface Requirements [R.ASR.100-199]

3.3.1 [R.ASR.100] Structural & Mechanical Interfaces

3.3.2 Electrical – Motor

3.3.2.1 Functional Requirements

3.3.2.1.1 [R.ASR.101] Motor

3.3.2.1.2 [R.ASR.102] Back-Drive Force

3.3.2.1.3 [R.ASR.103] Pressure Mapping vs. Stepper Motor Step Count

3.3.2.2 Interface Definition and Electrical Characteristics

3.3.2.2.1 [R.ASR.104] Electrical Connector

3.3.2.2.2 [R.ASR.105] Electrical Connector Pinout

3.3.2.2.3 [R.ASR.106] Electrical Cable Length

3.3.2.2.4 [R.ASR.107] Motor Electrical Characteristics

3.3.2.2.5 [R.ASR.108] Motor Commutation Scheme

3.3.2.2.6 [R.ASR.109] Power Isolation

3.3.3 Electrical – Pressure Transducers

3.3.3.1 Functional Requirements

3.3.3.1.1 [R.ASR.141] Pressure Transducers

3.3.3.1.2 [R.ASR.142] Accuracy

3.3.3.1.3 [R.ASR.143] Drift

3.3.3.1.4 [R.ASR.144] Response Time

3.3.3.1.5 [R.ASR.145] Start-Up Time

3.3.3.1.6 [R.ASR.146] Limited Life – Calibration Period

3.3.3.2 Interface Definition and Electrical Characteristics

3.3.3.2.1 [R.ASR.147] Electrical Connector

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3.3.3.2.2 [R.ASR.148] Electrical Connector Pinout

3.3.3.2.3 [R.ASR.149] Applied Voltage

3.3.3.2.4 [R.ASR.150] Steady-State Current Draw

3.3.3.2.5 [R.ASR.151] Output

3.3.3.2.6 [R.ASR.152] Power Isolation

3.3.4 [R.ASR.170] Regulator Position Sensor

3.3.4.1 [R.ASR.171] Pressure Mapping vs. Position Sensor

3.3.4.2 [R.ASR.172] Regulator Position Sensor Power Isolation

3.3.5 [R.ASR.180] Remote Ambient Pressure Referencing

3.3.6 [R.ASR.190] Interstage Test Port (TP-160/TP-260)

Environmental Requirements [R.ASR.200-299]

3.4.1 Pressure

3.4.1.1 [R.ASR.200] Ambient Pressure – Operational

3.4.1.2 [R.ASR.201] Ambient Pressure – Non-Operational

3.4.1.3 Ambient Pressure Change Rate

3.4.1.3.1 [R.ASR.202] Decreasing – Operational

3.4.1.3.2 [R.ASR.203] Decreasing – Non-Operational

3.4.1.3.3 [R.ASR.204] Increasing – Operational

3.4.2 [R.ASR.205] Temperature – Operational

3.4.3 [R.ASR.206] Storage and Transport Temperature – Non-Operational

3.4.4 [R.ASR.207] Humidity – Non-Operational

3.4.5 [R.ASR.208] Gravitational Fields

3.4.6 Dynamic Loads

3.4.6.1 [R.ASR.209] Acceleration Load Factors – Lunar

3.4.6.2 [R.ASR.210] Acceleration Load Factors – ISS

3.4.6.3 Random Vibration

3.4.6.3.1 [R.ASR.211] Maximum Expected Flight Level (MEFL) – Lunar Launch

3.4.6.3.2 [R.ASR.212] Maximum Expected Flight Level (MEFL) – ISS Launch

3.4.6.3.3 [R.ASR.213] Acceptance/Workmanship Vibration

3.4.6.3.4 [R.ASR.214] Operating Vibration

3.4.6.4 [R.ASR.215] Combined Load Factors – Launch

3.4.6.5 [R.ASR.216] Sinusoidal Vibrational Loads as Packaged

3.4.6.6 [R.ASR.217] Mechanical Bench Shock

3.4.7 [R.ASR.218] Lunar Dust

3.4.8 [R.ASR.219] Direct Current (DC) Magnetic Field

3.4.9 [R.ASR.220] Atmospheric Composition

3.4.10 [R.ASR.221] Rapid Fluid Impact

3.4.11 [R.ASR.222] Particle Impact

3.4.12 [R.ASR.223] Ionizing Radiation

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3.4.13 [R.ASR.224] External Electromagnetic Environment

Design and Construction Requirements [R.ASR.300-399]

3.5.1 [R.ASR.300] Hardware Identification

3.5.2 [R.ASR.301] Internal Components Burrs/Sharp Edges

3.5.3 [R.ASR.302] Standard Materials and Process Requirements

3.5.4 Maintainability

3.5.4.1 [R.ASR.303] Like-Component Interchangeability

3.5.4.2 [R.ASR.304] Inadvertent Contact Load During Maintenance

3.5.5 [R.ASR.305] Mechanisms

3.5.6 [R.ASR.306] Class S Bond

3.5.7 [R.ASR.307] Metallic Pressurized Hardware

3.5.8 [R.ASR.308] Thin Wall Pressure Boundaries (TWPB) Best Practices

3.5.9 [R.ASR.309] Welds

3.5.10 [R.ASR.310] Fracture Control

3.5.11 [R.ASR.311] Electrical, Electronic and Electromechanical (EEE) Parts

3.5.11.1 [R.ASR.312] Component Burn-In

3.5.12 [R.ASR.313] Soldered Electrical and Electronic Assemblies

3.5.13 [R.ASR.314] Rigid Printed Wiring Boards

3.5.14 [R.ASR.315] Red Plague Control

3.5.15 [R.ASR.316] Conductor Size Standard

3.5.16 [R.ASR.317] Wire

3.5.17 [R.ASR.318] Disallowed Materials

3.5.18 [R.ASR.319] Dissimilar Metallic Materials

4 QUALITY CONTROL AND DELIVERY

Quality Control Requirements [R.ASR.400-449]

4.1.1 [R.ASR.400] Quality Management System

Acceptance Data Package Requirements [R.ASR.450-499]

4.2.1 Acceptance Data Package

4.2.1.1 [R.ASR.450] Acceptance Data Package

4.2.1.2 [R.ASR.451] ADP Non-Conformance

4.2.2 [R.ASR.452] Materials Identification and Usage List

4.2.3 Pressure Mapping

4.2.3.1 [R.ASR.453] Pressure Mapping vs. Stepper Motor Step Count

4.2.3.2 [R.ASR.454] Pressure Mapping vs. Position Sensor

4.2.4 [R.ASR.455] Hazard Analysis

4.2.5 [R.ASR.456] Failure Mode and Effects Analysis

5 VERIFICATION

Nomenclature

Verification Methods

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Verification Requirement

Verification Matrix

APPENDIX A ACRONYMS AND ABBREVIATIONS

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LIST OF FIGURES

Figure Page

Figure 3-1 – Mechanical Configuration of POR/SOR

Figure 3-2 – Motor Harness Length

Figure 3-3 – Motor Commutation Diagram

Figure 3-4 – Nominal Airlock Repress Profile

Figure 3-5 – Random Vibration Profile

Figure 3-6 – PLSS and HUT Mounted Random Vibration Profile (Zotek F30 foam)

Figure 3-7 – Component Acceptance/Workmanship Vibration Spectrum

LIST OF TABLES

Table Page

Table 2-1: Applicable Documents

Table 2-2: Reference Documents

Table 3-1: Symbol Key for Notional Schematics

Table 3-2: ASR Operating Life

Table 3-3: Primary Oxygen Regulation Modes, Pressures, and Flows

Table 3-4: Secondary Oxygen Regulation Modes, Pressures, and Flows

Table 3-5: Operating Pressures Table

Table 3-6: External Leakage

Table 3-7: Motor Electrical Connector

Table 3-8: Motor Electrical Connector Pinout

Table 3-9: Motor Electrical Characteristics

Table 3-10: Motor Commutation Scheme

Table 3-11: Pressure Transducer Descriptions

Table 3-12: Pressure Transducer Electrical Connectors

Table 3-13: Pressure Transducer Electrical Connector Pinout

Table 3-14: Gravitational Fields

Table 3-15: Lunar Design Load Factors for Launch Vehicles (Unknown Orientation)

Table 3-16: ISS Design Load factors for Launch Vehicles (Unknown Orientation)

Table 3-17: Random Vibration Profile

Table 3-18: PLSS and HUT Mounted Random Vibration Profile (Zotek F30 foam)

Table 3-19: Component Acceptance/Workmanship Vibration Spectrum

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Table 3-20: Operating Vibration Spectrum

Table 3-21: Load Factors Combination Criteria

Table 3-22: Ionizing Radiation

Table 3-23: EMI/EMC Applicability

Table 3-24: Component Corner/Edge Radius

Table 3-25: ASR Mechanisms

Table 3-26: TWPB Best Practices Applicability

Table 3-27: Wire Selection

Table 5-1: Verification Requirement Nomenclature

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1 INTRODUCTION

SCOPE

CTSD-ADV-2241, Advanced Spacesuit Regulator (ASR) End Item Specification for the Exploration Portable Life Support Subsystem (xPLSS), establishes the requirements for design, performance, and verification of the Primary Oxygen Regulator (POR) and Secondary Oxygen Regulator (SOR) as part of the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS). All requirements in this document apply to both the POR and SOR, unless stated otherwise. This document is derived from previous xEMU specifications for Oxygen Regulator, Actuator, and Sensor, with updated and modified requirements to create a generic, unified specification for new designs for Advanced Spacesuit Regulators.

CONVENTIONS AND NOTATIONS

1.2.1 RATIONALE

A rationale statement is included for each requirement. The purpose of the rationale statement is to indicate why the requirement is needed, the basis for its inclusion in a requirements document, and to provide context and examples to stakeholders. It is important to note that a rationale statement is not binding, and it only provides supporting information. In the event there is an inconsistency between the requirement and the rationale, the requirement is binding and takes precedence.

1.2.2 DESIGNATIONS AND PRIORITIZATION

The convention used in this document to indicate requirements, goals, and statements of fact is as follows:

Designation Description

“Shall” Used to indicate a requirement which must be implemented and its implementation verified.

“Should” Used to indicate a guideline which must be addressed by the design but is not formally verified if the requirement is deemed not applicable to the design (ie.

electrical motor characteristics). Hardware developers are expected to take the applicable guidelines into account during design to ensure the highest probability for mission success of the hardware. Failure to meet the guidelines will inherently incur risk that may or may not be tolerable to the funding organization and may have adverse impacts on critical Program resources. All “Should” statements are left as flexible requirements for the hardware developer to attempt to implement if they are applicable to the final design.

Each guideline has an associated verification submittal statement that is intended to assist the hardware developer with a recommended method for verification. If applicable, these verifications are expected to be performed during the qualification stage of hardware delivery.

“Will” Used to indicate a statement of fact and is not verified.

1.2.3 “TBR” AND “TBD”

In some cases, the values or quantities included in this document have not been determined and are designated as “to be resolved” (TBR) or “to be defined” (TBD). Where approximate values or quantities are known and provide useful guides for development, these are shown along with the TBR notation. Where no approximate value exists, a TBD designation is provided in the place of the value.

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1.2.4 “RESERVED”

In cases where an entire sub-paragraph has yet to be defined but is being carried to show the need for the definition, a designation of “reserved” is placed in the respective location.

1.2.5 NOMENCLATURE

Each requirement contained in this specification is denoted by a unique identifier [R.ASR.XXX] that transcends traditional paragraph numbering to keep require ments traceability clearer and more achievable.

001-099 – Functional Requirements

100-199 – Interface Requirements

200-299 – Environmental Requirements

300-399 – Design and Construction Requirements

400-499 – Quality Control and Delivery Requirements

RESPONSIBILITY AND CHANGE AUTHORITY

Control of CTSD-ADV-2241 and changes thereto lie with the xPLSS group within EC5/Space Suit and Crew Survival Systems Branch of the Crew and Thermal Systems Division (CTSD).

2 DOCUMENTS

The documents listed in this section represent the documents that have been identified in part or in whole within this document.

APPLICABLE DOCUMENTS

The applicable documents listed in Table 2-1 have been explicitly identified within requirements statements (i.e., "shall" statements) and invoked as technical requirements for implementation. Each requirement statement identifies the applicable subsections of a document unless it has been deemed appropriate to invoke the entire document.

Table 2-1: Applicable Documents

Document Number

Revision/ Release Date

Document Title

AIAA S-080 A-2018

03/01/2018

Space Systems - Metallic Pressure Vessels, Pressurized Structures, and Pressure Components

AS9100 D

09/20/2016

Quality Management Systems - Requirements for Aviation, Space, and Defense Organizations

CTSD-ADV-1552 A

03/31/2021

Electrical, Electronic, and Electromechanical (EEE) Parts Plan

CTSD-ADV-1599 Basic 10/30/2019

Fracture Control Plan for the Exploration Extravehicular Mobility Unit (xEMU) Project

IPC-2152 Basic 09/2009

Standards for Determining Current Carrying Capacity in Printed Board Design

IPC-2221 C

12/2023

Generic Standard on Printed Board Design

IPC-2222 B

10/2020

Sectional Design Standard for Rigid Organic Printed

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Document Number

Revision/ Release Date

Document Title

IPC-6012 F

09/2023

Qualification and Performance Specifications for Rigid Printed Boards

IPC-A-610 J

03/2024

Acceptability of Electronic Assemblies

IPC-WP-113 A

10-2021

Guidance for the Development and Implementation of a Red Plague Control Plan (RPCP)

IPC J-STD-001 JS

01/2025

Space and Military Applications Electronic Hardware Addendum to IPC J-STD-001J Requirements for Soldered Electrical and Electronic Assemblies

ISO 9001:2015 E

09/15/2015

Quality Management Systems - Requirements

JPR 1700.1 M

10/02/2024

JSC Safety and Health Requirements

JPR 5322.1 H, Revalidation 11/2020

Contamination Control Requirements Manual

JSC 27301 H

02/08/2024

Materials and Processes Selection, Control, and Implementation Plan for JSC Flight Hardware

JSC 27472 B

06/28/2006

Requirements for Submission of Data Needed for Toxicological Assessment of Chemicals to be Flown on Manned Spacecraft

JSC-67035 A

08/2017

Best Practices and Guidelines (BP&G) for Thin Wall Pressure Boundaries (TWPB) for Human Spaceflight Applications

MIL-PRF-27210 J

08/07/2013

Performance Specification for Oxygen, Aviators Breathing, Liquid and Gas

MIL-PRF-27401 H

08/24/2023

Performance Specification for Propellant Pressurizing Agent, Nitrogen

MIL-PRF-27407 E

04/23/2024

Performance Specification for Propellant Pressurizing Agent, Helium

MIL-STD-810 H, 1

05/18/2022

Department of Defense Test Method Standard:

Environmental Engineering Considerations and Laboratory Tests

MIL-STD-3010 C, 1

05/10/2023

Department of Defense Test Method Standard: Test Procedures for Packaging Materials and Containers

MSFC-STD-3029 A

02/24/2005

Guidelines for the Selection of Metallic Materials for Stress Corrosion Cracking Resistance In Sodium Chloride Environments

NASA-STD-4003 A,1

02/052013

Electrical Bonding for NASA Launch Vehicles, Spacecraft, Payloads, and Flight Equipment

NASA-STD-5006 A, 2

11/19/2021

General Welding Requirements for Aerospace Materials

NASA-STD-5017 B

12/06/2020

Design and Development Requirements for Mechanisms

NASA-STD-5019 A, 4

07/29/2024

Fracture Control Requirements for Spaceflight Hardware

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Document Number

Revision/ Release Date

Document Title

NASA-STD-6016 C, 1

11/15/2023

Standard Materials and Processes Requirements for Spacecraft

SAE AS5202 A

01/07/2013

Aerospace Standard, Port or Fitting End, Internal Straight Thread, Design Standard

SLN13102110 2

12/12/2024

Oxygen Regulator OML, Advanced EVA Regulators

SSP 30237 T

01/17/2012

Space Station Electromagnetic Emissions and Susceptibility Requirements

SSP 30234 H

09/28/2015

Failure Modes and Effects Analysis and Critical Items List Requirements for Space Station

REFERENCE DOCUMENTS

The documents listed in Table 2-2 are identified but are not invoked within requirements statements.

Table 2-2: Reference Documents

Document Number

Revision/ Release Date

Document Title

CTSD-ADV-780 B

07/12/2020

Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS)

CTSD-ADV-1564 Basic 12/04/2019

Life Cycle Model for the Exploration Portable Life Support Subsystem (xPLSS)

EHP-10012 A, C3

02/18/2025

Extravehicular Activity and Human Surface Mobility Program (EHP) Systems Requirements Document (SRD)

EHP-10029 Baseline 11/01/2024

Extravehicular Activity and Human Surface Mobility Program (EHP) xEVA System to Artemis Systems Interface Requirements Document (IRD)

ESCG-4470-12-

TEAN-DOC-0049A

A 11/16/2012

Advanced Extravehicular Mobility Unit PLSS Component Level External Leakage Rates

H-EMU-000-001 06/16/2000 SOP Contamination (REDR)

JSC 63309 Recommendations for Exploration Spacecraft Internal Atmospheres

JSC 65829 B

03/20/2024

Load Combination Criteria for Components

MIL-STD-130 N, 1

08/26/2019

Standard Practice: Identification Marking of U.S.

Military Property

NASA-STD-3001 V2

09/13/2023

NASA Spaceflight Human-System Standard Volume 2: Human Factors, Habitability, and Environmental Health

NASA-STD-6001 B, 2

04/21/2016

Flammability, Offgassing, and Compatibility Requirements and Test Procedures

SE-S-0073 F

02/20/1994

Space Shuttle Fluid Procurement and Use Control

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SMC-S-016 06/13/2008 Space and Missile Systems Center Standard: Test Requirements for Launch, Upper-Stage and Space Vehicles

SSP 30312 Vol. 1 L 10/24/2014

Electrical, Electronic, and Electromechanical (EEE) Parts Management and Implementation Plan for the Space Station Program

SSP 30423 L

10/27/2014

Space Station Approved Electrical, Electronic, and Electromechanical (EEE) Parts List

SSP 41172 U

03/28/2003

Qualification and Acceptance Environmental Test Requirements - International Space Station Program

SSP 50005 E

06/30/2006

International Space Station Flight Crew Integration Standard (NASA−STD−3000/T)

SSP 50021 Baseline, DNC5 08/13/2018

Safety Requirements Document

SSP 50835 E

06/19/2018

ISS Pressurized Volume Hardware Common Interface Requirements Document

SSQ 25001 E

07/21/2011

Electrical, Electronic, and Electromechanical (EEE) Parts Upgrade Screening and Qualification Requirements

TR-2004(8583)-1 Test Requirements for Launch, Upper Stage, and Space Vehicles

3 ADVANCED SPACESUIT REGULATOR (ASR)

This section contains the technical design and performance requirements for the Advanced Spacesuit Regulator (ASR).

OVERVIEW

The function of the ASR is to regulate the flow of stored high-pressure oxygen to serve the following purposes:

1) Provide breathing oxygen for pressurization and suit leakage makeup as well as metabolic consumption for the following operational modes:

a. Intravehicular Activity (IVA) prebreathe

b. Extravehicular Activity (EVA) variable (set points allowing for flexibility in prebreathe protocol)

c. Decompression Sickness Treatment

2) Provide breathing oxygen for ventilation via system purge valves for the following operational modes:

a. IVA prebreathe

i. Denitrogenation

b. EVA variable (set points allowing for flexibility in prebreathe protocol)

i. Convective cooling

ii. CO2 removal

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The ASR as envisioned is a multi-stage, non-venting, external pressure reference regulator assembly with a variable final stage that is commanded between the set pressure ranges using a differential signaling serial bus connection to an on-board controller. The assembly also incorporates filters, a fill-port check-valve, a shut-off capability, and all associated mechanisms/actuators to facilitate set-pressure changes based on electronic commands.

Two ASRs are employed in the xPLSS. One serves as the Primary Oxygen Regulator (POR), and the other serves as the Secondary Oxygen Regulator (SOR). In a nominal EVA, all oxygen regulation is provided by the POR; the SOR is only intended for contingency operations and redundancy. The POR and SOR shall be identical in design but will have differing set points as defined by their respective controllers CON-150 and CON-250. Therefore, the term Advanced Spacesuit Regulator (ASR) will be used to reference both the POR and SOR. If the requirement is specific to either the primary or secondary systems, the POR and SOR terminology will be used respectively. Figure 3-1 and Table 3-1 depict the pneumo-hydraulic layout of the POR and SOR as well as ties to the POR/SOR controller, CON-150/CON-250. The POR and SOR controllers are NASA owned hardware and are not within the scope of this End Item Specification (EIS).

Interfaces and electrical details for these controllers are TBD and should not be a main driver within this

EIS.

ASR mechanical interfaces and volume constraints are detailed in the ASR specification control drawing (SCD), SLN13102110, Oxygen Regulator OML, Advanced EVA Regulators. Interface requirements are defined in Section 3.3 of this document.

Figure 3-1 – Mechanical Configuration of POR/SOR

Table 3-1: Symbol Key for Notional Schematics

Symbol Description

Filter

Check Valve

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(3) One pressure cycle is defined as the increase from <10% MEOP to >90% MEOP and back down to <10% MEOP. MEOP is 3750 psia per Table 3-5.

(4) One cycle is defined as pressurization to proof pressure. Proof pressure is 1.5 MEOP = 5625 psia per Table 3-5.

(5) One cycle is defined as pressurization to structural pressure. Structural pressure is 1.1 MEOP = 4130 psia per Table 3-5.

(6) One pressure cycle is defined as <2% full-scale to >98% full-scale pressure and back to <2% full-scale pressure. A cycle life of 2,500 cycles meets the cycle projection of 2,000 which is based on 20 EVAs with a scatter factor of 100. The desire is to eliminate the need to deterministically track the pressurization cycles for these pressure transducers.

(7) If a stepper motor is used, a cycle is defined as Home (zero) position, followed by movement through full stroke, and then return to the Home position. A cycle life of 2,500 cycles meets the cycle projection of 2,000 which is based on 20 EVAs with a scatter factor of 100. The desire is to eliminate the need to deterministically track the cycles for these stepper motors.

Table 3-2: ASR Operating Life

Component Function Cycles (minimum)

Minimum Duration (hrs)

Regulators (1)(2) Regulation 1648 2970

Shut-off Valve or Feature Open/Close 389 ---

Assembly (3) Pressurization 124 ---

Assembly (4) Pressurization to Proof Pressure 2 ---

Assembly (5) Pressurization to Structural Pressure

2 ---

Pressure Transducers (6) Pressure Measurement 2500 ---

Actuator/Motor (7) Regulation 2500 ---

3.2.1.2 [R.ASR.002] USEFUL LIFE

The ASR shall have a useful life of 6 years minimum without refurbishment, assuming that the usage rate does not exceed operational life [R.ASR.001].

Rationale: Useful life refers to the maximum life of the ASR and is comprised of a combination of both the operational life and the shelf life. Useful life begins at the item’s birth date which can be initial acceptance, date of manufacture, date of cure, etc. and extends through the end of operational and/or shelf life. This provides a tracking clock from the time wetted service is started and is considered the total "lifetime" from birthdate of the hardware. This requirement loosely complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.002] Useful/ Service Life.

3.2.1.3 [R.ASR.003] LAUNCH/LANDING CYCLES

The ASR shall operate after 6 terrestrial launch and landing cycles.

Rationale: The intent is to dictate that the xPLSS will be designed for multiple launches and landings in support of its yet undetermined missions. The details of what each launch/landing cycle entails depends on the vehicle chosen but is encompassed by the requirements provided in Section 3.3.6 Environmental Requirements.

The selected value is capable of supporting a 6-year rotation plan for 2 decades with margin. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.004] Launch//Landing Cycles.

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3.2.1.4 [R.ASR.004] MISSION QUIESCENCE

The ASR shall be capable of operating and meeting requirements after 400 days of quiescent IVA stowage with a goal of 3 years.

Rationale: This requirement presents the capability to pre-position xEVA System hardware or survive long duration exploration transits. xEVA systems will spend significant periods of time without crew presence and must still be able to function after crew arrives. In the quiescent stowage configuration, the EVA Suit will not require any periodic maintenance, and will remain in this configuration until a contingency or planned EVA event is imminent.

The quiescent period starts at hardware delivery for launch and ends at first use, and then between uses if applicable.

This requirement complies with EHP-10012, Extravehicular Activity and Human Surface Mobility Program (EHP) Systems Requirements Document (SRD), [EHP-R-129] Quiescence Stowage.

3.2.2 OPERATING FLUID

3.2.2.1 [R.ASR.005] GASEOUS NITROGEN

The ASR shall be compatible and operate using gaseous nitrogen per MIL-PRF-27401H, Performance Specification for Propellant Pressurizing Agent, Nitrogen, Type I, Grade B as a test fluid.

Rationale: Gaseous nitrogen provides a safe and effective method for performing development tests prior to oxygen compatibility testing and approval. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.006] Gaseous Nitrogen.

3.2.2.2 [R.ASR.006] GASEOUS OXYGEN

The ASR shall be compatible and operate using gaseous oxygen (GOX) per MIL-PRF-27210J, Performance Specification for Oxygen, Aviator's Breathing, Liquid and Gas, Type I as the working fluid.

Rationale: Gaseous oxygen provides the ability to feed metabolic consumption at the lowest possible suit operating pressure. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.007] Gaseous Oxygen.

3.2.2.3 [R.ASR.007] GASEOUS HELIOX

The ASR shall be compatible and operate using a mixture of 0.5% +/- .02% helium per MIL-PRF-27407E, Performance Specification for Propellant Pressurizing Agent, Helium, with Amendment 1, Grade A with balance gaseous oxygen per MIL-PRF-27210, Type I as the working fluid.

Rationale: Gaseous heliox provides increased resolution for preflight leakage checks but is not anticipated as a working fluid during mission events. Heliox has been used for this purpose during the Shuttle/ISS EMU Program per SE-S-0073, Table 6.3-38. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.009] Gaseous Heliox.

3.2.2.4 [R.ASR.008] GASEOUS HELIUM AND NITROGEN

The ASR shall be compatible and operate using a mixture of 0.5% +/- .02% helium per MIL-PRF-27407E, Performance Specification for Propellant Pressurizing Agent, Helium, with Amendment 1, Grade A with balance gaseous nitrogen per MIL-PRF-27401H, Performance Specification for Propellant Pressurizing Agent, Nitrogen, Type I, Grade B as a test fluid.

Rationale: Gaseous helium provides increased resolution for preflight acceptance leakage checks but is not anticipated as working fluid during mission events. This is relevant to the Primary, Secondary, and Ventilation loops.

This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.010] Gaseous Helium and Nitrogen.

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3.2.3 PRESSURE AND FLOW

3.2.3.1 PRESSURE REGULATION AND FLOW

3.2.3.1.1 [R.ASR.009] POR PRESSURE REGULATION AND FLOW (PRV-113)

The POR, when set to the respective set-point, shall maintain the lower stage output differential pressures above the ambient reference pressure as specified in Table 3-3 across the range of inlet supply pressures.

As a goal, the POR should be continuously variable between the highest and lowest of the specified set-points.

Table 3-3: Primary Oxygen Regulation Modes, Pressures, and Flows

Outlet Set-point(2,7)

Output Differential Pressure psid

Ambient Reference Pressure psia

Inlet Supply Pressure(4) psia

Mass Flowrate(3) lbs/hr

0((2a) 0 8 to 15.2 400 to 3750 0.005(5)

1(2b) 0.9 +/- 0.2 Vacuum(1) to 15.2 400 to 3750 0.02 to 5.6

2(2c,6)

4.3 +/- 0.2 Vacuum(1) to 15.2 400 to 3750 0.02 to 5.6

3(2d,6)

5.0 +/- 0.2

4(2d6) 6.2 +/- 0.2 Vacuum(1) to 15.2 400 to 3750 0.02 to 5.6

5(2e) 8.2 +0.2/-0.4 Vacuum(1) to 15.2 400 to 3750 0.02 to 5.6

Rationale:

(1) Vacuum is defined for test purposes as < 1 torr (0.02 psia).

(2) These set-points enable the following types of operations:

(a) IV mode for airlock operations

(b) Elevated IV pressure (formerly storage mode for Suitport where the suit pressure is maintained above the triple point of water with margin while minimizing the suit leakage)

(c) EVA mode at lowest nominal working pressure for the suit

(d) EVA mode with elevated pressure for reduced prebreathe

(e) EVA mode with elevated pressure for reduced prebreathe or DCS treatment

(3) The upper band of the mass flowrate cannot exceed 4.08 kg/hr [9 lb/hr] for a suit-free volume of 56.6 L [2 cu ft] without exceeding the limitations of a pressure rate of change of 13.5 psi/min. The upper band is currently set to 5.6 pph based on legacy ISS EMU sizing with the functional demands for the SOR down at 1.7 pph and 3.4 pph for the low and high flow purge scenarios at EVA conditions. The higher flowrate does support a more expedient denitrogenation purge during IVA conditions in which the purge valve mass flowrates are higher. This is intended to satisfy requirement [R.PLSS.000.059] Ventilation Loop Pressurization Rate.

(4) The actual low end inlet pressure (ullage pressure) for the regulator operational range is expected to be around 250 psia. However, since the 5.6 lbm/hr is only applicable to select denitrogenation scenarios the intent is that this flow rate is not needed at lower tank pressures. Therefore, descreased regulator performance (flowrate less than 5.6 lbm/hr) is allowed below 400 psia inlet pressure range assuming the regulator can still meet its other performance requirements.

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(5) This is equivalent to the internal lock-up leakage of the regulator without engagement of a shut-off capability.

(6) This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.100.002] Regulation and Flow (PRV-113).

(7) Max allowable excursion of +/-0.5 psi for < 10 seconds.

3.2.3.1.2 [R.ASR.010] SOR PRESSURE REGULATION AND FLOW (PRV-213)

The SOR shall be capable of being set and maintaining the minimum set-points defined in Table 3-4 while varying the ambient and supply pressures as indicated.

Table 3-4: Secondary Oxygen Regulation Modes, Pressures, and Flows

Outlet Set-point

Output Differential Pressure

[psid]

Ambient Reference Pressure

[psia]

Inlet Supply Pressure(3)

[psia]

Mass Flowrate(2)

[lbm/hr]

0 0

8 to 15.2 400 to 3750 0.005(5)

1 3.6 +/-0.1

Rationale:

(1) Vacuum is defined for test purposes as < 1 torr (.02 psia).

(2) The upper band of the mass flowrate is presently set to >5.6 pph based on legacy ISS EMU sizing with the functional demands for the SOR down at 1.7 pph and 3.4 pph for the low and high flow purge scenarios at EVA conditions. The higher flowrate provides support for suit pressure regulation to cover larger hole sizes as well as a more expedient denitrogenation purge during IVA conditions in which the purge valve mass flowrates are higher.

(3) The actual low end inlet pressure (ullage pressure) for the regulator operational range is expected to be around 250 psia. However, since the 5.6 lbm/hr is only applicable to select denitrogenation scenarios the intent is that this flow rate is not needed at lower tank pressures. Therefore, descreased regulator performance (flowrate less than 5.6 lbm/hr) is allowed below 400 psia inlet pressure range assuming the regulator can still meet its other performance requirements.

(4) This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.200.002] Regulation and Flow (PRV-213).

(5) This is equivalent to the internal lock-up leakage of the regulator without engagement of a shut-off capability.

3.2.3.2 [R.ASR.011] PRESSURES TABLE

The ASR shall have operating pressures as described in Table 3-5.

Rationale: This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.012] Pressure Schedule.

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Table 3-5: Operating Pressures Table

Component Operating Pressure to MEOP

Structural Pressure

(1.1 x MEOP)

Proof Pressure

(1.5 x MEOP)

Burst Pressure

(2.5 x MEOP)

Regulator Inlet Supply Pressure

[psia] 0-3750(3) 4130 5625 9375

Regulator Interstage Pressure(2)

[psia] 0-3750(3) 4130 5625 9375

Regulator Outlet Pressure(1)

[psid] 0-10.6 11.7 15.9 26.5

Pressure Transducers - High Pressure Absolute(4)

(PT-112, PT-115, PT-215, PT-216)

[psia]

0-6000 6600 9000 15000

Pressure Transducers - Differential(5)

(DP-114, DP-214)

[psid]

0-15 16.5 22.5 37.5

(1) This test is assumed to occur at ambient sea-level conditions such that the differential pressure in the system is referenced to 1 standard atmosphere.

(2) This value is configuration-specific under nominal operating conditions, however, with the requirement to tolerate a failed-open first stage, this value becomes the same as the inlet supply pressure.

(3) This is a carry-over from the Maximum Expected Operating Pressure (MEOP) for the Primary and

Secondary Oxygen Vessel (POV/SOV) that is part of the Primary and Secondary Oxygen Assembly

(POA/SOA).

(4) The high-pressure absolute scale is driven by the 3750 MEOP for the primary and secondary oxygen systems, along with the need to be able to proof test these systems to 1.5X MEOP (5625 psia).

(5) The reference pressure for the differential pressure transducer ranges from 0 – 14.7 psia.

3.2.3.3 [R.ASR.012] FILL-PORT BACK-FLOW PREVENTION

The ASR fill-port shall include a back-flow prevention check-valve to prevent gas back-flow into the oxygen charging circuit in the event of a loss of supply pressure.

Rationale: The main purpose of this requirement is to prevent back-flowing from the xPLSS oxygen system into the vehicle supply. This check-valve also prevents the discharge of the Pressure Vessel (PV) through a leaking quick disconnect located near the xPLSS oxygen recharge ports. This requirement complies with CTSD- ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem

(PLSS):

[R.PLSS.100.003] Charge Gas Back-Flow Prevention (PRV-113)

[R.PLSS.200.003] Charge Gas Back-Flow Prevention (PRV-213)

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3.2.3.4 [R.ASR.013] INLET FLOW OF FILL-PORT, CHECK-VALVE, AND FILTER

The ASR fill-port inlet flow, with a maximum pressure source of 3750 psia, shall be no greater than 6 lbs/hr with a maximum pressure drop of 50 psid.

Rationale: This is loosely based on the original Shuttle EMU specification. It is, however, not the requirement for this check-valve and filter to limit the flow; that will be performed by an external orifice that is part of the xPLSS.

3.2.4 [R.ASR.014] INLET OR SUPPLY TEMPERATURE

The ASR shall operate with a gas supply temperature of -50°F to 250°F.

Rationale: This range is based on previous xPLSS thermal analyses. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.MP.001] Materials and Processes. Verify the range of temperatures doesn’t affect the material properties.

3.2.5 LEAKAGE

3.2.5.1 [R.ASR.015] EXTERNAL LEAKAGE

The ASR shall limit external leakage rates to less than those dictated in Table 3-6 at a pressure of 3000 psia and a temperature of 60°F.

Rationale: This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.015] External Leakage – Component Level.

Table 3-6: External Leakage

Component Allocation of External Leakage

GOX

(scch)

GOX

(lbm/hr)

PRV including pressure transducers 6.00 1.89E-05

PV to PRV Interface Fitting 1.00E-02 3.15E-08

PRV to Oxygen Ventilation Loop Fittings 2.00 6.30E-06

3.2.5.2 INTERNAL LEAKAGE

3.2.5.2.1 [R.ASR.016] SHUT-OFF FEATURE OPEN OR DISENGAGED

The ASR with shut-off feature in the “open” position shall limit internal leakage to 26.5 sccm (.005 lbm/hr) GOX with a source pressure of 3750 psia, and the regulator outlet pressures maintained at 0.1 - 0.3 psid above regulation set points.

Rationale: This is based on an allowable lock-up leakage that is ~30% of the allowable EVA leakage rate of the suit, not considering metabolic consumption. Leakage rates markedly higher than this would risk over-pressurizing the suit volume were the suit to be exceptionally leak-tight and the metabolic loading low. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS):

[R.PLSS.100.002] Regulation and Flow (PRV-113)

[R.PLSS.200.002] Regulation and Flow (PRV-213)

3.2.5.2.2 [R.ASR.017] SHUT-OFF FEATURE CLOSED OR ENGAGED

The ASR with shut-off feature in the “closed” position shall limit internal leakage to 6 scch (1.89E-05 lbm/hr) GOX with source pressure of 3750 psia.

Rationale: This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.015] External Leakage – Component Level.

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3.2.5.2.3 [R.ASR.018] SUPPLY CHECK VALVE INTERNAL LEAKAGE

The ASR shall limit the internal leakage to 6 scch (1.89E-05 lbm/hr) GOX with a tank pressure of 3750 psia and ambient pressure at the supply input fitting.

Rationale: This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.015] External Leakage – Component Level.

3.2.6 [R.ASR.019] MASS

The ASR should have a mass that is less than 6.7 lbs in flight configuration.

Rationale: This requirement loosely complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.023] PLSS Assembly Mass (Dry) with an added mass tolerance based on proprietary spacesuit development efforts.

3.2.7 RELIABLITY

3.2.7.1 [R.ASR.020] FIRST STAGE FAILURE

The ASR shall include a lower stage capable of meeting regulation and flow operating requirements in the event that the first stage "fails open.”

Rationale: This is intended to add internal redundancy to the ASR in order to increase system robustness. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS):

[R.PLSS.100.031] Primary Oxygen Regulator Failure Tolerance (PRV-113)

[R.PLSS.200.029] Secondary Oxygen Regulator Failure Tolerance (PRV-213)

3.2.7.2 [R.ASR.021] FAIL OPEN MAXIMUM FLOW RATE

In the event of a failed open regulator, the ASR shall limit the flow rate to 7.49 lbm/hr GOX at a supply pressure of 3750 psia and temperature of 40 °F.

Rationale: The maximum flow of a failed open regulator must be balanced by the suit system relief valve to prevent system overpressurization. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS):

[R.PLSS.100.006] Primary Oxygen Regulator Flow Limiting (PRV-113)

[R.PLSS.200.005] Secondary Oxygen Regulator Flow Limiting (PRV-213)

3.2.7.3 [R.ASR.022] FAILURE MODE: CATASTROPHIC EXTERNAL LEAKAGE

The ASR shall be designed such that no single credible failure shall result in an external leakage greater than 1.69 lbm/hr at an outlet pressure of 3.7 psia.

Rationale: The external leakage flow for all credible failure modes needs to be less than make-up flow from the secondary oxygen supply for the required abort time of 60 min. Credible failures will be defined in the Failure Modes and Effects Analysis (FMEA). This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.034] Leakage Beyond Secondary Oxygen Make-Up.

3.2.7.4 [R.ASR.023] STEPPER MOTOR HARD STOP

If a stepper motor is used, the ASR should incorporate a capability to prevent the motor from driving the regulator past the maximum outlet pressure set point. This capability should allow for nominal operation at the maximum set point (including the upper tolerance limit) but prevent the PLSS Relief Valves (RV) from being triggered. The system RVs are set to trigger at approximately 8.6 psid.

Rationale: This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.100.002] Regulation and Flow (PRV-113)

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3.2.7.5 [R.ASR.024] REDUNDANT SEALS

The ASR shall incorporate primary metallic with redundant elastomeric sealing or single metallic static seal (not mission serviceable) or redundant elastomeric seals.

Rationale: Primary metallic seals are preferable for high-pressure ports. Previous xPLSS contamination testing resulted in secondary elastomeric seal damage on the inlet port. The added reliability to metallic primary seals in the high-pressure portions of the regulator will mitigate this effect. Integrated metallic seals such as flare fittings are not considered serviceable in-mission as would be permitted via the replacement of an elastomeric o-seal, rather they are assumed to require replacement. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.047] Redundant Seals.

3.2.7.6 [R.ASR.025] HAZARDOUS MATERIALS SUMMARY TABLE (HMST)

The ASR shall obtain an HMST per JSC 27472, Requirements for Submission of Data Needed for Toxicological Assessments of Chemicals and Biologicals to be Flown on Manned Spacecraft.

Rationale: This is in compliance with SSP 50021, which invokes the SRP process per SRP 30599, which then invokes JSC 27472. Since NASA-STD-3001 [V2 6047] requires a Toxicity Hazard Level rating of THL3 or less and [V2 6048] prohibits a THL4 rating, the HMST (which documents the ratings) must be obtained via the process outlined in JSC 27472. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.REL.006] Hazardous Materials Summary Table (HMST).

3.2.8 OXYGEN COMPATIBILITY

3.2.8.1 [R.ASR.026] CLEANLINESS

The ASR shall be initially cleaned internally to Level 100A or better and maintained to Level 100 or better and cleaned externally to Level VC-S and maintained to Level GC per JPR 5322.1, Contamination Control Requirements Manual.

Rationale: The specified cleanliness level for the xPLSS pressure oxygen loops is Level 100A per CTSD-ADV-780.

This rating limits the Non-Volatile Residue (NVR) to less than 1 mg/ft2 and the particle size distribution below 100 microns. Both of these limits are administrative controls intended to mitigate kindling chain and particle impact ignition mechanisms, respectively. For ASR assembly, lubricants such as Braycote 601 are used to prevent binding or drag on moving parts precluding the ability to maintain an "A" designation for NVR. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.017] Cleanliness.

3.2.8.2 [R.ASR.027] FILTRATION

The ASR shall include, between all active details and in front of critical details, filter elements which are constructed of Nickel 200 mesh and rated to 10 microns nominal, 25 microns absolute.

Rationale: The selection of this filter size and the specification of locations seeks to mitigate the particle impact ignition mechanism. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS):

[R.PLSS.100.038] Primary Oxygen Loop Supply QD Filtration (QD-186)

[R.PLSS.200.035] Secondary Oxygen Loop Supply QD Filtration (QD-286)

3.2.8.3 [R.ASR.028] CONTAMINATION TOLERANCE

The ASR shall not ignite or indicate signs of combustion when operated with up to 100 mg/ft2 of dodecane hydrocarbon oil coating the wetted parts/passages.

Rationale: As a result of the system-wide EMU contamination failure (H-EMU-000—001) in which the entire Shuttle EMU fleet was shutdown to investigate hydrocarbon contamination of the primary and secondary oxygen systems including all interfacing systems, the EMU Secondary Oxygen Pack (SOP) now utilizes a gas mass tracking system to administratively mitigate the risk of kindling chain contamination of the I-213 SOP

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Regulator and other system components. In order to increase system robustness and avoid the same logistical nightmare for the xEMU, the regulator and components need to be designed to mitigate ignition in the presence of kindling chain contaminants. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.007] Gaseous Oxygen.

INTERFACE REQUIREMENTS [R.ASR.100-199]

3.3.1 [R.ASR.100] STRUCTURAL & MECHANICAL INTERFACES

The ASR shall have the interfaces detailed in specification-controlled drawing SLN13102110, Oxygen Regulator OML, Advanced EVA Regulator.

Rationale: This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), [R.PLSS.000.025] PLSS Assembly Outer Mold Line (OML).

3.3.2 ELECTRICAL – MOTOR

3.3.2.1 FUNCTIONAL REQUIREMENTS

3.3.2.1.1 [R.ASR.101] MOTOR

The ASR shall incorporate an electrical motor used to control the output pressures as defined in Table 3-3:

Primary Oxygen Regulation Modes, Pressures, and Flows and Table 3-4: Secondary Oxygen Regulation Modes, Pressures, and Flows.

Rationale: Although a specific motor type is not being defined, some details, including a control scheme, for a hybrid-stepper motor-based actuator are detailed in the following requirements. These requirements are meant to serve as a placeholder for alternative motor concepts that can meet the commutation scheme and electrical requirements provided in [R.ASR.107] Motor Electrical Characteristics and [R.ASR.108] Motor Commutation Scheme. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS):

[R.PLSS.100.005] Primary Oxygen Regulator Actuation (PRV-113)

[R.PLSS.200.006] Secondary Oxygen Regulator Actuation (PRV-213)

3.3.2.1.2 [R.ASR.102] BACK-DRIVE FORCE

The motor shall resist retraction with a force >80 lbf externally applied with the motor unpowered.

Rationale: The back-drive force is needed to ensure that the motor maintains position while unpowered. This is most applicable during a powerloss to the ASR motor or other failure senarios where the spacesuit is unable provide remote regulation of the ASR. This requirement complies with CTSD-ADV-780, Subsystem Specification for the Exploration EMU (xEMU) Portable Life Support Subsystem (PLSS), R.PLSS.000.075 Common Linear Actuator Attributes.

3.3.2.1.3 [R.ASR.103] PRESSURE MAPPING VS. STEPPER MOTOR STEP COUNT

If a stepper motor is used, a pressure mapping vs.