CTSD-ADV-959_-_AEMU_PLSS_Schematic_-_RevA_10-5-2017.pdf

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

REVISIONS

DATE AUTHOR DESCRIPTION REV. LETTER

6/18/2012 C. Campbell Baseline N/C 10/5/2017 C. Campbell Significant restructuring of content to move the schematic update details and history to CTSD-ADV-1205 Removed suit port from the operations description xEMU schematic, descriptions, and operations updates for

PLSS 2.5 design

A iii

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

TABLE OF CONTENTS

Section Page

Table of Contents ......................................................................................................................................................... iv

Figures........................................................................................................................................................................... v

Tables ............................................................................................................................................................................ v

1.0 Introduction

2.0 xEMU PLSS Schematic Description

2.1 PLSS Component Nomenclature Definition

2.2 Primary Oxygen Loop

2.3 Secondary Oxygen Loop

2.4 Oxygen Ventilation Loop

2.5 Thermal Control Loop

2.6 Auxiliary Thermal Control Loop (ATCL)

2.7 Vacuum Manifolds

2.8 Power

2.8.1 BATT-590 – Auxiliary Thermal Control Loop Battery

2.8.2 BATT-690 – PLSS Primary Battery

2.8.3 BATT-790 – PLSS Accessory Battery

2.8.4 CHGR-840 – PLSS Battery Smart Charger

2.9 Controllers/Caution and Warning System (CWS)

2.10 Radio/Antenna

2.11 Display and Control Unit (DCU-685)

3.0 xPLSS Operations Description

3.1 Suitport Configuration

3.2 Airlock Configuration

3.2.1 Assumptions

3.2.2 PLSS to PGS Mate/Demate Operations

3.2.2.1 PLSS to PGS Mating

3.2.3 PreEVA Checkout - Manual

3.2.4 PreEVA Checkout – Automatic

3.2.5 EVA Sequences

3.2.5.1 Suit Donning

3.2.5.2 Leakage Check

3.2.5.3 Purge-Prebreathe

3.2.5.4 Depress

3.2.5.5 EVA

3.2.5.5.1 Vacuum Feedwater Recharge

3.2.5.5.2 Primary/Secondary Oxygen Recharge/Top-off

3.2.5.6 Repress

3.2.5.7 Suit Doffing

3.2.6 PostEVA Servicing

4.0 Acronyms and Abbreviations

5.0 References

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Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

FIGURES

Figure Page Figure 2-1 – xEMU PLSS Pneumo-Hydraulic Schematic

Figure 2-2 – xEMU PLSS Harness Diagram

TABLES

Table Page Table 6-1 - ISS EMU Prebreathe Protocols for 4.3 psia EVA Pressure v

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

1.0 INTRODUCTION

The eXploration Extravehicular Mobility Unit (xEMU) Portable Life Support System (PLSS) has been in development for ~10 years, starting with component technology maturation that the Exploration Technology Development Program (ETDP) sponsored beginning in Fiscal Year (FY) 2008. The base schematic and technologies were chosen in 2007 after an extensive trade study that engaged the full EVA community between the Johnson Space Center (JSC) and Glenn Research Center (GRC). The eXploration PLSS (xPLSS) as it is called, has been designed within the confines of currently fieldable technologies to operate in the potential range of environments that could be experienced during a potential exploration mission:

low Earth orbit (LEO) o Microgravity o Low radiation o Vacuum ambient

Moon – CIS lunar o Partial gravity o Elevated radiation o Vacuum ambient

Mars o Partial gravity o Elevated radiation o Low pressure carbon dioxide (CO2) ambient

For the Mars environment, some additional components will be required, but the PLSS is being scarred to accept those components without a significant redesign.

Much like the Apollo Extravehicular Mobility Unit (EMU), Space Shuttle/International Space Station (ISS) EMU, and early Constellation Program (CxP) Space Suit Element designs, the Advanced Extravehicular Mobility Unit (AEMU) PLSS is part of a larger system composed of a Pressure Garment Subsystem (PGS) and Informatics Subsystem with vehicle interfaces to a traditional airlock like that of the ISS. The PLSS is charged with the same basic life support functions of the previous efforts:

Pressurization Oxygen ventilation Carbon dioxide, water, and trace contaminant removal Thermal control

The detailed requirements for these functions are housed in the PLSS Development Requirements, CTSD-ADV-780

(NASA, 2015).

This document provides an overview of the xPLSS, its basic operation, and provides operational procedural sequences.

2.0 XEMU PLSS SCHEMATIC DESCRIPTION

The AEMU PLSS pneumo-hydraulic schematic consists of the following basic loops:

Primary Oxygen Loop Secondary Oxygen Loop Oxygen Ventilation Loop Thermal Control Loop Auxiliary Thermal Control Loop Vacuum Access Manifolds

Together, these loops perform the critical life support functions that enable autonomous operation separated from a vehicle. In subsequent sections, the schematic and function of the subject loops will be explained in detail.

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

2.1 PLSS COMPONENT NOMENCLATURE DEFINITION

The AEMU PLSS schematic uses a simplified nomenclature definition as follows:

CCC-LLNN

CCC = Component Type Identifier

LL = Loop Identifier

NN = Physical Component Identifier

Filters are not called out separately from their larger assemblies, but rather are denoted by filter rating as shown in Table 2.1-3.

Component Type Identifiers

“CCC”

Component

CKV Check Valve CON Controller DN Drain Port DP Differential Pressure Transducer FM Flow Meter FN Fan

FSA Feedwater Supply Assembly GS Gas Sensor GX Gas Exchange Scrubber HV Hand Valve HX Heat Exchanger OR Orifice P Port

PG Pressure Gauge PMP Pump PRV Pressure Regulating Valve PP Pitot Probe PT Pressure Transducer PV Pressure Vessel QD Quick Disconnect RV Relief Valve S Feed-through

SOV Solenoid Operated Valve TCC Trace Contaminant Control TCV Thermal Control Valve TP Test Port TS Temperature Sensor VP Vacuum Access Port

Table 2.1-1 – Component Type Identifiers

Loop Identifiers “LL” Primary Oxygen Loop 1 Secondary Oxygen Loop 2 Oxygen Ventilation Loop 3 Thermal Control Loop 4 Auxiliary Thermal Control Loop 5 Vacuum Manifold 10

Table 2.1-2 –Loop Identifiers

Filter Identifier Rating

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

2.2 PRIMARY OXYGEN LOOP

The primary oxygen loop provides oxygen for pressurization, metabolic consumption, and leakage make-up. It also provides gas at flowrates up to 5.6 pph to facilitate denitrogenation purge using the suit purge valve (SPV). It consists of two main components: the Primary Oxygen Regulator (POR) and the Primary Oxygen Vessel (POV) with associated instruments and brackets/connections. For in-situ charging, the loop accepts gaseous oxygen (GOX) from quick disconnect (QD-686/886) with a nominal charge pressure of 3000 psia at 60℉, and a maximum design pressure of 3750 psia based on thermal excursion post charging, without demand to 145℉. The gaseous recharge rate is limited by multiple orifices in the recharge path, including one integral with QD-686, as well as one located at the base of the Service and Cooling Umbilical (SCU-801), all intended to limit adiabatic compression heating during the recharge process. Reverse leakage from the tankage is protected by both a check valve integrated into the POR as well as the QD-686 poppet, which is closed when the SCU is demated from the Display and Control Unit (DCU).

The POV stores ~1.7 lbm of usable oxygen, which is then fed to the POR, a two-stage motor-settable mechanical regulator capable of being remotely set to ~8000 set-points between 0 (shut-off) and 8.4 psid; nominal Extravehicular Activity (EVA) set-pressures will be in the range of 4.1-8.4 psid with 4.3 psid being the historical set-point known from Space Shuttle/ISS EMU. The specific set-points used are dictated by inputs to the POR Controller, CON-150 via the POR_SET switch on the DCU. The crew has the ability to set the POR to OFF (0 psid), 0.4, 0.9, 4.3, 6.2, and 8.2 psid via the POR_SET control, and the exploration mission can define the specifics of those set-points to any variant within the 8000-step range between 0-8.4 psid. The POR_SET provides six discrete IO lines, toggled from the knob, connected to three DPDT micro-switches, enabling the input commanding and logic to tolerate multiple discrete bit-flips without issuance of a false positioning command. When operating, the outlet of the regulator is fed directly into the oxygen ventilation loop just upstream of the interface pad between the PLSS and Hard Upper Torso (HUT) hatch where it, in short order, is routed to the helmet inlet in the PGS. The POV includes a Resistance Temperature Device (RTD) measuring wall temperature to improve the determination of available oxygen mass during usage. The POR includes inlet, interstage, and outlet pressure transducers to assess the health of the regulators and provide feedback to the regulator controller, CON-150. An ambient pressure sensor, PT-116 is not physically attached to the POR, but provides a feedback signal to CON-150. The linear actuator used to set the outlet pressure includes a secondary linear position sensor that is physically integrated with the drive shaft to validate positioning of the load spring. The motor phase currents are also monitored by the controller to validate in-family performance throughout life of operations. The CON-150 monitors all of the sensors attached to the regulator, commutates the linear actuator to set the pressure, accepts commands for the pressure set-point directly via physical switch throws on the DCU, locally identifies and reacts to faults within the controller, and sends telemetry back to the Caution and Warning System (CWS) for further fault detection and computation.

2.3 SECONDARY OXYGEN LOOP

The secondary oxygen loop provides the redundancy for oxygen loop life support functions, but at a lower ventilation loop pressure, and it provides redundancy for the remainder of the ventilation loop life support functions via open loop oxygen ventilation flow through the SPV. The loop provides oxygen for pressurization, metabolic consumption, leakage make-up, CO2 washout, as well as, humidity and trace contaminant control. Like the primary oxygen loop, the secondary oxygen loop consists of two main components: the Secondary Oxygen Regulator (SOR) and the Secondary Oxygen Vessel (SOV) with associated instruments and brackets/connections. For in-situ charging, the loop accepts GOX from a dedicated port on QD-686, which is mated on the SCU side of the QD-886, fully isolating the primary and secondary oxygen loops when the SCU is not present. Like the POV, the SOV possesses a nominal charge pressure of 3000 psia, and a maximum design pressure of 3750 psia, based on thermal excursion post charging, without demand to 145℉. The SOV stores ~1.7 lbm of usable oxygen, which is then fed to the SOR, an identical regulator design to the POR, a two-stage motor-settable mechanical regulator capable of being remotely set to ~8000 set-points between 0 (shut-off) and 8.4 psid, with a nominal set pressure of 3.7 psid. The SOR operates as a nested regulator set to 3.5-3.7 psid, ~0.4 psid below the POR nominal set range of 4.1-8.1 psid for EVA conditions. The SOR Controller, CON-250 is commanded directly by the SOR_SET switch on the DCU. The SOR_SET is a ganged set of two DPDT switches that provide four discrete IO lines toggled by the crewmember selection of “OFF” or “ON,” enabling the input commanding and logic to tolerate multiple discrete bit-flips without issuance of a false positioning command. When the SOR_SET is set to “ON,” the CON-250 commutates the actuator on the 2nd stage regulator to set the output pressure to 3.5-3.7 psid via a stored-step count that is continuously checked against the linear position sensor that is physically integrated with the drive shaft to validate positioning of the load spring. The CON-250 and SOR_SET commanding works independently of the CON-150 or other controllers in the PLSS as well as the CWS. When the POR can no longer maintain the set pressure in the 4.1-

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

8.4 psid range and the pressure drops to ~3.7 psid, the SOR, which has been sitting in lock-up waiting to regulate since the depress sequence will begin to regulate and hold the suit pressure at 3.5-3.7 psid. The outlet of the regulator is fed directly into the oxygen ventilation loop just upstream of the interface pad between the PLSS and HUT hatch where it, in short order, is routed to the helmet inlet in the PGS. The SOV includes an RTD measuring wall temperature to improve the determination of available oxygen mass during usage. The SOR includes inlet, interstage, and outlet pressure transducers to assess the health of the regulators and provide feedback to the regulator controller, CON-250. The motor phase currents are also monitored by the controller to validate in-family performance throughout life of operations. The CON-250 monitors all of the sensors attached to the regulator, commutates the linear actuator to set the pressure, accepts commands for the pressure set-point directly via physical switch throws on the DCU, locally identifies and reacts to faults within the controller, and sends telemetry back to the CWS for further fault detection and computation.

2.4 OXYGEN VENTILATION LOOP

The oxygen ventilation loop provides for CO2 washout, humidity control, trace contaminant removal, and PGS inlet gas temperature control. To accomplish this, a centrifugal fan is used to move the loop at flowrates variable between 3 to 8 acfm with nominal set-points between 4.5 to 6 acfm. The goal of the integration with the redesigned Zsuit HUT/helmet is to lower the flowrate required for the ISS EMU Space Suit Assembly (SSA) (Apollo A7LB helmet) at 6 acfm to something closer to 4.5 acfm to save fan power and reduce the PLSS volume/mass. In following the schematic return from the Liquid Cooling and Ventilation Garment (LCVG) extremities, the ventilation flow is returned through the Trace Contaminant Control (TCC-360) cartridge, which includes a fine particulate filter and activated charcoal-trace contaminant scrubber. The final selection of the particular scrubber design will be influenced by multiple options presently being pursued under Small Business Innovative Research (SBIR), and assessment of applicability of products such as Ammonasorb II for Barnebey Sutcliffe (a phosphoric acid wash-coated activated charcoal capable of adsorbing NH3, as well as a wide range of trace contaminants).

From the TCC-360, ventilation gas flows through the hatch feed-through to the PLSS interface pad, and into an inlet header for the fan tree, which includes the RV-348 Secondary Positive Pressure Relief Valve (SPPRV), and returns from both of the multi-gas sensors. The RV-348 provides 2-fault tolerance to over-pressure failures from failed regulators, and single-fault tolerance to over-pressure failures due to RV-346 failure during airlock depress. Under nominal operations, the ventilation gas then flows into the FN-323, Primary Fan, which applies work to move the gas through the ventilation loop discharging the gas through an outlet check valve (CKV-325). Under a primary fan or other functional loss failure, the FN-324 Secondary Fan may be activated. FN-324 is identical to FN-323 for commonality, but through-out its life as a cold-spare unit, it will see much lower operating hours. When either fan is on and moving ventilation loop gas through its outlet check valve, the check valve on the opposing fan is checked and prevents back-flow. From the outlet of the fan manifold, the suit return multi-gas sensor (GS-300) uses the fan head-rise to sample a small stream ~150 sccm of the gas to determine the CO2 and water (H2O) content before it enters the GX-380, Rapid Cycle Amine (RCA) swing-bed. The RCA uses a special formulation of amines, referred to as SA9T, that are implemented in a two-bed thermally interconnected system, in which one bed adsorbs CO2/H2O from the ventilation loop, accepting gas from the fan outlet, and the other bed desorbs CO2/H2O to vacuum. When the CO2 readings from the helmet inlet gas sensor (GS-322) reaches a determined value, depending on the chosen algorithm (3mmHg for PLSS 2.0), the Ventilation Loop Controller, CON-350, commutates a rotary stepper actuator with integrated Rotary Variable Differential Transformer (RVDT) to position a rotary ball valve stack first to an equalization position, in which the both beds are isolated from both vacuum and the ventilation. At this point, the desorbing bed that is regenerated is equalized with the adsorbing bed that is saturating at about half of the suit pressure (~2.2 psia during an EVA at 4.3 psia). The valve is then moved to complete the bed swing connecting the regenerated bed to the ventilation loop and the saturated bed to the vacuum source to begin the next half-cycle. For PLSS 2.0 using a CON-350 prototype, the cycle time was reduced to <3 seconds, with the equalization time <1 second. Under conditions in which the gas sensor (GS-322) has failed, CON-350 will revert to a conservative time-based cycle, which is designed to remove enough CO2 for a high metabolic rate. During the bed-transition operation, the CON-350 positions the beds via step counting on the rotary actuator with position checks from the RVDT, and should the checks fail, the CON-350 can then position the bed via hard stop at the end of travel. From the RCA outlet, the ventilation gas travels to the HX-340 ventilation loop sensible heat exchanger where heat added by the fan and RCA is removed and cool dry gas exits where the ventilation loop temperature sensor (TS-320) senses the gas temperature headed to the PGS inlet. The heat exchanger is designed as a linear flow element, allowing a small mass flow meter attached to the HX-340 to measure the mass flow rate for the ventilation loop with the volumetric flow calculation determined by the CWS using the suit pressure calculated from the DP-114 or DP-

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

214. For conversion to the open loop flow configuration, the RCA may be in the OFF position permitting no flow through the component, or the outlet check valves on the fans will preclude the reverse flow. Just before the gas reaches the PLSS interface pad to hatch interface, a pitot probe (PP-391) pulls a small stream of gas (~150 sccm) through a sample line with a filter and orifice back to the helmet inlet gas sensor (GS-322), which then quantifies the species of H2O and CO2. The sample gas is then returned to the inlet of the fan using the pressure drop across the spacesuit to drive the flow. The clean, dry, low humidity, low CO2 gas is fed into the PGS and onto the oro-nasal region of the crewmember. At this point, the crew inspires the inlet gas and expires gas with elevated CO2 and humidity, which is washed downward by the inlet gas flow, and eventually out to the extremities where it is picked up and recirculated through the system. The CON-350 is controlled directly by the crew via mechanical switches located on the DCU. The RCA_SW offers three positions, CO2 – OFF – TM. In the CO2 position, the CON-350 monitors the GS-322 and performs a bed half-cycle when the CO2 value reaches a trip limit. In the OFF position, the rotary ball valve is parked precluding flow through either bed, and isolating both beds from each other and from either the ventilation loop or vacuum manifold. In the TM position, the CON-350 maintains a counter and performs a bed half cycle on a fixed-time interval. The FAN_SW offers three positions: PRI – OFF – SEC. In the PRI position, the CON-350 commutates the primary fan motor at a fixed speed. For the OFF position, the controller does not commutate fan motors and sits in quiescent mode monitoring the attached sensors and sending telemetry.

In the SEC position, the CON-350 commutates the secondary fan motor at a fixed speed. The power for the primary versus secondary fans are fed from independent power feeds from the main PLSS power bus, each with independent current limiters in the CWS. The CON-350 is capable of operating, regardless of the operation of other controllers.

Additional components located on the PGS include the Positive Pressure Relief Valve (PPRV) and SPV. The PPRV protects the suit and oxygen ventilation loop from over-pressurization in the event that either the POR or SOR fail open; it would also protect the suit during an airlock depress where the ambient pressure decrease is faster than the combined suit leakage, RCA ullage loss, and metabolic consumption. The SPV enables a nominal function for denitrogenation purge that occurs at the beginning of every EVA as the suit environment is transitioned from a mixed gas to a single gas oxygen environment. The SPV also enables the redundant life support function of the secondary oxygen loop, in which the valve is actuated to enable the open loop-purge mode needed; the SPV would offer the 30-minute abort time at the higher flow rate. The helmet purge valve will offer the lower purge flow capable of the longer abort time when accompanied by the Auxiliary Thermal Control Loop (ATCL).

2.5 THERMAL CONTROL LOOP

The thermal control loop performs primary thermal control for the suited crewmember and the PLSS. The loop is designed and sized to accommodate metabolic waste heat, electronics waste heat, and environmental heat leak in hot environments with the maximum rejection design point of 810W. To accomplish this, the loop includes a Feedwater Supply Assembly (FSA) that uses the suit ventilation loop pressure to compress the compliant bladder, which then pressurizes the thermal loop fluid to approximately the same pressure as the ventilation loop (slightly less given work performed on the bladder). This enables redundant pressurization for the thermal loop as the POR or the SOR can pressurize the thermal loop, meaning that a loss of the primary oxygen supply does not necessitate an open-loop abort as the secondary is capable of enabling the thermal loop operation. Water usage from the FSA is tracked by the Caution and Warning System (CWS-650) via utilization computed from the Spacesuit Water Membrane Evaporator (SWME). Should an external leakage occur which renders the utilization calculation invalid, a secondary leakage detection method using staged check valves is employed to offers a pressure drop signature at the input to the thermal loop pump (PT-432) with ~ 1 lb of feedwater remaining to enable an orderly termination on primary resources. After the FSA pressurizes the fluid, the fluid travels out of the PGS and into the PLSS where the LCVG outlet temperature sensor (TS-400) measures the water temperature via an insertion style RTD. Next, the fluid contacts the thermal control loop pressure sensor (PT-432), which measures the absolute loop pressure just prior to the pump inlet. The pump (PMP-423) moves the entire loop via an external gear positive displacement pump powered by a Brushless Direct Current (BLDC) motor running at a speed set by the thermal loop controller (CON-450). The nominal thermal loop flow is 200 pph, which is maintained throughout Intra-Vehicular Activity (IVA) and EVA operations. A cold-spare secondary pump (PMP-422) provides the ability to continue EVA operations or make an orderly termination in the event of a primary pump failure. It is independently switched from the pump switch (PUMP_SW) on the Display and Control Unit (DCU-685), fed by a redundant powerline and current limiter from the CWS-650, and commutated by a redundant BLDC controller in the CON-450. With the implementation of a positive displacement pump with high efficiency, the pump design is capable of generating higher pressures under a dead-head condition than can be tolerated by the other components in the thermal loop. As

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959 a result, a dual-bypass relief valve (RV-424) is placed across the pump outlet to inlet. In the event that a restricted flow-fault condition occurs, the bypass relief valve will open at ~15 psid to limit the overall pressure experienced by the other thermal loop components. From the pump outlet, the thermal loop fluid is pushed through the liquid side of the ventilation loop heat exchanger (HX-340); as noted in Section 2.4, this heat exchanger provides sensible cooling of the helmet inlet gas, as well as integrated ventilation loop flow measurement. From the HX-340 outlet, the thermal loop fluid moves out of the PLSS through the S-5 port, through the hatch on the Z-HUT, through the integrated water lines in the HUT, and into the DCU-685 common quick disconnect (QD-686). For operations in which the Service and Cooling Umbilical (SCU-801) is present and mated, the thermal loop fluid moves out toward the vehicle heat exchanger to enable vehicle-supplied cooling. That fluid returns to QD-686 where it is then routed back through the Z-HUT, and then through the finest filter in the thermal loop (F-448), before re-entering the PLSS at port, S-4. For operations in which the SCU-801 is not present, the QD-686 connects the vehicle interface inlet/outlet ports in a bypass, and then returns the fluid back through the Z-HUT, and then through the finest filter in the thermal loop (F-448), before re-entering the PLSS at port, S-4. Upon returning to the PLSS, the fluid is routed to the SWME (HX-440) inlet, which includes an absolute pressure sensor (DP-425A) and an RTD insertion probe temperature sensor (TS-441). As the fluid flows through the inner diameter of the ~28000 hollow-fibers, the back-pressure on the outside of the fibers is maintained via a stepper actuator controlled back-pressure valve such that the desired outlet temperature observed from the SWME is achieved. The exhaust water vapor is then rejected through the back-pressure valve to space vacuum. The latent cooling from the evaporation of a small portion of the thermal loop fluid then cools the remaining fluid passing through the SWME. Any gas entrained in the fluid is also removed at this point, as it readily passes through the membrane and out to space vacuum. This enables the system to be primed and wetted from dry, to remove incidental bubbles that could be introduced with mating/demating of loop QDs, and bubbles that could evolve from dissolved gases coming out of solution during reduced pressure operations.

As the fluid leaves the SWME (HX-440), it immediately contacts an RTD insertion probe temperature sensor (TS-

439) and an absolute pressure sensor (DP-425B). The outlet temperature sensor (TS-439) is used to control the SWME back-pressure position to achieve the 50℉ (10℃) set-point for the outlet water temperature. The two temperature sensors (TS-441 and TS-439) are used, along with other parameters such as the thermal loop flow-rate, to compute the heat rejection of the SWME and its associated water utilization. The two pressure sensors are used to determine the pressure drop across the SWME, which is then used to determine the thermal loop flow, along with competing computations from the positive displacement pump. From the SWME outlet instruments, the fluid enters the Thermal Control Valve (TCV-421), which is a linear actuator-based spool valve that either directs all flow through the LCVG, around the LCVG via a bypass, or some ratio in-between with a resolution of ~8000 steps. The TCV-421 position is manually controlled by the TCL_SET knob located on the DCU-685; it may also be controlled in an automated sense by the Auto-Cooling Control (ACC) algorithm running in the CON-450 if the TCL_SET is placed in ACC mode. At this point, the CON-450 computes a local metabolic rate based on the thermal loop heat balance, adjusts for ambient heat leak by measuring the values of the Thermal Micrometeoroid Garment (TMG) temperatures (TS-442, TS-443, TS-444, TS-445), and considers a comfort bias factor, then positions the TCV-421 as dictated by the control algorithm outputs to maintain crew comfort. The crew can over-ride this method at any time by manually positioning the TCL_SET to a given set-point. From the TCV outlet, the fluid flows either back to the pump inlet on a bypass leg or into the Z-HUT via P-5, through the hatch lines, to the Water Line Vent Tube Assembly (WLVTA), and ultimately to the Liquid Cooling and Ventilation Garment (LCVG) where the water effects heat removal from the skin of the crewmember. An inadvertent outcome of this approach is that, as the water temperature is reduced during periods of high metabolic activity to enable greater heat transfer to the water with a limited skin temperature range, the water tubes across the LCVG enclosed in the Pressure Garment form a shell and tube condensing heat exchanger in which all moisture pressure with a dewpoint above the water temperature condenses onto the LCVG. The increased moisture present increases the overall heat transfer coefficient for the LCVG (UA), which enables increased heat rejection from the crewmember. Upon subsequent low metabolic rate activity periods with warmer water temperatures in the LCVG, the ventilation loop slowly removes the condensed moisture via the RCA (GX-380). On the LCVG outlet/PLSS thermal loop return line, the FSA-431 provides make-up feedwater and sets the pressure for the loop based on the suit ventilation loop pressure as described earlier.

2.6 AUXILIARY THERMAL CONTROL LOOP (ATCL)

The ATCL provides redundancy for the primary thermal control loop life support functions, but at diminished capability designed to support an EVA abort to the vehicle safe haven for 60 minutes. The system sits idle with a dedicated auxiliary thermal loop controller (CON-550) monitoring instruments for health status determination during the EVA while operating on the primary system. When the crew determines that the primary loop has been

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959 lost and wishes to engage the ATCL, the ATCL_SW is set to “ON,” which signals to the CON-550 to turn on the ATCL pump and to open the back-pressure valve on the auxiliary evaporator (HX-540). The operation of these devices is powered independently from the primary systems using a dedicated battery, the ATCL battery (BATT- 590). This battery is constructed from the same battery modules that make up the primary and accessory batteries, but is dedicated to the ATCL alone. The ATCL consists of a small FSA of similar construction to the primary FSA, but sized for the reduced duration of 60 minutes. The fluid loop is fully redundant to the primary thermal loop in order to eliminate the single point failure of thermal control loop fluid leakage disabling both the primary and redundant functions. The pressurized fluid travels from the auxiliary FSA (FSA-531) through the Z-HUT hatch lines, through the P-6 port at the PLSS/HUT interface pad, to the pump inlet pressure sensor (PT-532). The PT-532 monitors the inlet pressure to the pump to detect the depletion of the FSA-531 and determine if PMP-500 is operating in the cavitation pressure range. The auxiliary thermal loop pump (PMP-500) moves the fluid via a positive displacement pump (same design as the PMP-423/PMP-422) with a lower speed set-point to achieve a nominal 100 pph flowrate and a reduced overall operating life requirement. With the implementation of a positive displacement pump with high efficiency, the pump design is capable of generating higher pressures under a dead-head condition than can be tolerated by the other components in the ATCL. As a result, a dual-bypass relief valve (RV-524) is placed across the pump outlet to inlet; this is the same component as the RV-424, but in a different location within the PLSS. In the event that a restricted flow-fault condition occurs, the bypass relief valve will open at ~15 psid to limit the overall pressure experienced by the other loop components. From the pump outlet, the ATCL fluid is moved to the inlet of the auxiliary evaporator (HX-540) also known as the Mini-Membrane Evaporator (Mini-ME). This component borrows heavily from commonality with the primary components using the same hollow-fiber module that is used in the SWME (HX-440); the SWME uses three of these modules. The stepper actuator back-pressure valve is also the same as that used on the primary system. The operation of the evaporator, is however, much simpler in that it is either ON or OFF and does not perform thermostatic control functions like the SWME. The HX-540 operates in a topping capacity to control heat storage for 60 minutes below 300 BTU in a neutral thermal environment with the low flow open loop ventilation flow from the helmet mounted purge valve (~1.7 pph). Like the SWME, the HX-540 directly cools the ATCL fluid flowing through its ~9300 hollow-fibers and also degasses the ATCL by directly removed entrained gas. The cooled ATCL fluid moving from the outlet of the HX-540 encounters the TS-501 RTD insertion probe thermal sensor, which monitors the fluid temperature leaving the unit. As stated, this sensor does not feed a thermostatic control loop, but is present instead to enable a functional checkout of the system at the start of each EVA. Because the HX-540 is wetted and sitting dormant under nominal operations, the TS-502 RTD insertion probe style temperature sensor is placed into the core of the hollow-fiber bundle as a direct verification that the fibers have not frozen precluding proper function. This could occur should the back-pressure valve on the HX-540 fail to close or leak during the EVA sequence with the ATCL fluid stagnant in the hollow-fibers. From the TS-502 temperature sensor, the ATCL fluid moves from the PLSS into the Z-HUT via the P-7 port and once inside the hatch volume enters the F-548 ACTL filter, the finest filter in the ATCL and one that is serviceable with access to the hatch cover. After the F-548 filters particulate from the ATCL fluid, it moves into a dedicated core torso run of tubing on the LCVG. This core torso minimizes the impact of the incorporation of the ATCL, while providing the maximum effective cooling for this function. The ATCL fluid, moving through the LCVG core torso run, pickups up waste heat from the crewmember’s core and transports it at ~100 pph. Leaving the LCVG outlet, the loop returns to the dedicated Feedwater Supply Assembly

(FSA-531).

2.7 VACUUM MANIFOLDS

With the removal of requirements to support SuitPort, the vacuum manifold requirements have been simplified. To enable the vacuum access required by the Rapid Cycle Amine (GX-380) to desorb the adsorbed CO2 and H2O, the vacuum manifold provides a ~1-in. line from the GX-380 rotary ball valve location within the PLSS, and transfers it to the back-plate where it is routed to an accessible location on the front of the suit (near DCU QD). For the airlock IVA configuration, a vacuum access jumper would be connected to the manifold to enable the RCA to desorb while the suit ambient was at cabin pressure. For the EVA configuration, the port would be open and enable desorption to available space vacuum. A pressure sensor, PT-1001 is included on the manifold line to enable the Caution and Warning System (CWS-650 to monitor the status of the manifold for the purpose of ensuring that proper operating conditions exist for the RCA.

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

The PLSS accessory battery (BATT-790) is responsible for powering Crit 3 loads such as the helmet camera, heated gloves, informatics, helmet lights, aux data port, dosimeter, and storage similar to that of the Rechargeable EVA Battery Assembly (REBA) on the ISS EMU Program. BATT-790, consists of two common battery modules of the same design as those used in BATT-690.

2.8.4 CHGR-840 – PLSS BATTERY SMART CHARGER

With the implementation of passive battery modules, the health status and hazard controls for the Lithium Ion chemistry are implemented in the “smart” charger. The PLSS implements a single Mighty-Mouse 805 85 pin charge-port connector that directly and independently accesses each battery module to provide a dedicated recharge current and monitor an integrated thermal sensor, full-string voltage, and mid-string voltage while charging. The charge profile will be a constant current-constant voltage (CC-CV) profile to trickle cut-off. Additional screening functions will be included to verify battery health during pre-charge and charge operations.

2.9 CONTROLLERS/CAUTION AND WARNING SYSTEM (CWS)

The PLSS operates with distributed controllers that are responsible for low-level functions such as motor commutation and sensor monitoring with internal telemetry streamed to the Caution and Warning System (CWS- 650). Some of the functions performed by the respective controllers are discussed in the relevant sections, but for summary purposes, the list of controllers is as follows:

CON-150 – POR Controller:

113E)

Signaling (LVDS) communications interface

CON-250 – SOR Controller:

interface

CON-350 – Oxygen Ventilation Loop Controller:

o Commutates the rotary stepper actuator positioning the GX-380 bed between A, B, equalize, and lock-up positions

isolated power input from the CWS o Excites and monitors attached instruments (GX-380F, PT-1001, DP-321, TS-320, FN-323D, FN-

324D) o Provides power to the attached multi-gas sensors (GS-322 and GS-300), then reads the RS-485 full-duplex output telemetry stream (this was set due to commonality with the ISS EMU InfraRed Carbon Dioxide (IRCO2) sensor replacement effort)

CON-450 – Thermal Loop Controller

isolated power input from the CWS

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959 o Excites and monitors attached instruments (TS-441, TS-439, DP-425A, DP-425B, PT-432, TS-

400, TS-442, TS-443, TS-444, TS-445, TCV-421C, HX-440D, PMP-423D, PMP-422D)

CON-550 – ATCL Controller:

monitoring functions.

interface Much like what is done in a modern car, the controllers are distributed such that they accept a single battery or vehicle supplied power rail, in this case, at ~28VDC. The controllers, as a result, are more modular as the interface to the PLSS is simplified to power, LVDS communications, and a few discretes, but does not involve monitoring or managing a series of power rails such as 12V, 5V, 3.3V, etc., since the controllers can make whatever is required to perform the functions on their side of the interface. The controllers are also physically located near the actuators being driven and near the sensors being excited and monitored as an On-orbit Replaceable Unit (ORU)-able part of the system. The controllers have isolated command inputs from the DCU-685, which each controller excites, and which the inputs return to that same controller. This means that should a controller fail or should the DCU display fail, the other controllers will continue to operate and respond to the DCU switches.

The Caution and Warning System (CWS-650), much like its ISS EMU namesake, is a monitoring system, not a control system. The CWS receives telemetry from all of the attached controllers, converts the raw counts to engineering units for PLSS instruments, packages the telemetry for downlink over ultra-high frequency (UHF) and through an isolated diagnostics port, computes consumables valves selecting the limiting consumable to determine EVA time, computes states and state transition logic, computes augmented parameters for system health/error checking, computes fault detection logic, generates messages for the DCU, generates tones for the radio to internal audio interface, communicates the messages to the DCU for display to the crew, accepts switch inputs from the crew via the DCU (CWS_SW, PWR_SW) to operate soft-menus for manipulation of the software, switches power between SCU-supplied vehicle power and internal battery (BATT-690), provides power distribution and current limiting to attached loads within the PLSS, directly monitors internal health sensors, monitors the BATT-690 voltage/current, then provides automated sequences such as leakage checks, purge timers, and prebreathe profile clocks.

2.10 RADIO/ANTENNA

The EV-701 Radio is powered by a current limited primary power bus feed from the CWS-650. It accepts telemetry from the CWS, and then makes a Time Division Multiple Access (TDMA) connection to the Space-to-Space Communications System (SSCS), specifically to the Space-to-Space Station Radio (SSSR) to enable communications with other EVA spacesuits and to transfer suit telemetry to the vehicle and then to ground. The Space-to-Space Advanced EMU Radio (SSAER), as the EV-701 is often termed, is a functional redesign of the Space-to-Space EMU Radio (SSER) currently flying on the ISS EMU. It seeks to implement the functions performed by the SSER, but in a Field Programmable Gate Array (FPGA) that is reconfigurable and capable of supporting future exploration needs with UHF communications. It also seeks to implement radio redundancy throughout, taking what has been implemented in the SSER, and further improving upon it for redundancy.

The antenna is intended to be a patch-style antenna with one located on each side of the PLSS main structure. Each antenna would be directly tied to one of the dual-redundant UHF radios within the EV-701 assembly.

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

2.11 DISPLAY AND CONTROL UNIT (DCU-685)

The DCU is attached to the anterior of the Z-HUT and serves as the main crew interface for control of the PLSS.

The DCU performs the following functions:

Provides the suit side of the common QD connection of vehicle services: oxygen, thermal loop/aux thermal loop, power, communications, data Provides thermal and auxiliary thermal loop fluids interface to the SSA HUT Provides the critical message display to the crew Provides physical controls for critical functions that are directly tied to the PLSS controllers Provides a physical suit pressure gauge reading with clear visibility to the crew Provides connections from the HUT to the SPV for hand access (either hand) with visible verification Provides control of power supply switching or transfer between vehicle and on-board power Provides an automated checkout connection to enable remote commanding of switch positions

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

3.0 XPLSS OPERATIONS DESCRIPTION

The PLSS Operations Description defines behavior of the PLSS in conjunction with the larger xEMU System, while interfacing with various vehicle configurations. This is not intended to replace the xEMU Operations Concept Document, but rather to provide a more detailed description of how the PLSS is expected to operate in context of the xEMU Operations Concept for the purpose of requirements development and PLSS design.

3.1 SUITPORT CONFIGURATION

DELETED

The suit port configuration was removed from xPLSS requirements and is no longer being pursued.

3.2 AIRLOCK CONFIGURATION

Given that the pre-launch processing, pre-launch stowage, and post-return destow operations are dependent on the details of the Program and vehicle architecture needs, these areas are not considered at this point. Rather, the focus of this behavioral description is spent on the pre-EVA, EVA, and post-EVA operations details. This section focusses on the airlock style of vehicle-to-suit interface with special consideration for the airlock interface style presently available on the ISS.

3.2.1 ASSUMPTIONS

Cabin pressure = 14.7 +0.5/-0 psia Cabin mixture = 21% oxygen (O2) balance N2

3.2.2 PLSS TO PGS MATE/DEMATE OPERATIONS

Depending on the particular launch configuration, logistical needs for suit sizing, or inflight maintenance (IFM) operations, the PLSS may be removed from or installed onto the PGS.

For cost savings related to launch adapter development, it is expected that the PLSS will be launched to the ISS in the Short Extravehicular Mobility Unit (SEMU) Launch Adapter in an M03 bag. This will be separate from the DCU and HUT as the SEMU stack-up, because the suit is too large to fit.

3.2.2.1 PLSS TO PGS MATING

PLSS Assembly:

1. Destow the PLSS and remove protective cover from the PLSS interface pad

2. Clear the TMG from the mating interfaces

3. Mount the PLSS into the EMU Don/Doff Assembly (EDDA)

4. Open the hatch and remove the protective cover

5. Verify/disconnect the Water Line Vent Tube Assembly (WLVTA)

6. Verify/disconnect the comm/biomed connector

7. Depin the hatch from the HUT

8. Take hatch, and engage the two lower mushroom bolt/trailer hitches onto the PLSS

9. Hatch can be rocked out from the PLSS at the top by ~10 deg

10. Mate the HUT interface pigtail connector to the hatch

11. Inspect and make sure that no FOD is present at the hatch to PLSS interface pad

12. Rock the hatch back into the PLSS interface pad and start the 4 captive fasteners

13. Torque the four fasteners to XX in-lbs

14. Hang the PGS onto the hatch and re-pin the hinges

15. Open the hatch (swing the suit out)

Schematics and Behavioral Description for the Advanced EMU (AEMU) Portable Life Support Subsystem (PLSS) CTSD-ADV-959

DCU Assembly

NOTE: If this is to be performed in the ISS Equipment Lock as assumed, position the HEPA filtered air hose such that core flow is encompassing the oxygen connections at the PLSS backplate.

7. Carefully remove the PLSS side connector cap on the primary oxygen loop connection.

NOTE: This may vent a small amount of oxygen depending on the leakage of the regulator check valve. We may have to add steps and a tool to vent this line before mating if we want to protect for leakage from the check valve on the regulator assembly. ISS EMU depressurizes the tankage as a precaution; that is another option but will come with complications as venting both charged tanks on two suits will dump 7-8 lbs of oxygen into the airlock and take 30+ minutes at maximum regulator flowrates especially if there is a desire to get below ullage pressure. We could also look at the implementation of a QD here but it would involve greater complexity, pressure losses, etc to improve an infrequent operation.

8. Remove the connector caps and mate the DCU to PLSS primary high pressure oxygen line to the primary oxygen line connection.

9. Remove the connector caps and mate the DCU to PLSS secondary high pressure oxygen line to the secondary oxygen line connection.

3.2.3 PREEVA CHECKOUT - MANUAL

This section focusses on the suit…