Attachment B1- EHP-10069_Rev A_Final.pdf

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EHP-10069

REVISION A

National Aeronautics and Space Administration

EFFECTIVE DATE: SEPTEMBER 23, 2025

LUNAR SURFACE INTEGRATION PHASE

POWER SPECIFICATION

Verify that this is the correct version before use.

Revision: A Document No: EHP-10069

Release Date: SEP 23 2025 Page: 2 of 116

Title: Lunar Surface Integration Phase Power Specification

This document has been approved for public release per DAA # 20250010797

REVISION HISTORY PAGE

Revision No.

Change No.

Description Release

Date

Baseline EHP- C0630

Initial release - approval and release authorized by signed Directive EHP-D0630

09/18/2024

A EHP-

C0962

• Applicability refined for Lunar Surface Phase programs and Design Reference Missions (DRMs)

• Closure of several TBX items

• Removal of Interface III and deletion of all associated requirements

• Multiple "shall" statements revised to "will" to reflect non-binding factual declarations or intent

• Deletion of select redundant or outdated requirements to improve consistency and remove conflicts with parent-level documentation

• Clarification added to support alignment with M2M-R-0083 and supporting architecture documentation

• Overall update to comply with Lunar Surface Phase Integration Specification Template - Addition of HLS program effectivities and Nomenclature Update

09/23/2025

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TABLE OF CONTENTS

SECTION PAGE

1.0 INTRODUCTION

1.1 Purpose

1.1.1 Ground Rules and Assumptions

1.2 Scope

1.3 Lunar Surface Phase Applicability

1.4 Mission Effectivity

1.5 Requirement Language

1.6 Measurement Units

1.7 Change Authority/Responsibility

2.0 DOCUMENTS

2.1 Applicable Documents

2.2 Reference Documents

2.3 Order of Precedence

3.0 REQUIREMENTS

3.1 Surface System Self Compatibility with Quality of Provided Power

3.1.1 Power Exchange

3.1.2 Surface Payloads (Utilization)

3.1.3 xEVA System Interfaces

3.2 External Power Requirements

3.2.1 Power Management and Distribution

3.2.2 Normal Operations

3.2.3 Abnormal Operation

3.2.4 Integrated Subsystem Architecture

3.2.5 Universal Subsystem Performance Requirements

3.3 Physical Characteristics

3.4 Reliability

3.5 Maintainability

3.6 Safety

4.0 VERIFICATION

4.1 Requirement Verification

4.1.1 Responsibilities

4.1.2 Verification Approach

4.1.3 Verification Methods

4.1.4 Verification Matrix

5.0 RISKS

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TABLES

Table 1.1-1 Lunar Power Exchange Ground Rules and Assumptions Table 1.5-1 Convention and Notations Descriptions Table 2.1-1: Applicable Documents Table 2.2-1: Reference Documents Table 3.1-1 Interface Capabilities Table 3.2-1 Trip Protection Setpoints Table 3.4-1 Lunar Power System Environmental Stressors Table 4.2-1: Verification Matrix Table B-1: To Be Determined Table B-2: To Be Resolved Table C-1: Surface System Project Allocation Matrix Table D-1: Design Reference Mission Description Table E-1: Commonly used Connector Pin-Out Functions Table E-2: Cross Reference Connector Design Requirements Table G-1: Human-Rated Spacecraft Power & Electronics Standards

FIGURES

Figure 1.1-1 External Power Exchange Interconnect 7 Figure 3.2-1 Interface Definition 19 Figure 3.2-2 Normal Operations EPS Interface Definition 22 Figure 3.2-3 Normal Load Step Transient – EPS (Transmit Interface 24 Figure 3.2-4 Normal Load Step Transient - EPS (Receive Interface) 25 Figure 3.2-5 Interface Stability 26 Figure 3.2-6 Nyquist Stability 26 Figure 3.2-7 Source Impedance Interface Definition 26 Figure 3.2-8 Source Impedance Magnitude (Transmit) 28 Figure 3.2-9 Source Impedance Phase (Transmit) 28 Figure 3.2-10 Source Impedance Magnitude (Receive) 29 Figure 3.2-11 Source Impedance Phase (Receive) 29 Figure 3.2-12: Large Signal Stability - EPS 31 Figure 3.2-13 Surface System EPCE Normal Transient Response - Transmit 35 Figure 3.2-14 Surface System EPCE Normal Transient Response - Receive 35 Figure 3.2-15 Load Impedance Interface Definition 37 Figure 3.2-16 Load Impedance Magnitude (Transmit) 38 Figure 3.2-17 Load Impedance Phase (Transmit) 38 Figure 3.2-18 Load Impedance Magnitude (Receive) 39 Figure 3.2-19 Load Impedance Phase (Receive) 39 Figure 3.2-20: Large Signal Stability 41 Figure 3.2-21 Abnormal Voltage Transients - EPS 44 Figure 3.2-22: EPS Non-Normal Voltage Range – Transmit 45 Figure 3.2-23 EPS Non-Normal Voltage Range –Receive 45 Figure 3.2-24 Abnormal Voltage Transient – EPCE 49 Figure 3.2-25 EPCE Non-Normal Voltage – Receive 50

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1.0 INTRODUCTION

The Lunar Surface Integration Phase is responsible for integrating Extravehicular Activity and Human Surface Mobility Program (EHP) (xEVA System, Lunar Terrain Vehicle (LTV), Pressurized Rover (PR), Human Landing System (HLS) Program (Integrated Lander, Human-Class Delivery Lander (HDL), and Multi-Purpose Habitat (MPH)) on the lunar surface. EHP is the delegate lead for the Lunar Surface Integration Phase in accordance with M2M-30003, Moon to Mars (M2M) Systems Engineering Management Plan. In leading the Surface Phase, EHP will integrate with other programs that interface with Extravehicular Activity (EVA) suits and mobility assets on the surface. The Lunar Surface Integration Phase Specifications contain requirements which ensure interoperability, and compatibility across the lunar surface architecture as it evolves with each

Artemis mission.

Establishing a unified power interface on the lunar surface is essential to establishing reliable lunar surface operations. Potential failures including solar array deployment issues, solar tracking errors, vehicle damage, interruptions in power supply and full battery recharging, etc. can all lead to reduction in power availability and lead to loss of a vehicle or limit operations. Implementing an adaptable, standardized power exchange capability that enables energy sharing among multiple assets can increase overall reliability and operational success.

The lunar south polar region experiences significant variations in illumination conditions as documented in the M2M-30044, Lunar Surface Data Book. During certain portions of the lunar year, there is significantly more and longer eclipse periods that drive the energy storage requirements. During these periods of extended darkness, there is limited ability to generate power from solar arrays. An external power exchange interface enables dynamic energy sharing between surface assets, ensuring operational continuity if local generation or storage falls. Nearby assets can compensate, maintaining critical mission functions. By facilitating interoperability across systems, the standardized power exchange interface simplifies integration of new technologies, eliminating the need for complete power architecture redesigns.

1.1 PURPOSE

Due to the multi-lateral nature of interfaces on the lunar surface (each surface asset may interface with every other surface asset in some capacity), managing interface requirements by traditional Interface Requirement Documents (IRDs) is not viable. For that reason, Lunar Surface requirement specifications serve multiple purposes, including specifying performance requirements to successfully meet M2M campaign objectives, ensuring interoperability, and establishing common interfaces for the Lunar Surface Architecture. This is accomplished by deriving system- and subsystem-level performance requirements from parent-level functional requirements, tailoring international interoperability standards, and establishing interface requirements that ensure compatibility between any systems that meet the Specification.

The EHP-10069, Lunar Surface Phase Power Specification defines technical requirements and interface parameters necessary for external power exchange interoperability across applicable lunar surface assets. It is a critical enabling specification that supports multi-lateral operations across mobility, infrastructure, and augmentation systems. This specification directly addresses [M2M-R-0083] Lunar Exploration Power Exchange from the M2M-30002, Artemis Requirements Document (ARD), which requires Artemis surface elements to have the capability to send and/or

Release Date: SEP 23 2025 Page: 6 of 116 receive power through an external interface. EHP-10069 defines the interface characteristics, performance thresholds, and verification methods necessary to meet the intent of [M2M-R-0083].

These requirements are also integrated into the broader Lunar Surface integration architecture through EHP-10147, Artemis Lunar Surface IRD <TBD-EHP-10069-040>, which levies EHP- 10069’s power interoperability content, alongside other domain specific specs (communications, navigation, software) across applicable Artemis Programs.

While EHP-10069 defines technical interoperability content, its content is:

• Driven top-down by M2M-30002, ARD [M2M-R-0083]

• Flowed down through EHP-10147 <TBD-EHP-10069-040> to assure cross-system interface compatibility on the Lunar Surface

Excluded from governing xEVA system interfaces (governed in EHP-10029, Extravehicular Activity and Human Surface Mobility Program (EHP) xEVA to Artemis Systems IRD) and xEVA compatibility interfaces (governed in EHP-10028, Extravehicular Activity and Human Surface Mobility Program (EHP) xEVA System Compatibility Standards). EHP-10069 is therefore a key implementing document for cross-program power interoperability within the M2M campaign and a foundational spec to enable architecture-level flexibility and resilience.

The purpose of this document is to define external power interface and power quality requirements specific to power exchange hardware operating within the Lunar Surface Integration Phase. These requirements address the interoperability of electrical power systems at external interfaces, such as mobility vehicles, habitation modules, landers, and external power augmentation systems.

EHP-10069 provides the technical basis for power system interoperability. including allowable transients, impedance, and interface stability parameters, which are referenced and levied through higher-tier integration documents. These definitions help ensure safe and effective external power exchange across interconnected lunar surface power systems.

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FIGURE 1.1-1 EXTERNAL POWER EXCHANGE INTERCONNECT

Figure 1.1-1 illustrates the standardized 120 Vdc interface defined in EHP-10069, showing how generation sources, mobility vehicles, and multi-purpose habitats connect into a common power exchange domain. Power generation can be provided by solar arrays, fission surface power, and fuel cells/batteries, each capable of delivering energy into the domain through a 6 kW-rated, one to one, universal interface rated at 120Vdc nominal. On the consumer side, the MPH, LTV, PR, and other pre-formulation lunar surface elements (including landers, logistics modules, and future rovers) draw from or contribute to this interface. Arrows denote directionality of exchange, with the PR identified as receive-only and other assets supporting bi-directional transfer.

1.1.1 Ground Rules and Assumptions

TABLE 1.1-1 LUNAR POWER EXCHANGE GROUND RULES AND ASSUMPTIONS

A.1 Surface assets will be capable of sending and/or receiving power from sources external to and separate from the element power systems.

A.2

Surface assets required to externally recharge battery will design their system such that their battery can receive power from the power exchange interface for recharging.

A.3

Physical connectors at the power exchange interface will be designed to support peak power requirements, ensuring compatibility with a 6 kW-rated universal hardware interface for reliable and efficient energy transfer.

A.4

External power exchange will occur via standardized and ruggedized connectors, ensuring compatibility across various operational scenarios, including human EVA crew interaction and externally robotic-assisted connections.

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TABLE 1.1-1 LUNAR POWER EXCHANGE GROUND RULES AND ASSUMPTIONS

A.5 Mechanical power connectors will not be powered when disconnected and cannot be manually disconnected/connected unless unpowered.

A.6

The actual power available or absorbed at any given time depends on environmental factors, upstream generation and storage status, and competing demands across interconnected assets. Therefore, interface ratings should not be interpreted as a guarantee of continuous supply or acceptance capability across all operational periods.

1.2 SCOPE

The scope of the Lunar Surface Integration Phase Power Specification is to provide additional context and decomposition to requirement [M2M-R-0083] Lunar Exploration Power Exchange captured in the M2M-30002, Moon to Mars (M2M) Artemis Requirements Document (ARD), tailor the International Space Power System Interoperability Standard (ISPSIS), and establish common interfaces for Electrical Power System (EPS)/ Electrical Power Consuming Equipment (EPCE) within the lunar surface power architecture.

All requirements within this specification drive common interfaces. Therefore, these requirements are expected to be implemented in interface control documents (ICDs) between all the applicable interfacing systems. This may also drive joint interface verification between interfacing systems, as described in Section 4.0 Verification.

This document ensures commonality, reliability, safety, and power interoperability between Lunar Surface Systems. External power exchange is designed to be highly adaptable and to support a range of use cases that include conceptual external power augmentation, distributing power to core loads in off-nominal scenarios, powering mobile vehicles, supporting lunar habitats, and enabling the formation of a larger, resilient lunar power grid. This flexibility is essential for both immediate operational needs and long-term scalable infrastructure development on the Moon and, eventually, on Mars.

1.3 LUNAR SURFACE PHASE APPLICABILITY

The requirements in this specification are applicable to the development of all Lunar Surface Integration Phase Programs/Projects. Each requirement contains the Allocation to the Artemis Systems along with first design reference mission (DRM) effectivity

Agreements for both EHP and HLS allocations will be controlled and decomposed through a centralized Lunar Surface Integration Phase Specification Allocation and Effectivity Matrix EHP- 10172 <TBR-EHP-10069-038>. For the purposes of this document, “Artemis Lunar Surface System” is considered to include the following:

• EHP: LTV, PR

• HLS: Integrated Lander, HDL, MPH <TBR-EHP-10069-038>

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Government Furnished Equipment (GFE) hardware is included in the respective Program/project documentation responsible for completing its certification.

Additional details on the definition of each Artemis System are documented in EHP-10147, Artemis Lunar Surface Interface Requirements Document <TBD-EHP-10069-040>.

1.4 MISSION EFFECTIVITY

Lunar Surface Design Reference Mission (DRMs) are found in M2M-30007, Artemis Integrated

Concept of Operations.

DRM 3: Lunar surface sortie configuration at the south pole consisting of only HLS (Initial Capability) and xEVA, with two astronauts on the lunar surface. This is the expected DRM for

Artemis III.

DRM 4: Lunar surface sortie configuration at the south pole consisting of only HLS (Sustained Capability) and xEVA, with two astronauts on the lunar surface. This is the expected DRM for

Artemis IV.

DRM 5: Lunar surface sortie configuration at the south pole consisting of HLS, xEVA, and LTV, with two astronauts on the lunar surface. This DRM also adds the option of Gateway EVAs from the Gateway Airlock Module starting Artemis VI. DRM 5 is the expected DRM for Artemis V and

VI.

DRM 6: Lunar surface sortie configuration at the south pole consisting of HLS, xEVA, LTV, and PR, with two astronauts on the lunar surface. This DRM also includes the option of Gateway

EVAs from the Gateway Airlock Module. This is the expected DRM for Artemis VII.

DRM 7: Lunar surface sortie configuration at the south pole consisting of HLS, xEVA, LTV, PR, and MPH, with four astronauts on the lunar surface. This DRM also includes the option of

Gateway EVAs from the Gateway Airlock Module. This is the expected DRM for Artemis VIII.

Other DRMs may eventually be added for non-polar lunar surface sorties, and for further development of the Artemis Basecamp.

1.5 REQUIREMENT LANGUAGE

The convention used in this document which indicates requirements and statements of facts is as shown in Table 1.5-1, Convention and Notations Descriptions. This table and its conventions and descriptions only applies to designations employed in requirement statements in Section 3.0. It does not apply to designations employed in verifications in Section 4.0.

Release Date: SEP 23 2025 Page: 15 of 116 systems and allows any surface asset, regardless of size or mission phase, to utilize a common power interface.

Mission Applications and Benefits

Extended Lunar Access: In regions with prolonged darkness or poor solar access, power exchange allows assets to remain operational without relying solely on onboard energy reserves.

For instance, a system with 250-hour storage may support operations over 10 km², compared to just 1 km² for a 100-hour system.

Crewing Flexibility: The interface supports both crewed operations, such as habitat life support or EVA turnaround times, and uncrewed operations such as rover hibernation recovery, and uncrewed recharge cycles.

Contingency Support: In off-nominal scenarios, such as solar degradation, unexpected load increases, or environmental damage, systems can receive supplemental energy from neighboring assets to maintain critical functionality.

Energy Sharing Across Missions: Systems with surplus power can deliver energy to others operating at a deficit. This collaborative approach reduces redundancy, increases effective range, and improves mass efficiency across the surface architecture.

Adaptive Power Routing: Reconfigurable interfaces allow energy to be dynamically redirected in response to asset availability, status, or localized power interruptions. This improves resilience and continuity for time-sensitive or safety-critical functions.

Environmental Planning Considerations

Long-duration power planning is supported by Lunar Orbiter Laser Altimeter (LOLA)-derived illumination data from the Lunar Reconnaissance Orbiter (LRO), which models site-specific solar conditions over the 18.6-year lunar precession cycle. These datasets identify areas of limited solar exposure and inform interface placement, system sizing, and use-case prioritization.

Shadow modeling helps determine when to rely on external energy sources during unfavorable illumination periods.

LOLA digital elevation model products are publicly available through the NASA Planetary Geodesy Data Archive Portal and are recommended for use in energy planning simulations and architectural analysis. https://pds-geosciences.wustl.edu/missions/lro/lola.htm.

Surface Systems Power Exchange

Artemis Lunar Surface Systems will be capable of transmitting or receiving power at a nominal voltage of 120 Vdc to or from another lunar surface asset, using an interface with hardware rated for 6-kW. The 6-kW hardware rating establishes the universal baseline for the Lunar Surface Power Exchange interface. All participating surface assets, whether generating, consuming, or relaying power, are expected to interoperate on this 6-kW standard. This ensures a common physical and electrical foundation across the architecture, simplifying integration, logistics, and future extensibility. The 3 kW and 5 kW interface ratings are not independent interface types but scaled applications of the 6-kW universal interface. They exist only to

Release Date: SEP 23 2025 Page: 16 of 116 accommodate elements of different size and power demand, preventing unnecessary oversizing for small systems. The differences between these ratings are limited to switchgear sizing and minor impedance adjustments; the underlying hardware capability and interoperability remain anchored in the 6-kW universal design.

It must be emphasized that this is a 6-kW universal interface. The lower nominal ratings are provided solely to ensure compatibility for smaller elements and should not be interpreted as alternate baselines. Elements must be designed to their true power demand and not undersized simply to align with a 3 kW or 5 kW designation. By maintaining this universal 6 kW standard, Artemis Lunar Surface Systems gain plug-and-play compatibility, balanced redundancy, and simplified extensibility. This approach reduces the risk of fragmentation, ensures resilient power exchange across nominal and contingency operations, and supports the long-term scalability of the lunar power architecture.

Subsystem Power

The implementation of a standardized power exchange architecture is critical to sustaining lunar surface operations and enabling energy resilience across mission-essential assets. Core mobility and habitation elements, not limited to the LTV, PR, and MPH, are equipped with power transfer capabilities to ensure continuous operation under variable surface conditions. These systems support either bidirectional power exchange or direct power reception, facilitating operational flexibility and interoperability across the lunar surface infrastructure. The following requirements establish the power transfer specifications for each system, ensuring efficient energy distribution and alignment with standardized interface protocols.

[EHP-PWR-R-3002] LTV Power Transfer

LTV shall have the capability to send and receive bidirectional power at a nominal voltage of 120Vdc and facilitate no less than 3-kW of bidirectional power exchange (Interface II) on an interface with hardware rated for 6-kW, where applicable in this document.

Rationale: Within this framework, Interface II is established to ensure appropriate power system sizing that meets moderate load demands such as scientific payload operation, auxiliary system recharging, or off-nominal recharge support. The 3-kW nominal value incorporates real-world effects including transmission losses, voltage drops, and environmental derating (thermal, cabling, connector inefficiencies), guaranteeing reliable performance without oversizing the interface. Hardware rated at 6-kW maintains consistency with the standardized surface power interface and provides necessary margin to support future scalability and prevent connector redesigns. This requirement promotes mission flexibility, asset resilience, and enables distributed power-sharing capabilities on the lunar surface.

Allocation: LTV

[EHP-PWR-R-3003] PR Power Transfer

PR shall have the capability to receive power at a nominal voltage of 120Vdc and support a power reception interface capable of receiving no less than 5-kW (Interface I), on an interface with hardware rated for 6-kW, where applicable in this document.

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Rationale: The Pressurized Rover functions as a vital mobile habitat, life support system, and crew transport within the Foundational Exploration (FE) segment. Its significant energy requirements demand a higher power intake capability to enable efficient and timely battery recharging. Power reception with a 5-kW capability (Interface I) allows the rover to replenish substantial energy reserves during limited periods of illumination or to effectively leverage external power augmentation for prompt recharging.

Allocation: PR

[EHP-PWR-R-3004] MPH Power Transfer

The Multi-Purpose Habitat shall have the capability to send and receive bidirectional power at a nominal voltage of 120Vdc and facilitate no less than 3 kW (Interface II) of bidirectional power exchange on an interface with hardware rated for 6 kW, where applicable in this document.

Rationale: A 3-kW bidirectional power exchange capability (Interface II) allows the MPH to provide or receive power from other surface elements as mission conditions require, such as recharging visiting vehicles, supporting external systems, or receiving supplemental power during peak demand. This nominal rating is designed to account for real-world factors like voltage drop, cable losses, and environmental derating, ensuring consistent performance without unnecessary oversizing. Use of 6 kW-rated hardware ensures compatibility with the common interface standard and provides sufficient margin for future scaling and operational robustness across various surface scenarios.

Allocation: HLS

3.1.2 Surface Payloads (Utilization)

Surface Systems implement dedicated, unidirectional power interfaces designed to support Surface Payloads. These utilization interfaces operate independently from LSEPE and xEVA System Power interfaces, ensuring isolated power delivery without reliance on other surface assets. This separation promotes reliable operation of deployed payloads and preserves mission flexibility.

The Surface Payload power interfaces consist of standardized nominal pathways at 120 VDC, 28 VDC, and 3–28 VDC, accommodating a range of payload classes from high-power systems to low-power or precision instruments.

These power interfaces are defined and allocated through the following governing documents:

M2M-30002, Moon to Mars Artemis Requirements Document (ARD): Allocates the utilization power interfaces to Surface Systems to support Surface Payloads.

M2M-30038, Moon to Mars Utilization Interface Requirements Document, : Establishes power distribution specifications for the Surface System EPS, ensuring consistent and standardized power delivery.

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M2M-30035, Artemis Payload Interface Definition Document, : Defines the payload-side power reception interface for Surface Payloads, ensuring compatibility with the Surface System EPS and standardized power integration.

3.1.3 xEVA System Interfaces

This specification is not applicable to, nor does it address interfaces with the xEVA System or any of the xEVA System components.

Technical definitions, compatibility requirements, and detailed power consumption profiles for xEVA operations are maintained in EHP-10029, xEVA to Artemis Systems Interface Requirements Document (IRD).

3.2 EXTERNAL POWER REQUIREMENTS

The integrated Surface System EPS/Surface System EPCE will follow this specification, for all stages of assembly on the Lunar surface. Power quality applies to all powered hardware of a system. Interactions include electromagnetic interference (EMI), regenerative energy, and system transients resulting in power surges and spikes. Bidirectional power exchange requirements apply to a one-to-one interface, distributing power over no more than 100 meters. Bidirectional power exchange means the same surface asset can either provide power (EPS) or consume power (EPCE) at any given time via a single external connector and will adhere to all the EPS and EPCE requirements. Power sources supplying power at the power exchange interface will follow all EPS requirements and all power loads receiving power at the power exchange interface will follow all EPCE requirements.

For cables greater than 100 meters, the requirement will be determined by the element integrator or mitigation strategy will be performed by Element EPS Integrator. The EHP Power specifications are a subset of legacy space crewed power quality specifications to allow interoperability among elements. The requirements will be validated at two key measurement interfaces to ensure the integrity of power delivery across the system's 100-meter as noted.

Transmit Interface: This measurement point is defined at the EPS output, prior to the cable connection. Evaluating performance at this stage verifies that the EPS operates within all specified conditions and establishes a baseline for the power quality at the source. The EPS shall remain compliant with section 1000 of this specification during operation.

Receive Interface: The receive interface is located at the input of the EPCE, positioned at the far end of the 100-meter cable. Measurements at this point capture the electrical characteristics after the signal has been influenced by the cable. This assessment ensures that, despite potential losses, noise introduction, or attenuation over the 100-meter transmission, the delivered power remains within the required system parameters. The EPCE shall adhere to section 2000 during operation.

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FIGURE 3.2-1 INTERFACE DEFINITION

3.2.1 Power Management and Distribution

This section defines how power is generated, managed, and distributed across Artemis Lunar Surface Systems to ensure stable and efficient energy transfer. The Surface System EPS is responsible for supplying 120Vdc external power, regulating voltage levels, and preventing high-voltage transients that could disrupt operations.

[EHP-PWR-R-1005] Power Management – EPS

The Artemis Lunar Surface System EPS which distributes 120Vdc external power shall have the capability to control the magnitude of the voltage and the direction of current flow both into and out of the Powered System by an external command. Applicable to bidirectional interfaces only.

Rationale: External command could be manual or from telemetry. This is to allow system power flow control switching between a source and load.

Allocation: LTV, HLS

[EHP-PWR-R-1006] Power Transfer Efficiency – EPS

The Artemis Lunar Surface System EPS which distributes 120Vdc external power shall facilitate power transfer at a nominal voltage of 120Vdc to another lunar asset with an efficiency of at least 80% under lunar operating conditions outlined in SLS-SPEC-159, Cross-Program DSNE.

Rationale: The 80% efficiency threshold is derived from legacy EPS standards and ensures effective energy utilization. Efficiency is defined as the ratio of delivered power—calculated as EPS output voltage multiplied by EPS output current—to the input power, which is the product of EPS input voltage and EPS input current, when supplying nominally powered loads.

Measurement shall be conducted at the connector transmit interface on the EPS output to verify compliance with efficiency standards.

Allocation: LTV, HLS

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[EHP-PWR-R-1007] Power Management Flow Control – EPS

The Artemis Lunar Surface System EPS responsible for distributing 120Vdc external power, shall actively manage power generation, resource utilization, and demand to always maintain alignment with available power storage capacity.

Rationale: Dynamic regulation of power generation and storage capacity optimizes system performance by preventing excessive load conditions that could lead to equipment failure.

Additionally, ensuring continuous alignment between resource demand and available storage capacity prevents power shortages that could compromise mission-critical functionality.

Allocation: LTV, HLS

[EHP-PWR-R-1008] Nominal Voltage Setpoint – EPS

The Artemis Lunar Surface System EPS responsible for distributing 120Vdc external power shall have the capability to establish and regulate a nominal voltage setpoint throughout power distribution.

Rationale: Maintaining a defined nominal voltage setpoint is critical for ensuring stable power distribution and mitigating voltage fluctuations caused by cable length variations. This supports efficient energy transfer and enhances system interoperability under both nominal and off-nominal conditions.

Allocation: LTV, HLS

[EHP-PWR-R-1009] Generate Power – EPS

The Artemis Lunar Surface System EPS, when utilizing power generation devices operating outside the non-normal voltages as specified within this specification, shall maintain specified power quality at the power exchange interface by regulating generation and distribution to prevent high-voltage transients and ensure stable, compliant energy transfer across all interfacing systems.

Rationale: This requirement is established to mitigate excessive voltage transients at the power exchange interface, preventing operational disruptions or electrical stress on connected systems.

External power generation sources that deviate from standard operating conditions during power transfer may require additional analysis and testing to validate that transient behaviors remain within acceptable thresholds. This ensures the system continues to meet performance standards under variable conditions without compromising interface stability.

Allocation: HLS

[EHP-PWR-R-1010] Power Storage – EPS

The Artemis Lunar Surface System EPS, when utilizing power storage devices operating outside the non-normal voltages as specified within this specification, shall maintain specified power quality at the power exchange interface by regulating storage and distribution to prevent high-voltage transients and ensure stable, compliant energy transfer across all interfacing systems.

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Rationale: This requirement is established to mitigate excessive voltage transients at the power exchange interface, preventing operational disruptions or electrical stress on connected systems.

External power storage source that deviates from standard operating conditions during power transfer may require additional analysis and testing to validate that transient behaviors remain within acceptable thresholds. This ensures the system continues to meet performance standards under variable conditions without compromising interface stability.

Allocation: HLS

Power Management and Distribution – EPCE

[EHP-PWR-R-2010] Power Storage – EPCE

The Artemis Lunar Surface System EPCE, equipped with power storage devices operating beyond the defined non-normal voltage range within this specification, shall regulate energy storage and consumption to ensure strict power quality control at the power exchange interface.

Rationale: This requirement is designed to mitigate excessive voltage transients that could impact the power exchange interface, preserving overall system stability. External power storage sources that operate outside standard conditions when transferring or exchanging power may require supplementary analyses and testing to validate that transient behaviors remain within defined operational thresholds. These additional evaluations ensure continued system compliance and prevent voltage irregularities that could disrupt critical functionalities.

Allocation: HLS

3.2.2 Normal Operations

Normal Operations – EPS

For the bidirectional Artemis Lunar Surface System, the requirements will be validated at two key measurement interfaces unless noted otherwise to ensure the integrity of power delivery across the system's 100-meter cable:

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FIGURE 3.2-2 NORMAL OPERATIONS EPS INTERFACE DEFINITION

Transmit Interface (EPS Output): This measurement point is defined at the output of the EPS before the cable connection. Evaluating performance here confirms that the EPS meets all specified conditions. It establishes a baseline for the power quality leaving the source.

Receive Interface (EPCE Input): The receive interface is located at the EPCE input, i.e., at the far end of the 100-meter cable. Measurements taken at this point assess the electrical characteristics after the cable has influenced the signal. This ensures that the transmitted power, after potential losses, noise introduction, or signal attenuation by the 100-meter cable, still complies with the overall system requirements.

The following requirements are applicable to Surface Assets sending or receiving external power on the Lunar surface.

[EHP-PWR-R-1021] Steady State Voltage – EPS

The Artemis Lunar Surface System EPS shall have the capability to supply the steady-state voltage at the power exchange receive interface in Figure 3.2-2 Normal Operations EPS Interface Definition, within the range of 98Vdc to 136 Vdc for Surface System EPCE from no load to a rated capacity of the system.

Rationale: The voltage ranges include the expected voltage swing for a power system that is comprised of power generation and power storage devices. The applicable interface is measured downstream of a 100-meter cable rather than at the EPS output, which EPS designers should consider. Reference Appendix G for cable derating guidance.

Allocation: LTV, HLS

[EHP-PWR-R-1022] Inrush Current – EPS

The Artemis Lunar Surface System EPS at the transmit interface shall support load inrush currents of:

0.012 A*Sec / A for loads with currents 0A < i < 10A.

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0.00253 A*Sec / A + 0.0947 for loads with currents 10A < i < 200A

Rationale: Any circuit level energy storage in the Surface System EPS (filter capacitors, etc.), can both draw a startup surge (HEOMD-003-04: PWR120-2009), and deliver a surge into external faults. While this inrush/surge requirement does not consider source/load margin, the EPCE designers need to determine sufficient margins to avoid nuisance tripping of source switchgear from protection circuits. Designers should consider minimum values of a margin of 120% of rated output when connecting loads that are not predetermined. The ampere-seconds/ampere are normalized inrush ampere-second current divided by the source current rating of the source. The value of 0.012 ampere-seconds/ampere is equivalent to a capacitance of 1000 microfarad (μF) for a 10 Amp source at 120 VDC as determined by the equation: C = Q/V: C = 0.012sec*10A / 120 V = 1000μF.There is no discontinuity at 10A as the 10A source in the second equation:

((0.00253sec*10A) + 0.0947) / 120 V = 1000 μF.

Allocation: LTV, HLS

[EHP-PWR-R-1023] Surge Current – EPS

The Artemis Lunar Surface System EPS at the transmit interface shall support load surge currents of:

0.012 A*Sec / A for loads with currents 0A < i < 10A.

0.00253 A*Sec / A + 0.0947 for loads with currents 10A < i < 200A

Rationale: Any circuit level energy storage in the Surface System EPS (filter capacitors, etc.), can both draw a startup surge (HEOMD-003-04: PWR120-2009), and deliver a surge into external faults. While this inrush/surge requirement does not consider source/load margin, the EPCE designers need to determine sufficient margins to avoid nuisance tripping of source switchgear from protection circuits. Designers should consider minimum values of a margin of 120% of rated output when connecting loads that are not predetermined. The ampere-seconds/ampere are normalized inrush ampere-second current divided by the source current rating of the source. The value of 0.012 ampere-seconds/ampere is equivalent to a capacitance of 1000 microfarad (μF) for a 10 Amp source at 120 VDC as determined by the equation: C = Q/V: C = 0.012sec*10A / 120 V = 1000μF.There is no discontinuity at 10A as the 10A source in the second equation:

((0.00253sec*10A) + 0.0947) / 120 V = 1000 μF.

Allocation: LTV, HLS

Reverse Current due to Normal Operations – EPS

The Artemis Lunar Surface System EPS only accepts reverse currents under abnormal nominal operations.

Rationale: Loads, mainly motors and other inertial loads need to be designed as to not normally supply reverse currents (re-gen) into the distribution system and potentially raise the bus voltage to unacceptable levels, causing the unintended tripping from other devices within the system.

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[EHP-PWR-R-1025] Normal Load Step Transient Voltage- EPS

The Artemis Lunar Surface System EPS shall operate within the Normal Transient Voltage Envelope shown in Figure 3.2-3 Normal Load Step Transient – EPS (Transmit Interface and Figure 3.2-4 Normal Load Step Transient - EPS (Receive Interface), measured at the transmit interface, under all nominal operational scenarios.

Rationale: defined at EPS common connector output which interfaces EPCE common connector. Normal load step transients occur during nominal operations and are expected during the intended application, this excludes dynamic load switching, load startup, load failure, and source failure conditions.

FIGURE 3.2-3 NORMAL LOAD STEP TRANSIENT – EPS (TRANSMIT INTERFACE

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FIGURE 3.2-4 NORMAL LOAD STEP TRANSIENT - EPS (RECEIVE INTERFACE)

[EHP- PWR-R-1026] Start Up – EPS

The Artemis Lunar Surface System EPS shall establish and regulate power distribution at the power exchange interface within 1 second of system startup, ensuring reliable energy transfer to its interfacing asset in accordance with the specifications outlined in this document.

Rationale: This guarantees operational readiness for mission-critical systems, preventing delays in power delivery while maintaining stable voltage and current levels in accordance with system specifications. By enforcing a rapid power-on sequence, the EPS supports seamless integration with interfacing hardware, minimizing disruptions and ensuring alignment with defined electrical parameters for sustained lunar operations.

Allocation: LTV, HLS

[EHP-PWR-R-1028] Max Load Step Size – EPS

The Artemis Lunar Surface System EPS shall accommodate step load variations up to 3 kW, ensuring stable power delivery and preventing excessive discharge or system instability. This specification applies to the EPS common connector output interfacing with the EPCE common connector.

Rationale: This requirement prevents unintended voltage dips, transient disruptions, or overload conditions that could impact connected systems, storage devices, or distribution components.

The specified 3 kW limit is defined at the EPS common connector output, which directly interfaces with the EPCE common connector, ensuring standardized power delivery across the exchange interface. By designing for controlled load adaptability, the EPS enhances system resilience, operational efficiency, and long-term sustainability in the lunar environment.

Allocation: N/A

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[EHP-PWR-R-1032] Source Impedance – EPS

The Artemis Lunar Surface System EPS output impedance shall be measured and shall have a magnitude no larger than the interface source magnitude limits defined in Figure 3.2-8 Source Impedance Magnitude (Transmit) and shall remain within the phase limits defined in Figure 3.2-9 Source Impedance Phase (Transmit). While these verification criteria are levied on the transmit side for the source vehicle/element, both the transmit and receive ends of the interface are required to maintain stability to ensure consistent and reliable power exchange throughout the system.

Rationale: The Surface System EPS impedance value is required to calculate the stability margin of the source/load combination at the user input terminals. This specification addresses a generic interface where the Surface System EPS and the Surface System EPCE share a common connection. While this requirement addresses transmit-side parameters, stable operation of the receive side is supported through the corresponding provisions applied to that end. It is important to note that the EPS impedance may vary significantly with load and current direction. Pure source impedance excludes the DC component or “wire resistance” of the transmission cable. The figures in this document assume worst-case EPS source impedance at the power exchange interface, incorporating all AC components of its upstream transmission cable, and are valid for lengths up to 100 meters; other cases will be assessed individually. For Interface II EPCE to receive power from a 6-kW EPS, they must also meet the applicable Interface I EPCE impedance limits.

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FIGURE 3.2-10 SOURCE IMPEDANCE MAGNITUDE (RECEIVE)

FIGURE 3.2-11 SOURCE IMPEDANCE PHASE (RECEIVE)

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[EHP-PWR-R-1033] Bi-Directional Stability – EPS

The Artemis Lunar Surface System EPS shall maintain electrical impedance across the full input/output range to enable stable bidirectional power exchange when connected to another active Powered System of equivalent performance. This ensures power transfer in either direction while keeping the impedance ratio outside the forbidden zone between 30 Hz and 100 kHz. To achieve this, the system shall always operate in one of the following defined states:

Dead Face State: Voltages shall not exceed 5VDC, and no connections shall be present at the interface.

Quiescent State: The EPS/EPCE shall assess the state of the connected system and transition to the appropriate operational mode as needed.

Power Receiver State (EPCE): The EPCE shall function according to the requirements defined in Section 2000, ensuring controlled power intake.

Power Transmitter State (EPS): The EPS shall distribute power in accordance with the specifications outlined in Section 1000, maintaining system-wide stability and interoperability.

Rationale: Two interconnected Surface System EPSs must maintain stability during bidirectional power exchange. If |ZS| > |ZL|, further analysis is required to assess system stability. The Nyquist criterion provides a refined methodology for stability assurance, offering a less conservative approach that ensures robust power transfer between systems.

Allocation: LTV, HLS

[EHP-PWR-R-1034] Large Signal Stability – EPS

When subjected to short-duration source-side transient voltages, transient responses of the Artemis Lunar Surface System EPS, measured at the transmit interface, shall remain below 10 percent of the maximum response amplitude within 1 millisecond as shown in Figure 3.2-12:

Large Signal Stability - EPS.

Rationale: The system may be subjected to transient voltages from its own EPS and is required to dampen out when subjected to a large pulse rather than become unstable and infinitely oscillate at the power exchange interface. It is imperative that all resonances be minimized by providing circuit damping both at the input circuit to each individual load and at the system/subsystem level.

Short duration transient responses are defined system or device response to a disturbance in an electrical system brought about by a sudden change of load or system voltage under nominal conditions.

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FIGURE 3.2-12: LARGE SIGNAL STABILITY - EPS

[EHP-PWR-R-1035] Local Stability – EPS

The Artemis Lunar Surface System EPS, including all connected subsystems and equipment, shall maintain functional stability and not exhibit malfunction, degradation, or unintended behavior in response to voltage surges, ripples, transients, or other electrical disturbances.

Rationale: Local electrical stability is essential to maintain system reliability and performance, both in isolation and when operating in parallel with other loads. Instabilities may degrade subsystem functionality or induce unexpected behaviors. To support effective design, implement strategies from MIL-HDBK-241, Appendix B, which offers guidance for managing input and output electrical characteristics. While EHP-10107 does not directly verify local power stability, it complements this requirement by ensuring electromagnetic compatibility during transient susceptibility testing. Together, these practices promote system resilience to both conducted and radiated electrical disturbances.

Allocation: LTV, HLS

[EHP-PWR-R-1036] Independent Instabilities – EPS

Any disturbance arising on a single powered interface of the Artemis Lunar Surface System EPS shall not compromise the stability of the bus associated with the power exchange interface.

Rationale: In a bidirectional power system, any instability originating in the EPS should not cascade into the EHP power interface. This requirement ensures that the system operates outside the critical "forbidden zone", a range wherein interactions among interfacing systems could trigger wider instability. By enforcing this boundary, the design prevents localized disturbances from affecting the overall power exchange performance and system safety. This approach is essential for maintaining operational integrity and reliability in systems where power flows in both directions, ensuring that each subsystem remains robust and decoupled from disturbances in another.

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[EHP-PWR-R-1039] Ripple Voltage Spectrum - EPS

The Artemis Lunar Surface System EPS shall limit the amplitude of each discrete spectral component of the ripple voltage at least 6 dB below the corresponding CS101 and CS114 susceptibility levels specified in EHP-10107, Electromagnetic Interference Requirements for Subsystems and Equipment.

Rationale: Maintaining a 6 dB margin below the EMI conducted susceptibility limits in EHP- 10107 ensures a conservative buffer that minimizes the risk of cumulative EMI at the power interface, supports interoperability with susceptible loads, and reduces likelihood of emissions-related noncompliance during system integration and test.

Allocation: LTV, HLS

[EHP-PWR-R-1040] Ripple Amplitude - EPS

The Artemis Lunar Surface System EPS shall be less than 3.5 Vrms in a bandwidth of 30 Hz to 10 MHz.

Rationale: Ripple voltages overlaid on the 120 VDC system can significantly affect instrumentation and other sensitive loads. The overall conducted ripple amplitude is the cumulative effect of contributions from both sources and loads.

Allocation: LTV, HLS

[EHP-PWR-R-1041] Peak Ripple Voltage - EPS

The Artemis Lunar Surface System EPS shall have a peak ripple voltage less than 6 Vp when measured in the time domain with a bandwidth of at least 10 MHz.

Rationale: Ripple voltages superimposed on the 120 VDC bus degrade power quality and can introduce errors or malfunction in avionics, communication systems, and other sensitive loads.

Excessive ripple can also accelerate wear on capacitors, converters, and filtering elements, reducing overall system reliability. By bounding the peak ripple voltage within 6 Vp when measured in the time domain with a bandwidth of at least 10MHz, the EPS maintains compliance with electromagnetic compatibility practices, prevents cumulative ripple buildup from interacting destructively between…