A Methodology for Architecting Self-Sustaining Environmental Control and Life Support Systems (ECLSS) For Lunar Habitats
Author(s)
Chen, Leon
Advisor(s)
Editor(s)
Collections
Supplementary to:
Permanent Link
Abstract
Since the Apollo era, lunar exploration has served as a proving ground for advancing human spaceflight, technology development, and the pursuit of sustainable off-world operations. Sustaining human presence on the Moon, however, presents distinct logistical, environmental, and operational challenges. Unlike missions to the International Space Station (ISS), lunar operations must rely on systems that can function autonomously for extended periods, as the high cost, delay, and risk associated with Earth-based resupply limit mission flexibility. Extreme temperature variations, radiation exposure, and abrasive lunar dust further intensify these challenges, demanding the development of self-sustaining habitats capable of producing and recycling essential resources locally.
This dissertation establishes a comprehensive methodology for architecting self-sustaining Environmental Control and Life Support Systems (ECLSS) for long-duration lunar habitats. The approach integrates subsystem-level modeling, full-system simulation, and In-Situ Resource Utilization (ISRU) analysis within a unified Python-based framework known as HELIOS. The methodology simultaneously addresses internal ECLSS loop-closure performance and external ISRU integration, providing a quantitative foundation for evaluating scalability, mass efficiency, and sustainability across evolving mission architectures. This research aims to bridge the gap between high-fidelity subsystem design and mission-level sustainability assessment—creating a replicable, data-driven framework for future lunar and planetary habitats.
The research is organized into three major phases.
First, subsystem-level models were developed for key ECLSS functions within the HELIOS simulation framework. Each subsystem, covering both air and water strings, was validated against ISS performance data and system behavior, and extended to represent lunar surface conditions. This established and validated HELIOS as a robust methodological platform for assessing architectural feasibility under variable mission and environmental parameters. High-fidelity simulations of 24-month crewed missions were then conducted to project consumables usage, closure rates, and system mass evolution over time. The results of this first experiment, the loop-closure evaluation, demonstrated that the baseline ISS-derived configuration is unable to sustain crewed operations beyond approximately 485 days due to limited oxygen recovery capacity. Incorporating one Sabatier reactor extended mission duration beyond 730 days, confirming the feasibility of achieving a standalone self-sustaining architecture through advanced oxygen recovery. Additional sensitivity analyses on the number of Sabatier units revealed diminishing returns beyond two, indicating an optimal balance between closure efficiency and added system mass. An extended evaluation on food hydration requirements further reinforced these findings. Under the baseline configuration, achieving the required ≥ 80% hydration fraction was found to be operationally impractical without exceeding available water reserves. Integration of one Sabatier reactor, however, provided sufficient oxygen and water recovery to maintain hydration needs while significantly improving design freedom in mission planning. Together, these results validate the HELIOS methodology as an effective quantitative tool for linking subsystem-level technology performance to mission-scale sustainability outcomes, establishing a repeatable process for assessing and optimizing future self-sustaining ECLSS designs.
Second, an architectural evaluation was conducted to determine whether the self-sustaining ECLSS configuration identified in Experiment 1 could be justified in terms of total system mass over long-duration missions. This phase expanded the HELIOS framework to include both development and sustaining phases, enabling a holistic lifecycle mass assessment across varying loop-closure rates. Seven configurations, ranging from low to high closure levels, were modeled to quantify the trade between system complexity, initial mass, and resource consumption over time. The results demonstrated that while high-closure configurations introduced greater initial hardware mass and subsystem integration complexity, they yielded a significant reduction in cumulative consumables transported from Earth. This trade produced measurable breakeven advantages for long-duration missions, with mass parity occurring beyond approximately 730 days of operation. Among the evaluated configurations, the high-loop-closure design achieved the lowest total system mass demand when both development and sustaining phases were considered. These findings validated that regenerative ECLSS architectures are not only technically feasible but also mass-efficient for sustained lunar operations. An extended breakeven analysis quantified the full-duration spectrum of mass parity across closure configurations, confirming that the long-term benefit of regenerative systems increases with mission duration. This analysis also provided a methodology for determining mission-specific closure targets based on duration, resupply cadence, and available launch mass. Collectively, these results reinforced the HELIOS framework’s capability to perform end-to-end mass assessments, establishing a transparent, data-driven approach for justifying advanced ECLSS technologies within future lunar and deep-space mission architectures.
Third, the integration of ISRU technologies was examined to determine their capacity to reduce the environmental and logistical constraints on ECLSS loop-closure requirements. This phase established a lunar site-selection methodology within HELIOS to couple habitat location with available local resources, illumination, and terrain accessibility. Two representative ISRU processes, carbothermal reduction (CR) for oxygen generation and water extraction (WE) from icy regolith, were modeled to quantify their influence on overall life-support performance using a Design-of-Experiments (DoE) approach. The resulting ISRU–ECLSS integrated model demonstrated that incorporating even moderate in-situ production rates can substantially alleviate internal loop-closure demands, enabling self-sustaining operation without driving subsystems to maximum reclamation efficiency. Sensitivity analyses across production rate, duty cycle, and regolith composition showed that ISRU contributions scale favorably with habitat growth, providing increased operational flexibility and redundancy as infrastructure expands from a single station to a multi-module settlement. Furthermore, the extended evaluation quantified the power impact of integrating ISRU systems, revealing that power availability and scheduling strongly influence achievable production rates and, consequently, overall system sustainability. Collectively, these results confirm that coupling internal ECLSS recycling with external ISRU supply forms a balanced and resilient design strategy, reducing dependence on Earth-supplied consumables and supporting the long-term feasibility of lunar surface habitation.
Beyond subsystem optimization, this dissertation extends the analysis into a system-of-systems context, linking life support architectures with habitat siting, infrastructure, and logistics. A structured site selection process was developed, considering illumination availability, terrain slope, and volatile accessibility across key south polar regions such as Shackleton, Nobile, and Connecting Ridge. Results indicated that coupling high-closure ECLSS designs with sites offering both persistent sunlight and accessible ice deposits yields the most mass-efficient and sustainable outcomes. This coupling underscores that internal system performance and external resource environments must be co-optimized rather than treated as independent design problems, thereby advancing the holistic understanding of lunar habitat architecting.
In summary, this research delivers a scalable and quantitative methodology for developing self-sustaining ECLSS architectures that integrate internal resource recovery with external resource utilization. The HELIOS framework enables transparent, parametric trade studies across mission scales and provides the computational foundation for future multi-objective optimization, integrating mass, power, cost, and logistics within a unified decision environment. The outcomes of this work advance both the theory and practice of sustainable habitat design, demonstrating that self-sustaining life support architectures are not only technically feasible but can also be systematically justified through mass-efficient, data-driven analysis. The developed methodology also provides a decision-support foundation for integrated habitat and mission architecting, bridging detailed subsystem modeling with high-level planning to inform technology selection, resource strategy, and infrastructure development across future lunar and Martian programs.
Ultimately, this dissertation establishes a foundation upon which future research can build increasingly integrated design methodologies that couple environmental resources, mission operations, and system engineering principles. By doing so, it supports NASA’s long-term vision of a self-sustaining human presence beyond Earth and provides a roadmap for extending these principles to Martian and deep-space habitats, where autonomy, resilience, and sustainability will define the next era of exploration.
Sponsor
Date
2025-12
Extent
Resource Type
Text
Resource Subtype
Dissertation (PhD)