Date of Award

2026

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical and Aerospace Engineering

Advisor 1

Jeffrey Allen

Advisor 2

Brad King

Committee Member 1

Paulus Van Susante

Committee Member 2

Andrew Oliva

Abstract

Phase change materials (PCMs) are of interest in spacecraft thermal control because their latent heat capacity can provide passive thermal buffering during transient or cyclic heat loads. PCM behavior is often treated using idealized assumptions such as repeatable phase transition temperatures, consistent thermal accessibility across cycles, and full latent recovery. However, practical PCM behavior may be affected by non-ideal phenomena such as supercooling, interfacial resistance, and degradation of internal transport accessibility. This thesis examines the system-level relevance of these effects for low Earth orbit (LEO) spacecraft thermal control and identifies the operating conditions under which non-ideal PCM behavior becomes design-relevant.

A reduced-order four-node thermal model representing electronics, a PCM enclosure wall, PCM, and a radiator was developed to simulate transient thermal response under repeated orbital cycling. The model was first used to establish a reference LEO architecture and determine whether PCM provided meaningful thermal buffering under spacecraft-like conditions. The reference configuration was found to be largely radiator-driven, with the PCM providing only small but repeatable peak electronics temperature reduction within a limited operating corridor. The model was then applied to more latent-relevant cases, where transient thermal protection relied more strongly on PCM engagement. Pure PCM and composite PCM representations were used to evaluate how selected non-ideal behaviors influenced system-level thermal response.

Results showed that non-ideal PCM behavior becomes most consequential when spacecraft thermal control depends on a few Kelvin of PCM-provided separation from a component temperature operating limit. In the latent-relevant cases, supercooling delayed latent heat release and increased maximum electronics temperature, interfacial resistance limited access to the latent reservoir, and internal transport degradation reduced the practical effectiveness of composite PCM over repeated cycles. These effects did not make PCM universally ineffective in LEO but demonstrated that PCM usefulness is strongly dependent on system configuration and its external and internal thermal environments. The results indicate that non-ideal behavior should be evaluated as a system-level design concern when PCM performance determines whether or not narrow component-level temperature margins are preserved.

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