Numerical examination of the effect of contact pressure on thermal resistance i̇n materials used i̇n space vehicles

Over the past few decades, space technology has undergone a remarkable transformation, evolving from a field primarily driven by government programs into a broad, multidisciplinary domain that now encompasses commercial, academic, and industrial stakeholders. During the course of my research, I've come to recognize that one of the most crucial challenges in this evolving landscape lies in understanding how spacecraft materials perform under the extreme and often unpredictable conditions of space. These include rapid thermal cycling, intense radiation exposure, micrometeoroid impacts, vacuum-induced stresses, and the absence of gravity. The materials selected for spacecraft construction are directly tied to mission success, especially for long-duration explorations where material degradation or thermal instability could pose critical risks. In this study, I've focused on a specific aspect of this challenge: understanding how contact pressure influences thermal resistance in space-grade materials. Contact pressure—defined as the normal force applied per unit area at the interface of two solid surfaces—plays a key role in determining how heat is conducted across those surfaces. In vacuum conditions, where convective heat transfer is not possible, thermal conduction through contact interfaces becomes the dominant mode of heat transfer. Through this lens, factors such as surface roughness, material hardness, elastic or plastic deformation, and interface cleanliness take on heightened importance. A clearer grasp of how these parameters interact is essential for improving the thermal management systems of future spacecraft. The topic of thermal contact resistance (TCR) is not new, but it is certainly evolving. Foundational models were developed as early as the late 1960s—Yovanovich's work in 1969 laid the groundwork using Hertzian contact theory and surface micro-topography assumptions. Since then, the field has expanded significantly. Newer approaches consider fractal surface geometries, nonlinear temperature effects, and empirical validation under extreme conditions such as cryogenic environments or microgravity. In my own literature review, I found the semi-empirical model proposed by Bahrami et al (2004) particularly relevant, as it integrates both contact pressure and surface roughness. Sun et al. (2024) further advanced this by testing aerospace-specific material pairs under vacuum. A recurring theme across the literature is that thermal contact resistance typically decreases with increasing contact pressure, often following logarithmic or power-law behavior (Mikic & Rohsenow, 1966). However, many of these studies rely on idealized conditions or simplified geometries. My research contributes to closing this gap by simulating realistic contact scenarios using actual aerospace materials under space-like conditions. I've also incorporated multi-condition numerical modeling to explore the interaction between contact pressure, material behavior, and thermal performance more holistically. The materials I selected for this work—aluminum alloys (6061-T6, 7075-T73), carbon fiber-reinforced polymers (CFRPs), and ceramic matrix composites (SiC-based)—reflect current usage in spacecraft structure and thermal systems. Aluminum alloys remain a backbone for spacecraft due to their excellent thermal conductivity and lightweight strength. Their compliant nature under load leads to relatively low TCR values, although oxidation at contact points can interfere with heat transfer. This has led to the use of coatings such as anodized films or thermal pastes. CFRPs are another class of materials I examined. Their high strength-to-weight ratio and thermal dimensional stability are ideal for many space applications. However, their anisotropic conductivity—strong along the fiber axis but weak across it—complicates thermal modeling. The epoxy resin matrix tends to deform under pressure, slightly improving contact, but overall TCR remains higher than metals. These materials are commonly used in components like antenna booms and structural supports. Ceramic matrix composites, such as SiC, were also evaluated due to their exceptional temperature resistance and stability. However, they present unique challenges: they are brittle, non-compliant, and possess relatively high surface roughness and porosity. Achieving good thermal contact with ceramics typically requires high contact pressures. Despite these limitations, their chemical inertness and heat tolerance make them indispensable for systems like engine nozzles and heat shields. Throughout my analysis, I considered real-world applications and mission case studies to reinforce the modeling work. For instance, thermal control systems on the International Space Station rely heavily on effective TCR management, using both active components (e.g., ammonia loop radiators) and passive ones like multilayer insulation (MLI). I also examined systems on robotic platforms that face extreme lunar and Martian temperature fluctuations, where optimized contact between structural materials and power systems (e.g., RTGs) ensures stability and longevity. The Artemis mission, with its advanced CFRP-aluminum hybrid structures and ceramic-tile heat shields, further highlights the importance of robust interface performance under launch and re-entry conditions. Looking forward, emerging technologies hold great promise for improving thermal contact behavior. During this research, I became particularly interested in the following innovations: • Smart thermal interfaces using shape memory alloys that adjust contact stiffness in real-time, • Nano-coatings (e.g., graphene) that reduce surface resistance while enhancing emissivity, • Embedded sensors that provide real-time thermal performance data from interface zones, • 3D-printed lattice structures that offer tailored mechanical compliance and thermal conduction, • Machine learning algorithms trained to optimize material combinations and contact pressures for specific mission profiles. In addition to these forward-looking strategies, I believe future research should also investigate the long-term evolution of thermal contact behavior under radiation exposure, contamination, fatigue, and delamination. These effects could have serious implications for mission reliability and material reusability, especially in deep-space or planetary habitats. In conclusion, my work supports the view that thermal contact resistance (Mikic & Rohsenow, 1966). is more than just a material property—it's a multidisciplinary engineering problem involving materials science, numerical modeling, surface physics, and mission planning. By combining theoretical models with application-focused simulations, and by aligning my findings with actual mission requirements, I hope to contribute both practically and academically to the growing knowledge in this field. As space exploration moves into more demanding environments, dynamic, sensor-integrated, and adaptable interface solutions will be key to ensuring the efficiency and safety of next-generation spacecraft systems. Keywords: thermal contact resistance, space materials, contact pressure, thermal conductivity, spacecraft systems, CFRP, ceramic composites, aluminum alloys, mission design, interface optimization, thermal modeling, adaptive materials, nano-coatings, smart interfaces.