Soft materials in aerospace: from discrete functional elements to integrated system enablers

Soft materials are attracting increasing attention in aerospace engineering because they provide combinations of compliance, multifunctionality, and environmental adaptability that are difficult to achieve simultaneously with conventional rigid materials. This review summarizes recent progress in the use of elastomers, hydrogels, aerogels, shape-memory polymers, and related composites for aerospace applications, with emphasis on impact and vibration mitigation, sealing and leakage control, intelligent actuation and deployable structures, thermal insulation and management, radiation protection, flexible sensing, and multifunctional integration. Across these areas, the role of soft materials is shifting from passive auxiliaries toward functional material platforms that couple structure, actuation, sensing, transport regulation, and protection. The literature also shows that several key barriers remain unresolved. Soft materials in aerospace must operate under coupled thermal, mechanical, chemical, vacuum, radiation, and atomic-oxygen environments, yet current understanding of long-term degradation, cross-scale failure, and function retention under such conditions remains limited. In addition, many reported applications are still evaluated mainly through laboratory-scale demonstrations, leaving a substantial gap between proof-of-concept performance and mission-relevant validation. Predictive theories linking molecular design, microstructural evolution, and system-level behavior are still insufficient. This review identifies four closely related directions for future progress: coupled multiphysical and mechano-chemical theories for deformation, aging, and failure; accelerated testing and lifetime prediction methods linked to realistic service conditions; lightweight system architectures integrating structure, actuation, sensing, and protection; and AI-assisted design combined with 4D printing and other advanced manufacturing approaches for rapid optimization and mission-specific customization. Overall, soft materials should be developed not merely as discrete functional elements, but as enabling platforms for future aerospace systems under extreme environments.