A SYSTEMATIC REVIEW OF MULTIDISCIPLINARY DESIGN OPTIMIZATION IN STEALTH UAVS AND LOITERING MUNITIONS: INTEGRATION OF CFD, FEM, ADVANCED MATERIALS, AND LOW-OBSERVABILITY TECHNOLOGIES

Abstract

Multidisciplinary Design Optimization (MDO) is an essential design methodology for balancing the aerodynamic, structural and electromagnetic performance goals of the stealth unmanned aerial vehicles (UAVs) and loitering munitions. In addition to performance of individual subsystems, computational evidence is beginning to emerge that shows integration of low-observability constraints into MDO is a factor in the effectiveness of the system level platform. The role of CFD, FEM, advanced materials and radar signature management technologies in a unified MDO, however has not been studied systematically. The purpose of this review was to seek to combine the evidence of the integration of these disciplines in the context of stealth UAVs and loitering munitions and to assess what they offer in terms of promoting platform performance. The systematic review was conducted based on PRISMA guidelines. An extensive review was conducted in Scopus, Web of Science and AIAA Digital Library up to May 2025. The PICO framework was used to identify studies that discussed the design of stealth UAVs or loitering munitions as well as the reporting on MDO integration between at least two of the four disciplines that were targeted: CFD, FEM, advanced materials, and low-observability technologies. The Engineering Study Quality Assessment Tool, modified to consider the risk of bias, was used to assess the risk of bias. Seven studies were included following PICO criteria in which the formal multi-disciplinary integration in a context of human-relevant UAV or loitering munition design was required.Of the 9,847 records initially identified, seven studies were included according to PICO criteria which required the formal multi-disciplinary integration in a context of human-relevant UAV or loitering munition design. The evidence is conclusive and very strong that the synergistic integration of geometric shaping, structural optimization and choice of radar absorbing material in a single MDO design leads to reductions in RCS and aerodynamic-structural improvements that are not attainable using sequential single discipline approaches. The results are: surrogate-based and adjoint MDO frameworks allow for design space exploration superior to that provided by gradient-free methods; both RAM layer properties and the coupled CFD-FEM methods can be used to explore the design space for the reduction of signatures beyond just geometric shaping; coupled CFD-FEM methods can be used for simultaneous structural mass reduction and aeroelastic load alleviation. Dedicated MDO frameworks for loitering munitions, on the other hand, are still not well-represented in the literature and only few and inconsistent treatments of compact-planform specific design challenges. Assessment of risk of bias suggested low to moderate risk for all included studies, mostly due to the lack of aerodynamic and/or experimental RCS data. This systematic review will show that integration of MDO—especially with the aerodynamic-signature coupling relationship—can contribute to stealth UAV performance, and allows for system-level trade space navigation across disciplines. An early integration of low observability constraints, starting at the design phase is a good and much desired direction, but there is a need for special high fidelity validation campaigns and loitering munition-specific MDO frameworks.