Unmanned aerial systems (UAS) play a critical role in modern defense applications due to their versatility, cost-effectiveness and reduced risk to human operators. However, as the complexity of missions increases, so do the engineering challenges associated with controlling mass characteristics and weight management. This report identifies and analyzes these challenges from an engineering perspective, considering the principles of lightweight design-material-, structure- and system-based-and references relevant literature sources.
Key challenges in controlling mass properties and weight management
Figure 1: Key challenges for mass properties and weight management in UAS.
Balanced lightweight construction with simultaneous structural integrity
Minimizing weight while maintaining structural integrity is crucial. Advanced composite materials (e.g. CFRP, GFRP) offer a high specific strength ratio, often need to be bulletproof and have complex failure mechanisms. Optimized structural geometries such as stiffened panels must be carefully designed to avoid loss of stability due to buckling. [1]
Focus management (CG)
Correct positioning of the center of gravity is essential for flight stability. Shifts in the center of gravity due to fuel consumption or changing payloads can affect aerodynamic stability and controllability. Analysis tools such as the finite element method (FEM) help to evaluate and control these effects. [2]
Weight gain during development
Changing requirements and iterative design processes often lead to unexpected weight increases. Robust weight management, for example through weight analysis trees (weight breakdown structure) and regular design reviews, is essential. [3]
Modularity of the payload vs. mass optimization
Defense missions require modular payloads for operational flexibility, but this leads to additional structural and integration mass. Multifunctional and integrated designs offer solutions. [4]
Fuel/energy storage mass
Energy density limits restrict the range of UAS. While fuel has a high energy density, conformal tanks and structural batteries are the subject of current research. [5]
Thermal and electromagnetic shielding
Stealth and survivability require radar absorbing materials (RAM) and thermal protection systems, which add mass. Functional gradient materials (FGM) can enable locally adapted material properties. [6]
Dynamic loads and vibration stability
Lightweight constructions are prone to flutter and resonance phenomena. The calculation of natural frequencies and a corresponding dynamic analysis are necessary to avoid instabilities. [7]
Production and inspection of lightweight structures
Thin-walled and fiber-reinforced components are difficult to manufacture and inspect. Advanced manufacturing processes and non-destructive testing (NDT) methods are necessary to guarantee performance without high safety margins. [8]
Bibliography
- [1] Kaw, A. K. (2005). Mechanics of Composite Materials. CRC Press.
- [2] Roskam, J. (2002). Airplane Design Part VI: Preliminary Calculation of Aerodynamic, Thrust and Power Characteristics. DARcorporation.
- [3] Raymer, D. P. (2012). Aircraft Design: A Conceptual Approach. AIAA.
- [4] Torenbeek, E. (2013). Advanced Aircraft Design: Conceptual Design, Technology and Optimization of Subsonic Civil Airplanes. Wiley.
- [5] Zhang, X., Zhao, Y., & Wang, C. Y. (2018). Energy storage systems in UAVs: A review. Applied Energy, 228, 242-255.
- [6] Bartolo, P., et al. (2012). Functionally graded materials: A review on advanced manufacturing methods. Materials Science Forum, 706-709.
- [7] Hodges, D. H., & Pierce, G. A. (2011). Introduction to Structural Dynamics and Aeroelasticity. Cambridge University Press.
- [8] Campbell, F. C. (2010). Structural Composite Materials. ASM International.
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