The development and induction in-service of Unmanned Air Vehicles (UAV) systems in a variety of civil, paramilitary and military roles have proven valuable on high-risk missions. These UAVs based on fixed wing configuration concept have demonstrated their operational effectiveness in recent operations. New UAVs based on rotary wing configuration concept have received major attention worldwide, with major resources committed for its research and development. In this thesis, the design process of a rotary-wing aircraft was re-visualised from an unmanned perspective to address the requirements of rotary-wing UAVs - Vertical Take-off UAVs (VTUAV). It investigates the conventional helicopter design methodology for application in UAV design. It further develops a modified design process for VTUAV addressing the requirements of unmanned missions by providing remote command-and-control capabilities. The modified design methodology is automated to address the complex design evaluations and optimisation process. An illustration of the automated design process developed for VTUAVs is provided through a series of inputs of the requirements and specifications, resulting in an output of a proposed VTUAV design configuration for

Performance-based landfill design approach is a relatively new design approach adopted recently in solid waste management and applied in USA, European Union countries and some developing-economy countries like South Africa. This approach rejects the strict design criteria and accommodates a design that selects the most appropriate design components of a landfill (final cover, bottom liner, and leachate collection system) and their design details to result in the best overall performance with respect to performance criteria (groundwater contamination and stability) considering the system variables (climatic conditions of the site, site hydrogeology, and size of the landfill). These design components, performance criteria and design variables involved in decision process make performance-based landfill design a complex environmental problem. Decision support systems (DSS) are among the most promising approaches to confront this complexity. The fact that different tools can be integrated under different architectures confers DSSs ability to confront complex problems, and capability to support decision-making processes. In this thesis study, a DSS to aid in the selection of design components considering the design variables and performance criteria for performance-based landfill design was developed. System simulation models and calculation modules were integrated under a unique DSS architecture. A decision support framework composed of preliminary design and detailed design phases were developed. The decision of appropriate design components leading to desired performance was made based on stability issues and vulnerability of groundwater, using knowledge gathered from DSS. Capabilities and use of the developed DSS were demonstrated by one real and one hypothetical landfill case studies.