The normal air vehicle design process, whether for manned or unmanned vehicles, presents little opportunity for reducing time or cost. Problems identified late in the design process often lead to delays and cost overruns. However, the development of advanced UAS capability makes true rapid prototyping possible providing system integration and flight testing much earlier in the design process.

CAeS is leading the world in the provision of rapid prototyping capability through the use of sub-scale flight demonstrators as proven in our ground-breaking work on the Boeing Blended Wing Body (X-48) programme.

The current air vehicle design process has evolved to meet the needs of the manned system. Manned vehicles are very expensive to produce, spend a long time in service and have to be designed to be safe – particularly from the pilot's point of view. For these reasons the design process is also expensive, highly complex and takes a long time to complete.

Over the past 20 years the use of computer modelling has developed rapidly and computational tools are used extensively in aerodynamic and structural design and in the design and evaluation of the flight control system. So much work is now done in simulation that use of many of the traditional tools such as wind tunnels, structural test machines etc have been reduced to a very low level and, in some cases, has been removed.

However, the traditional approach to air vehicle design does suffer from a number of problems

  • It is very difficult (near impossible) to compress the process into a shorter time period.
  • It is very difficult to reduce cost
  • In some important areas, e.g. aerodynamics, the physics used in the simulations is not accurate under the flight conditions and, therefore, there is excessive uncertainty in the predictions. This adds risk to the programme technically and financially.
  • Many of the problems and issues that cause delays and cost overrun towards the end of a programme are the result of errors, etc introduced in the early project stage i.e. first 24 months. If better information can be made available in the very early stages, the whole programme can be better controlled
  • Since design cycle times are so long, design teams do not get the opportunity to hone skills on a significant number of flying vehicles. The lack of experience adds to programme risk.

All these issues point to the need for the production of a flying vehicle at the very earliest stage in an aircraft, (manned or unmanned) programme. Until recently, this was impossible for manned systems. However, the development of advanced UAV capability makes “rapid prototyping” possible.

Rapid Prototyping has the potential to deliver total aerodynamic definition including all control effects, derivatives and damping terms. For certain classes of Unmanned Air Vehicles (UAV) these could be accurate full scale values. In projects for which the prototype is a scale model, there would be scale effects to allow for. However, the design team still gets good data and design tools that can be evaluated against the sub-scale data.

  • Total flight dynamics capability, provided that the moments of inertia are correctly represented. Again this could be full scale or scaled down (or up).
  • A prototype flight control system design, this is particularly valuable since this is a critical component in any vehicle programme and is a high risk item.
  • Hard data for tool and process validation.
  • A better understanding of system integration issues at a very early stage, e.g. novel control systems or novel propulsion concepts.
  • All vehicle programmes – manned, unmanned, civil and military could benefit from rapid prototyping. All system builders – large and small - can use rapid prototyping to reduce their exposure to risk considerably.

Cranfield Aerospace is leading the world in the provision of rapid prototyping capability through the use of sub-scale flight demonstrators on the Boeing Blended Wing Body (X-48) programme.

  • Parameter identification – this allows the extraction of aerodynamic data from the flight dynamic data collected from the Flight Control System (FCS) and its associated sensors.
  • Robust FCS design – the classical approach to FCS design is complex, highly iterative and requires specialist skills. This is the approach used in manned systems. However, for unmanned systems, “robust” methods can be used to produce FCS which are simple and highly tolerant to poor quality input data. These systems are commonly used in missile FCS design.




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