This paper describes the current status of knowledge regarding the impact of aviation on the atmosphere. The growth of the aviation industry is likely to continue in the future and at present there are significant concerns that this will adversely affect climate and local air quality in the vicinity of airports. Indeed, it is possible that air quality may become a constraint to increased capacity of some large hub airports. Currently the radiative forcing impact from aircraft emissions, other than CO2, are not accounted for in the International Civil Aviation Organization emission trading scheme proposals. Taking only this approach, emissions trading could, in theory, increase the radiative forcing, rather than decrease it. The study of improved ‘environmentally friendly’ flight is still in its infancy, however any proposed and actual new developments, in terms of technology and operational practice, should include an environmental assessment.

Closed-form equations for the evaluation of forces on a body in compressible, inviscid and viscous flows are presented. The expressions which are used to calculate lift and drag require only knowledge of the velocity field (and its derivatives) on an arbitrarily chosen contour enclosing the body. Various forms of the force equations are presented, both for two-dimensional and three-dimensional flows. The work is an extension of earlier research by Noca) developed for incompressible flows. The equations are implemented on a number of two-dimensional aerofoil cases and the results show excellent agreement with surface and wake integration approaches.

For generalised Hohmann and bi-elliptic transfer orbits, we applied small tangential impulses at peri-apse and apo-apse to acquire the precise destination elliptic orbit stemming from an initial orbit. There are four cases for this correctional or improvement process. We take into consideration the first configuration for the time being. We determined the four relationships connecting the increments in major axes and eccentricities with the correctional increments in velocities ΔvA, ΔvB at points A, B for the generalised Hohmann case. We assigned the three relationships - for the bi-elliptic transfer - connecting slight changes in major axes with small increments in velocities at points A, B, C due to motor thrusts.

Coupling an unsteady flow-solver with a structural model offers the opportunity to simulate aeroelastic behaviour of wings and rotor blades. The moving and deforming surfaces resulting from unsteady simulations require deforming meshes during the simulation, and it is common to use simple interpolation of surface displacements and velocities onto the initial undisturbed mesh. However, aeroelastic simulations can result in large displacements and deformations of solid surfaces, and simple interpolation of perturbations results in poor grid quality and possible grid crossover. A new interpolation technique is presented which is still simple in that it is driven solely by surface motion, but represents rotational effects near the solid surface, to maintain grid quality there. Furthermore, the scheme is fully analytic, so is very cheap computationally and results in grid speeds also being available analytically. Results, in terms of unsteady grid motion and flow solution, show the scheme to be effective and efficient.

This paper relates to a recent project in which the aim was to devise a procedure that could be used to identify the linearised transfer functions of the longitudinal motion of the solar powered airship Lotte from flight test data.

Using a non-linear mathematical model of the Airship, a linearised state space model was derived numerically and this was used to derive the response transfer functions, which formed the theoretical results. A test procedure was then developed to identify the transfer functions experimentally from frequency response data obtained in simulated flight tests. Initially, the linearised model was used and the test procedure was refined until a suitable level of coherence between the experimental and theoretical results was observed. The test procedure was then applied to simulated flight test data from the non-linear model, and finally sensor noise was added in order to represent actual flight test conditions as closely as possible. Unfortunately, the results were inaccurate and in some cases, they were unacceptable. When the test procedure was applied to the non-linear model, significant errors were seen in all the results. The addition of sensor noise led to heavily distorted results and a further degradation of the resulting transfer function estimates.

It was concluded that meaningful results could not be achieved unless frequency response data with a higher resolution could be obtained and the effects of sensor noise could be reduced. Presently, no test procedure has been developed that would be of any use in a practical situation. However, a number of ways of possibly improving the test procedure or otherwise improving the quality of the results were conceived near the end of the project. It is therefore the purpose of this paper to account for the shortcomings that were encountered in the project and to introduce briefly the unexplored remedies, in the hope that these may be of some benefit to future identification studies.