An aerodynamic design method is presented for high-performance conventional-concept airship. The emphasis is put on the following points: 1) LTA equipped with vector-thrusters, 2) LTA having extremely excellent transportation efficiency to be developed in future, 3) Simple and clear designtarget-diagram, 4) How to determine the installed power, 5) How to estimate volume and surface area of gas envelope, easily and quickly.
The problem of determining optimal cruise trajectories is examined for a performance index that is a linear combination of time and fuel, and an application of the singular perturbation method to the optimization problem is discussed. It is shown in this paper that use of the singular perturbation technique combined with a multiple time scaling approach leads us to obtain a control solution that has an algebraic feedback form. The condition of optimality for a steady-state cruise is checked by the II test which consists of the second order derivatives of the criterion. Concerning with the optimality of the steady-state arcs, it is found that there exists a periodic control that can reduce fuel consumption if the weighting coefficient on fuel is large. The optimal trajectories using the periodic control are calculated in a numerical example and show that about 1 percent increase of fuel economy is achieved for the case of the minimum fuel trajectory.
One of the important material problems for the spacecraft in the low earth orbit is a degradation of materials caused by atomic oxygen. In this study, the effects of atomic oxygen on carbon based materials which will be used for long duration structures are simulated numerically using molecular dynamics method. The graphite structure is chosen as the target material in the analysis. The interactions between each of the carbon atoms, atomic oxygen, carbon monoxide and carbon dioxide which are produced by chemical reactions, are approximated by a two-body potential (the Lennard-Jones potential) function. The energy changes in chemical reactions (oxidation) are regarded as the changes of the potential energy functions. The numerical analysis is shown for the arrival of single atomic oxygen with high energy, its reaction with a carbon in the graphite and the atomic rearrangement in the graphite. The results giving only some examples in a specified condition, this method can generally show the effects of kinetic energy of atom, reaction processes, target materials, surface temperatures etc, suggesting a new approach to the study of material degradations in space.
The research of the next generation supersonic civil transport is being conducted extensively in a few countries. The major environmental problems of the supersonic civil transport are sonic boom, noise and engine emissions. In this paper, we evaluated potentialities of future supersonic civil transport from a viewpoint of sonic boom and airport noise. We defined three factors: boom factor, the degree of the influence by the sonic boom, CT factor and C2T factor, both representing the cost and time saving effects. The calculation results show that the supersonic civil transport had reasonable values of CT and C2T with acceptable range of boom factor in the pacific oversea flight.