LA MÉCANIQUE CÉLESTE

From time immemorial, man has observed the celestial vault. Always present above his head, the planets and stars have stimulated man's imagination, arousing in him the desire to reach them. Quickly, he dreamed at night that he "had found the secret of freeing himself from the laws of gravity, so that his body having becomae indifferent to going up or down, he could do one or the other with equal ease and according to his will" tells us Brillat-Savarin. This dreamlike flight mobilizing itself under a light impulse is the very impression of the pure leap, of an impulse forever suspended. Man becomes, through his dream, a light and floating being, thus finding the maternal matrix. But our desire to fly, as old as humanity, requires nevertheless a surpassing of the body, which alone struggles to rise. But how to solve this problem of the mechanics of flight? How to find this dynamic allowing us to free ourselves from the laws of gravity? This quest, which up to now was only visual, was gradually transformed into a physical project. To reach these extreme altitudes, man had to make sure that the centrifugal force and the terrestrial attraction compensate each other exactly. To ensure that the chosen vehicle receives a mathematically exact impulse, man had recourse to the old celestial mechanics. Thus was born the science of astronautics, capable of predicting the trajectory and speed of any projectile. The voyages out of our atmosphere are then drawn, but where is it a question of going? This flight towards the sky, will make us imagine with envy the flight of the astronauts in weightlessness, becoming thus revealing agents of this underlying dream. With the celestial mechanics, I make myself the vessel of an imaginary voyage, transporting us in the confines of the world, a voyage in the history of the mechanics of propulsion and towards the space vacuum. Thus reminding us that the imaginary was and will be very often the ideal vehicle of the simulation of the learned proposals. Thanks to the Cité de l'Espace and to ISAE SUPAÉRO, and more particularly to Serge Gracieux and Laurent Joly who have been able to devote time to enrich my research and to nourish a little more this imagination through discussions, readings and laboratory visits.

Manon Lanjouère