• calculate the energy requirements for such failure to be realized; • for the given mode, identify the minimum laser pulse time required to heat up the given thickness, area, volume; • calculate the laser power flux density requirements that will given the required energy. Thus the limiting parameters would be: • total energy flux required; • pulse duration of the laser; • power flux density at the surface of the object. Thus by limiting above parameters, the use of lasers as anti-satellite weapons can be limited. Appendix I Central to the question of the interaction of lasers with materials is the issue of laser heating. The equation governing this heat transfer for unit area can be simply written as: This is a special one-dimensional steady state case of the Fourier law of heat conduction, where Q is energy at the surface, t is time, T is temperature at surface, x is direction of heat flow. It is of course possible to solve the generalized Fourier law of heat conduction [23] and a variety of approaches exist [12, 13, 14, 15, 16], For a laser with a pulse duration of t and Q energy absorbed by the material, the above equation can be approximated to: where Ax is the thickness of the layer heated by the laser pulse. For unit area of the material the volume of the heated area=Ax. The total energy absorbed by unit area of the material Q=Cp ■ p^xNT where Cp is specific heat, p is density, Axis the thickness of the absorbed layer and AT is the rise in temperature. Substituting this, equation (A2) can be written as: Equation (A3) gives the thickness of layer heated up, given a laser pulse of duration At. This depends only on material properties of specific heat Cp, thermal conductivity K, and density P. For a given At the thickness of the heated layer depends on the factor
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