A global theoretical approach and scaling laws in the plasma of the electrothermal launcher

Summary form only given. Some theoretical points concerning the ablation plasma of an electrothermal launcher are examined. Assuming a stationary plasma and combining dimensional analysis with energy conservation, the scaling laws for the plasma are derived as a function of the electrical energy W. Each variable of the plasma (mass M, temperature T, resistance R) is proportional to some power of W (W/spl alpha/, for M, W/spl beta/ for T, W/spl gamma/ for R), where the exponents /spl alpha/, /spl beta/, and /spl gamma/ are obtained analytically. It is also shown that the efficiency /spl eta/ satisfies 1-/spl eta/=K/R, where K is a constant. A nonstationary energy conservation equation is also studied. Taking into account ablation and thermal and ohmic energy, it appears that the temperature of the plasma cannot exceed an upper limit which depends on the charge voltage and the geometry of the cartridge. Physically, this condition corresponds to a configuration in which the rate of ablation is sufficiently high. Therefore, the temperature of the plasma cannot increase any more.