On the basis of well-known model of temperature- stimulated cathodic diffusion (TSCD) obtained mathematical expressions to determine the probability of fracture cathode electric propulsion for the three modes of forced endurance test. This change modes with independent basic parameters TSCD (load) – cathode temperature, ion flux density and ion energy. It is shown that the proposed method allows to vary widely predict the parameters of loading and the resulting characteristics of the physical mechanism at constant TSCD. Found that estimates of the probability of TSCD by several orders differ from the experimental values of the coefficients of cathode sputtering. We discuss possible reasons for the discrepancy of experimental and computational results theoretically and ways to overcome them.