The way the solver works is by iterations ... having initial guess, and using it to calculate the residuals which is used to modify the guess ... by repeating this process, the values of the residuals keeps decreasing and the solution converges. However, if the initial guess is too far from the solution, the the 2nd guess might be further away ... and as iterations proceed, the values become too large and/or too small ... for example velocity = 1e+35 ... n