  In this paper I calculate the possible alteration of the gravitational field
in a superconductor by using the time-dependent Ginzburg-Landau equations
(TDGL). I compare the behaviour of a high-Tc superconductor (HTCS) like
YBa_2Cu_3O_7 (YBCO) with a classical low-Tc superconductor (LTCS) like Pb.
Finally, I discuss what values of the parameters characterizing a
superconductor can enhance the reduction of gravitational field.
