TetherCalc is software package designed to calculate the dynamics of space tether systems. Multipoint mathematical model presented in the book "Dynamics of Tethered Satellite Systems" is the basis of the software package. In this model the tether is considered as a chain of the material points connected by massless viscoelastic bars. The model takes into account the interaction between the cable and the atmosphere. The spacecrafts connected by the tether can be considered both as material points and as rigid bodies. TetherCalc provides possibility to simulate the deployment of the tether from one of connected spacecrafts and retraction of the tether on its board. Simulation results can be obtained in the Greenwich geocentric coordinate system and in the barycentric coordinate system associated with one of the spacecraft.

Integration of the system of differential equations is carried out by the Runge-Kutta of 4th order with automatic step-size selection. The program is written in c++ and can be run in Windows. As an example of the complex results of the modeling of the space elevator fall in the atmosphere.

On the following video falling of the top end of the elevator after rupture is shown.