In this thesis we conduct numerical studies on plasma-spacecraft interactions by examining two different shapes of spacecrafts, a rocket and a satellite. They are simulated by a cylinder and a box corresponding to the rocket and the satellite respectively. We will make use of the DiP3D code developed by Wojciech with modification to the object handling of the code. By using polygon fill method we can build the object by ways of ray tracing whether we are outside, inside or on the surface of the object. This is done by using the corner coordinates of the object. Our simulation objects have different dimensions and different shapes and we discover that this has profound impact on the spacecraft. The charging over the spacecrafts turn out to be anisotropic and we retrieve different potential profiles for the two objects. The anisotropic potential results in a dipole electric field which also seems to differ in intensity for the two objects. For the cylinder we yield a stronger electric field in the upstream than in the downstream while in the case of the box the intensity does not seem to differ by much. Furthermore the study shows agreement with the previous work concerning the temperature ratio and the wake structures forming behind the object. The wake structures in particular seem to depend on the flow and the object dimension as the electrostatic wake structure is also significantly different in the two cases.