The direction and the magnitude of the solar radiation pressure are depending on the distance between sun and sail as well as the sail attitude. The orbital dynamics of solar sailcraft is in many respects similar to the orbital dynamics of other spacecraft, where a small continuous thrust is applied to modify the spacecraft's orbit over an extended period of time. However, other continuous thrust spacecraft (e.g. using electric propulsion) may orient its thrust vector into any desired direction and vary its thrust level within a wide range, whereas the thrust vector of a solar sail is constrained to lie on the surface of a ‘bubble’ directed away from the sun. Nevertheless, by controlling the sail orientation relative to the sun, solar sailcraft can gain orbital angular momentum and spiral outwards – away from the sun – or lose orbital angular momentum and spiral inwards – towards the sun.