Orbits

Orbital decay

Orbits can be artificially influenced through the use of rocket engines, which change the kinetic energy of the body at some point in its path. In this way, changes in the orbit shape or orientation can be facilitated. Solar sails or magnetic sails are forms of propulsion that require no propellant or energy input other than that of the Sun, and so can be used indefinitely for station keeping. (See statite for one such proposed use.) Satellites with long conductive tethers can experience orbital decay because of electromagnetic drag from the Earth's magnetic field. As the wire cuts the magnetic field it acts as a generator, moving electrons from one end to the other. The orbital energy is converted to heat in the wire.