 Characteristic energy

In astrodynamics a characteristic energy (), a form of specific energy, is a measure of the energy required for an interplanetary mission that requires attaining an excess orbital velocity over an escape velocity required for additional orbital maneuvers. The unit of the characteristic energy is km^{2}s^{2}.
Characteristic energy can be computed as:
where
 is the orbital velocity when the orbital distance tends to infinity. Note that, since the kinetic energy is one half mv^{2}, C_{3} is in fact equal to twice the magnitude of the specific orbital energy () of the escaping object.
Contents
Parabolic trajectory
For a spacecraft that is leaving the central body (e.g. earth) on a parabolic trajectory:
Hyperbolic trajectory
For a spacecraft that is leaving the central body on a hyperbolic trajectory:
where:
 is length of semimajor axis of orbit's hyperbola.
See also
References
 Wie, Bong (1998). "Orbital Dynamics". Space Vehicle Dynamics and Control. AIAA Education Series. Reston, Virginia: American Institute of Aeronautics and Astronautics. ISBN 1563472619.
Categories: Astrodynamics
 Celestial mechanics
 Energy in physics
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