Inastrodynamics, the characteristic energy (
Every object in a 2-body ballistic trajectory has a constant specific orbital energy 
where 
is the standard gravitational parameter of the massive body with mass 
, and 
is the radial distance from its center. As an object in an escape trajectory moves outward, its kinetic energy decreases as its potential energy (which is always negative) increases, maintaining a constant sum.
Note that C3istwice the specific orbital energy
A spacecraft with insufficient energy to escape will remain in a closed orbit (unless it intersects the central body), with
where
is the standard gravitational parameter,
is the semi-major axis of the orbit's ellipse.If the orbit is circular, of radius r, then
A spacecraft leaving the central body on a parabolic trajectory has exactly the energy needed to escape and no more:
A spacecraft that is leaving the central body on a hyperbolic trajectory has more than enough energy to escape:
where
is the standard gravitational parameter, is the semi-major axis of the orbit's hyperbola (which may be negative in some convention).Also,
where 
is the asymptotic velocity at infinite distance. Spacecraft's velocity approaches as it is further away from the central object's gravity.
MAVEN, a Mars-bound spacecraft, was launched into a trajectory with a characteristic energy of 12.2 km2/s2 with respect to the Earth.[1] When simplified to a two-body problem, this would mean the MAVEN escaped Earth on a hyperbolic trajectory slowly decreasing its speed towards 
The InSight mission to Mars launched with a C3 of 8.19 km2/s2.[2] The Parker Solar Probe (via Venus) plans a maximum C3 of 154 km2/s2.[3]
Typical ballistic C3 (km2/s2) to get from Earth to various planets: Mars 8-16,[4] Jupiter 80, Saturn or Uranus 147.[5] To Pluto (with its orbital inclination) needs about 160–164 km2/s2.[6]