Editing Characteristic energy (section)

==Non-escape trajectory==
A spacecraft with insufficient energy to escape will remain in a closed orbit (unless it intersects the [[central body]]), with
<math display="block">C_3 = -\frac{\mu}{a} < 0</math>
where
*<math>\mu = GM</math> is the [[standard gravitational parameter]],
*<math>a</math> is the [[semi-major axis]] of the orbit's [[ellipse]].

If the orbit is circular, of radius ''r'', then
<math display="block">C_3 = -\frac{\mu}{r}</math>