# Talk:Terminology

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## Energy for all orbits with the same SMA aren't identical

I'm not sure if I made a logical error here, but the claim, that for all orbits with the same SMA around the same body the energy is identical is incorrect:

 “ All orbits with the same semi-major axis have the same energy. ”

When you reorder the formula there is something like this ${\displaystyle E=\epsilon _{k}\cdot m+\epsilon _{p}\cdot m}$ where ${\displaystyle \epsilon _{k}}$ and ${\displaystyle \epsilon _{p}}$ are the kinetic and potential energy divided by the mass. So ${\displaystyle E=\epsilon \cdot m}$ and as ${\displaystyle \epsilon }$ (the specific orbital energy) is identical for all orbits with the same SMA (see specific orbital energy on Wikipedia), ${\displaystyle E}$ additionally depends on the mass of the craft.

I would suggest to write the section in a manner that covers also the SOE. It is easier to calculate because you don't require the mass of the craft and it has still the same implication: Is the sum greater than zero it is a hyperbolic orbit. — xZise [talk] 13:42, 22 September 2013 (CDT)