[jzila]

Potential energy is energy, so it's not quite correct that New Shepard had 0 joules at 100km. At 100km and 0 velocity it'll have about 1 gigajoule of energy per metric ton of mass.

[lutefisk]

Potential energy is not energy that you can give to a payload unless you want to have it fall 100km back to earth.

[jzila]

Sure, but it's energy that a rocket needs to impart nevertheless.

[gfodor]

The point was that the measurement is what it can impart on a payload (presumably one going UP.) So your point doesn't seem relevant.

[jzila]

I think the point was to illustrate the difference in energy requirements for the rocket to impart to the payload.

That said, re-reading Elon's article, he did explicitly say _kinetic_ energy in the 120GJ figure, in which case 0 is the right number for New Shepard at 100km.