[muyyatin]

But, ignoring things like air resistance, the lower the thrust is, the more delta-V/energy it takes to escape?

For instance, if you had a rocket with a fixed delta-V and it used all of its energy almost instantaneously, say it escapes from Earth. But if you lower its thrust so that it is not accelerating upward (lower than the force of gravity), it could use the same delta-V without leaving the ground.

[garmaine]

No, it’s the things you’re “ignoring” which keep it on the ground. A solar electric thruster provides less thrust than the surface weight of the spacecraft it is pushing, but it is nevertheless able to push a probe to escape velocity and beyond over months or years of continuous thrust.

[muyyatin]

If it's in orbit, yes. I thought the discussion was based on something sitting on the surface of the Earth.

[garmaine]

That’s what I was talking about.