Sent that too soon...


on 3/27/01 1:48 PM, Dipperstein, Michael at mdippers@HARRIS.COM wrote:

> I never understood escape velocity.  What is the direction of it's vector, and
> how is it determined?  Is the 25,000 MPH figure an initial velocity, away from
> the Earth, with a deceleration due to Earth's gravity, and not other
> acceleration?

That is correct; it is the initial speed required, directly away from the
center of mass, to escape the gravity well in absence of other acceleration.

> It would seem like an object already in orbit would have an escape velocity
> based on it's orbit.

An object in a higher orbit, therefore, requires a smaller initial velocity
to escape Earth's gravity. That's why it's more efficient to launch
deep-space missions from a space station (rather than trying to accelerate
all of the required fuel to the surface escape velocity).

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