# Re: MARS HYBRID DESIGN II (First Draft)

```Kelly Starks writes:
> >David gave me these numbers
> >Pluto's mean orbital velocity is 4.74 km/sec.
> >Earth's mean orbital velocity is 29.79 km/sec.
> >
> >Are these right?  They seem backwards.
>
> I'ld agree.   It seems odthat you'ld accelerate out from the inner system
> to a slower velocity.  I suppose you might be losing the dif to potential
> energy changes.
>
> But I suppose it isn't critical for our discusion.  Assumeing a beam
> diameter 40 times the dimeter of earth.  4.76Km/s will still have you cross
> the beam in 31 hours.

This is the paradox of orbital mechanics.  To go from a faster
you have to accelerate twice -- once to raise the apoapsis of your
orbit, again to raise the periapsis.  So, in other words, yes, your
acceleration goes largely into raising your potential energy rather than

An elliptical orbit has a higher orbital velocity at periapsis than a
circular orbit of that radius, and a slower orbital velocity at apoapsis
than a circular orbit of that radius.

If orbital velocities got faster and faster the farther out you went,
how could there be such a thing as escape velocity?  How far out would
you have to go before orbital velocity got close to the speed of light?
It really wouldn't make any sense.

On another note:

Could we all try to avoid quoting huge amounts of each other's letters
only to add a few lines of comment?  It's redundant (I swear there are
now dozens of copies of all the same material from overagressive
quoting) and also very hard to read, as it requires paging through large
amounts of stuff we've all read already to get to the few new items of
comment.  I think it's a good rule of thumb to have less quoted material