# Re: MARS HYBRID DESIGN II (First Draft)

```Brian Mansur wrote:
>
> Brian 10:15 CT 3/5/96
>
> >Kelly Starks x7066 MS 10-39 wrote:
> > Pluto moves MUCH faster than Earth.  Your mirror would quickly move out of
> > the beam.  even if the beam was larger than Earths orbit.
>
> >David
> >Pluto's mean orbital velocity is 4.74 km/sec.
> >Earth's mean orbital velocity is 29.79 km/sec.
>
> Why is the mean orbital velocity of Pluto 4.74 compared to a much larger
> 29.79.  Did you get the numbers mixed up.   I'm confused.

Nope, you can even do the math yourself.  I got the numbers
from the LANL solar system web site, though.  Let's see if
we can do this ourselves:

Earth orbits at around 148,800,000 km from the sun, right?
That's a circumference of 934,937,974 km.  It does this
in around 365.25 days, or 31,557,600 seconds.  That gives us
29.63 km/sec.  Pretty close to the LANL value.  I assumed
it was a perfect circle, and it's not.  Okay, now let's try
Pluto.  It orbits at 5,913,520,000 km (around 39.74 AU).
It revolves around the sun once every 248.54 years, or
7,843,325,904 seconds.  The circumference of Pluto's orbit
is 37,155,741,978 km.  That gives us 4.74 km/sec.  Wow,
dead on to LANL's value.  I must say I'm impressed,
especially considering the eccentricity of Pluto's orbit.
I assume the mean distance value is for an "equivalent circle".
That would explain the accuracy of my results.

David

```