NEA trajectory / relative velocity

Hi Al,

No argument re your physics, but a major one with your interpretation of
the result. If Earth's mass is as domininant re the asteroid's mass as
the Sun's is to ours, then as far as we humans' rocket engineering and
fuel are concerned the velocity differences will indeed amount to a high
delta V - even if for general astronomical puposes there may seem little
difference.

Best wishes, Andy.

Al Globus wrote:

>
> andy-nimmo wrote:
>
> > Hi John,
> >
> > You say, "Quite the contrary: Its orbit is very like ours
> (definition
> > of NEA). Similar mean distance from the Sun necessarily means that
> its
> > velocity around the Sun is similar to ours around the Sun. Hence,
> low
> > Delta-V requirement." This is simply untrue. For its velocity to be
> > similar to ours in a similar orbit it would have to have similar
> mass
> > to us, and none of these do.
>
> What matters is the ratio between the mass of the Sun and the object
> orbiting about it. If the masses are reasonably similar they each
> orbit
> about.in between them. As long as the sun's mass is sufficiently
> dominant, the satellite effectively orbits around the center of the
> sun
> regardless of its mass.
>
> The equation is: GmM/r^2. So if m <<<< M variations in m don't
> matter
> much.
>
> > --
>
> Al Globus
> aglobus@..., (650) 604-4404
> http://www.nas.nasa.gov/~globus/home.html
>
> The dinosaurs weren't spacefaring. We are. I don't think that's an
> accident.
> Maybe we are life's taxi to the stars.
>
> I think we should:
>
> 1. Devote half of NASA's budget ($7 billion) to reaching NASA's 2020
> goal of
> reducing launch costs to Low-Earth-Orbit to $220/kg with a 0.01%
> failure
> rate.
> This should enable space tourism. The resulting orbital hotels will
> need
> to
> develop efficient orbital life support and other necessary
> technologies.
>
> 2. Build orbital space colonies. The materials in the largest asteroid
>
> are
> sufficient for orbital colonies with a combined surface area about 500
>
> times
> greater than Earth's. Eros alone could make over ten thousand space
> colonies,
> each with about about 10 square kilometers of 1g living area.
>
> 3. After a few generations of orbital living, people won't need their
> colony
> to be near Sol. Then small groups of colonies with populations in the
> tens-of-thousands can set out on multi-decade journeys to nearby
> stars.
>
> Except the launch goals, none of this is even a little bit official.
>
[www.newaydirect.com]