Re: Interstellar Propulsion idea using an Asteroid and a few comets!

From: AA Institute (abdul.ahad_at_ntlworld.com)
Date: 08/16/04 

Date: 16 Aug 2004 09:53:25 -0700

hex@mailmoka.ro (Hex) wrote in message news:<393e5637.0408150803.18c1c2d4@posting.google.com>...
>
> Sorry, but your ideea is not very useful.
> The first reason is that the density of material going further out
> decrases very rapidly.
> Of course there may be suitable bodies the Kuiper belt and even the
> Oort cloud, but you have to understand that most of the mass is
> concentrated in the "inner" solar system.

I hear what you say and I think when you say "inner" solar system, you
mean the solar system as far as we define its boundaries within the
heliopause and such like (i.e. as far as we can *see* material objects
beyond the orbit of Pluto).

The conventional view that I always had of the solar system coalescing
into the Sun and nine planets from a flattened proto-planetary disk,
always supports the view that the bulk of the mass should always be
concentrated towards the centre. So how come the gas giants (Jupiter,
Saturn, Uranus and Neptune) are in the *outer* solar system and the
tiddler terrestrial planets are in the *inner* solar system? Probably
through some random irregularities in the uniformity of the
proto-planetary disk? I always had a common sense notion that
F=G(m1*m2)/r^2 would dictate the massive planets to be further in than
they are.

In theory, the force of gravity is *infinite* in its reach (F <> 0
until r = infinity), hence the Sun's sphere of influence goes as far
as Alpha Centauri and beyond... albeit the strength falling off
rapidly in line with the inverse square law. Hence you would expect
the bulk of the mass to concentrate near the centre of our solar
system (which it does, generally). But the Sun has made some 20
revloutions around the Milky Way galaxy since its formation (4,500
million / 225 million years). Within that time, it has passed through
dense gas clouds, star and planet forming regions, brushing the outer
edges of proto-planetary disks of other stars, attracting and shedding
swarms of comets, it may even have swapped planets with other stars
(are we certain that Pluto is a *native* member of our own solar
systeme???) etc. etc.

There is every reason to suppose there may be swarms of comets out
there, where the solar illumination is too tiny and the cosmic night
sky's miniscule flux of 1/300th of a full moon light illumination
(thanks to my own little evaluation!) is too tiny to enable visual
detection by current telescopes.

> Also, a sphere grows 8 times when you double it's radius. So a 1 ly
> sphere would be almost 40 bilion times the volume of a sphere going
> all the to Pluto.
> It's fairly easy to see that the average mass density is very low, and
> goes down quickly as you go out inner solar system.

That's to be expected of course based on elementary Maths relating
radius to volume.

> And another problem with your system is speed... you can't accelerate
> continously as you assume.

It will have to be a *slow* route to the stars, hence the need for
this to be a "generation" starship of a miniature *world* size, which
makes it a hollowed out asteroid as probably one easy solution. Why
invent cheap imitations when nature has already provided ways and
means?

Perhaps an asteroid of #243 Ida's mass and density is too tall an
order for a starship design, but what would be a better solution is a
lower density asteroid that is perhaps of a class known as an 'Earth
approacher' rather than a 'main belt' asteroid candidate. That would
be easier to excavate if its of a lower density and if its of a lower
mass, then relatively easier to change its orbit.

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