Keeping your habitat on the track

"Tom Tucker (Olympia)" wrote:
>
> From: "Dr. Omni"
> To:
> Sent: Wednesday, November 29, 2000 1:05 PM
> Subject: [spacesettlers] Keeping your habitat on the track
>
> > From: "Tom Tucker (Olympia)"

> > > The use of nuclear or solar powered electrical plasma rocket engines is
> > > perhaps the most efficient means of orbital modification over periods of
> > > many months.

Compared to ion drives they are a lot more efficient of power. Always
assuming anyone can get them to work (they run really HOT).

> > Or perhaps electromagnetic mass drivers - it would even be a nice way to
> get
> > rid of the trash ;-). Even though the "heuristics" that I propose above
> can
> > greatly minimize the need of adjusting the trajectory of your habitat,
> there
> > will be occasions when some active compensation will be needed anyway. For
> > instance, when a mass coronal ejection hits the habitat, F in the equation
> > above will be much greater that the typical value, I guess...
> >
> Tom - The expenditure of mass for propulsion means that it must be restored
> from some source such as an asteroid.
> Recycling of all garbage should be a goal.

Probably. However when you consider the thousands of tonnes needed to
make
a habitat the costs of mass probably won't be so great- there's no way
to build a habitat if the cost is $10,000/lb. Does anyone have a rough
figure
on the underlying costs of launching mass from the moon or an asteroid
to
HEO? I suppose mass launchers get close to pennies a pound. It must cost
more than that on earth.

> A rock launched from the colony may oneday return unless carefully launched
> into an orbit that results in a slower orbital velocity than the colony.
> Aiming back, along the path of travel, would be best.

Yes, actually to a first approximation, firing trash out doesn't work.
In LEO some of the astronauts remark about being surrounded by
the 'moons of uranus' or some such phrase- the toilet vented to
the outside...

This wasn't a short term thing...

For a small change of orbit, the new orbit takes almost
exactly the same time as the old orbit and intersects in two places.