Keeping your habitat on the track

From: "Dr. Omni"
To:
Sent: Wednesday, November 29, 2000 1:05 PM
Subject: [spacesettlers] Keeping your habitat on the track

> From: "Tom Tucker (Olympia)"
> To:
> Sent: Wednesday, November 29, 2000 2:52 AM
> Subject: Re: [spacesettlers] Re: Heat management, recycling, $, and space
> ores
>
> > Darren, etal.,
> >
> Tom, etal.,
>
> > You are correct. I believe the force for a solar sail is on the order of
1
> > newton per square KM. Launching and retrieving space craft will have
much
> > larger affects, especially if a catapult is used.
> >
> For the case of a habitat in the asteroid belt orbiting the sun with the
> same face (mirror set) turned to the sun, the effect of incident solar
wind
> and sunlight can be considered mostly constant, and thus one can simply
> compensate it by using a orbital speed smaller than that that would be
> necessary in a pure vacuum with no additional forces. Instead of
considering
> just the gravitational force of the Sun, M*G/R^2 (where M is the mass of
the
> Sun and R the orbital radius of the habitat), you would actually to
consider
> M*G/R^2-F (where F is the outward force given by solar wind/sunlight) when
> calculating the orbital speed. (Actually, the photomechanical effect of
> sunlight would be negligible, although solar wind has to be considered.)
>
> As for launching and retrieving spacecraft, I think that catapults should
be
> used only for launching craft from asteroids, moons and planets, where any
> recoil effect would be vanishing small. Although there are scenarios where
> maybe that would not be a problem. For example: imagine a habitat that
> retrieves spaceships coming from all directions and launch spaceships to
all
> directions, all the time; in a long time range, all those launchings and
> retrievals will pretty much cancel each other, and the orbit of the
habitat
> will be stable at large.
>
Tom - The use of catapults or a rotating tether would be far more economical
then the expenditure of rocket fuel. If the colony is near a magnetic field
(e.g. earth, Jupiter, etc.) then an electrically charged tether can be used
to restore the orbit.

> > 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.
> >
> 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.

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.