From: Mark.OLeary@newcastle.ac.uk (M.D. O'Leary)
Newsgroups: alt.fan.pern
Subject: Re: Colony ships, among other things...
Date: 8 Apr 92 12:34:50 GMT
Organization: University of Newcastle upon Tyne, UK NE1 7RU

J'shua expounded:                                                                 
                
>                                   2 -------------\
>                               . . o. .            >- Lagrangian Points
>                            4 '    1    ' 5-------/
>                           .              .
>                          .  X     y       .
>                          .        O Pern  .
>                           ,              ,
>                            .            .
>                              ' .  3 . '  \_ Moon Orbit
>
Hey what a cute ASCII sketch. I love it.
>
>Horkey dorkey: The .... line is the orbit of a moon. O is Pern, o
>is one of the moons. 1-5 are the Lagrangian points (No, they are
>.....stuff deleted....
>X is an estimated Geostationary point.... for a planet like Mars
>this is actually outside one of its moon's orbits, and between
>the other's. 'y' is where you want to be                      

The position of '1' (and `3`) depends on the relative masses of the planet and
the moon. With a small planet (! see recent discussions) and a large or dense
moon, `1` would be much closer to `y` than 'X'
>
>Anyway, you can't mainitan an orbit of 'y' over one spot on the
>planet without 'stationkeeping' - you need to FIGHT to stay
>there.                                                         
Therefore, you HAVE to park in a gravitationally stable point: the colonists
were thinking long term about this, and only had the 'sump tanks' available for 
stationkeeping fuel reserves...

>suspect Anne has them trapped in the magnetic fields of Pern
>(which rotate with the planet) - she does tend to like
>electromagnetic effects (see ATWOP). Plus, this lets the planet
>itself munch some of the power requirements.

As does the Lagrange case, to a much greater extent. You'd have to be really 
tricky to get this to work, tho'. Suggestions?
                                        

>----------------------------------------------------------------------
>Minor ATWOP Spoilers:
>
>Next Question:
>Now, how the SHARDS do you get gravity in the ship? They don't
>have Artificial Gravity, or Jaxom would have flipped them on.

Agreed. No artificial gravity, or the ship drive would be much more efficient.
   
>Spinning? Lets take a look....

Yes, lets! I love this mans ASCII drawings! Yummy! 
>
>                                                  ____        
>            __                   __            _-'    `-_      
>           |  \|\               /__\          /  \ |  /  \     
>           |HH||\-__       __--//__\\________|    \| /    |     
>           |HH||-__ --|-|--  ||_/__\_========| ____/\____ |     
>           |HH||- __--|-|--__|| \__/ ________|     \/     |     
>           |HH||/-           --\\__//        |    /| \    |     
>           |__/|/               \__/          \_ / |  \ _/
>            ''                                  `-____-'
>


OK to get 0.5g in living compartment and 0g in cargo space on 'vanes', just
have the living 'sphere' roitate relative to a 'still' central spindle.
This also allows ships etc to dock 'head-on' with no relative spin, and
still maintain gravity for crew in other areas (Also allows zero g for cargo 
unloading!). The sphere would be split into several concentric levels, onion 
style fro crew accom. There would in fact be a gravity gradient- low near the 
spindle, higher towards the outer skin.   
I belive this answers these points...
>If the whole ship spun, you'd have one hell of a time
>docking/undocking everything, and the central column of the ship
>would be unusable (the difference in gravity head-feet would make
>you dizzy.)

But,
>you dizzy.) Also, just spinning the sphere would put tremendous
>tidal forces and shearing forces on the ship.

This is just an engineering problem, surely? Yes, you'd need really good
bearings to transfer the thrust from the column to the sphere without
stopping the spin, but....
Maybe the outer sphere is fixed, and only the inner part of the sphere
rotates?

>In any case, how were the decks arranged inside the ship? I
>always assumed they were layered within the sphere, 'back to
>front' so that during acceleration/anti-acceleration, youCd bD
>properly pressed to the floor. IE, on that diagram, like this:
>                        gravity pulls you <-  ||||||||||||| 

On a multi-year journey, with 'low-tech' (by SF standards) drives, you could
arrange for acceleration and deceleration to be only in terms of microgravities.
I think the acceleration/deacc was v.slow: when they arrived in the
rukbat system, they  were just coasting (since they took so long to get to   
Pern!) Also, this is safer: low speed in systems, where prob of hitting
space flotsam is higher...

>Anyone have 1/2 a clue how it would work?
>
>Joshua 

Wel, what do ya think? Is this a good 'nuff explanation?

This was my 5p-worth, anyway.

Mark aka Raphe (now known as the woman hater...)
Newsgroups: alt.fan.pern