Super-habitats

Lucio,

>On 9/3/06, Darren > wrote:
>(...)
>> I am afraid that I have become somewhat obsessed with the idea if these
>> hyper-habitats, I have read about how Larry Niven had to invent a special
>> kind of unobtainium just to make his Ringworld work, I can understand this
>> as basically it is a single span bridge with out any ends but as I was
>> thinking about it I started to wonder if you really would need unobtainium.
>
>Yours obsession is fascinating, so keep writing about that. ;-)

Thanks for the encouragement. Before I start on my comments perhaps a short
personal note is called for, just to give you some idea of the background I
am writing from and so that if I slip and make a comment without a reference
you will understand what I am saying.

I am 46 years old and work in a technical area of a police force, the
electronic forensic section (18 12 yrs), my technical background (outside
my work specialty) has been patchy, so my knowledge base is very broad but
in many areas very shallow, in others very deep. My wife is a lovely lady
(and I love her dearly), we have been together for more than 25 years now,
while she is a sci-fi fan, likes technology and works in a kind of
technical area (biology, nursing), she is also one of the most tech
illiterate persons Ive ever met, she will watch the TV with a picture that
is almost unrecognisable because she is unable to work out that pressing ONE
button will switch you from the normal transmitted broadcast (for which we
have no antenna) to the Hi-Def Wide-Screen picture from the cable or
satellite systems (which has no need of a regular antenna), if it has power
running through it then without me at home, it doesnt happen, well, it
mostly doesnt happen.
I often use her to sound out ideas to see what kinds of things people think
about space projects (by people I mean somebody other than those of us
singing in the choir). She has always been uncertain about the idea of
living in something as large as an island 3, not really being able the
understand that it is so large she would not be able to think of it as
living inside but the idea of something the size of these super-habitats is
one she is enthusiastic about. I have to wonder how many others out there
are just like her.

Grrrr ,
I am typing this at my desk at home (currently on extended leave on doctors
orders nothing serious, Im happy to say), from where I sit I can see the
main TV in the lounge room and the Discovery channel is on and one of few
things guaranteed to light my fuse just came on, an advert/public service
announcement from those paragons of veracity and honour, ECO
(http://www.oneearth.org/ ), the advert (and lets not kid ourselves, it was
an advert, begging for money) was giving the usual message, use less,
recycle more. Now there is nothing wrong with that but go to their site and
you soon see that what they are really saying is lower your standard of
living and that is wrong, very wrong. This particular ad really get to me
(my wife is sick of hearing my rant every time it comes on, ),
it goes on about imaging that you live on an island and how your family is
growing and how you must take care because you can only have so many on your
island, then it tells us that in a way we all live on an island and how
while the Earth is big it isnt big enough to support too many, it can
support our need but not our greed. Then comes the line that makes me grind
my teeth, it says, So please, use only what you need, its not like we can
go shopping somewhere else. With a shot of the Earth from space as the
background. I want to grab them and yell into their faces LOOK UP. The
irony of it this time is the show that had just finished was about going to
Mars and possible colonies, the final shot of the show was of a hollowed out
asteroid going off to the stars. , okay, sorry about that but I had to
get it out of my system

>
>> All you really need is a material that can support itself and any load
>> against a 1G pull for the distance between any supports, that of course is
>> the rub, between any supports. The ring wouldnt have any supports or would
>> it?
>
>The designs that I have seen are "self-sustained", i.e., no supports.

This is true but if you had a very strong material and formed it into a
ring, placed this at your axis of rotation (with a central column for the
attachment of other rings or not) and from this ring hung the material of
your end-caps/air retention wall (call it what you wish), this could act as
the support of the ring, kind of like the cables of a suspension bridge. In
fact you could make then actual cables (made of the same material as the
central ring) and down lower where you need to keep in the air use a lighter
material to fill in the gaps to make a solid wall.

>> In order to hold in
>> the air you are going to need a wall/end cap, the question is how high do
>> you need them to be?
>
>I really don't have a precise number, but taking Earth as an example,
>were the "edge of space is defined at an altitude of 100 Km, I would
>think of walls 100Km high.

No, 100Km would not be high enough, any air above this would just leak away
and there is still a lot of air at that height. I will bow to anybody with
solid information about a reasonable height but until I get that I think
half way would be a reasonable place to start, with a 5,000 Km wide ring,
that 2,500 Km radius, so half way gives you a wall 1,250 Km high, run the
cables up to 2,000 Km height to place your ring, then if you have an axle
with other rings joined on (lets be greedy and assume that at lest one
other ring is in place and there are plans for more (even number all
counter-rotating naturally), this gives you 500 Km to the centre of
rotation, a 1,000 Km wide gap, have a 500 Km wide axle (no reasons for this
other than its half the distance) with 6 spokes (again no reason for the
number) connecting the ring to the axle. This gives you room for your ships
to come through if you want (but I have to say I am still uncertain about
this, it would be much safer and I think better to have ship scooped up into
a magnetic braking system on the underside of the ring, in fact, stealing
from Mr Niven, around the edge of the ring :)
Now about the axle (if there is one), at 500 Km wide, this is far bigger
than any island 3, it wouldnt be able to rotate faster than the ring as a
whole but there is no reason why parts of it couldnt, picture a series of
rings (going to have to think of some new names), around the axle, they
could be fitted flush with the axle or stand proud and could be say, 100 Km
wide (tiny compared to a 5,000 Km X 15,000 Km habitat), this would give you
the equal to what most of us consider habitats, they could spin faster than
the axle or even in counter rotation to the axle to give you an effective
micro-g work area. Access to them by trains running up spokes from the ring
to the axle. Think BIG. Have the axle project from the ring by 500 km at
each end and you now have an axle that is 16,000 Km long, the axle ring
being 100 Km wide with a 100 Km gap between them, you have 80 axle rings,
thats a cluster of habitats all by itself.

I have put the size of this thing at 5,000 Km wide and 15,000 Km long, these
number are in a way arbitrary. The 5,000 Km figure came from the Analog
article, that being the size of the sphere in the story. I seem to recall
some discussion about the stability of single cylinder habitats and problems
with cylinders with a greater than 3:1 length/width ratio, so 5,000 Km wide
gives you 15,000 Km long.

>> I have to wonder how you would know you were in a habitat, the ground
>> would seem flat to you, the ground curving above you might not be obvious
>> on something this size, it might disappear into the haze. There is the star
>> field at night but cities on the far side might look like stars, the sun
>> would look different and a central axle would stand out but is there
>> anything else?
>(...)
>
>Flatness may be a matter of choice. Some habitat designers may wish to
>build mountainous regions. (It is interesting to see that this kind of
>structure would lead to new professions with pompous names like
>"continent designer" and "mountain range designer.) Some of the
>mountains and islands could even be "natural" - in fact small
>asteroids transplantated to the inner surface of the habitat. Of
>course a more natural-looking environment with mountains of solid rock
>and oceans kilometers deep would add *a lot* of structural stress and
>probably call for smaller habitats, so in the end people may opt by
>shallow seas and fake mountains made of some foam-like material.

If you look at what we do on oceans or bodies of water now, other than
commercial fishing, I can see no reason to have deep water, we really on use
the top couple of metres. For swimming beaches the water should would not
need to be more than, say, 5 metres. Some places, reefs, caves and other
diving attractions, could have deeper water, for safety it should be around
10 metres for the most part with some sections going to perhaps 100 meters
for the most skilled divers. Then there are the fishing beaches and river
and lakes. My father-in-law is an avid recreational fisherman, sorry did I
say avid, I meant insanely obsessed. For this you would tailor the water to
the depth needed by the fish in the area, some would be shallow, 1-2 metres
and some deep, up to 100 metres, I see this as the limit really, deeper than
that is not needed. The most popular and expensive houses are situated near
the water (okay, I know this is not always true but 99%), for that reason I
can see our habitat having a lot of water or rather water frontage, the
bodies of water would not be very large, lots of rivers, lakes and a number
of seas were you would have beaches, they would be long and winding but
not very wide. One question that arises is do you go to the trouble and
expense to put in waves? For that matter would you have to? Waves are a
function of currents, underwater topography and the action of wind over
large bodies of water, on something this big you may have natural waves.

As for the mountains, I can see no reason to put in real, solid masses that
big, you would have to counterbalance them and have an equal mass on the far
side of the ring. That doesnt mean you cant have a couple of mountain
ranges or even caves for those insane people who enjoy such things ( I went
cave diving once, then I regained my sanity). For your mountains, if you
wanted real rock, how about this, final a real lump of rock about the size
you want (an asteroid that is not a pile of rubble) give it the outside
shape you want and then hollow it out so you have a mountain that is just
10-20 metre thick, put it on your ring with a supporting structure under it,
so it doesnt collapse under its weight.

A habitat of this size gives you some interesting lifestyle changes from
what you have here. With high speed mag-lev trains running in vacuum on the
underside of the ring you have transit times that could make intercity
travel possible for the work commute. Here in Canberra it takes me around
15-20 minutes to get to work and the people here think Im crazy for being
so far from work. When I lived in Sydney I would take 1-1 12 hours to get to
work and people thought that was normal, I now know of people who take 2+
hours to travel to work, each way. I would have to work it out but without
going up the spokes, how long would the longest trip by train be, assuming
you limit yourself to 1G in vacuum under the rim of the ring? What would it
be, a little under 50,000 Km (3.14 x 15,000 + 2,500, to start with before
bothering with the maths). One hell of trip. Still, with high speed
transport you could work in the city and live in the small rural village
and still not take more than an hour to get to work.

I have to go and pick up my son from school so Im going to leave it here
but I still have a few ideas buzzing in the back of my head, when they a
fleshed out I post them.

Darren