First Ark to Alpha Centauri

"AA Institute" wrote in message
om...
"Laura" wrote in message:

It might even, in a very hypothetical situation, be useful as
camouflage.
Perhaps that could be worked into the story, as an unintended but
ultimately
beneficial side effect :-)

You mean it might stop the nightmares? No, that would spoil the story.
I have decided to shelve my asteroid idea and go for a complete
synthetic construction in Earth orbit. So, I have had to rename the
ship too, it's not called the "Aster-Com" any more... the 'Aster'
element originally stood for 'asteroid'...

http://uk.geocities.com/aa_spaceagen...acentauri.html

No, I actually meant to inadvertently avoid destruction or worse at the
hands of hostile passers-by on the way. Unlikely, I know, but might make for
an exciting and even humorously ironic episode in the movie :-)
In any event it would be good for stopping particle impacts - something a
synthetic thin-skinned vessel would be very susceptible to given the very
long duration of the voyage.
It's your story, though :-)

"Laura" wrote in message ...
"AA Institute" wrote in message
om...
"Laura" wrote in message:

It might even, in a very hypothetical situation, be useful as
camouflage.
Perhaps that could be worked into the story, as an unintended but
ultimately
beneficial side effect :-)

You mean it might stop the nightmares? No, that would spoil the story.
I have decided to shelve my asteroid idea and go for a complete
synthetic construction in Earth orbit. So, I have had to rename the
ship too, it's not called the "Aster-Com" any more... the 'Aster'
element originally stood for 'asteroid'...

http://uk.geocities.com/aa_spaceagen...acentauri.html

No, I actually meant to inadvertently avoid destruction or worse at the
hands of hostile passers-by on the way. Unlikely, I know, but might make for
an exciting and even humorously ironic episode in the movie :-)
In any event it would be good for stopping particle impacts - something a
synthetic thin-skinned vessel would be very susceptible to given the very
long duration of the voyage.
It's your story, though :-)

It's an idea, sure. The story probably looks kind of gloomy and
quiet... definitely there'll be some humour and bright moments! Just
because the starship is sailing in dark waters... plenty of bright,
sunshine (simulated by lights) and picturesque scenes inside will keep
things lively...

There is a fine balance between realism and dullness!

I wonder if cosmic rays can make objects of certain chemical
composition "glow in the dark"? So the ship might pass through a zone
of glowing gas or icy meteoroids acting as substitute for shooting
stars on Earth!

AA

"AA Institute" wrote in message
[....]
Actually, I have come up against a major major obstacle: tensile
strength of asteroidal material when you rotate the beast fast enough
to give you one - g of Earth gravity. It's not feasible, when the
asteroid is 5km in radius!!!

My god it's sheer high rotation speed is going to shred the thing
apart! Now, why the hell did I not think of something as basic as
that???

The rotation speed "v" would be v = (Rg)^0.5. So for my Aster-Com..

All hope is not lost Abdul :
Rotation speed is only an intermediate number. Did you do the
calculation which determines the stress forces in the material for
an asteroid of radius R ?
After all, speed is irrelevant. Only stress is important to determine
if your asteroid will stay in one piece, and how thick the wall needs to be.

I have the feeling that the problem is not so bad, especially if you
scale the asteroid to a factor 10 larger (to 100km radius or so).
That might be needed any way, since the population should be in
the tens of thousands.

Also, you could reduce the artificial gravity to 0.5g. That would make
a fun story also (imagine anything that is fun at low gravity..)

Rob

"Rob Dekker" wrote in message news:XMjpd.26786

since the population should be in
the tens of thousands.

Cheers, Rob. You need such a large number of people to keep the gene
pool wide over 500 generations, right?


Also, you could reduce the artificial gravity to 0.5g. That would make
a fun story also (imagine anything that is fun at low gravity..)

Oh it's so much fun with a rotating starship like that. You could spin
up/spin down to adjust the level of gravity... that should keep the
generations entertained!
I have settled for a synthetic construction in the end, since there is
hope that in 200 years time when the ship launches, we will have made
great strides in material science to come up with much tougher
synthetics that could withstand the stresses. I also read somewhere
that low density bodies such as comets break up on close approaches to
planets within the Roche Limit. Since my starship is going to use
close gravity assisted fly-by's of giant planets like Jupiter and
Saturn for initial escape from the solar system, I felt it will be
better to use a synthetic construction...

Abdul

"AA Institute" wrote in message om...
"Rob Dekker" wrote in message news:XMjpd.26786

since the population should be in
the tens of thousands.

Cheers, Rob. You need such a large number of people to keep the gene
pool wide over 500 generations, right?


Right. Otherwize you will end up with a bunch of mutants and sick people,
or most likely they will just die out before they make it even halfway.
Nature is pretty harsh when it comes to small gene pools.

Incidentally, most so are most human social and religious rules :
It is NOT acceptable behavior to marry your cousin.

"Rob Dekker" wrote in message . com...
"AA Institute" wrote in message om...
"Rob Dekker" wrote in message news:XMjpd.26786

since the population should be in
the tens of thousands.

Cheers, Rob. You need such a large number of people to keep the gene
pool wide over 500 generations, right?


Right. Otherwize you will end up with a bunch of mutants and sick people,
or most likely they will just die out before they make it even halfway.
Nature is pretty harsh when it comes to small gene pools.

I agree. However, accommodating a number of people beyond a couple of
thousand is going to be a real problem in my fictitious starship of
just 6 mile (diameter) x 9 mile (length) cylinder. To give the mission
the fairest possible chance I will go for people from every single
race on Earth...from aborigines through caucasians to negros... and
mongoloids! Only hope is they don't start to hack each other to death
in their cultural divides..

Incidentally, most so are most human social and religious rules :
It is NOT acceptable behavior to marry your cousin.

Yes in most countries that's true. Pakistan is one nation well known
for making it some kind of a 'rule' to keep marrying within first and
second cousins. I know, because a couple of friends of mine from that
country were forced to do this. It's very very bad practice, it makes
the offsprings have all sorts of weird allergies like exma, and other
illnesses since the diseases do not get a chance to get diluted over a
wider gene pool.

I'm very glad to say that where I come from in Bangladesh, we don't
have such a silly practice of 'in-breeding'! Ugggghhhh!

Abdul

"AA Institute" wrote in message
om...
"Rob Dekker" wrote in message news:XMjpd.26786

since the population should be in
the tens of thousands.

Cheers, Rob. You need such a large number of people to keep the gene
pool wide over 500 generations, right?

Your web page said 50,000 years, that's between 2000 and
2500 generations.

Oh it's so much fun with a rotating starship like that. You could spin
up/spin down to adjust the level of gravity...

Not easily - conservation of angular momentum. Letting very
large masses move away from the ship and pulling them back
in would do it, like a skater's arms, but the range will be
limited. Also there will be a narrow band to prevent calcium
loss from bones. A change of a few percent wouldn't even be
noticed.

... Since my starship is going to use
close gravity assisted fly-by's of giant planets like Jupiter and
Saturn for initial escape from the solar system, I felt it will be
better to use a synthetic construction...

Check how fast you can get this way. A single pass will give
a small increase which you can build up until you reach escape
speed but after that, you cannot turn back for another boost.
The real problem however is how you stop at the other end. You
cannot use the same technique since you cannot control your
entry into the system sufficiently accurately and even tiny
errors in measurements from Earth prior to launch time mean
the planets may not be where you want them when you get there.

George

"AA Institute" wrote in message
om...
"Laura" wrote in message
...
"AA Institute" wrote in message
om...
"Laura" wrote in message:

It might even, in a very hypothetical situation, be useful as
camouflage.
Perhaps that could be worked into the story, as an unintended but
ultimately
beneficial side effect :-)
....
No, I actually meant to inadvertently avoid destruction or worse at the
hands of hostile passers-by on the way. Unlikely, I know, ...

It's an idea, sure. The story probably looks kind of gloomy and
quiet... definitely there'll be some humour and bright moments! Just
because the starship is sailing in dark waters... plenty of bright,
sunshine (simulated by lights) and picturesque scenes inside will keep
things lively...

Lights would be inside. Calculate how much total power
your nuclear reactor (or whatever) will produce then you
can work out the outer skin temperature to radiate that
amount. Enrgy is conserved so no matter how you use the
power, eventually it ends up as heat. If the temperature
is too low for comfort, good thermal insulation on the
skin will raise the internal temperature. You could also
gold plate the outside.

Camouflage tries to blend in with the background. The ship
would glow with long wavelength infra-red against a cold
background but it's hard for us to even spot brown dwarf
stars, never mind an object only a few miles across. In
fact we have great trouble finding rocks within the solar
system.

....
I wonder if cosmic rays can make objects of certain chemical
composition "glow in the dark"? So the ship might pass through a zone
of glowing gas or icy meteoroids acting as substitute for shooting
stars on Earth!

http://www-ssg.sr.unh.edu/tof/Outrea...nterdepth.html

75% hydrogen, 25% helium, both transparent, at about 1 atom
per cc, and a tiny amount of fine, black dust. Although the
density is very low, you may still need to consider drag
over such a long voyage.

George

"George Dishman" wrote:

Your web page said 50,000 years, that's between 2000 and
2500 generations.

Out of interest, what formula do you use for this? I just did a
simplistic 50,000/100 to get 500 generations! (Assuming a lifespan per
person of 100 years)

It's not that simple , right?!


Oh it's so much fun with a rotating starship like that. You could spin
up/spin down to adjust the level of gravity...

Not easily - conservation of angular momentum. Letting very
large masses move away from the ship and pulling them back
in would do it, like a skater's arms, but the range will be
limited. Also there will be a narrow band to prevent calcium
loss from bones. A change of a few percent wouldn't even be
noticed.

In this mission, no such spin ups/spin downs are planned... so I wont
have to worry too much here. Once the ship reaches its nominal 1-g of
artificial gravity (at a biosphere rotation speed of c. 800 km/hour)
using its spin thrusters, it should stay at that speed indefinitely.
If *small* adjustments are needed along the journey, the spin
thrusters will be used.


... Since my starship is going to use
close gravity assisted fly-by's of giant planets like Jupiter and
Saturn for initial escape from the solar system, I felt it will be
better to use a synthetic construction...

Check how fast you can get this way. A single pass will give
a small increase which you can build up until you reach escape
speed but after that, you cannot turn back for another boost.
The real problem however is how you stop at the other end. You
cannot use the same technique since you cannot control your
entry into the system sufficiently accurately and even tiny
errors in measurements from Earth prior to launch time mean
the planets may not be where you want them when you get there.

It's complicated, hence this is only a fantasy voyage...

(AA Institute) wrote:
"George Dishman" wrote:

Your web page said 50,000 years, that's between 2000 and
2500 generations.

Out of interest, what formula do you use for this? I just did a
simplistic 50,000/100 to get 500 generations! (Assuming a lifespan per
person of 100 years)

It's not that simple , right?!

You don't plan to have children when you're 100? I'll be happy if I
hold out that long; I expect my balls will have shriveled long before
then. 25 years is, very roughly, a generation. People tend to have
kids around that time (+/- 10 years, very roughly). That may not be
all that's important evolutionarily, but the genetics are fixed at
conception, and that's what we're talking about.


Tim
--
Foo.