Engineering Newsletter

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

Timothy replies to Kelly:

>Oh, I still say there is no significant difference between a suicide flight,
>and a flight where the crew are abandoned with enough supplies to last them
>their life.  I am frankly shocked that you and Tim could seriously suggest
>such a horrific and ruthless option.  Thats like sending a team to antartica,
>on a one way trip to the pole with no resuply and recovery runs!  "Hey guys,
>go there, explore, radio back what you find, and here's 50 years supplies and
>parts for you to live out you life with."

Summarizing what I write in this letter:
- We have to discuss what is necessary for a small colony.
- You can't compare Antarctica with a new planet full of life.
- We (or I) don't see it as dropping people without any regard, but as a well
  organized lifetime adventure.
- Do things break down or get lost faster than one can repair or replace them?

>This really isnt a problem Tim.  All large systems have to distribute their
>strructural loads amoung enough structure to get the job done.  The shuttle
>tanks for example weight 30 tons, yet can carry about 750 tons of fuel at
>multiple G accelerations, and provide expensive structural bracing for the
>fources of the attached solid boosters and orbiter.  Our starship design
>would be comparativly trivial.

For these shuttle tanks the bottoms have the highest pressure while the top
has a low pressure. (It could be left open, at least for the matter of
pressure).
So the weight of the tanks isn't the main clue but the size of the bottom is
(assuming that every part of the bottom gets the same pressure).
So a tank with a large bottom and the same weight has much less pressure at
that bottom. (The total force stays the same, the surface gets bigger).
So it would be wise to build the walls of the tanks thick at the bottom and
thinner at the top. Also the welds are more likely to break at the bottom
than at the top.
What I'm trying to say is thus that the bottom part is most vulnerable, 
For the pressure at the bottom of the shuttle tanks, I can estimate:
  (assuming a 3.5 metre diametre of the bottom)
(750+30 tons)*3g/(10 m^2)=830*3000=2.34E6 Pascal
That means it is still 170 times less than the maximum pressure (about 4E8 Pa)

So a large and heavy spaceship could be build but the load-surface should be
large enough. The load surface is in fact equal to the surface of the ends
of the beams that are connected to the engine. So taking long beams makes no
difference, only taking thick beams does.
Now where I was going to, if the ship becomes very large and the engine
surface too small there isn't enough support-surface and the thing can't work.
I realize of course that it takes a big ship to make these problems real.
But how big will the support-surface of the engine for the Asimov be? 300
square metres (and engine with a radius of 10 metres) would mean that the
Asimov could weigh about 3E10 kg.

>>-----These extra engines should NOT be placed at the back
>> (that would not change the problem) but along the side of it.
>
>Sorry they have to be at the back.  Otherwise they would be blasting the
>sides of the ship.

Maybe a cone shaped vessel with the largest radius in front
(anti-streamlined) would work.

How had you planned to connect the torus-shaped hab-rail to the ship? The
loads of a 100 metre arm should be multiplied by 100!

>You keep missing the point that the ship doesn't need to be generating the
>power to accellerate the fuel.  Tus it would need as much fuel for power.
> The over all energy expenditure of the systems is irrelavant.

It is indeed clear to me that the ship does need less power, because it
doesn't need to accelerate its own fuel. But if the over all expenditure of
the system is irrelevant, why is it such a problem to accelerate a 1:1000000
ship:fuel combination? Such a ship would accelerate, it just needs a lot of
engines (or one very powerful one).
By the way I still don't see how you possibly can say that the amount of
energy needed doesn't matter. (Yes, I know as long as we have no working
method...)

============================================================================

>What electric cars are now, is exotic impractical and dangerous (and oddly
>not particularly clean).  Fusion fuel can be mined and stored fairly easily.
> Anti-mater is a nightmare to hold in quantity, and in our case difficult to
>use efficently.  Again certainly beyond the tech of 2050.

Yes, but so is 1E18 Watt during a few years. (You would create the same
energy in a day as the Sun would in a second)
OK, enough about anti-matter, I hope I've made clear what the advantages are
if we can use this techniques savely. I accept that 2050 will not be ready
for anti-matter but I also have strong doubts if any technique can handle
the high power we need. What I expect to happen in the futere is that
anti-matter will find its way at the same time that such enormous power
finds it way.

>Would you say the same about missions to the Earths poles?  Fairly common and
>trivially cheap compared to this.  A far, far more habitable environment than
>any alien planet is likly to offer.  Yet no one has attempted to colonize
>Antartica.  What would be the point?

On the poles you won't find a whole new planet full of life. If we indeed
knew there were only a few boring planets with nothing more than dust, we
would probably go somewhere else or not go at all.

>A base I could agree to, but not a colony.  They are too isolated and to
>dependant on that long supply line from earth.  Thou they are rich in
>resorces (ore and fuel).  Without the infastructure and personel to exploit
>it, thats irrelavant.  Without something big to attract major numbers of
>people here (which you seem to agree) they would stay to smal to be an
>independant population.  At best they'ld be people rotated back to earth with
>the next supply run.

How many people should there be for an independant colony? I think 100
people should make a living possible. You indeed cannot expect large
factories, but these aren't necessary since there are not many people.

>> You may argue that building a colony is difficult in an alien environment,
>> but by that time we will have some experience in building things on the
>> Moon or Mars.
>
>Moon and mars are also unsuitable (low gravity).

Yes, but they will have build structures for people working there for a few
months.

>More important you keep
>expecting them to live off the land.  Thats like droping a hundred people in
>kansas with a small truck load of gear each, allow no trade with the out
>side, and expect them to build a ultra-modern city.  

I'm not sure I know what Kansas is like, but surely if they had some
habitation-modules from the year 2050 they could prosper.
The modules have a self sustained climate, their only input is energy (from
a small anti-matter-tank :) or just plain old solar-panels). Not only its
climate is self-sustained but also vegetables and other food would would be
grown. So now that you have your first-aid life support for one or two
persons in say 300 cubic metres, you want something to do. OK in Kansas you
probably could do nothing at all, but on TC you might want to get out. So
what you need more is a bunch of basic construction machines and
ore-extracters. These indeed are the things that use the most room and weigh
the most. But they also could be used by more than one person. Now I'm
interested to know what would be the minimal amount of machines to start at
a reasonable level. (say the level of our current technology, meaning
pentium-computers, Scanning microscopes etc.)
I've not a good idea of what to take, do you? (Has this subject been
discussed before?)

- Life sustaining habitats.
- Nano tech would be a great help for ore extracters
- Machines to make simple metal, plastic forms.

A lot of these machines we probably need on the Asimov during its 25 year
mission, most computer won't last for 25 years continuous work. Taking with
us a lot of reserve chips seems a bit too simplistic to me.
(Even the food growing-machines are nessecary, eating 10 year old food all
the time is yuck)

>Again you seem to be assuming they have tremendous resources of equipment and
>time.  They would be extreamly limited, and given the dangerous nature of
>their mission.  They are probably going to be losing stuff (people and
>equipment)  fairly quickly.  Without Earth benificent supply runs.  They are
>going to be in bad shape fairly soon.

How fast are they loosing too much supply in a two-way mission? Even such a
mission should stay there for about 10 years researching planets.
They will be loosing stuff but if it goes in the rate you are predicting,
then every mission is suicide.

>> The people going there aren't the people who really want to retire, these
>> are people that are born for exploration and research. (They really exist)
>> My guess is that they wouldn't sit all the time in some ship or
>> compartment,
>> but that they would allow themselves to go to the planets surface (in
>> spacesuits).
>
>Most of them will never be able to go to the planets.  After a while none of
>them will be able to as the equipment runs out.  If they have to plan on a
>long stay, they'll have to curtail exploration fairly quickly in order to
>save the equip for more practical uses.

That may indeed be the case, but a 10 year exploration with 100 people is
hardly enough to do any real research of a complete solarsystem. Not to
mention refueling or building complete beaming-arrays (only advanced
nano-tech or anti-matter might overcome that problem).

>No its more fundamental than that.  Theirs just too many people.  The more
>people the more corrdination efforts.  For example I worked in the Space
>Station Freedom headquarters along with a few thousand other people.  NONE of
>us actually worked on the space station.  We worked to coordinate information
>between all the groups.  The more people, the harder it is to keep everyone
>informed.  On a big goverment project, everyone has to know what everyone
>else is doing.  The more agencies, the more paths of interaction.  Since
>governments tend to demand everything is monitored to the finest detail.  The
>vast bulk (maybe 80%-90%) of the group effort is in meeting and reports to
>keep everyone else informed.

What if everyone informed themselves? It's like the internet, people make
information available, othera read it and if they don't agree, they discuss
it with the author, after discussing they come to a common conclusion (if
not, that's because of stubbornness) which is made public again.
Also not all people need to know about everything in such a big project,
there are many specialized groups, but they should not loose the survey of
the project.

>> Maybe even one country is too big?
>
>Certainly one buracracy is!

Then there may be a big problem, because such a big project would need a lot
of people.

>These people all wanted to come back.  They wanted to go back out to the bush
>again, but not forever, and not to die.

Going to the bush doesn't take 5 to 7 years plus 5+ years of preparation. I
only wonder those people come back, do you know that? I can lively imagine
that there are also people who want to stay simply because the find that
special lifestyle so fascinating.

>Why not radically differnt?  Life on earth is all based on a couple of basic
>chemical and anitomical tricks.  There isn't anything special about those
>tricks.  MANY others would work as well.  I imagine most life out their will
>be radically different from that here, and may have a few times as long as
>Earth had to develop.

The main tricks are based on storing and retreiving energy in and from
molecules, that energy comes from the sun or from planet-heat (vulcanos).
Are there many easy reactions that can do that back and forth. (a cycle
reaction is probably to unlikely)
On Earth that reaction is H2O+CO2 <--> O2+CnHm by the use of sunlight.
Then there are aerobic creatures, that rely on (I hope I'm right) Sulphur or
phosphor oxides for energy, but that is a single way reaction, once the
sulphuroxide is used it is not reused. Also this substance is not likely to
be available in large quantities for several billion years.

I'm not sure how many basic trick theres are, but I think it would be very
likely that the alien creatures use oxigen and CnHm as main food. Assuming
this basic trick, a lot of conditions are already set. And if the basic
conditions are set, so are the creatures that spring from it.

>I suggested that a few months ago and got no interest.  I suppose it moves
>this project from a serious attempt to figure out if we could do it in 2050.
> To a science fiction club.

Then we should end the discussion about engines with the conclusion that
only exotic fuels and/or enormous powerstations could make the trip
possible. The techniques needed are only in a early theoretical stage and
the size of what is necessary is (almost) beyond imagination and reasonabless.

>> You can never tell :) people are worring about many things (like asteroids
>> colliding with Earth or the Asimov :))
>> If humanity ever becomes extinct, it will be likely that it is not because
>> of natural disasters.
>
>Well nature is our worst enemy, but then we are very hard to kill.

Even on a planet 10 ly away?

>More to the point we could built fleets of O'Niel sized space colonies here
>for far less than this project.  And they wouldn't have the resorce, access,
>and communication limits of a star colony.

You say these colonies are dependant on Earth, what if such a disaster
happens, then they won't have much resources any more.

>I would say just the oposite.  Life on a T.C. colony will be hard and very
>limited.  The planets would be ignored, and the platform colony would need a
>lot of work to equip and maintain.  They would be far more dependant and
>under the control of whoever runs the supply flights, then a similar colony
>in Sol space.

At sol there can't be planet based colonies because of the wrong gravity.
(only Venus has a comparable g but it's a bit hot out there)
You keep saying that it takes a lot of effort to keep the colony working, I
wonder if that is true: Do you need to repair a lot in your house? (not a
personal question) OK, a house on a barren planet would be different, but I
cannot believe that everyone is constantly busy repairing things.

>If you didn't already have the credientials,you wouldn't be offered a ride.
> (You would be stunned at the credentials NASA can require for astrounauts
>that only get to fly every yeear or three.  On the other hand the turn over
>rate among the astronuate is pretty high.  They are highly competative
>people.  After they do this, they want new chalenges and get bored.

Probably the normal astronauts are suited for such a trip. If they indeed
want new challanges every few years, they are probably on the wrong trip.
This trip is a carreer for life, even if you make it a two-way trip.

>> Also it doesn't have to be a new start but a first very defiant start.
>
>??  Defiant of what?  Defiannce doesn't work very well when you are dependant
>on others.

I think I meant challenging, those damn dictionaries..

Timothy