Re: Engineering Newsletter

[KellySt@aol.com]

Zenon!  

I did get you letter but was going to try to shuffle the catagories around
and see if I could come up with something.  I will respond!

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."


Timothy replies to Kelly:
> 
> >> I think that staging would not solve a more fundamental problem:
Pressure
> >> One can see the engine as a force pressing on the back of the ship. We
want
> >> a certain acceleration a. The heavier the ship gets, the bigger the
force
> >> that is needed to get that acceleration (F=m*a). But assuming the
backside
> >> of the ship stays about the same, the pressure (p=F/Area) gets bigger
and
> >> bigger. ---
> >
> >Do you mean the thrust loads?  If so we will need to take that into
> >consideration.  But we can use some of the fuel or reaction mass as
structure
> >(ice perhaps?) and the structure needed to carry the load shouldn't be a
> >major fraction of the fuel mass.
> 
> I'm not sure of what you mean with thrust loads.

Thrust is the presure on the ship from the engines that shoves the craft
along.

> What I meant was that the beams that connect the engine with the ship may
> not be able to stand the load. It's like you were pulling a very heavy cart
> with a sewing thread. For most metals the pull- or press-strength is about
> the same and in the magnitude of 4E8 N/m^2
> 
> You have a solid beam of iron (7.8E3 kg/m^3) with sizes 10x10x5000 metres.
> It would weigh 10*10*5000*7.8E3=3.9E9 kg
> Now you want to accelerate is with 9.8 m/s^2 you do that by equally
> excerting pressure at the 10x10 area.
> That would mean a pressure of (3.9E9*9.8)/(10*10)=3.8E8 N/m^2
> As you can see the pressure is almost to is maximum and any unperfection
---


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.


>-----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.



> >>I don't agree with you on that (yet?), I will expect an answer on
> >>my letter of 01-05 10:55.
> >
> >What letter?  The ones in my inbox don't have that time?

I just got it, never saw it before thou.  Responce below.


> >> >>      * Power from installations at Solar system
> >> >
> >> >Beamed power or fuel launchers have the advantage of offloading the
need
> >to
> >> >carry the heavy fuel (and power systems) with the ship.  That improves
the
> >> >ships power to weight ration significantly.  But the systems are
difficult
> >to
> >> >do, limit range, and don't seem to help us to slow down.
> >> 
> >> Also they have a not so good efficiency. (A big part of the beam just
flies
> >> along the ship without being used.)
> >
> >Thats true of beamed power, not launched fuel.
> 
> The advantage of a lower ship:fuel ratio is that it needs less energy. If
> one decides to launch that fuel instead of adding it to the ship from the
> start, there is not much gain: Although the weight of launched fuel is
less,
> there is a large extra amount of energy needed to launch that fuel.
> It follows from calculations that the total gain is not so big as you would
> have thought. But what you have added is a complicated launch method.

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.
============================= the lost letter ===========
> Timoty replies to Kelly:
> 
> >Fusion is an extreamly usefull general purpose technology.  Anti-matter is
> >far less so, and far more dangerous on the scale we would need.  I
wouldn't
> >expect a lot of anti-mater ships in 50 years.
> 
> You shouldn't see anti-matter as a fuel, but more as efficient energy
> storage. Why is anti-matter not a fuel? Because we have to make it.
> Coparing these two is like comparing a petrol car with an electric car. The
> energy for an electric car has to come from other fuels. Although the
weight
> advantage with electric cars may not be evident yet there are other
> advantages. One of the advantages is the independancy of the origin of the
> fuel source. If it is fusion, fission or solar energy all are easely
> converted to electric energy which is relative easy to handle.
> So what car-batteries are for us now, anti-matter will be for fast
spacevessels.

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.

> >Oh, that would be beyond the resources and tech of the project.  Also it
seem
> >a waste of time.  Sort of novelty project for the record books.  With no
> >practical reason to stay perminently there the bases would be prefab ghost
> >towns.  Future missions to other solar systems would have to be based out
of
> >dynamic, growing, large scale, civilizations.  Not out of a staging camp
in
> >the middle of nowhere.
> 
> If it really is to get a entry in the record books and not much more that
> would really be a shame of all resources. If people really want to do that,
> I see the end of humanity near.

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?

> About growing civilizations, I don't think that western cultures will
expand
> that much. In the US the birthrate is 2.05 per female, in Europe it's about
> 1.8. So that would mean that population will decrease.
> The mean reason that Earth's population is still increasing are the less
> developed countries which have birthrates of 4 to 7.
> I think that families in developed countries have less children because of
> the care these children need (financial but also social/tutorial).
> So this means that we probably never need to go to other places.

Well I wasn't refering to growing in population (and actually you have all
thouse birth rates to high), but growing technically, economically, etc...
 Obviously games like these are only for the very rich.

> But if we want to explore and discover new places we may want outposts at
> many places. So building small colonies would not be that crazy then.
> These colonies would have two purposes, the outpost and a research
function.
> There would probably many researchers that like to check a foreign planet.

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.

I keep coming back to the isolation.  It takes to long to get a ship out
there and back, and costs too much to send it for this to be a colony or even
a sustainable outpost.

> >Forever?  Do you expect earth to keep funding these people in this base
> >forever?  With continuous supply flights from sol to keep them going?  We
> >couldn't even keep the moon program going for more than a few months after
it
> >planted its flag.
> 
> After some time they could have build a small colony with all facilities
> needed to live and work. The energy they need comes from TC itself. So
Earth
> would need funding them, but since they have build a "nice" place in the
> middle of an interesting place they may be interested to hear something of
them.
> 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).  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.  

Not likely.

> >> Why don't you expect them to do that? I still don't see that as suicide,
> >> they can live perfectly healthy lives.
> >
> >Thats like condeming somone to spend the rest of their lives in an
> >apartment/shoping mall!  Good researchers will want to retire or go on to
> >other projects.  Not sit around in a worn out ship, in the middle of
nowhere,
> >with nothing to do.
> 
> Other projects, they have all the choice they could have. Who's going to
> tell them that they cannot do what they want. The only limits are the ones
> of themselves.

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.

> 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.

> >Sorry, no.  In large projects like this the sum of the parts is the lowest
> >common denominator of everyone.  It becoming a big issue in the U.S.  The
> >more people you get on a project, the less energy and inovation is
avalible.
> > Things get bogged down, lost in committe misunderstanding, ecetera.
 Costs
> >can go up to hundreds of times what a small tight group could do it for.
> 
> And do you know why this happens, because everyone wants his own share and
> no one is prepared to accept an idea of an other because that will mean a
> loss of personal profit.

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.

> >Thats one of the reasons that over the last decade or two, NASA has been
> >incapable of trying, or developing, cutting edge technologies or programs.
> 
> Maybe even one country is too big?

Certainly one buracracy is!

> >> Exploration isn't much fun? What else drives people to such far
places...
> >
> >Curiosity, greed, a chalenge, desire for fame or acomplishment.
 Exploration
> >is generally horiobly uncomfortable and life threatening.  But its very
> >chalenging, and its atractive to know your one of the few to ever do
> >something, know something, etc...  Even if you know its killing you.
> 
> Sorry, I had a more lossy idea about the word exploration than you did, I
> meant approximately what you wrote.
> 
> >Like an anthro professor my wife had.  He loved studying aborigional
tribes
> >in the backwaters of the Amazon, but he frely admitted everyone who does
it
> >expect that they've paid with decades off their life expectancy.
> 
> So that means a return trip won't be necessary.

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

> >Since your dealing with radically differnt life forms.  Its unlikely the
old
> >rules, or solutions, would hold.  We mostly will be starting from scratch.
> > After all, we have no experience with alien biospheres.
> 
> I doubt if they are so radically different, all lifeforms have to abide the
> laws of nature. Maybe some of them have found tricks that have not been
> found on Earth but that is why we are going there.
> And still if we know what doesn't work the chances of finding 
> something that does work are enlarged.

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.

> >We're in a serous bind.  The tech we can expect in 50 years isn't enough
for
> >a T.C. flight.  Or all but the most modest interstellar flights.  NOr
would
> >they be that likely to be interested in footing a huge program.  Yet if we
> >back up the date by a hundred years we could be much more confident that
they
> >could do it, and do it affordably, but we wouldn't have any credible idea
> >how!
> 
> So maybe we should say "a priori" that certain techniques are 
> available. And discuss how and why these could be used.

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.

> >Put another way.  Are we that likely to be so afraid of human extinction,
> >that we'll rush to do such a project in 50 years?
> 
> 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.

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.

> >Oh certainly.  The united states gets several million of them a year!
 But,
> >another star doesn't offer much opportunity.  It isolated, expensive, no
> >markets to go to, few resorces that you can get at.  No home world to go
to
> >on vacation to.  Your very dependand on the supply line from Sol, and
their
> >for far less independant than you would be in a colony in Sol.
> 
> You indeed can't go on vacation, and it probably never will have more than
> 1000 inhabitants for the first 100 years. But as every place where people
> live, they will adapt themselves and the environment. Not all people want
to
> become rich by selling stuff, a lot of them just want a place to life as
> they like with the "sky" as the only limit. As I said before dependancy is
> only a short time (if at all), once there is TC-light and gravity they can
> grow food just as on Earth. So the first necessaries of life should not be
> that difficult.

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.

> >Also, the kind of people we would send on such a ship.  Would be the
ellete
> >that would have a lot of opportunity back home.  The people who want a new
> >start, wouldn't be sent on the ship.
> 
> If you are 25 to 30 how sure can you be that you are a member of that
elite.

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.

> 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.