Re: Re: starship-design: doable drives

[KellySt@aol.com]

In a message dated 10/7/98 7:29:04 AM, ajcrowlx2@ozemail.com.au wrote:

>Hi Group,
>
>KellySt@aol.com wrote:
>
>> In a message dated 10/5/98 10:20:23 AM, ajcrowlx2@ozemail.com.au wrote:
>>
>>
>> >
>> >The most believable scenario achieveable by
>> 2050
>> >that I've seen is the analysis by Dana Andrews on the economics of laser
and
>> >particle-beam propelled probe systems, but that's assuming a lot of Belt-
>> based
>> >infrastructure. If Inertial Confinement fusion can be properly developed
then
>> pulse
>> >propulsion might become viable, but that still has major problems with
>> neutron
>> >damage since any forseeable system will involve deuterium, and so
deuterium
>> >reactions that produce neutrons. Which is why I prefer beamed power
>> scenarios,
>>
>> Ah you don't have to use fusion fuels that produce neutrons in a pulse
fusino
>> system.
>
>Such as? What fuels can we use? Lithium? Does anyone know how to start a
lithium
>reaction?

Add the right isotope of Lith a bit of hydrogen, and a LOT of power.  ;)


>>
>> >but
>> >they need lots and lots of power - kilo-terawatts [petawatts?] - and
that's
>a
>> bit
>> >hard to provide. Huge focussing solettas, giant gas-core reactors and/or
>> fusion
>> >systems would be required. Is any of that achieveable by 2050?
>>
>> You could build fleets of space solar power platforms, but unless you have
>> masive space based automated mining and manufacturing systems, you couldn't
>> afford them.  But then perhaps perfecting such systems could drive a
government
>> to fund such a program as a show piece.
>
>Perhaps we assume too little by not factoring in nano-assemblers and von
neumann
>replicators. PersonallyI can see such being available by 2050, so maybe huge
>solettas won't be unreasonable. 

There so high leverage they would alter the fabric of society and technology.
Past that we can't really guess what the tech would be like, or if manned
flighed would be replaced by robot AI birds.  (Thou those would be very hard
to get funding for.)

However some type of major jump in AI or automatino tech seem virtually
assured by 2050.



>I suspect any really high energy system will be
>some sort of thermal generator system rather than photovoltaic. Higher
efficiency,
>at least in principle.
>
>>
>>
>> >
>> >I don't see star-flight by humans really happening until the Solar System
is
>> filled
>> >with mobile cylinder cities and large scale mining of fusion fuels is
>> underway.
>> >That could happen by 2100, or 2150. By that stage more people will live
off-
>> Earth
>> >than on and large-scale closed-cycle habitation in space will be common-
>> place.
>> >Alongside such developments I would also see longevity and cyber-
>> augmentation,
>> >plus
>> >various gene engineering techniques being well developed. We might not be
>> able
>> >to
>> >go the stars, but They might make themselves able to trek across the void.
>>
>> These are a lot of assumptions.
>
>True.
>
>> The one thing we did all agree was that we
>> couldn't seriously predict what the science or economics past 2050 would
>> credibly be.
>
>I doubt it'll be totally alien, though my scenario of Sol Space filled with
>independent CylCits is pretty radically divergent to most [outside of
>space-interest groups.]

Advabxed nano replicators or trans human inteligence AI's could shake stuff up
pretty radically.  Or a few breakthroughs in physics (zero-point energy,
inertial damping, kenetic energy systhasis, etc) could make our stuff look
pretty dated.  Then of course if someone does figure our a Albuquen(sp) warp
drive system...  ;)


>> >
>> >I know we're discussing realiseable systems, but really how feasible are
>> fusion
>> >drives and multi-staging to get to 0.3 c by 2050? We haven't got fusion
>> pulse,
>> >we
>> >haven't got a closed space-going ecology, we haven't got high-strength,
high-
>> Tc
>> >superconductors and God-knows what else we might need. So who's to say
what
>> is
>> >possible?
>>
>> We do have pulse fusion systems that could reasonably be developed in the
next
>> 50 years into functioning drives.
>
>We do? Have you seen DoD research that the rest of us haven't?

Comercial research in pulsed fusion reactors got pretty far in the 80's, and
several promising alternate fusion concepts are gathering dust.  I said they
"could reasonably be developed", not that they were working. 


>>  Life support and food storage that would
>> last a 30-40 years for a round trip is fairly doable.  And thats about all
we
>> need to build a 40ish% of c system.
>
>0.4c! Are you kidding? What sort of mass-ratio do you need for that using
fusion?
>1000/1?

Its listed in the Explorer pages or Fuel/Sail.  As I remember it was about 100
to 1, with boost to speed from external power.



>>  Given a BIG checkbook a combined beamed
>> power and fusinon system COULD be built in mid 21st century.  However
unless
>> some manufacturing advance brings that cost WAY down, no one WOULD pay for
it.
>
>Perhaps we should invoke ultra-cheap nano-systems so starflight is possible
by
>2050.
>
>>
>>
>> >If go conservative we could build an Orion system that'd reach Alpha
>> >Centauri in 400 - 120 years - that'd break the Global Economy to make.
What
>> would
>> >it take to launch +300,000 tons of fusion bombs and equipment? A thousand
>> HLLV
>> >flights? At a billion a shot? Then there's actually making all those
bombs,
>> and
>> >the
>> >risks of terrorism and so forth.
>>
>> Actually it would be harder to do multi century flight, and really stupid
to
>> do it.  Obviously in a century or two science and technology will make
>> incredible strides, so unless you can get there in a couple of decades, you
>> should just wait for a faster ship.
>
>Which is why I posited Orion. It is unreasonable for manned starflight, but
my
>point was it's what we can do NOW.

But it is too slow to be worth doing.


>> >
>> >So what do we discuss? The physically possible, but what about the humanly
>> >possible? What sort of people will cruise the stars? Not the middle-class
>> liberals
>> >that flash around at warp-speed on "Star Trek" and carrying on like it's
some
>> >god-damn soap-opera! It'll be people who want the stars for a whole
variety
>> of
>> >reasons, but they'll be living and working together. Flying island states
are
>> more
>> >likely than career-enhancing star-cruisers. Starflight won't be a part of
a
>> life,
>> >it'll be a life.
>>
>> Unlikely, even more unlikely then Star Trek types.  Flying cities need to
pay
>> their way.  You can't just take off with them.  Thats like buying and
removing
>> Manhatten.
>
>It won't be if they're independent.

Now a days we can't even make countries completly independant, citys need
major interaction.



>>
>> Since the resources of this star system could support any conceivable
>> planetary civilization for  tens of thousands of years.
>
>Millions if it's static.

Static systems would die quicker, but if you assume a little recycling or tech
advancement it goes well beyond that.


>> There'd be no need
>> to pull up stakes and move on for greener fields.  So why build and launch
a
>> interstellar colony?
>
>Why? Why not?

Loss of money, isolation, reduced access to new technology, Danger,
generatinos of hardshio[ compared to styay at homes with no obvious up side
ever.



>> >
>> >So I assume fleets of colonisers because that's what it will take. Not
small
>> scale
>> >Explorers. They're only feasible if a mission is just a couple of years,
not
>> >several decades. To do that you'll need ships doing +0.999995 c, and
that's
>> really
>> >silly.
>>
>> Can'y say a ship that fast (or faster) would be silly.  We can't build it,
but
>> someday we'll be able too.
>
>Assumes more than we can know. I believe we'll be able to, but that's no
guarantee
>it'll ever happen. The really silly aspect is the accelerations required. At
a
>gee
>it takes years to get around, even when we're counting tau time and not flat
time.
>Anything quicker requires higher accelerations. Unless you cancel inertia or
want
>to float in a tank like a newt, then it's impossible to fit a starflight into
just
>a couple of years. Small groups wouldn't survive over the years realistically
>needed to get between stars, so I think the minimum would be ~ 500. A Greek
city
>state size of 10,000 - 30,000 would be better, and more likely to spend a few
>years processing Jovian gases or comet ices to get the fuel.
>
>But I'm just guessing. Anyone got a way of boosting a ship to 0.999995 c in a
>hurry?

1 G would get you to light speed in about a year ship-time.


>Adam

Kelly