--- In spacesettlers@yahoogroups.com, sraj wrote:
>
> Lucio mentioned use of:
> nuclear-powered
> > fully-reusable launchers (now that the anti-nuclear green
movement
> > hopefully is starting to decline)
Don't count on it. In fact, it looks like the con servers are
about to self detonate.
As an ecologist, I will still fight tooth and nail to keep
Nuclear Rockets from being fired in atmosphere.

>
> ... Is such a rocket possible?
Very possible and well understood for theory.

I would have thought that it would be
> difficult to design a nuclear rocket for launch from Earth, due to
the huge
> energy requirement in a very short time.
I'm not sure what you are saying here, but the point I'd like to
make is, Nuclear powered rockets shouldn't be used in atmosphere,
and the energy requirements of such a system are irrelevant, because
nuclear power resolves almost any power requirement you could think
of.

>
> But nuclear powered rockets will be ideal for interplanetary
travel -
> preferably designed to use any material as 'reaction fuel'. Have
such
> rockets been conceptualized?
Yeah, and there are a whole lot of very different ways of nuclear
powering a rocket. Some are pretty sloppy and some are pretty clean.
Some use the nuclear energy potential right there at the ignition
chamber, and some use the nuclear power energy potential to drive
electrical or magnetic or microwave ignition systems. There are all
sorts of designs, theories, and the list goes on and on. I'm only an
amatuer rocket scientist, so I'm not good for deeper details.

>
> Selvaraj
>
> From: "Lucio de Souza Coelho"
> To:
> Sent: Wednesday, April 05, 2006 4:50 AM
> Subject: Re: [spacesettlers] Re: Future direction for Humanity?
(was
> DonDavisarticle)
>
> > On 4/4/06, Don Davis wrote:
> > (...)
> >> One day it is not impossible that there will be major wars
between
> >> the major countries on the South American continent. I recall
> >> Argentina working on nuclear technology, but I haven't kept up
on who
> >> down there are likely to get atomic weapons soon.
> >
> > I know nothing about the Argentinian nuclear program. However,
during
> > the military dictatorship that ruled Brazil from the 60's to the
80's,
> > nuclear technology advanced enormously here (our first nuclear
plants
> > are from that time) and there are clues that the military may
have
> > tested, or anyway planned to test, a-bombs.
> >
> > Anyhow, in our current political environment I don't see any
trend of
> > development of nukes across the continent. (Although in a vaguely
> > related issue there is a growing lobby for construction of more
> > nuclear plants, since our hydroelectricity is close to the limit
and
> > fossil fuels are a dead end.) However, if some day in the future
the
> > bomb becomes attractive, we have the technology for enriching
uranium,
> > so I don't think that much research would be needed. The atomic
genie
> > is out of the bottle not only here, but all over the world.
> >
> > (...)
> >> Space planes are apparantly impossible to refine to the point
of
> >> becoming a practical method of getting into space. Every new
project
> >> to create a space plane after the shuttle has died a miserable
death
> >> with only Buran actually being test flown, an ominous sign that
our
> >> abilities to invent as we need, as was factored into Project
Apollo,
> >> is in decline. Perhaps if the priority traditionally given to
military
> >> projects was given to a practical reusable spaceplane with no
regard
> >> to development costs it could be done. The pathalogical
draining of
> >> resources into the means for warmaking makes doing any other
major
> >> project that much more difficult.
> > (...)
> >
> > Thanks, you managed to get this thread closer to the topic of
this list!
> > :-)
> >
> > I think that chemical rockets have reached the practical limit of
> > technological advance, and that may exclude space planes.
> > Nevertheless, I think that there *are* advances still to be
explored
> > in cheap access to space, but I think that they pass for complete
> > paradigm shifts in either economic or technological principles.
> > Assembly-line rockets (preferably Big Dumb Busters), nuclear-
powered
> > fully-reusable launchers (now that the anti-nuclear green
movement
> > hopefully is starting to decline) or, who knows, if we are lucky
even

sraj wrote:
>> Lucio mentioned use of:
>>> nuclear-powered fully-reusable launchers (now that the
>>>anti-nuclear green movement hopefully is starting to decline)

kucitizenx wrote:
> Don't count on it. In fact, it looks like the con servers
>are about to self detonate.
> As an ecologist, I will still fight tooth and nail to keep
>Nuclear Rockets from being fired in atmosphere.

I'd like to remove partisan politics from it. It's about how a thing
could be designed and built to satisfy even a pessimist's wildest
nightmares about an accident. I like to believe that tinkerers
(humans) can find ways, but this is a hard one. There's a lot of
thought about how a thing could be built to be self-correcting or
self-containing even if the vehicle fragments itself, but Murphy can
always have the last word, and the consequences of a big release are
severe.

>> ... Is such a rocket possible?

> Very possible and well understood for theory.

The difficulty would lie in getting any decent mass fraction for
cargo after reaction mass, reactor mass, and any shielding for the
crew & passengers. It would probably take a lot of dead weight to
make it safe & secure enough get it past the detractors -even the
moderate ones.
It's highly unlikely, and unnecessary with all the other ways of
getting to orbit. Sea Dragon is a good one that comes to mind for
single large cargoes, as are any of the various sorts of space
elevators and the wild variety of zero-staging options for getting
something like a spaceplane off the ground (laser thermal, rail/sled
driven HTO, etc).

>> But nuclear powered rockets will be ideal for interplanetary
>>travel - preferably designed to use any material as 'reaction
>>fuel'. Have such rockets been conceptualized?

see neofuel.com for an online source.

For space travel, also there's Orion "Old Bang-Bang", the atomic-bomb
driven ship, which was conceptualized in ways to use just about
anything for "reaction mass" -the propellant that's vaporized and
directed at the back of the ship to push it. Yes, even Orion can gain
a lot from ISRU. Something like 2/3 of each "pulse unit bomb" mass is
the propellant.
Anything from various ISRU ices to tungsten or iron to something
refined from the crew's solid biological wastes was studied, and it
involves tweaking (possibly major) of the yields and masses and such
factors.

I still wonder about the possibility of designing sub-
kilotonne "clean" or maybe "fusion only" bombs for lifting a huge
interplanetary liner from a floating ocean spaceport. Even if they're
possible and cheap enough, there's still the firing system from
magazine feed to detonation at the right time/place to work out. For
a ground launch of such a beast, the frequency of detonations is so
rapid it's quite a problem. There's also the seeming nonsensibility
of designing a thing to do both: lift from the ground, and function
in deep space.
It really is easier to lift it in pieces into high orbit -for a
small ship- or build it there, for consideration of long-term travel
among a space-faring civilization. Just use it only in space (where
the raw power of nuclear pulse really is needed and seems to be the
natural evolution of spaceflight as we understand it). Cross the
solar system from one Kuiper cloud space settlement to another within
a relatively few years. Cross the inner solar system in weeks or
months, no consideration of synodic periods or energy saving
trajectories needed.

I don't know how much help it'll be, but there's a board specifically
to talk about such things:

NUCLEARSPACE MESSAGE BOARD (ACTIVE)
This web site functions to promote the use of nuclear power in space
to further robotic and human exploration of our solar system and
beyond. Our purpose is to enhance the technological use of nuclear
power and propulsion.

http://www.activeboard.com/directory/preview.spark?forumID=33011

I think it's do-able and safeguards can be hotwired.

Should be space-launched or moon launched.

Asteroidal/cometary materials can be utilized (many asteroids have Uranium
as well).

Can't escape public opinion nor keep something like this a secret very
easily - at least not on earth.

There would need to be plenty of oversight, obviously.

George

On 4/15/06, John Frazer wrote: