nuclear powered rockets

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