Moon first?

That is why you need to build a space station to get to Mars. The vehicle
that allows astronauts to move from Earth orbit to Mars orbit and back again
is effectively a space station with an engine attached. Astronauts will have
to learn to live in space for about 9 months at a stretch in order to get to
Mars. Zubrin's proposal even allows for rotating the space craft to provide
gravity, this vehicle can be thought of as the first step towards larger
O'Neill habitats. That may be a bit of a stretch. But I'd allow that such a vehicle might enable later human visits to NEA's, and thus might help to further High Frontier in that way. True but there is more excitement in exploring Mars, I think if we learned anything from Apollo it's that we'd best not make our future space plans based on public excitement, as such excitement can quickly die, leaving us with no sustained presence. I prefer space goals with potential for economic usefulness, as I consider them to be sustainable regardless of the changing level of public interest or boredom. there is very little
chance of finding life on an asteroid. We do not yet know that there is much chance of finding life on Mars. The launch facilities could be constructed on floating platforms in the
middle of the Pacific Ocean, far away from where anyone lives. I don't know that theobjections over the plutonium on Cassini were predicated on the assumption that any of it would necessarily come down where people live. Any
radioactive particles that escaped a nuclear shuttle would sink to the bottom
of the Ocean, You may find to your surprise that there are ecologist who are far from being radical extremists who would nonetheless object to dropping radioactive particles into the Earth's oceans. Those are hard conditions and would slow the development of the high frontier
considerable. I'm not convinced of it. In fact Gerard O'Neill was asked point blank by a congressman if it wasn't true that High Frontier needed a nuclear spacecraft, as someone else had suggested. O'Neill unhesitatingly said no, and characterized the suggestion as an example of "queue logic". I've been waiting 2 decades for an SSTO and so far none have
appeared. We've gone through Scramjets, the Delta Clipper, Delta-Y, and
Delta-Z vehicles, the X-33, X-34, Vernture Star series, and all these
privately financed initiatives of the 80s, 90s, and today and they've dropped
by the wayside one by one. This goes to show how difficult it is to build an
inexpensive vehicle powered by chemical rockets only. From this we can only conclude that building inexpensive launch vehicles is difficult. That this difficulty is due to the fact that we're not trying nuclear propulsion may be an unwarranted conclusion. It can certainly be argued that at least where government efforts are involved, they are going about it the wrong way from an economic point of view. It's been argued (and probably correctly) that the key is scale of operations, and that if we could just get into economies of scale, then even expendable chemical rockets would give us the launch costs we'd like to see. Nuclear rockets may be
the only way to go right now unless you are willing to wait for ultra high
strength, ultra light materials that can handle cyrogenic temperatures for
storing liquid hydrogen, and survive the searing temperatures of blast off
and reentry. Not so sure about "ultra high strength, ultra light materials", but as for the rest, I think we already have that. We've had it since we first began using hydrogen propellant, and ablative heat shields. Now we have reusable heat shields, and are working on metal ones. I think the initial minor use of nuclear engines is acceptable
rather than waiting for the perfect environmentally friendly to launch things
into orbit. Hey, if you can swing it politically, more power to you. But I can see even myself being just a little bit nervous about launching a nuclear engine into space, and ideologically, I couldn't hardly be further away from the anti-Cassini crowd.
Regards,