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Old December 3rd 09, 09:21 PM posted to sci.space.policy
Doug Freyburger
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Default Nuclear Orion Memories

William Mook wrote:

12) dispatch laser beaming systems to remote star systems for two-way
interstellar commerce.

At this point we have achieved a transport system that allows commerce
between stars at 1/3 light speed.

If the development of black hole based technology is successful along
the lines described (or others) then we can imagine building black
hole forges at Sol and any star system we have reached, and with these
support 30 day journeys between star using extreme dilation to good
advantage.

So, we have an expanding shell moving outward at 1/3 light speed and a
network of high speed 'gates' consisting of two black hole bodies
orbiting one another at near light speed - large enough to dispatch a
reasonably sized ship at very nearly light speed.


The black holes orbitting each other would have tides strong enough to
atomize any ship. Building them big enough to not have that problem
would take many solar masses.

Period Number Spanning time

50 years 1,200 stars 5 months
100 years 9,200 stars 11 months
150 years 33,500 stars 16 months
200 years 79,400 stars 21 months
250 years 155,100 stars 27 months
300 years 268,100 stars 32 months

Assuming we started expanding along these lines in 2050 - a three year
journey to the 'rim' and back in 2350 that took three years ship time,
would return the crew and passengers to Earth in 2650 - so travel deep
into space and back would also be travel into the future as Einstein
predicted.


If a species developed interstellar travel, how long would it take to
span a galaxy? Depending on the numbers it ends up anywhere in the 1
million to 20 million year range. That's long enough for species to
differentiate but short in comparison to the lives of stars.

The fact that we have not seen aliens suggests that no species has
developed interstellar travel, or they are now extinct and we have
evolved since thei last visit (consistant with the 20 million year time
span), or they do not visit planets like Earth routinely.

I have considered fusion drives that can propel ships to well under %1
of C. Such ships would give us access to the comets in the Kuiper belt
and Oort cloud. The Oort cloud is far enough from the Sun that solar
radiation would require much less shielding than travel in the inner
systems. The comets in the Oort cloud are so far apart that fusion
drives would be needed for commerce, but once out there the total
resources available there would be far larger than the total resources
available on the surfaces of planets. Also comets may thinly fill all
of interstellar space not just be bound to stars.

When I think that through I think that once out away from the Sun
there's no longer much incentive to go star to star. Comet to comet is
closer, less resource intensive, and less limited. I suspect that
interstellar civilizations end up nearly ignoring inner solar systems,
if any such civilizations exist.

If civilizations use comets in interstellar space, they would span a
galaxy in a time scale of 10s of millions of years. They should be
visible from there fusion flames, shouldn't they? We don't see fusion
flames.

That's as far as I had considered until you mentioned neutrino jets for
propulsion. We would not see such flames without a lot more effort than
pointing telescopes and looking for light or looking for X-ray and gamma
ray bursts with satellite telescopes. Satellite telescopes do see X-ray
and gamma ray burst that are currently attributed to natural events.
Could they be fusion flames? But if neutrinos could be used for
propulsion there would be no fusion flames.

How to focus both the neutrinos and anti-neutinos to eject in the same
direction to make neutrinos into a rocket flame? They would tend to be
created in matched pairs going in opposite directions so they would tend
to cancel out. Solve that problem, find a way to generate lots of them,
and neutrino rockets could work very well. Extremely advanced science
and technology compared to our current level - Using fusion torches to
go comet to comet is much closer to our current level.