

Tau Ceti's planets nearest around single, Sun-like star - morphics
http://www.bbc.co.uk/news/science-environment-20770103

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Tichy
Just looked on Wikipedia, it is 12 light years away. So how long to get there
with conventional technology? I suspect speed isn't even the worst problem,
harder to deal will radiation?

Also I suppose any such mission would have to be fully automated, remote
debugging would be too frustrating with a 24 year round trip for information.

Have there been any spacecraft besides Voyager even launched beyond the
boundaries of our solar system?

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randallsquared
Using 1960s engineering (and many, many nuclear bombs), an Orion-powered
starship could make it there in less than 150 years, one-way. And no slowing
down; it would be a flyby.

[http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...](http://en.wikipedia.org/wiki/Project_Orion_\(nuclear_propulsion\)#Interstellar_missions)

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rdl
Can't you just turn around midway and start throwing bombs out in front of
your path of travel to slow down?

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jasonkester
One of the interesting things in that Wikipedia link is that you only need to
run your Orion for 36 days to get it up to speed. Beyond that, detonating more
bombs won't accelerate you any further.

So yes, you could turn it around. But surprisingly it seems you can wait until
a month before arrival to do so. The downside, however, is that your max
velocity gets cut in half if you bring enough bombs to slow down.

With better explosives, you could get a higher max velocity and therefore
closer to the "accelerate halfway, decelerate halfway" ideal case, but at the
moment such explosives don't exist.

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rdl
I'm not sure how that works out.

Do 36 days of acceleration at the beginning (or spread it over a year to
reduce peak acceleration) -- go from 0 to 0.1c or whatever the cruise speed
is.

Coast for ~100 years.

Spend the last year going from 0.1c to 0.

It does mean you have to carry twice as many bombs, and carry half of the
bombs for 149 years, but bombs are really lightweight relative to the ship. It
also means you can't just jettison the pusher plate, which is probably a
bigger deal.

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randallsquared
In this case, the weight of the bombs is larger than the rest of the ship: 50K
tons for the ship structure, 300K for the weight of the bombs [1]. Twice as
many bombs essentially doubles launch mass.

Orion is a great concept for tooling around the solar system easily, but what
it buys us over interstellar distances is that it makes macroscopic payloads
and reasonable travel times _possible_ ; they're still not easy.

[1] Table 2 in
[http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nu...](http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nuc_rocket/Dyson.pdf)

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duopixel
What if instead of braking Orion itself, it just drops off a lighter satellite
that is able brake without expending so much energy?

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Tichy
I'd think it would still have to brake using Orion technology, so it is
doubtful if it could be built smaller than Orian itself.

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JoeAltmaier
It could use solar wind, or gravity-slingshot (which can slow as well as
accelerate a satellite). So yes it could be much smaller.

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martinkallstrom
Perhaps Tau Ceti is even close enough to not be trapped to the paradox of
interstellar travel: "No matter when you launch a voyage somewhere, some one
else will build a better spaceship and get there before you."

Is there a sci-fi novel about this? (an interstellar space voyage for a remote
planet discovers humans launching after them already have colonized it when
they get there)

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wazoox
"The forever war" uses the time dilation of relativistic travel, which is a
related concept.

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ndonnellan
I remember playing Outpost as a kid. Tau Ceti was definitely the best bet. I
loved/hated the fact that you could send your colonists to a solar system that
wasn't habitable and then the game would just be over in 5mins; your creepy AI
giving you the bad news.

\- <http://en.wikipedia.org/wiki/Outpost_(video_game)>

