

Sending a spacecraft to Alpha Centauri - antoviaque
http://boingboing.net/2011/02/11/incredible-journey-c.html

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rubidium
"In other words, we could all too easily become lost in the virtual worlds we
make for ourselves, and lose interest in the stars. Or, more probably, we
could squander our resources and experience profound and irreversible
technological regression. Sometimes, I pessimistically hold with some
combination of these two extremes."

I believe indifference to exploration and learning is the biggest threat.
We've shown a remarkable ability to take useless things (buried dead
organisms, uranium) and make them useful resources, so I'm not as concerned
about that.

~~~
salemh
I'm always fascinated by the lack of "space" like exploration projects for the
ocean. Seemingly closer access, as if not difficult technical problems, but
with greater access to actual resources. Thoughts as to why?

<http://oceanexplorer.noaa.gov/>

Meh link: [http://www.huffingtonpost.com/george-spyros/colbert-
report-d...](http://www.huffingtonpost.com/george-spyros/colbert-report-dr-
robert_b_166979.html) _One of the biggest issues facing the oceans is a lack
of awareness. You can't see what goes on in the ocean the same way you see
what happens in a forest or in an African savanna. So people don't know that
we waste 54 billion pounds of fish every year while 8 million people die of
starvation. They don't know that every single fishery will have entirely
collapse by 2048. Or that 90 percent of all large predators in the oceans are
gone. And if people could see that. If people could see the amount of waste
and destruction in the oceans they wouldn't stand for it for a second.

It should be noted however that perviously Dr. Ballard has, in the process of
drumming up enthusiasm for increased funding and interest in ocean
exploration, touched on the rich bounty of resources yet to be tapped beneath
the sea floor. As always, the needs of man and nature are not mutually
exclusive should we choose. Balance between the amazing scientific and
educational benefits often described by Ballard and the interests of commerce
can be achieved if we keep our eye on the prize._

[http://roastedpinebark.hubpages.com/hub/Ocean-Exploration-
Ne...](http://roastedpinebark.hubpages.com/hub/Ocean-Exploration-Needs-More-
Funding) _“The ocean is home to the greatest diversity of the planet. It’s
still ironic that there are more footprints on the moon than there are on the
bottom of the sea, and we’re only 7 miles away,” says biologist Sylvia Earle
(Marino). Ocean exploration does not receive the amount of funding that it
should, especially compared to the space program._

<http://www.thespacereview.com/article/1202/1> Answers me a bit: _It is common
for books on undersea exploration to include a throwaway comment about how we
know far more about the surface of the Moon than the bottom of the ocean, or
how more people have been into space, or on the Moon, than have reached the
bottom of the sea. These comparisons are often not terribly accurate. Every
year thousands of sailors travel under the oceans in military submarines,
thousands of commercial divers work on pipelines, cables and oil rigs,
thousands of hobbyists engage in recreational diving, and hundreds of
researchers travel to great depths in the interests of science. Robots
regularly venture where humans do not. What is usually fueling these claims is
jealousy, or more politely, professional envy: the United States spends
billions of dollars exploring space every year, and far less money exploring
beneath the sea.

There are many similarities between deep sea exploration and space
exploration, and also some important differences. Deep sea exploration has
existed for nearly twice as long as space exploration, and followed a
different path. But the differences are diminishing and the two endeavors are
starting to look more and more like each other. More importantly, deep ocean
exploration is having a major effect upon space exploration._

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jxcole
My opinion is that we have not given anti-matter a serious enough thought. It
certainly is expensive to create now, but it seems like the scientists are and
were focused on creating antimatter to confirm it's existence and properties.
Once they were able to confirm these things, they moved on to trying to use
their devices to confirm the existence of other things, like the Higgs Boson
(a noble effort). Has there actually been a concerted effort in the physics
community to design a more efficient anti-matter creation/storage mechanism?

~~~
twp
Do the back-of-the-envelope calculation on antimatter. I did it once, then
mislaid the results. First question: make it or farm it?

If you want to _create_ antimatter then, at the very best, energy in = energy
out. The energy required to accelerate a small mass of human seeds +
associated robot farmers (say 100kg total) to a reasonable speed and to slow
it down around the star at the other end is enormous, and a sizable fraction
of the annual energy consumption of the entire human planet. It might not be
impossible to realise, but it will require as much of a political effort as a
scientific/engineering one.

Of course, antimatter from space colides with our planet every second, so why
not just harvest it? Imagine the entire planet covered with a web that
captures every particle of antimatter arriving from space. Well, it would take
hundreds of millions of years to harvest enough energy though antimatter to
send that 100kg mass to a nearby star.

Chemical rockets aren't going to get us there. Antimatter is currently the
densest energy source known to man, and it's not enough. Barring the invention
of warp drives, we're stuck here. Make the most of it.

~~~
jxcole
I was mostly thinking of your first version, where antimatter is really more
of a battery. We would create it from some energy source at the launch site
and use it as the most efficient rocket fuel of all time.

Most of my thoughts on anti-matter (though of course I am totally unqualified
in every regard) is that the biggest problem with rockets these days is fuel
efficiency. We are wasting most of the energy of putting something into space
because most of the weight we put into space is actually the weight of the
fuel and engine. A minority of the weight of the rocket on the ground is the
actual payload intended for space.

There are, to my mind, three competing emerging technologies that could solve
the mass-weight ratio problem. They all involve kissing chemical rockets
goodbye.

1) Nuclear

2) Anti-matter

3) Energy-beaming technology.

I feel that number 1 gets too much attention.

Obviously, if we ever want to get to other stars, we will have to get to other
planets first. But I think once we get a solar-system wide economy our options
will be much wider.

I also feel that making predictions about what the human race is capable of
in, say, 10,000 years of technological development is silly. Even if you look
200 years back at what people predicted about what we would be capable of now
you see wild inaccuracies.

I think that anti-matter could work for an interstellar rocket though.
Consider what would happen if we built a factory that could convert 90% of the
solar energy hitting the planet mercury into antimatter fuel. I bet that you
could create an interstellar rocket from that.

Maybe we'll never be able to do it. But I wouldn't count your chickens just
yet.

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kristianp
This kind of thing would require large scale industrialization of space (in
orbit around various places). If we are doing that, why not create a black
hole starship?

Microscopic black holes have been theorized as power sources for starships.
The power source is the Hawking radiation that is intense for microscopic
black holes, with a mass of around a million tonnes according to calculations
in [1].

Apparently, creating a black hole "would require millions of times less energy
than a comparable amount of antimatter" [2]. We would need to learn more about
quantum gravity first though.

[1] <http://arxiv.org/pdf/0908.1803> [2]
<http://en.wikipedia.org/wiki/Black_hole_starship>

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zeteo
The key to a successful interstellar probe is probably miniaturization. You
only need about 5kg of Pu-239 (energy density ~8.8e13 J/kg) to accelerate a
1kg payload to 10% of the speed of light (energy requirement ~4.5e14 J). A
single large H bomb (2.1e17 J) could accelerate 100kg to 0.2c.

~~~
Groxx
As shrapnel, yeah. Not much can survive those kinds of accelerations. So you'd
need to carry a bunch of smaller ones with you, or shoot them at the probe as
it accelerates (harder and harder to do), at which point we have the same
current problems - large masses, or shooting things at other things to propel
them.

\--

After thinking about it for a bit, I don't think miniaturization for very-
long-range probes would work very well anyway. You can't focus signals beyond
a certain degree, dictated by your reflector size, so you either need a lot of
power to send signals long distances or very large reflectors to compensate
for lower power.

The reflectors could conceivably be something like a solar sail - huge and
light - but you still have to carry it and deploy it and ensure it stays
focused as you approach other stars (solar winds). You're stuck with rigid and
heavier or flexible and useless, and if it's big enough it'll push you away
from the star regardless of its ability to hold a shape.

At which point we're pretty much stuck with using, thus carrying, more power
beyond the inflection point. No clue where that would be, but I doubt it would
bring us past all but the closest stars, if any.

~~~
zeteo
Yes, of course you wouldn't directly use an H bomb, the idea was that the
quantities of fissile materials needed to propel a 100kg interstellar probe to
0.2c are easily within reach of several nations. Controlled fusion can be
achieved in very confined spaces:

<http://en.wikipedia.org/wiki/Hohlraum>

I agree that communication equipment is a major problem. The best way to solve
it is probably to oversize the local equipment: a dedicated space telescope
and a powerful orbital laser. This may let you get away with a very
lightweight emitter/receiver pair on the probe itself.

~~~
Joakal
Assuming there's no microscopic debris in space and it's pretty empty,
wouldn't it be possible to accelerate faster than c relative to Earth and get
there sooner in terms of body age? I mean gradual increase of acceleration, of
course.

I understand that Earth will just see the ship time flow more slowly.

~~~
johngalt
Lorentz factor only makes a large enough difference when you're very close to
the speed of light.

Edit: changed from 'c' to 'the speed of light'

~~~
Joakal
c, as in Earth's view of ship's speed?

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MikeCo
Probably the most interesting question from the comments: "How important is
the time gap of interstellar travel?"

The information we gather today about the state of the universe is terribly
"out of date" considering we are looking into the past. If we found a pale
blue dot, it could be gone by the time we could manage to get there.
Alternatively, there may be one in the making that we don't recognize but
would be habitable by the time we made it there. We should solve the FTL
travel problem first. :)

~~~
maaku
Planets don't disappear in a matter of years. Even in the 100,000 to few
million years it would take to traverse the entire galaxy they wouldn't
disappear (although any life would evolve significantly).

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Apocryphon
I'd just be happy with a sequel to Sid Meier's Alpha Centauri, one of those
franchises that has languished and whose reappearance, alas, seems as far away
as an actual mission to Alpha Centauri.

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dmoney
There are ways to get from planet to planet with almost no energy:
[http://en.wikipedia.org/wiki/Interplanetary_Transport_Networ...](http://en.wikipedia.org/wiki/Interplanetary_Transport_Network)

There must also be ways to get from star to star. If there are Sun-Earth
Lagrange points, there must be Galaxy-star Lagrange points, and a way to
transfer from the Sun's to Alpha Centauri's. This would probably take a while
though.

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duggan
I always liked the concept I read about in an Asimov short story years ago;
the (rough) idea being that you somehow "pin" a ship/probe to the CBR/fabric
of the universe and let the solar system / galaxy accelerate away at 2.1
million km/hr.

Note: I am obviously not a physicist, so feel free to demolish my fantasy :)

~~~
Groxx
Sounds like a one-way trip

~~~
Joakal
Much like time travel if it was possible.

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maeon3
We need a new method of transportation through space. Could the higgs boson be
removed from a neutron so that it would not interact with the higgs field? We
could create a tin can sized ship with it and accellerate the near zero mass
object close to light speed and decelerate just as easily if zero mass fuel
could also be made.

~~~
andrewingram
This does assume that the higgs boson is real and we can come up with a way of
manipulating it at relatively low power levels. Not much good in the short
term if it takes the power output of a star to achieve :)

Alastair Reynolds' Revelation Space series of hard sci-fi has quite a bit
about ships called Lighthuggers that basically travel at about 0.95c and
exploit relativity to achieve short journeys for crew members when hundreds of
years pass in the real world. A more advanced technology in the books is one
which reduces the inertia of an object to achieve even higher speeds, the
higgs isn't mentioned explicitly IIRC but I think it's what the books are
getting at.

~~~
blake8086
.95c only gives a time dilation factor of ~3x, that's not very much.

~~~
andrewingram
Yeah, they still used sleeper technologies, but were only sleeping for 30
years rather than 100. But the universe takes the view that sleeper technology
is dangerous and shouldn't be used heavily, it also only slowed down
metabolism rather than freezing it ala stasis.

