h a l f b a k e r y"It would work, if you can find alternatives to each of the steps involved in this process."
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Shine a laser beam on your target planet and drop nanobots into the beam. Photons strike the nanobots and imbue them with momentum, eventually accelerating our little "nano-nauts" to some useful fraction of c.
A second, annular laser beam of higher energy surrounds the first beam to keep the little
nano-nauts on course. The second beam actively contains the bots (some science types down under figured this out already).
The beams are controlled to track the target planet, again with the second beam keeping the nano-nauts contained in the accelerating central beam.
Turn the central beam off when it's time to decelerate the nano-nauts. If we play nice, the target planet's sun will slow things down with its solar wind.
With a bit of luck, some of our little friends will arrive at the target planet intact. Hopefully we pre-programmed them with instructions, otherwise we can send them orders via laser pulses.
Harvesting raw materials at their destination, the nano-nauts build power stations, farms, habitats, and cloning vats. We then use the laser beam to transmit encoded brain scans of each of us, which are implanted into the colonizer clones as memories.
Hey this could happen!
http://www.reuters....ilner-idUSKCN0X91YE
[the porpoise, Apr 12 2016]
Yup. Another Halfbakery idea adopted?
http://www.nytimes....n-hawking.html?_r=0
[doctorremulac3, Apr 13 2016]
[link]
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//Turn the central beam off when it's time to
decelerate the nano-nauts.
With a bit of luck, some of our little friends will
arrive at the target planet intact.// |
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Sp.: "Turn the central beam off when it's time to
stop accelerating the nano-nauts.
With a bit of luck, some of our little friends will
impact the target planet at an appreciable fraction
of c." |
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Indeed, Max, decelerating would be a concern. I thought I could hand-wave through that bit. I will suggest that, if we ask nicely, the target planet's sun might project enough solar wind to slow things down to a reasonable approach speed. Solar wind would increase as we approach, so it might work out nicely. A solar parachute, if you will. Idea updated. |
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Laser propulsion of solar sails as a form of
interstellar propulsion is a pretty well-discussed
idea already, and has been for a few decades. And
so has interstellar colonization via replicating
nanomachines, although mostly among the more
out-there singularity types. |
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The only difference in this concept, as far as I can
tell, is the novel concept of a beam aiming system
so precise as to track a planet over interstellar
distances, and the idea that one should eschew the
traditional solar sail and instead use a beam orders
of magnitude more intense, so that the requisite
photon pressure can be applied to the much
smaller area of the payload itself, rather than
spread out over a sail. |
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//Solar wind would increase as we approach, so it
might work out nicely// Well, if you rely on solar
flux to decelerate, then the maths will probably
come out that you gain no advantage by using a
laser
to accelerate in the first place. |
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What I mean is that acceleration and deceleration
have to match, so you may as well use the sun to
accelerate, and the distant star to decelerate. |
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I could be wrong. But it smells of symmetry. |
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[Max], I suppose it depends on the superposition of the photon density curves of the laser and the distant star, or something. Acceleration at this end may be very small and gradual. At the distant star it might be more sudden. |
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[Hive] that is an apt summary. I would also add that the payload survival rate need not be 100% or even 1%, so I see that as a bit of a difference too. |
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Sounds a bit like "Router" by Strossy.... |
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//Acceleration at this end may be very small and
gradual. At the distant star it might be more
sudden.// |
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I'm not convinced. The acceleration will be some
sort of U-shaped curve - highest (acceleration)
near to earth/sun, and highest (deceleration) near
the distant star. |
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If you rely solely on the light from each star (sun
and distant star), the curve will be a symmetric U.
If you try to speed things up by using a laser at
this end, then the deceleration at the other end
will not be enough to stop the nanonaut. |
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You can think of it like a ballbearing in U-shaped
track. If the U is symmetric, a ball released at the
top of the left arm will come to rest at the top of
the right arm. If you raise the height of the left
arm (equivalent to using a laser to add
acceleration), the ball will just fly off the end of
the right arm. |
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In other words, I suspect that you cannot gain an
advantage by using a laser to boost the
acceleration as the thing leaves earth, unless you
can arrange for a laser at the other end to
increase the deceleration. |
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How about this: The first batches splat on the
planet until they build up a molten metal crater. |
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Pause & let cool. Hope the crater is close enough
to parabolic & reflective (with the metal from the
nanobots). |
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Now, you have a mirror on the planet, which could
reflect your laser back to slow down your approach
for the subsequent batches. |
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[Max], you might be right. I don't know, though. |
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Think of the laser as a long weak spring and the distant star as a short strong spring. The long spring launches a marble across the floor. The long spring stops expanding and the marble keeps rolling. Eventually the marble hits the short spring, which slows it down with greater force over a shorter distance. |
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The analogy may not be appropriate, which is where the concept might fall down. I don't know. I find light unintuitive. |
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\\Think of the laser as a long weak spring and the
distant star as a short strong spring.\\ |
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Ah - I thought the point of the laser was to drive the
things faster than by solar radiation alone? |
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In any case, your laser's thrust will be _added_ to
that from the sun, so you'll still have a problem even
if the laser is weak. |
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//Sounds a bit like "Router" by Strossy... |
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Apologies for obscurity...it's part of the book Accelerando, written by Charles Stross. Some people decide to go interstellar traveling, they copy their minds into a coke-can sized substrate, and (this bit from memory) plan to build bodies at the other end by using nanoware. |
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Maybe neutrinos are exactly this idea, on a large
scale, but coming from a distant civ? |
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I mean, our current tech leads us to believe we know
how small things are, but each decade, we seem to
discover even smaller things. |
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Well, if the destination star is brighter, we'd need the laser to balance the "U". |
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Of course all this sounds like people are assuming that the acceleration from the solar sail is larger than the acceleration of gravity for the star you are approaching (and the sun). That may be true for a very large yet light object, but maybe less likely for a nanonaut. I suspect that you'll need to approach the star indirectly to enter a highly elliptical orbit. Hopefully you can get just enough impulse from your solar sail to drop below escape velocity during the first appraoch. Over many orbits with the sail exposed for half the orbit, you can bleed off some energy. |
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How does that laser cooling work? Maybe those flavor lasers
will slow a thing down. |
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//but each decade, we seem to discover even smaller things. |
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//Mint lasers can only add the coloured stripes, |
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Send the dna of mint in the same laser beam that writes the stripe. |
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I read a little about laser cooling.
1. Laser photon thing, gets it excited.
2. In its excitement it emits a photon of higher energy than the one that hit it.
3. Coolth ensues. |
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If that photon were emitted from a random direction as regards the thing, this should slow it. Emitted back towards original laser will not slow. Lateral emission will move laterally which will be corrected by annular laser. Emission from front of thing will cause it to slow. |
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Looks like something similar is afoot [link]! |
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How did I miss this 2 years ago? It's pretty much exactly what Hawking and Milner propose (apart from the building stuff at the destination).
I've long suspected that Hawking would be the kind of guy that would stalk the Halfbakery... |
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The Starshot plan is ambitious. From the ArsTechnica article about it, it has this detail: |
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"The small spacecraft will be equipped with a light sail, and a phased array of lasers in the 100GW range will provide the sail with enough push to get the craft moving at roughly 20 percent the speed of light in just a matter of minutes." |
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The most powerful (readily available) continuously operating lasers are Industrial cutting lasers which work at up to 5kW. Focusing 20,000 of these lasers at something a few metres in diameter at the distance of the moon (and beyond) is pretty amazing. |
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Laser light diverges, so to increase range you can fire a laser through telescope. The Hubble telescope can (theoretically) resolve feature on the moon of 200 metres. A telescope would need a diameter of 100 meters to resolve a feature 10 metres in size on the moon (and thus you need that size telescope to fire lasers at a 10 meter solar sail). |
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If Hawking launches a line of traditional flenting products
we'll have him bang to rights. Although I suspect only the
genuine article is good enough for that speech box thing. I
can detect the timbre of a Rentisham's potted capacitor a
mile away. |
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