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The BBC and the Guardian both carry stories about an unmanned interstellar spacecraft designed to reach the Alpha Centauri system "within a generation" (30 or so years).
The spacecraft would be miniaturised to the size of an average silicon chip, and be propelled by a solar sail which would receive a boost from a powerful laser on the Earth.
Milner's Breakthrough Foundation is running a project, backed by Hawking, to research the technologies needed for such a mission, which they think will soon be feasible.
takyon: The campaign is called Breakthrough Starshot. Breakthrough Initiatives also announced the release of initial observational datasets from the Breakthrough Listen 10-year SETI effort.
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Stephen Hawking and Yuri Milner's $100 Million Interstellar Spacecraft Plan
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The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
There *__is* intelligent life on Earth, but I leave for Texas on Monday.
(Score: 0) by Anonymous Coward on Wednesday April 13 2016, @03:18AM
Interstellar RFID tag? A little small for anything useful. Who's going to keep the laser running for years? If it's that small then maybe it can use starlight (all spectrum) to propel it's self. I propose we paint a magnet dark on one side and white on the other. The magnet will keep aligned with the magnetic field of our sun and then reflective side would stay towards it.
Where's my 100 million now?
(Score: 2) by takyon on Wednesday April 13 2016, @03:42AM
I was under the impression that the badass laser would be able to accelerate the tiny lightweight spacecraft to 0.2c with a very short pulse duration, maybe hours long, not years. The whole setup is intended to weigh about 2 grams, 1 gram for the craft/chip, 1 gram for the meter long solar sail.
Laser Propulsion Could Get Craft to Mars in Just Days [soylentnews.org]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 5, Insightful) by c0lo on Wednesday April 13 2016, @04:43AM
Guardian FA:
So 100 GW laser working in Earth atmosphere - so, it needs a wavelength the atmosphere is transparent to - this rules out infrared and UV, thus VIS only.
The best efficiency seems to be for Diode pumped - solid-state laser [wikipedia.org] - 48% theoretically achievable effciency.
Thus the power will need to be at least twice of that - 200 GW - highly probable more than that.
And this working for 2 minutes - which means an energy of 24 TJ.
Some comparisons now:
Atacama, eh? 200 GW is 00/16=12.5 times more than the installed power capacity in Chile [wikipedia.org]
I don't dare to think what material that sail needs to be made of, I highly suspect we are speaking about unobtainum.
Any radiation absorption in that sail is going to vaporize it (assume a 10-6 absorption coefficient - that's five 9-s reflectance - and from 24TJ means 24MJ are absorbed - that's enough to boil more around 5 cubic meters of water).
---
Guess what - that reflected energy needs to go somewhere.
To have a precise trajectory to Alpha Centauri, one need to be extremely precise - so I suspect an extremely precise normal incidence on the sail (after some 100,000 kilometres on the trajectory, even multiple beams from a laser array will look like a single beam)
So that reflected light? If you are as precise as you need to be, almost all that 100 GW of laser comes back to you, the emitter.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Gravis on Wednesday April 13 2016, @06:03AM
The only sustainable type of laser at high energy levels are free-electron lasers [wikipedia.org]. Also, you need to be constantly generating a large amount of power which would work using lots of large solar panels. Finally, you don't want to place the laser on Earth, the Earth is moving around the Sun!
(Score: 2) by c0lo on Wednesday April 13 2016, @06:25AM
The vest efficiency in the 5%-10% range. Many high powered ones can sustain lasing only for microseconds at >500kW.
But no, you can use other lasers if you use them as an array (the way they plan to use).
At the current PV efficiency (say 33%) and taking 1kW/m2 the solar constant, 200 GW is equiv to 600e6 sqm of panels.
A trifle really, "only" a square with about 25km side.
Pricewise? If they use those $100 millions budget only to buy PV panels, they can afford them only if the price is under $0.17/sqm.
Nah, not gonna happen.
And yet, this is exactly how they plan to do it. Perhaps the plan to compensate for Earths movement during those 2 minutes of acceleration.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 1) by anubi on Wednesday April 13 2016, @06:56AM
I second the notion... Earth is a terrible place to put the laser....
You know how the lensing effect of temperature layers of our atmosphere makes the stars appear to twinkle, or make mirages appear? Isn't that same lensing effect going to make it damn near impossible to get the light out precisely without the lensing effect randomly deflecting the laser ever so little one way and the other, to make it very erratic to hit its intended target?
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by c0lo on Wednesday April 13 2016, @07:25AM
See astronomical seeing [wikipedia.org] - after all, there's only one Hubble telescope in space and a great deal of large ones on Earth - this is how they manage [nature.com].
But... I don't know what shining a 100GW laser will do to the atmospheric air - I think they don't know either.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Interesting) by GreatAuntAnesthesia on Wednesday April 13 2016, @08:15AM
I think this is the closest "what if" to your question: https://what-if.xkcd.com/13/ [xkcd.com]
(Score: 2) by butthurt on Wednesday April 13 2016, @11:03AM
I was thinking of the one that supposes "What if all of the sun's output of visible light were bundled up into a laser-like beam that had a diameter of around 1m once it reaches Earth?"
https://what-if.xkcd.com/141/ [xkcd.com]
(Score: 1) by anubi on Wednesday April 13 2016, @08:19AM
Thanks! I did not know that phenomena had a name, but I knew it existed.
I extrapolated from how much wavering I observe from about ten miles of atmosphere after the light traveled light-years to get to me, and considered - at the angles I observe - what the mistargeting of the laser would be if I were trying to hit a target thousands of miles away with the laser on Earth... it seems to me ( gut feeling ) - that it would be damned near impossible to hold the laser onto the target - after its random perturbations by our atmosphere.
I wonder how to sense the phenomena in realtime for correction? Maybe use a nearby star and correct for what the atmospherics did to its light?
It seems like trying to use a laser ten feet underwater to hit something a mile up in the air... but you can't do anything about all the waves.
Interesting point you bring up about the interaction of that much laser light with atmosphere. I have no feeling about this one yet, but if anyone here has worked with high power lasers on the ground, have you noticed anything smelly ( like ozone ) that gets released when that much energy is traveling through the atmosphere as light? I do know high voltage will stress the air so much I get ozone and various nitrogen compounds ( even the diesel engine in my van stresses the air enough to form various oxides of nitrogen ) .
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by Grishnakh on Wednesday April 13 2016, @05:32PM
It seems like it'd make a lot more sense to just build the giant laser in space, and use it there: no problems with the Earth's movement (the laser could maneuver independently), no problems with atmospheric attenuation, etc. You could also allow it to transfer power over a longer period to the crafts.
(Score: 1, Informative) by Anonymous Coward on Wednesday April 13 2016, @08:52AM
Finally, you don't want to place the laser on Earth, the Earth is moving around the Sun!
Anything residing in our Solar system must either move around Sun, get away of it very fast, or drop into it. Even all of Lagrange points are moving.