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Or just in orbit. Way easier, no need to overcome moon's gravity.
How could you store enough power in orbit to fire it?
Oddly the most practical use for this is as an interstellar weapon. You don't need to solve the problem of communicating back to Earth, you just need a little terminal guidance. If an iPhone weighs 100 g and we use a non-relativistic formula for energy at 1/4c, that is 2.8 x 10^14 joules, a ton of TNT equivalent is about 4.1 x 10^9 joules, so that is a cool 70kT -- The impact velocity would be high enough to break th…
I completely don't advocate this, but the 9-year-old-boy part of my brain thinks it'd be pretty awesome to announce our presence to the universe by attacking a star system.
Does that mean that the US will be the winning civilization?
"civilization"? You mean like when Ghandi was (allegedly) asked what he thought of Western Civilization, and replied, "I think it would be a good idea!"
How is such thing able to communicate back with earth? Doesn't it require a lot of energy to create signal that we will be able to receive on earth (or satelite)?
"At its destination it would beam back pictures of the star’s planets with its on-board laser. No current observatory could possibly pick up such a signal—but the kilometre-wide launch array should be able to. The optical systems used to meld the output of the lasers could be used in reverse as a vast and sensitive telescope."
http://www.economist.com/news/science-and-technology/2169687...
Is there something i dont get here?
How is such thing able to communicate back with earth? Doesn't it require a lot of energy to create signal that we will be able to receive on earth (or satelite)?
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I love these napkin calculations. The relativistic effect shifts the frequency by 22.47% for 0.2c. Given a 445nm laser (the powerful blue ones), that's 545nm when redshifted (green). It's a bit of a jump, but that wavelength is still smack in the "solar atmospheric absorbtion spectrum window" -- you won't lose much of the energy in the atmosphere. Reading this page diagonally [ http://www.edmundoptics.com/resources/a…
Umm... 0.5% of 100GW is 500MW, or about the power of a nuclear reactor. The spaceship won't survive a millisecond. We need way better than 99.5%.
Upon further reading, looks like you can achieve >99.9998% reflectance for a 10% wavelength band (in this case, in the infrared). [http://www.crystallinemirrors.com/wp-content/uploads/2013072...]
Still, you're right in saying that it's probably still quite a ways off.
So the whole thing should weigh in the order of several grams, yet it should be able to deflect 100GW of incoming radiation near perfectly (otherwise it will instantly vaporize) while maintaining structural integrity under the acceleration of 60,000g for two minutes? And whatever laser sources we're using must track this smartphone-sized object during these two minutes across several million kilometers. Perfectly. (I…