Bill Nye's bonkers LightSail spaceship unfurls solar sails at last The Planetary Society says its LightSail spacecraft has finally deployed its 32 sq metre solar sails. The Earth-orbiting craft is now harvesting energy from the momentum of the Sun's photons, we're told. Motor is running! Sail is Deploying!!! 39 Years after Prof. Sagan spoke of it! — Bill Nye (@BillNye) June 7, 2015 It's …
" giant battery of lasers to start a craft on its way to Barnard's Star, run by a guy named Eddie."
Strangely (as I write SF), I was pondering this last week and wondering how the lasers :
a) Were powered
b) could compete with a star at any distance (beam spreading)
c) could compete with a load of suitably angled giant parabolic mirrors collecting and focusing the light on the fleeing probe.
Actually that part of the story doesn't work.
Certainly though it's more Larry Niven than Star Trek.
I can see the mirror design although I'd have to work through configurations to see what would cancel the momentum on the ingest side with the counter-momentum on the beam side. There's no counterpart I can think of from the days of sail. That's interesting. I was raised on science-fiction and having been a career sailor, I think about the conditions out there a lot. A properly non-claustrophobic, solitary individual would be perfect for the run to, say, Mars delivering supplies for the eventual colony. [That way you can front-load your colonization mission.] I say non-claustrophobic as just the case with submarines, you'll start your run buried in food-stuffs. Yeah, I could do that. A stack of tablets (just in case they die) and I'd be ready in a heart-beat. The reason for the human is to cope with the seriously unexpected (meteorite damage, &c).
That's for the future. For now, great job on handling that unexpected "stuff." ---->
Don't forget that this is the *second* light sail mission --- and it's just a test-bed, at that (it's way too low to do anything other than burn up almost immediately). The *first* was JAXA's Ikaros. Launched five years ago alongside their Venus probe, it passed Venus after six months and is now... somewhere (and I haven't been able to find a reference). It was last contacted in April this year.
Ikaros is interesting because it's got LCD panels on the sail which allow the albedo to be changed; it's steerable. They reckon it's getting about 1 mN of thrust.
"... it passed Venus after six months and is now... somewhere (and I haven't been able to find a reference). It was last contacted in April this year."
Seems to be hibernating at the moment. Bit of info ...
http://global.jaxa.jp/projects/sat/ikaros/topics.html#topics4743
@Andy The Hat:
From your link:
According to the last data acquired in May, the position of the IKAROS is about 110 million kilometers away from the Earth, and about 130 million kilometers from the sun. No anomaly was found in the IKAROS from data we have obtained.We anticipate that it will come out from the 5th hibernation mode in the winter of 2015.
I'd been wondering what had become of this curious and intriguing little beasty.
Thanks for the heads up.
Momentum (p) = mv (i.e, mass times velocity)
Mass (m) = e/c2 (i.e, energy divided by the square of the speed of light)
So p = ev/c2
Hence momentum is a derivative of energy. (The velocity component of momentum can similarly be derived from e; that exercise is left to the reader.)
To collect momentum, one must collect energy. Your phrasing may be more precise, but it doesn't make the other incorrect.
Well yes, but if you're going to use the conversion of energy into mass in order to make the article writer 'correct' then you also make a Hell of a lot of other statements correct.
"I had Energy for breakfast."
"I thought you had toast?"
"Mass = ev/c² . Don't try to correct me!"
Let's use the right terms, eh?
Hmm, not really: energy & momentum have very distinct conservation laws:
http://en.wikipedia.org/wiki/Noether's_theorem
Notably, a perfectly elastic collision can change momenta but not energy. The fact that typical collisions involve both energy and momentum transfer is not quite the point.
from: http://www.satobs.org/LightSail-A.html
1 40661U 15025L 15159.06218063 .02648498 00000-0 67226-1 0 94
2 40661 55.0136 260.3261 0243391 227.2228 135.1229 15.14087982 04
or, on heavens-above.com
// of course, overcast at my location today and tomorrow night...
I assume the idea is to use trajectories that combine the push outwards from the sun with gravitational slingshots from other planets. Although I am nowhere near good enough at maths to know how you might do something like that.
So kind of like combining the wind with currents on the ocean? (I'm not a sailor so that analogy might be bollocks)
In order to sail into the wind/photons a craft must have (a) sails angled so that the "lift" created is forward of the beam and (b) lateral resistance against water/space. The first requirement can be met by boats and also by spacecraft, the second requirement cannot be met by spacecraft.
Solar sails don't work anything like sailing with wind.
The sail's not going to lift anything against solar gravity, so the only part of your acceleration vector that's of particular interest is whether it's speeding up your orbit or slowing it down. If the former, you'll move outwards. If the latter, you'll move inwards.
There is a solar sail mod for KSP, if you want to play with one.
Like most science FICTION, this is more fiction than science. The solar photon thrust will drop off dramatically with distance. Any dust, or astroids in solar orbit with wipe this toy from any planned route. Typical for the NYE GUY....theater devoid of science merit.
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