back to article 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 …

  1. Swarthy Silver badge

    Next up:

    The Kickstarter campaign for the giant battery of lasers to start a craft on its way to Barnard's Star, run by a guy named Eddie.

    1. David Given

      Re: Next up:

      That's crazy talk.

    2. Mage Silver badge

      Re: Next up: Crazy Eddie

      " 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.

      1. Anonymous Coward
        Pint

        Re: Next up: Crazy Eddie

        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." ---->

        1. Phil O'Sophical Silver badge
          Coat

          Re: Next up: Crazy Eddie

          you'll start your run buried in food-stuffs.

          Which will also be the radiation screening, and to make sure you don't suffer as the journey unfolds you'll have to save all your waste and keep it as a protective layer.

          Solitary sounds like a good idea to me...

          1. Muscleguy Silver badge

            Re: Next up: Crazy Eddie

            Waste has the advantage of being denser, though unless you plan to boost a LOT of water out of the gravity well you will need to scavenge 99% of the water for reuse. Gonna need a very, very good RO unit and changing the membranes will not be pleasant.

      2. Grinning Bandicoot

        Re: Next up: Crazy Eddie

        Mage, I believe it was Pournelle who used the laser boost from Baja California.

        Anyone remember Echo from the 50s., its orbit was altered and the balloon was deformed from the solar pressure that should have been proof of concept.

  2. David Given

    Don't forget about Ikaros!

    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.

    1. Andy The Hat Silver badge

      Re: Don't forget about Ikaros!

      "... 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

      1. AbelSoul
        Pint

        Re: Seems to be hibernating at the moment.

        @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.

  3. JeffyPoooh
    Pint

    "PIC"

    An "Artist Conception" doesn't count.

    .: disappointed :.

    .

    .

    .

    (I'd use the Joke Alert, but I like Beer better.)

    1. HildyJ Silver badge
      Megaphone

      Re: "PIC"

      Here's the first pic

      http://planetary.s3.amazonaws.com/assets/images/spacecraft/2015/20150608_ls-a-partial-01P02_1600x1200_30-1_T0_47_33_D20_0_70_out_1_f840.jpg

      Ongoing blog by Jason Davis is at

      http://www.planetary.org/about/staff/jason-davis.html

  4. Richard Boyce

    Energy vs momentum

    The sail isn't for harvesting energy from the sun (that's plentiful near Earth), it's for harvesting momentum, which you need to change speed and/or direction.

    1. diodesign (Written by Reg staff) Silver badge

      Re: Energy vs momentum

      You must be fun at parties.

      C.

      1. mIRCat
        Coat

        Re: Energy vs momentum

        Wot? Parties?

    2. Steve Knox
      Boffin

      Talk to The Apples In Stereo

      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.

      1. h4rm0ny

        Re: Talk to The Apples In Stereo

        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?

        1. stucs201

          Re: Let's use the right terms, eh?

          Obligatory XKCD:

          https://xkcd.com/1322/

      2. Paul Kinsler Silver badge

        Re: Hence momentum is a derivative of energy.

        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.

  5. Peter Simpson 1
    Thumb Up

    TLE - in case someone wants to try a real photo

    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...

  6. Lars Silver badge
    Happy

    Changing direction...

    ..is a bit of a joke, it's "down wind" until you can catch wind from some other direction, drifting along like a yacht without any lateral plane area. Interesting all the same.

    1. Paul 25

      Re: Changing direction...

      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)

      1. Anonymous Coward
        Anonymous Coward

        Re: Changing direction...

        That's not bollocks but I'd rearrange it to be constant winds and tidal-whirlpools. I can't recall when if ever someone had to slingshot that way at sea. Small sailboats in riverine conditions, likely around. Not my thing though; deep blue sea sailor.

      2. Muscleguy Silver badge

        Re: Changing direction...

        I take it you do not sail anywhere near the gulf of Corryvrackan then? ;-)

    2. Marshalltown

      Re: Changing direction...

      Nope. If you build a system where sails can be trimmed, you could tack across or even into the "wind."

      1. Martin Budden Silver badge

        Re: Changing direction...

        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.

        1. David Given

          Re: Changing direction...

          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.

  7. Faux Science Slayer

    Solar photons decrease with the square of the distance....

    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.

    1. This post has been deleted by its author

    2. F0rdPrefect
      FAIL

      Re: Solar photons decrease with the square of the distance....

      Bill Nye is just the current spokesman.

      This project has been in the pipeline for years before he became the mouthpiece for the Planetary Society

      (PS Member for over 15 years)

  8. Michael H.F. Wilkinson
    Pirate

    In my mind's eye ...

    I can see space pirates with black sails, preparing to board this craft. SHIVER ME TIMBERS!!!!!

    ;-)

  9. Winkypop Silver badge
    Pint

    Giant space goon bag!

    In space, no one can hear your next order!

    http://en.wikipedia.org/wiki/Box_wine

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