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dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

Light Sailing:
   A Powered Light-sail, in the form of a gigantic "parachute," with tension lines attached to the metalized sail canopy at many points in a grid pattern which maintains the paraboloidal shape, such that the reflected sunlight will be reflected to a blackbody coated surface situated at the parabolic focus which covers the spacecraft, and from which the grid pattern of tension lines radiate, parachute-wise.
The heat resulting from the concentrated sunlight can (a) melt water-ice fueling a throttleable flash steam jet (b) generate thermal-electric current for an ion jet modirected sunwards. Payloads would be located outboard of the jet power assembly.
  The sail and tension lines (according to recent internet disclosures) will comprise only a small percentage of the all-up mass of the "ship," to make the limiting light-powered acceleration as high as possible. Deformation of the canopy, when the jet-powered payload acceleration exceeds the limit will tend to de-focus the sunlight, thereby decreasing payload acceleration until its drag restores the parabolic shape, which re-focuses the sunlight, and so on. 
  Minimal steering capability would be possible by means of  collectively programmed reeling-in or -out of the tension lines where they emerge surrounding the heat collector.
  A bonus will be the ability of the huge canopy to receive and transmit microwave data.
  Anyway, assuming this configuration of "powered light-sail" rig is practical, any number of relatively simple and reliable probes could be sent off, in any direction in-or-out of the ecliptic, chasing comets, etc.
  Economical cargo transport out to Mars-space naturally comes to mind, as another application....

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soph

Member

Registered: 2002-11-24

Posts: 1,492

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

wouldnt this system lose effectiveness tremendously as the distance from the sun increases?

Phobos

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Registered: 2002-01-02

Posts: 1,103

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

wouldnt this system lose effectiveness tremendously as the distance from the sun increases?

You could always use a very powerful laser instead of relying on sunlight if you want to speed things up.  This is the first time though that I've read about the possibilities of using the concentrated light to run steam generators.  Interesting idea!

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To achieve the impossible you must attempt the absurd

soph

Member

Registered: 2002-11-24

Posts: 1,492

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

would it be possible to send lasers to orbit around other bodies in the solar system, to assist further out missions?

Phobos

Member

Registered: 2002-01-02

Posts: 1,103

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

You could put lasers just about anywhere you wanted to as long as you had enough power to keep them viable.  According to people like Robert Forward it would be possible to use lasers to accelerate a lightsail to relativistic speeds using a lense only about 100 meters in diameter provided you could pump hundreds of terrawatts of power into it.  That kind of energy is impossible to generate with today's technology but it might be possible once we tame fusion or find some other exotic power source that could pull it off.

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To achieve the impossible you must attempt the absurd

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

wouldnt this system lose effectiveness tremendously as the distance from the sun increases?

Yes, but out to distance of the asteroid belt, in a sphere surrounding the Sun, it should serve the purpose until other means not yet achievable are developed. My purpose is to attempt the do-able as soon as possible!

soph

Member

Registered: 2002-11-24

Posts: 1,492

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

when phobos mentioned lasers, what i was getting at was that you could put multiple "laser stations" in the outer system to propel missions.  isnt voyager still powered by nuclear reactors?  we could use those to power lasers, no?

Phobos

Member

Registered: 2002-01-02

Posts: 1,103

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

when phobos mentioned lasers, what i was getting at was that you could put multiple "laser stations" in the outer system to propel missions.  isnt voyager still powered by nuclear reactors?  we could use those to power lasers, no?

The laser I spoke of earlier would be sufficient to carry you out several light years before becoming too diffuse and weak to be useful.  You shouldn't really need to place laser stations throughout the Solar System as one sufficiently powerful laser would be adequate even though having more wouldn't hurt.  For lightsails that are meant for the outersolar system I've wondered if solar pumped "lasers" would give signficant boost once the sunlight has become too weak.  You could maybe station the solar pumped laser satellites throughout the solar system and have them concentrate sunlight on the lightsail.  It might be impossible though to keep the sunlight concentrated in a long enough beam.

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To achieve the impossible you must attempt the absurd

dicktice

Member

From: Nova Scotia, Canada

Registered: 2002-11-01

Posts: 1,764

Re: Light-sail propulsion - Solar photon-driven sailing alternatives

Yes...and all that sunburn! But seriously, light sails gain you easy access to the volume of space above and below the plane of the ecliptic. Think of all that solar energy "going to waste" out there. Tempting maybe, as a new topic of discussion?