New solar sail proposal might win one of NASA's Centennial Challenges near term.

[exoscientist]

NASA unveils its toughest challenges yet. <br />17:15 09 February 2006. <br />"The Station-Keeping Solar Sail Challenge A solar sail pushed through <br />space by the force of the Sun's photons to a target could earn $2.5 <br />million with an equal amount available for keeping a solar sail for 90 <br />days at a fixed point in space." <br />http://www.newscientistspace.com/channel/human-spaceflight/dn8701-nasa-unveils-its-toughest-challenges-yet.html<br /><br />Via Solar Array to the Outer Planets. <br />"New Scientist is covering the work of Rudolph Meyer (UCLA), who <br />envisions a vehicle that sounds for all the world like a cross between <br />a solar sail and an ion engine. And in a way, it is: Imagine a flexible <br />solar panel a solid 3125 square meters in size, and imagine this <br />'solar-electric membrane' weighing no more than 16 grams per square <br />meter, far lighter than today's technology allows." <br />... <br />"Update: Geoffrey Landis was kind enough to forward the complete text <br />of his comments to New Scientist (the magazine quoted only the last <br />sentence). Landis wrote: "Professor Meyer suggests an interesting <br />thought-experiment about what may be possible in the future. The solar <br />array needed for his mission requires reducing the mass of solar arrays <br />by several orders of magnitude from existing technology." <br />http://www.centauri-dreams.org/?p=638 <br /><br /> The solar sail is required to only weigh 50 kg for 3125 square meters. <br /><br />But a recent advance involving carbon nanotubes can produce thin sheets <br />of arbitrary size for which a 1 kilometer square sail, or 1000m x 1000m <br />= 1,000,000 square meters, would only weigh 30 kg: <br /><br />Researchers produce strong, transparent carbon nanotube sheets. <br />"Strength n <div class="Discussion_UserSignature"> </div>

 

[exoscientist]

I should distinguish more clearly the use of pure solar sail <br />propulsion and the solar cell powered ion engines discussed by Rudolf <br />Meyer. For Meyer's proposal you need not only a very thin light weight <br />material to act as a sail, but in fact this material would also have to <br />consist of solar cells, a much more stringent requirement. <br /> NASA's Centenial Challenge only mentions a solar sail. But Meyer's <br />proposal should probably qualify at least for the transport part if not <br />the station-keeping part - especially when you consider a remarkable <br />new advance in the fuel efficiency of ion engines: <br /><br />Super-powerful new ion engine revealed. <br />11:21 18 January 2006 <br />NewScientist.com news service <br />Emma Young <br />"Tests on a prototype called the Dual-Stage 4-Grid (DS4G) thruster, at <br />ESA's Electric Propulsion Laboratory in the Netherlands showed that <br />DS4G's two-step process produces an ion exhaust plume that travelled <br />at 210 kilometres per second - more than 10 times faster than <br />possible with the engine in SMART-1, and four times faster than the <br />latest prototype ion engine designs. This would mean a spacecraft could <br />carry much more weight for a given amount of fuel, or it could go <br />further, faster. <br />"Crewed or heavyweight robotic missions to Mars become a distinct <br />possibility. And there's even talk of interstellar missions [beyond <br />the solar system]," says Orson Sutherland of the Australian National <br />University in Canberra, who led the team that built the engine, in a <br />project coordinated by Roger Walker of ESA's advanced concepts team in <br />the Netherlands." <br />http://www.newscientistspace.com/article.ns?id=dn8599 <br /><br /><br /> Robert Zubrin and Dean Spieth have discussed pure solar sail <br />propulsion in this report: <br /><br /><br />Ultra-Thin Solar Sails for Interstellar Travel <</safety_wrapper> <div class="Discussion_UserSignature"> </div>

 

[chriscdc]

There is a slight flaw in the use of transparent nanotube films for use in solar films. In that they don't interact strongly with optical light. Although they do react strongly in the microwave spectrum but I can't remember anything else.<br />You could try adding a metal film or a molecules that will interact with the light falling on it. <br />Oh well I hope to be looking into this area in a few years.<br /><br />A better place for this thread might be in the space business and tech.