[FPSPACE] FW: Centauri Dreams - Interstellar Sails and Their Precursors

[LARRY KLAES]

>From: Centauri Dreams <gilster at mindspring.com>
>Reply-To: Centauri Dreams <gilster at mindspring.com>
>To: ljk4 at msn.com
>Subject: Centauri Dreams
>Date: Tue, 27 Nov 2007 14:07:35 -0600 (CST)
>
>Centauri Dreams
>
>///////////////////////////////////////////

>Interstellar Sails and Their Precursors
>
>Posted: 27 Nov 2007 08:20 AM CST

>http://www.centauri-dreams.org/?p=1597
>
>
>Lou Friedmans work on solar sails dates back to his days at the Jet 
>Propulsion Laboratory where, in the 1970s, his team began work on a 
>rendezvous mission with Halleys Comet. It was a mission that never flew, 
>but you can read about its planning stages in Friedmans book Starsailing: 
>Solar Sails and Interstellar Travel (Wiley, 1988). That title is, as far as 
>I know, the first book-length study of this technology, though it has since 
>been joined by Colin McInnes key text Solar Sailing: Technology, Dynamics 
>and Mission Applications (Springer/Praxis, 1999).
>
>Now executive director of The Planetary Society, Friedmans interest in 
>solar sails led to his work on the Societys Cosmos I mission, unfortunately 
>lost during the launch attempt in 2005. His interest in interstellar issues 
>remains keen as well, as evidenced by an article he recently wrote for 
>Professional Pilot magazine. Making Light Work runs through solar sail 
>basics for an audience that may seem surprising, but I can tell you from my 
>own flying days that as we used to wait in the pilots lounge for students 
>to arrive, we would often kick around outlandish concepts like deep space 
>missions (and there were always a few dog-eared copies of Professional 
>Pilot scattered around the room, out of date and thoroughly read).
>
>Friedman speculates about sails kilometers wide in the area of 0.1 microns 
>in thickness, ultralight films that would, when the photons from sunlight 
>lost their punch, take advantage of huge laser installations that could be 
>focused for interstellar distances. Now were into Robert Forward territory 
>and also in range of feasible interstellar missions. For as Friedman notes, 
>solar sails are the only technology we currently have that could complete 
>such missions in a single human lifetime:
>
>What is exciting is that we know the way forward. We don’t have to invent 
>some new physics (like matter/antimatter engines) and we don’t have to 
>conjure up new technologies from science fiction (such as interstellar 
>ramjets scooping up and using interstellar hydrogen molecules). Rather, 
>it’s all a matter of engineering—make the light sail materials thinner, 
>the spacecraft lighter and the lasers more powerful.
>
>Of course, the demands are still huge, power on the order of 100 gigawatts, 
>which means power stations located in space, assembled in the inner solar 
>system where solar radiation is much higher than here on Earth (presumably 
>sails would be involved in ferrying the needed materials). And then theres 
>the problem of sail construction, conceivably handled by making the sail 
>out of plastics whose evaporation would leave only the needed molecules to 
>reflect sunlight and laser photons. Imagine a square kilometer sail 
>weighing just a few kilograms, its electronics sprayed onto the sail rather 
>than flying as a separate payload.
>
>Solar sail technology is no idle dream. After extensive study at Marshall 
>Space Flight Center, NASAs basic sail design has reached the point where 
>space testing is the logical next step even as research continues in 
>European venues like Germanys DLR. When we begin a serious push into solar 
>sail technologies, well need to test these designs in near-Earth orbit, and 
>then move out into the Solar System. A logical mission for early sails will 
>be, as Friedman notes, a replacement for the Advanced Composition Explorer 
>(ACE), a mission nearing the end of its lifetime.
>
>ACE operates at a libration point where the gravitational forces of Sun and 
>Earth balance, some 1.5 million kilometers from Earth. A sail mission that 
>could monitor solar weather (and warn us of solar storms) could offer a new 
>kind of station-keeping, one that uses the momentum imparted by photons to 
>stay in position closer to the Sun without the need of remaining at the 
>libration point. Such a position would, among other things, allow greater 
>early warning of potential ionospheric disruptions.
>
>The range of sail missions available in coming decades will be huge, but if 
>we keep at it, we may get to the point where building the kind of laser 
>well need for an interstellar mission becomes possible. Solar sailing is 
>the kind of next-step technology that moves us from one-shot mission 
>spectaculars like Apollo into the realm of a stable and long-term human 
>presence expanding into the Solar System. For the short term, we need to 
>keep doing what Friedman and sail advocate Gregory Matloff are doing, 
>explaining and arguing for the needed steps to get sails into nearby space 
>where their value for more complex missions will be obvious.
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