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A New Spacecraft to Explore on Waves of Light
- ars 17y ago"In principle, a solar sail can do anything a regular sail can do, like tacking." No it can't. Can it? So far as I understand, tacking requires the water of the ocean to redirect your momentum. There is nothing that would do this in space.
- wtallis 17y agoI don't think you could sail "upwind" using just a solar sail, but you could use the sail to reduce your angular momentum about the star and then let gravity pull you back toward the sun.
- olefoo 17y agoGravity, the spacecraft's own mass, and the angle of incidence of light on the sail. The definition of tacking for solar sails is that your vector is at an angle to that of the incident sunlight. In other words you are able to generate some sideways motion rather than just getting pushed.
- camccann 17y agoA wind-driven land vehicle can tack just as well as a sailboat can, and possibly better. If memory serves me, in the fully general case, all that's required is an exploitable difference in velocity at the interface of two media (ground/air, water/air, etc.) to extract energy and move in arbitrary directions (or even do counterintuitive things, like go faster than either medium as a sailboat tacking downwind does). In space, a solar sailcraft is embedded in a single medium. So, no, no tacking.
- ars 17y agoWhy has he been downmodded? Downmods below 0 are ONLY for spam, and "me too" like posts!
- InclinedPlane 17y agoThere are two forces in play: the propulsion of the sail due to the Sun's light, and gravity. By directing the thrust of the sail against the orbital momentum of the spacecraft it will be pushed initially slightly farther from the Sun but also slowed down in its orbit, causing gravity to pull it closer to the Sun.
- ryanwaggoner 17y agoThis is really fascinating technology, and it'll be awesome to see it actually take shape, but I'm not sure I agree with this: “Sailing on light is the only technology that can someday take us to the stars,” said Louis Friedman, director of the Planetary Society, the worldwide organization of space enthusiasts. It may be the only available technology today, but there are many theoretical technologies that are probably more practical for interstellar journeys. http://en.wikipedia.org/wiki/Interstellar_travel#Proposed_methods_of_interstellar_travel http://en.wikipedia.org/wiki/Interstellar_travel#Proposed_me...
- rms 17y agoI am confident that within the next 40 years we will take one of these technologies beyond the theoretical -- we're going to find an exoplanet with conditions that support life and it's going to set off an extraordinary scientific mission.
- ryanwaggoner 17y agoHopefully we also develop radical life extension so I can go :)
- rms 17y agoIf Alpha Centauri has an earth-like planet around it, we will know about it in our lifetimes. http://news.nationalgeographic.com/news/2008/03/080310-centauri-earth.html http://news.nationalgeographic.com/news/2008/03/080310-centa... This will be a very interesting universe once my other consciousnesses are floating around exploring it.
- 10ren 17y agoLarry Niven used a solar sail in several stories, e.g. "The Fourth Profession" and "The Mote in God's Eye". You can leave a "laser canon" on the launch world. That way, you can leave your rocket engine at home, where there are resources to fuel, maintain and improve it You can tack against the solar wind. You can - and this is the really cool one - use magnetic flux, if present in that region, to turn (even through 90%), by giving the space craft an electric charge. I've forgotten the details of how you change the net charge of a spacecraft, but I guess you could easily jettison electrons (or protons).