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I have a physics question that I need some help with:

"Proxima Centauri is a star in the Alpha Centauri solar system, it’s the nearest star to our sun (4.24light−years) http://en.wikipedia.org/wiki/Listofneareststars. How large of a solar sail would be needed to accelerate a solar sail of mass m to a velocity which will get the ship to Proxima Centauri in two lifetimes?"

I'm assuming that the time is 160 years for 80 years each lifetime. Can anyone help?

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Well this question is quite a pickle to be given as a casual physics problem. The acceleration is non-constant and to give perfect mathematical treatment would require fairly difficult calculus. Instead, you're forced into making the (perfectly valid) assumption that all the acceleration happens close to our sun. You will then need to imagine a formula for the V you get from $r$ to infinity. While $1 AU$ sounds like a natural choice for $r$, it's unspecified, and 1 AU is not very smart. NASA would surely opt for gravitational assists to the inner solar system to unfurl it there. –  AlanSE May 20 '13 at 19:47
Related: physics.stackexchange.com/questions/64642/…. –  dmckee May 20 '13 at 20:00
Thanks for the help, I've explained it to my professor and he is giving me a pass as long as I explain why it is not so easy to solve. –  Matt Simmons May 20 '13 at 20:14
Welcome to Physics Stack Exchange, Matt! This is a relatively interesting question, but at the same time, this is not really a homework help site. If you are confused about some specific conceptual issue you've encountered while trying to solve the problem, feel free to edit your question to ask about that and I'll be happy to reopen it. See our FAQ and homework policy for more information. –  David Z May 20 '13 at 21:16
Would suggest doing some reading, especially books by Giovanni Vulpetti, Les Johnson and Greg Matloff (ISBN 0387344047 - Solar Sails: A Novel Approach to Interplanetary Travel, Springer, 2008). –  Deer Hunter May 20 '13 at 22:21
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closed as too localized by David Z May 20 '13 at 21:14

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