
A New Spacecraft to Explore on Waves of Light - robg
http://www.nytimes.com/2009/11/10/science/space/10solar.html?_r=1&hp=&pagewanted=all
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ryanwaggoner
This 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_me...](http://en.wikipedia.org/wiki/Interstellar_travel#Proposed_methods_of_interstellar_travel)

~~~
rms
I 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
Hopefully we also develop radical life extension so I can go :)

~~~
rms
If 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-centa...](http://news.nationalgeographic.com/news/2008/03/080310-centauri-
earth.html)

This will be a very interesting universe once my other consciousnesses are
floating around exploring it.

------
ars
"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.

~~~
camccann
A 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
Why has he been downmodded?

Downmods below 0 are ONLY for spam, and "me too" like posts!

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10ren
Larry 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).

