Sailing the solar wind.

I just finished an article (yep, wiki) abour the solar winds. I have read other material, and find the phenomena pretty interesting. that aside:
I’ve read in science fiction about space travel using the solar wind, hereafter referred to as “sw”. :wink: I’ve also seen a movie or two about the subject. I think Star Treck even had a episode about Kirk’s uncle, or someone, sailing the sw.
Science fiction can be fun, but I’ve also read that such a thing may be theoretically possible. Sails would be huge (almost said “massive” ;)) and cumbersome, but would only be used for extremely long voyages. The idea sounds cool to me.
But, is sailing the sw possible? Will it, or could it, be a way to the outer planets?
Live long and prosper.
mangeorge, no kind of trekky.

Here is an old thread that addresses some of your questions: [thread=324185]Questions about how Solar Sails work[/thread]. Most of the impulse will actually come from momentum transfer from emitted light, not the solar wind (ejecta from the Sun).

Note that solar sails are really only useful in the in-system; by the time you’ve gotten to Jupiter the incidence of solar radiation (and wind) is about 1:25 what it is at Earth orbit, and at Saturn’s orbit it is virtually negligible, barely more than a very bright star. Solar Sailing: Technology, Dynamics and Mission Applications is supposed to be a good reference on this, though I haven’t read it yet.

I’ve actually been doing some reading on this recently for some work I’m doing; if you want more detail this, submit a question to Dex to the Mailbag and tag it for me to respond to. I kind of owe more articles as a guest contributor anyway. (Sorry, Dex; I got sidetracked by work. Lame excuse, I know.)

Stranger

Thanks, Stranger. That’s exactly what I wanted.
No sail for my Honda, I guess. :slight_smile:

Then you’ve read Arthur C. Clarke’s The Wind From The Sun ?

It should also be noted that there are two different basic ideas you can use to exploit the radiation pressure from the Sun. The most obvious is to just let it push you straight out, against gravity. Unfortunately, the light pressure from the Sun falls off in just the same way that the Sun’s gravity does, so you would need an exceedingly thin sail to pull that off (with very high surface area per mass), and it would have to be exceedingly large to carry any sort of useful payload. If your area-to-mass ratio isn’t extreme enough, then you’ll just end up in a Keplerian orbit, just with a lower effective mass for the Sun.

The practical way to do it is to go into one of those Keplerian orbits, but to then change the effectiveness of your solar sail in some way (tilt it to one side, roll it up, etc.). You start off in an elliptical orbit (almost all orbits are elliptical to some degree), and you open your sail to the maximum when you’re on the outgoing half of your orbit, but close it on the incoming half. This way, when you’re going out, you go out a little bit faster than you would without the sail, but going in, you’re not slowed down by it, so you’re gradually putting more and more energy into your orbit. The effect is that your orbit will gradually grow larger and larger, until the farthest point of it is as far out as you want to go. To come back in, you do the reverse: Open the sail on the incoming leg, and close it on the outgoing leg.

Maybe next. I’m determined to read Walt Whitman before I croak. Same thing? :stuck_out_tongue: