The trouble with solar sails is they become less effective as they go further from the Sun. Why not use a solar sail to build up lots of energy relatively close to the Sun (i.e., at L1 near Earth)?

Pivot a radial array of long spokes about a heavy mass. At one end of each spoke attach a tackable solar sail. The sail is adjustable so that the pushing effect of incident solar radiation can be modulated. Each sail is opened/turned when the push goes the right direction and closed when coming round again. At the end of one of the spokes, attach your spaceship.

Now wait a while for the array to spin up to the desired angular speed, and then detach your spaceship at the appropriate time and watch it go hurtling off into deep space.

The spokes should be as long as possible to reduce centripetal forces. And [MechE]'s idea of having a hub where cargo and very brave humans could be lowered in. The hub means you never have to stop the rotation and the thing might just keep accelerating, giving us an ever increasing range into space (until it tears itself apart).
-- the porpoise, Nov 12 2015

Ultracentrifugal satellite launcher Similar, but not solar wind powered. [the porpoise, Nov 12 2015]

Launch from angular momentum Nanotube_20fuel
conceptually related [Voice, Nov 12 2015]

//At one end of the rod attach a one-way solar sail, which is like a one-way mirror,//

There is no such thing. A one way mirror reflects an equal amount of light on each side, it's just that there's much less light on the "transparent" side.

That being said, you can you a solar sail to "tack".

The correct structure is the rod with solar sails on both ends, and they fold or spread or angle as needed to get the desired thrust. The ship is launched from one end, and the sails are balanced to return the rod to the correct orbit.

Issue two: //solar wind is nice and strong// The "solar wind" has nothing to do with the operation of a solar sail. The solar wind is charged particles, a solar sail works on the basis of photons. Of course, the photon flux is also higher closer to the sun, but that brings us to...

Issue three: a //close solar orbit // is a much, much lower energy orbit than earth's. Assuming a terrestrial starting point, the energy spent to decelerate to a low solar orbit is going to be more than any physically possible structure could impart to your ship. (IE your structure falls apart before your ship has enough energy to return to earth orbit. You're far better off building this structure in earth orbit and accepting the longer run up time necessitated by the lower thrust. Especially since you're only going to be launching cargo with this, which doesn't care about time delays. And you'll only be launching cargo because...

Issue 4: Centripetal acceleration. To get any appreciable velocity out of this device, the centripetal acceleration at the ship end is going to be much, much greater than humans can withstand. I'll admit, I can think of a way to fix this (the ship with 99.9% of the mass is spun up, the humans are lowered from the hub in a transfer capsule at a constant 1-3 g, and the two parts mate and launch in the same motion, so the capsule never experiences high g, and the loss in angular momentum due to the capsule transfer is relatively low.) but, any solution is much more complex than the basic launching system, and still doesn't have humans sitting in the ship waiting for it to spin up.

All of that being said, the basic concept is not impossible.
-- MechE, Nov 12 2015


All good points [MechE]. Thanks. I will update the idea.
-- the porpoise, Nov 12 2015


This is less efficient than just saving up the electricity. And since you're adding mass to the system to be accelerated the device will be pushed closer to the sun at each launch with a force proportional to launch force. It will have to push itself back out again.
-- Voice, Nov 12 2015


//This is less efficient than just saving up the electricity.//

How do you use pure electricity to launch? Unless you are proposing a catapult type launcher, which is much harder to build.

It's also even more subject to the issues with it's orbit shifting after use since it has no way to correct it's orbit, whereas this idea can just adjust it's sails.
-- MechE, Nov 12 2015


You couldn't build a big solar sail and woven carbon nanotube line to put a craft up into space.
-- travbm, Nov 13 2015


//The trouble with solar sails is they become less effective as they go further from the Sun.//

The solution is obvious: just build a large parabolic reflector around the sun to send all its light in the direction of your spacecraft.
-- Wrongfellow, Nov 13 2015


I really like this idea. This could maybe also be used to launch things perpendicularly to the ecliptic, which is traditionally difficult.

// And since you're adding mass to the system to be accelerated the device will be pushed closer to the sun at each launch with a force proportional to launch force. It will have to push itself back out again. //

Which will happen naturally as a side effect of the solar sails that spin it up.
-- notexactly, Nov 13 2015



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