There is always pressure due to solar wind (particles with mass) and pressure due to photons (no mass but transferring momentum nevertheless). But there is no way to tack (have the nose of the vessel point at an angle substantially perpendicular to the wind velocity vector and receive thrust NET thrust along the vector pointed towards the nose of the craft). There is no water to have a keel or center board to allow for this maneuver. I mean, you could have a keel board but there is no water for the vessel to operate in.

This makes the maneuver(s) to be accomplished by the solar wind and/or light pressure, one from the particles streaming from the sun that are not photons and one from the photon pressure. Since photons are massless, one of the neatest proofs of the quantum mechanical nature of the universe was to see the successful translation by (who else) Einstein with the formula

p=hk where p is momentum, k is Planck's constant, and k is an integer.

So when a photon is captured or reflects/scatters, it transfers momentum. This equation is used to determine how much momentum is being transferred.

Without tacking (sailing velocity change perpendicular to the wind) this means that only net OUTWARD force (wind or photon pressure) from the sun may be applied. To achieve a higher orbit, one must speed up the spacecraft at a point with a net acceleration TANGENT to the orbital velocity at that point and the raising of the orbit will occur "on the other side of the orbit".

So for a net speed up and raising of the orbit, one would need to have the "sail" aided by the total sun pressure on one side of the orbit, and rotate the craft so much less sail area is exposed on the other side of the orbit. This will cause small kicks upward in the orbit.

I hope you see that you need a very complex control system to rotate the spacecraft to modify its sail angle with respect to the sun. That piece of engineering HAS NOT BEEN ACCOMPLISHED SUCCESSFULLY BY PROFESSIONALS.

NASA has tested solar sail technology in a vacuum chamber.

Finally, the last nail in your "Way Out Thinking Coffin" is delivered by the efficiency of your propulsion system.

If you want to see this be successful, in oh, your life time, you need a huge sail. The initial orbit needs to be high enough that atmospheric drag on this huge sail does not degrade the orbit faster than you can raise it.

on and on, ad nauseum, ad infinitum. The problems of doing this are simply beyond us and again, no professional group has succeeded.

It is nice to have these Way Out Crazy Ideas to shoot down because it forces you to think your way through problems with them.

What did I miss?

Bob N4HY

Idle-Tyme wrote:

Hi all,

This is now WAY out in crazy thinking. But we all know how a wind speed anemometer works right? The flat side has more resistance to the "Wind" than the rounded front side, so it has greater pressure exerted on it right? This would even work with not so much half spheres as in a traditional anemometer but with like pyramids shapes i would also think.

Now does solar "Wind' have pressures similar to air "Wind"? obviously it does or they wouldn't be thinking if trying to use it right?

I know it's exceedingly small amounts of pressure. but if we were to launch into an orbit that is as close to the equator as possible and the bird deploys as large as possible equivalent of an anemometer cup and it's positioned so that it's base is perpendicular to the solar wind when it is directly at right angles to the earth and sun.

This tiny push, and then 180 deg later less push then 180 deg later more push etc.

think this bird could ever so slowly in a spiral raise it's orbit?

Crazy? what's anyone think? Joe WB9SBD

Date: Tue, 1 Dec 2009 11:20:45 +1100 To: [email protected]; [email protected] From: [email protected] CC: [email protected] Subject: [amsat-bb] Re: Boost To higher Orbits?

At 11:17 PM 11/30/2009, Bob McGwier wrote:

...

p=hk where p is momentum, k is Planck's constant, and k is an integer.

So when a photon is captured or reflects/scatters, it transfers momentum. This equation is used to determine how much momentum is being transferred.

So, the discussion is about the fundamentally different ways to cause force to be applied to the satellite.

Most of the time we operate by Newton's 3rd law, throwing parts of the satellite out one end, with the knowledge that doing so will push the remaining parts of the bird in the other direction. We call them rockets.

Conservation of Momentum is just another aspect of Newton's 3rd law. Any time you cause something with mass to move differently, there's always a got to be a balancing force. Bouncing photons off a sail is only different from a rocket in that the rocket is shedding parts of itself as it works, while the photons are external. And a they are lot lighter (no pun intended), so it takes a whole lot of them to have the same effect, making it less than practical.

Looking at the other laws of physics we have Bernoulli's principle, where the increased velocity of a fluid over a curved surface causes a pressure drop which can push the surface in the direction of the lower pressure. We call them propellers and lanteen sails. Is there any way to use this principle with the solar wind? I think that was answered as a theoretical yes, but a practical no.

So what remains? What about magnetic or electrostatic forces? Friction? Anything else I missed?

It would sure be nice to be able to propel a satellite without tossing bits of it overboard.

Greg KO6TH

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