[amsat-bb] Re: Boost To higher Orbits?

[Bob McGwier]

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


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