This invention project is what I cooperating with an English inventor Paul Toomer. His idea of U-tube fascinating me.
His website:
http://magnetic.free.energy.mysite.freeserve.com/
http://www.ufoseek.com/cgi-bin/jump.cgi?ID=1830
The Draft Patent:
rps
An illustration:
euler 
Exploring the solar system with propellers???? (Maybe not as crazy as it looks)
Ok, reads crazy, but take a look at http://wjetech.50webs.com/#propellers (very short page), maybe a non conventional but simple idea may be practical.
Give it a minute of thought before invoking the law of conservation of momentum, closed systems, etcetera
Actually working model is available to all that wish to play with it.
Also available are detailed instructions to build and test the device using LEGOS.