http://www.inter-corporate.com/forums/Fieldpropulsion.Engineering.html ...it's an address(and others on the same forum) where you can find some considerations about a possible manner,procedure to drive out,extract ,pump out power in a gravitational field,by means of a retarded,decelerated down fall.Normally,in gravity,a free pendular motion has two periodic equally times:move downward( fall) time=move upward(rise) time,or in a loop,circular evolution we have fall/180 * and rise/180*.But with a fall/270* and rise/90*?You can get the idea (and motion...) better if you "put into changing positions" some drawings,available at "Stellarotor"-site,or more attractive to discover,bring to light your personal thinking of fancy regarding this viewpoint.The thing about some topics(including mine...) is that I can talk theory until I am blue in the face:results are what matter.We are living more by acts then by ideas,but an useful idea can be a first step for a productive,rewarding action.Success!All the Bests!/Alex