Albert ninestein

Thanks, I assumed this may be the case. I don't have the skills to make a detailed calculation.

As there are some Physics experts on this forum please can someone explain why my idea of a free energy machine doesn't work. Please consider a helium filled blimp on the ground attached to a tether which is in turn attached to an electrical generator. As the blimp rises the tether turns the generator to produce electricity. Once the blimp reaches a set altitude a compressor stored on-board the blimp compresses some of the helium into an onboard storage tank so the blimp then sinks slowly back to earth and the tether is wound in during the descent. Once on the ground the helium is released back into the blimp so it floats upwards again and turns the motor repeatingthe cycle. The tether contains an electrical cable that powers the onboard compressor from a battery stored on the ground which is charged during the ascent. Let's assume the blimp is contained within a very tall frame so it only goes up or down. Would the energy used to compress the gas to make the blimp return to earth and the energy required to wind the tether back in during the descent be greater than any energy produced during the ascent?

Thanks, I'll stick with the day job and leave it to an expert to develop interstellar travel!

Sorry for old thread revival. I was googling the (impossible) idea of recycling rocket exhaust in a closed system which this topic shows doesn't work to get forward motion. My thoughts that led me here were a closed cylinder with a device at one end that launches a lump of ice backwards towards the rear of the cylinder. If the rear of the cylinder was open then the lump would exit the craft and there would be a positive thrust (I think). What would happen if the cylinder was now closed and after launching the lump of ice a series of lasers were fired at it from within the cylinder so it was vaporised before if hit the rear of the cylinder and cancelled out the forward momentum gained from launching it reward. Is there any possibile configuration of this setup or do you still end up with the same mass of steam instead of ice going backwards (sorry no drawing but hopefully my description is clear).