<font color="yellow">Not true. Every pound shaved off the upper stage of a launch vehicle means another pound of payload. I don't know the figure for all launch vehicles -- but for the Falcon 1 -- there was a note in their updates which indicated each pound shaved off the first stage meant about 1/7th of a pound increase in payload. </font><br /><br />Oops! Sorry about that. Should have known better. To explain myself. True, the technology has to mature some before use, but in case the space elevator concept isn't practical for any reason like space debris, political, etc, nanotubes would make great composites. And the reason why nanotubes could bring down the cost of space travel is because every pound shaved off the upper stage means an extra pound in orbit. Launch vehicles prices are per launch, not per pound. Launching a 10 ton payload from a $190 million dollar Delta IV heavy will cost the same as launching 25 ton payload from a $190 million dollar Delta IV heavy. Using a compositive lets you launch a few extra tons per payload for the same cost if a nano-compositive upper stage is the same cost as the aluminum one. Although, after looking at the Delta-IV as a base example, if you did cut the weight by half for both stages and using the assumption that 1 pound shaved off the first stage=1/7 pound of payload and 1 pound shaved off the upper stage=1 pound of extra payload, all you get is 3 extra tons. Then again, the extra three tons could be used to make the space craft reusable (parachutes, wings, added heat shields) and maybe even a SSTO.