[geeks] Carbon nanotube buckytape

[wa2egp at att.net]

> Drifting topic:
> 
> Same basic problems for rockets: the rockets greatly outweigh what
> they lift because their propulsion is so inefficient.  That's another
> fascinating area of research.  What we need is not a rocket, but a
> space-propeller, we just don't know what to push against.
> 
> One physisist whose talk or paper I read explained it like this:
> 
> If you replace "spacecraft" with "submarine", it is relatively easy to
> show just how inefficient a rocket is.
> 
> Imagine the submarine has a water-rocket instead of a screw
> 
> To cross the Atlantic, a submarine would have to store all of the water
> that would normally pass through a screw, plus all the water needed to
> generate thrust to move the water itself (the reactive mass).
> 
> In other words, it would be just as ridiculous as trying to build a
> reactive propulsion system to reach Alpha Centauri.  The fluid ratios
> are simply horrible.  A rocket is the same: the fluid you pass through
> (volume of space occupied by rocket) is tiny compared to the fluid you
> must store on board.
> 
> That's why all spacecraft we have are forced to cruise powerless for
> over 90% of their mission, with bare minimum maneuver abilities.  It's
> not just that we can't cover distance, we can't even maneuver well over
> short distances.
> 
> It's obviously in the realm of science fiction, but the end results of
> any kind of space screw are so compelling that its not ignored any more.
> 
> The most current research is on quantum vacuum and how it might be used.
> You still must provide the energy of course, but you no longer have to
> provide the reactive mass of a rocket.  
> 
> Anyway, combine that with a space elevator, and things would change very
> quickly.
> 
> 
> 
> -- 
> shannon "AT" widomaker.com -- ["If you tell the truth, you don't have to
> remember anything" -- Mark Twain]

A better example is you car will get better gas milage if you only fill the
tank halfway and run it until (almost) empty than if you filled the tank and
ran it until if was half empty.  I remember an old saying in the early days of
the space program: "A pound of payload costs a ton of fuel."

Bob