Arthur C. Clarke has invented or
popularized a number of futuristic
inventions through his novels. I will try to briefly explore the
realisticness of his dreams in this novel.
The invention that makes Clarke's space elevator possible is
(as described in the book) a thin
filament ("several microns thick") that he describes as "a continuous
pseudo-one-dimensional diamond crystal--although not actually pure
carbon ... several trace elements ... It can be mass-produced only in
the orbiting factories where there's no gravity to interfere with the
growth process." He claims that this would be able to
support at least
a couple hundred pounds.
This isn't too terribly far from the description of a carbon nanotube.
Only time will tell exactly how close.
It remains to be seen what size and
configuration of nanotube will be able to hold that much and if zero gravity is
actually required to manufacture it.
Current experimental tests of 1.5nm single wall nanotubes show strength of
60GPa. Extrapolation to a 3 micron tube might allow 300g. Of course,
this is not valid, as we can't construct a 3 micron nanotube yet, and
even if we did, it would be multiwalled, not single walled. A thicker
fiber will probably be necessary to carry enough weight.
Also, current research can construct nanotubes as long as 150 microns.
For longer fibers, right now we would have to make a rope combining
multiple tubes together. Clarke suggests making a flat "tape" that could
be gripped. He suggests a tape four inches wide could support several
hundred tons without noticing.
In the course of the book, nanotube fibers are used for the following purposes:
- extremely light climbing rope for rock climbing
- cutting device (able to cut a tree in a few minutes)
- a researcher accidently slices his thumb off with a filament
In the book, he starts by dropping four tapes from geostationary orbit,
and then from the top of the tower, builds the ground terminal from the
bottom up in orbit, lowering towards the ground as it is completed. The ground
tower is intended to be buried partially underground, and acts as
both passenger terminal and weather protection for the bottom
of the completed tower.
To be fair, Clarke gives Yuri N. Artsutanov credit for inventing the
space elevator in 1957. Artsutanov built his ideas on those of
Konstantin Tsiolkovsky, and three others independently came up with the
same idea in the succeeding decade.
In 1966, John D. Issacs published a paper on skyhooks using
diamond cables.
In 1975, Jerome Pearson wrote a technical paper that inspired this
this book.
In 1999, NASA held a workshop seriously considering
this possibility. NASA estimates that the estimated strength needed
for a nanotube fiber in a rope would be around 60Gpa. Experimental
results with carbon nanotubes so far seem to match or exceed this.
Other technology devices described in this book include limb regeneration (working on it)
and a talking cardiovascular monitor (exists, sort of),
large scale white lasers, and weather control using orbiting lasers.
Finally, as a partial rebuttal to jobby's excellent writeup,
the conversations with
Starglider follow two common themes that run through
several
other
of
Clarke's books. Starglider gives him the opportunity to both explore
our far distant future and briefly consider the impact of a passing
visit by aliens on our society. Also, this section is not merely an add-on
that can be ripped away without loss. Starglider is well tied into the plot
in a handful of places, and is even a major motovator of several of the
minor characters.
credits:
http://science.nasa.gov/headlines/y2000/ast07sep_1.htm
http://www.nas.nasa.gov/Groups/Nanotechnology/publications/1997/applications/