Nanotech for space travel.

Carbon nanotubes have been proposed as the material to form a cable for a "space elevator".

Research with self-assembling structures in biology have led to some methods of generating nanotubes.

Nanotubes self-assemble into circuit elements.
"WEST LAFAYETTE, Ind. — Nanotubes measuring just 100 atoms in diameter have been created from designer molecules that were customized to self-assemble into angstrom-sized circuit elements, according to researchers at Purdue University.
"Professor Hicham Fenniri's research group developed the nanotube "parent" molecules, which self-assemble in water first into tiny rings. The rings then snap together into long tubes. The outside of the seed molecules harbor "hooks" on which to hang other molecules, which functionalize the resulting nanotube for a specific electronic application."
http://www.eetimes.com/at/news/OEG20020326S0038

DNA parts make versatile nanotubes.
"Although rosette nanotubes are relatively strong, they are not as strong as carbon nanotubes. Where there is high mechanical stress, “carbon nanotubes may be more advantageous,” said Fenniri. “However, the rosette nanotubes can be modified to become mechanically very strong -- several orders of magnitude stronger than nylon, for instance,” he added."
http://www.trnmag.com/Stories/060601/DNA_parts_make_versatile_nanotubes_060601.html


Self-Assembled Actin-Membrane Tubules.
"Researchers have made self-assembling multilayer tubules with a structure curiously similar to the outermost components of bacterial cell walls. These "artificial cell walls" form when the researchers mix together two biological materials: negatively charged rods of actin (a protein involved in the contraction and expansion of muscle) and positively charged artificial versions of the membranes that form the protective coverings of cells. The resulting structures have potential applications in drug delivery systems and nanofabrication."
http://www.aip.org/physnews/graphics/html/selfass.html

Though these current nanotubes formed by using biomolecules are not made of carbon it may be possible to adapt the method to produce carbon nanotubes.

Another possible method of creating nanotubes arises from the research on the effect of laser illumination of artificial "cell" membranes or vesicles. It has been found that when cylindrical vesicles are laser illuminated, the vesicles undergo a beading or "pearling" effect:

The Pearling Instability
http://www.aip.org/physnews/graphics/html/pearling.htm

Pearling Instability of Cylindrical Vesicles
http://galaxy.mpikg-golm.mpg.de/th/work/Pearling/

This might be able to be extended to the creation of nanotubes by laser illuminating a planar sheet of the active material. Then you would expect the same type of periodic constrictions to occur, but in the case of a plane sheet it would result in cylindrical tubules.


Metallic hydrogen has also been proposed as a possible material for a space elevator:

The Space Elevator.
by Arthur C. Clarke
(Originally Published in 'Earth Oriented Applied Space Technologies'. Vol. 1. Pergamon Press Ltd. 1981.)
http://www.ian-andrew.co.uk/ACCspaceE.html

Exotic Matter and Materials for Tomorrow
http://www.hightechcareers.com/docs/exotic.html

This metallic hydrogen is close to being achieved:

Hydrogen metal on the horizon.
10 April 2002
"Scientists have long expected solid hydrogen to become a metal when it is compressed, but so far electrical conductivity has only been detected in liquid hydrogen. Now an experimental study of solid hydrogen at pressures up to 320 GPa predicts that it will become metallic at a pressure of 450 GPa - over four million times atmospheric pressure. René LeToullec and co-workers at the CEA in France also found that solid hydrogen becomes opaque - or 'black' - under compression (P Loubeyre et al 2002 Nature 416 613)."
http://physicsweb.org/article/news/6/4/6

However, the feature of solid metallic hydrogen that would make it good cable material is its lightness. This might also work for solid nitrogen. Solid semiconducting nitrogen has been achieved:

Novel nitrogen is a semiconductor.
9 May 2001
"A new form of nitrogen that behaves as a semiconductor could be a future source of energy, according to Russell Hemley and colleagues of the Carnegie Institution of Washington in the US. The group compressed nitrogen gas to create the 'non-molecular' nitrogen - an opaque solid that releases a flood of energy when it reverts to its well-known diatomic form (M Eremets et al 2001 Nature 411 170).
"The team then reduced the pressure on different samples at a variety of temperatures. Remarkably, they found that the semiconducting state persisted at normal atmospheric pressure at temperatures below 100 K. A pronounced hysteresis effect arises because the change in phase lags behind the change in pressure."
http://physicsweb.org/article/news/05/5/5

There are conflicting theoretical studies about whether metallic hydrogen would retain its solid form and electronic properties when the pressure was released. This study on nitrogen suggests that it could.

Aside from its possible use as a cable material it is known that such forms of solid nitrogen would exceed current rocket fuels in efficiency:

New rocket fuel?
Solid nitrogen could pack double the punch of existing space propellants.
May 14, 2002
http://www.nature.com/nsu/020513/020513-2.html

Solid metallic hydrogen should be even more efficient.

The studies on semiconducting nitrogen and metallic hydrogen involve very small amounts using diamond anvils. How to make larger amounts?
Nanotech may also provide a means to create these materials in large amounts:

Nanocages of layered BN: super-high pressure nanocells for formation of solid nitrogen.
Abstract Submitted to the NANOTUBE'02 Workshop.
http://dielc.kaist.ac.kr/nt02/abstracts/P155.shtml

This method might be able to create the high pressures required for nitrogen and for hydrogen with one other extension: the nanotube piezoelectric effect.

Spontaneous polarization and piezoelectric properties of Boron-Nitrogen nanotubes.
Abstract Submitted to the NANOTUBE'02 Workshop.
http://dielc.kaist.ac.kr/nt02/abstracts/P155.shtml

Carbon Nanotube Actuators.
Science, Vol. 284, No. 5418, 21 May 1999, pp. 1340-1344.
http://www.sciencemag.org/cgi/content/full/284/5418/1340

The idea would be to fill the nanotubes with the desired gas and use the nanotube piezoelectric properties to compress the gas to the solid state.


Bob Clark