Week 10
 This week I talk to about latest study. The study is carbon nano tube (CNT). Do you know carbon nano tube? Carbon nano tube is fiber which is discovered recently. Carbon nano tube mainly has three kinds, Single-walled nano tube, Double-walled nano tube, Multi-walled nano tube. Carbon nano tube is expected to be used in many field. Carbon nano tube has some natures. Carbon nano tube has 10th higher thermal conductivity and 1000th higher resistance properties of electric current density than copper. This nature is expected as new semiconductor and fuel battery. Carbon nano tube is half weight of aluminum and 200th stronger than iron. For this nature, Carbon nano tube is thought to be used space elevator.
 Space elevator is elevator from the earth to space (geostationary obit). This system can cost down the cost of transportation for space. By contrast with rocket, space elevator do not harm environment and do not explode and do not fall. And we can go to the space not only space pilot but also elderly people, children and physical disability people. The origin of space elevator was Konstantin Eduardovich Tsiolkovskiy who is called father of space travel. It is written that the centrifugal force and gravity balance in a point (geostationary orbit radius) if you build a tower from the equator to the space. In 1959, Yuri Artsutanov announced the concept of space elevator which extend cable up and down from geostationary orbit. By end of 20 century, the material for cable had not been found. So people thought space elevator as the thing in science fiction. But in 1991, Sumio Iizima discovered carbon nano tube. By discovering carbon nano tube, we can build space elevator theoretically. In Japan, Oobayashi team is planing to build space elevator. The team announced that they realize space elevator by 2050. But the problem of space elevator is not only technical problem. If space elevator is built, the cost of construction of trial calculation is 1 or 2 hundred million yen. Which country does pay the cost? And countries which is on the equator do not have technological strength and financial power. There are many problems to realize space elevator.

 There are not only positive point but also negative point in carbon nano tube. In 2008, a nature of possibility is discovered. The nature is that carbon nano tube is carcinogenic material. And it is announced that products which is used carbon nano tube technology have possibility of health hazard like asbestos.
　Carbon nano tube has many ways to purify, Arc discharge, Laser ablation, Plasma torch, Chemical vapor deposition (CVD), Super-growth CVD. But mass production way do not establish.

If carbon nano tube is mass produced and space elevator is built, how do you think our life is change? Carbon nano tube will afford us mass profit. I want Oobayashi team to build space elevator early. And I want to go space travel. I wish that study of carbon nano tube progress.
Thank you for 10 week reading.