Posts Tagged‘carbon nanotubes’

Carbon Nanotubes Break Barriers for Moore’s Law.

In the last decade there’s been a move away from raw CPU speed as an indicator of performance. Back when single cores were the norm it was an easy way to judge which CPU would be faster than the other in a general sense however the switch to multiple cores threw this into question. Partly this comes from architecture decisions and software’s ability to make use of multiple cores but it also came hand in hand with a stalling CPU speeds. This is mostly a limitation of current technology as faster switching meant more heat, something most processors could not handle more of. This could be set to change however as research out IBM’s Thomas J. Watson Research Center proposes a new way of constructing transistors that overcomes that limitation.

Carbon Nanotube Transistors

Current day processors, whether they be the monsters powering servers or the small ones ticking away in your smartwatch, are all constructed through a process called photolithography. In this process a silicon wafer is covered in a photosensitive chemical and then exposed to light through a mask. This is what imprints the CPU pattern onto the blank silicon substrate, creating all the circuitry of a CPU. This process is what allows us to pack billions upon billions of transistors into a space little bigger than your thumbnail. However it has its limitations related to things like the wavelength of light used (higher frequencies are needed for smaller features) and the purity of the substrate. IBM’s research takes a very different approach by instead using carbon nanotubes as the transistor material and creating features by aligning and placing them rather than etching them in.

Essentially what IBM does is take a heap of carbon nanotubes, which in their native form are a large unordered mess, and then aligns them on top of a silicon wafer. When the nanotubes are placed correctly, like they are in the picture shown above, they form a transistor. Additionally the researchers have devised a method to attach electrical connectors onto these newly formed transistors in such a way that their electrical resistance is independent of their width. What this means is that the traditional limitation of increasing heat with increased frequency is now decoupled, allowing them to greatly reduce the size of the connectors potentially allowing for a boost in CPU frequency.

The main issue such technology faces is that it is radically different from the way we currently manufacture CPUs today. There’s a lot of investment in current lithography based fabs and this method likely can’t make use of that investment. So the challenge these researchers face is creating a scalable method with which they can produce chips based on this technology, hopefully in a way that can be adapted for use in current fabs. This is why you’re not likely to see processors based on this technology for some time, probably not for another 5 years at least according to the researchers.

What it does show though is that there is potential for Moore’s Law to continue for a long time into the future. It seems whenever we brush up against a fundamental limitation, one that has plagued us for decades, new research rears its head to show that it can be tackled. There’s every chance that carbon nanotubes won’t become the new transistor material of choice but insights like these are what will keep Moore’s Law trucking along.

The Space Elevator: Sensible Science or Fantastical Folly?

You know for all the writing on space I’ve done over the past few years I’ve never once mentioned one of the most intriguing ideas in this field: the space elevator. I’m not sure why I avoided it to be honest as the idea has good foundations in science and manages to generate a whole lot of interesting debate whenever it’s mentioned. It’s not like I haven’t talked about completely theoretical space technologies before either so today I’d like to introduce you to the space elevator concept and go over why it might (and might not) be the technology we should be pursuing in order to fundamentally change the way we access space.

At it’s core the space elevator is a simple idea. You see there’s an orbit around the earth where a satellite will, for all intents and purposes, remain steady over a point on the earth. Currently this space is filled with GPS and meteorological satellites since their mostly fixed position is highly desirable for such applications. These are referred to as geostationary orbits and they all lie directly above the earth’s equator. Theoretically then if you were to put a satellite at one of these orbits and then connect it directly to the place on earth which it hovers over you could then gain access to space by simply running up the cable, a damn sight more elegant than strapping everything to the top of a giant explosion and pointing it upwards.

This idea has numerous advantages over chemical rockets, not least of which is the significant reduction in cost in getting payloads into orbit. Most designs have the runners, the vehicles which “run” up the cable, being powered either directly from the cable itself or by power beaming technologies. This means that you’re not taking all your fuel up with you making the potential payloads much cheaper to deliver into orbit as you can use electricity generated on the ground. The end in geostationary orbit could also be used as a launch platform, enabling much bigger spacecraft to be built and launched into our solar system. It sounds like the perfect solution to many of the challenges behind getting into space but of course there’s always a catch.

The biggest challenge that a space elevator faces is finding a material capable of anchoring a satellite to the earth. Such a material needs to be light with an extremely high tensile strength, far beyond that of any metal or fiber that’s currently available. It also has be manufactured in great lengths on the order of 36000KMs to be able to reach the required height for geostationary orbits. To date the only material that has all these characteristics is carbon nanotubes which match the required strength and weight almost perfectly with the added benefit of being able to conduct electricity. However the inability to make them in lengths any greater than a few centimeters means that until mass fabrication method is discovered carbon nanotubes are unfortunately a pipe dream effectively killing any space elevator before it gets off the ground.

There are also many other factors that need to be considered before a working space elevator can be created. Whilst there’s little danger from the cable breaking to people on the ground (it would most likely flutter harmlessly down to earth) both the runners and the station need considerable contingency systems to be able to deal with this event. Also for payloads that require a non-geostationary orbit (I.E. low/high earth orbits) a space elevator does not provide any velocity to the craft, meaning to achieve a proper orbit you still need to hit Mach 25 unless you want to come back down to earth in a hurry. This is much easier when you’re in space, but it still means that you have to carry up significant amounts of fuel if that’s you’re goal.

Despite these problems however a space elevator is still an extremely attractive possibility and since most of the required technology is already available the idea is now starting to gain traction. Japan is planning to allocate some $10 billion into building the world’s first space elevator and whilst I’d forgive you for not taking them seriously Japan does in fact have a very good space program, they even run supply missions to the International Space Station. Such a commitment to the idea means that the space elevator has a strong possibility of becoming real in the next couple decades, and the flow on effects will have global implications.

Space was once only a realm for dreamers, then super governments and then finally the mega-rich. However the continued revolutions in this industry are driving the cost of space access down to unprecedented levels, serving to make space travel as commonplace as airline travel is today. It’s not going to happen today or in the next 10 years even, but we’re are on the cusp of a fundamental change to the world around us and it is on the back of a space elevator that we shall achieve it.