Space saving satellites

Ken Teo and a team  in the Department of Engineering at the University of Cambridge have come up with a much more efficient and compact way to send signals from satellites by using an array of carbon nanotubes to create a device that replaces conventional heavy, bulky, high temprature, microwave amplifiers.

There are typically 50 microwave amplifiers on board a satellite, each weighing about 1kg and measuring about 30cm in length. Currently it costs about £10,000 to send a single kilogram of payload (data) into space. Hence there is an obvious advantage, both in terms of cost savings and extra payload which can be carried, if the weight and size of the microwave devices are reduced.

The microwave amplification devices used in space today are based on what's known as hot cathode technology. But not Teo's. Teo and his team have developed a cold cathode source, based on carbon nanotube technology. Like its heavy counterpart, it too can deliver electrons directly at microwave, or gigahertz, frequencies and hence can also be used in these microwave devices  - but with potential weight and size savings of up to 50%.

To create the device, Teo and his team laid out the nanotubes in an array, with every nanotube having roughly the same height and diameter. When these carbon nanotube needles are subjected to an electric field, such as that from an electromagnetic wave, they release electrons from their tips. So by injecting radio frequency waves at the nanotubes, they are able to cycle them on and off at the frequency of the injected wave and thus create an electron beam at high frequency.

Teo says that the use of new amplifiers based on the technology will not only reduce the cost and increase the capability of conventional satellite systems, but will also enable the drive towards very low cost micro-satellites which weigh about 10kg.