Down to Earth: Space plasma drills

06 February 2018

Interview with

Dr Stuart Higgins, University College London

Stuart Higgins has been drilling into this mystery, in Down to Earth...

Stuart - This episode: how a space plasma drill being developed for Mars has already led to a more portable and efficient electric vehicle charger for use in the home.

Is there life on Mars? If there is it may well be hiding below the surface and Scientists from the European Space Energy (ESA) want to dig into the red planet on future missions to see what they can find. However, drilling deep underground is hard enough on Earth, let alone on another planet. ESA has funded a Norwegian company to study a new drilling technique called plasma channel drilling which they hope will allow more efficient and deeper drilling on Mars.

Plasma channel drilling was first developed by researchers at the University of Strathclyde in Glasgow. It works by placing two metal plates on the surface of a piece of rock and applying a very short, but very high power, pulse of electricity between them. The voltage between the metal plates can reach up to 50,000 volts with a peak power of 100 megawatts. That’s the equivalent of a million 100 watt light bulbs, albeit for less than 50,000th of a second.

The drill head is surrounded by water and, as the voltage quickly ramps up, something unusual happens. Rather than the electrical current taking a shortcut through the water, it turns out that under these extreme conditions the rock provides less electrical resistance - a plasma channel is formed in the rock. The electrical current can pass through this plasma, heating and expanding it rapidly to cause the rock to break up apart.

After the researchers licensed out this technology, it was eventually picked up by a Norwegian company who are now aiming to turn it into a viable space plasma drill for future missions. The key to the effectiveness of the plasma drill is its power supply which needs to rapidly produce pulses of high voltage. Room and available power are always limited onboard spacecraft so this forced the company to develop a new form of electrical transformer. A transformer is, essentially, two coils of wire wrapped around a common metal core and it’s used to turn low voltages into high ones and visa versa.

The Norwegian company developed a new transformer design that both generates higher voltages and is also extremely compact. In doing so, they realised that the same technology could be used to improve the way electric vehicles are charged at home. The company could produce the size of a home car charger, which is effectively a giant phone charger for your car, from around 100 kilograms to about 2 about kilograms using the transformers it developed for space plasma drilling.

And unusually, while the technology hasn’t yet been used in space, the spinoff from it is already available to consumers back here on Earth. So that’s how developing a space plasma drill for Mars helped lead to portable home chargers for electric vehicles.

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