Diamond path to space travel

If you were looking for something special to give this holiday season, you can cross one thing off your list: the 123-carat blue diamond unearthed in June at the famous Cullinan mine in South Africa.
Provided photo An exceptional 122.52 carat blue diamond recovered at the Cullinan mine in June 2014Courtesy Petra Diamonds
Provided photo An exceptional 122.52 carat blue diamond recovered at the Cullinan mine in June 2014Courtesy Petra Diamonds
If you were looking for something special to give this holiday season, you can cross one thing off your list: the 123-carat blue diamond unearthed in June at the famous Cullinan mine in South Africa.

It's already been sold in its rough, uncut state for almost US$28 million (Dh103m)

Still, if you're quick you may be able to get a bid in for the even bigger, brilliant white diamond found just a few weeks later at the same mine.

At 232 carats, it weighs as much as 10 cubes of sugar, but won't cost a whole lot more.

That's because it lacks the exclusivity of the blue diamond, which owes its rare colour to atoms of boron trapped in its crystal cage.

It has been an astounding year for the mine, whose name is forever linked to the behemoth found glinting in sunlight in a shaft wall in 1905.

Weighing in at more than half a kilogram, legend has it that workers originally discarded it as “obviously” fake until it was retrieved and examined by the mine manager. Now recognised as the largest yet found, the Cullinan became part of the crown jewels of England.

Although the rich and famous cherish them for their beauty, scientists value diamonds for their many other exceptional attributes.

Their nickname of “ice” comes from their extraordinary thermal conductivity, five times that of copper, which transmits heat so efficiently they feel ice-cold to the touch.

At the same time, most diamonds conduct electricity very poorly, the exception being blue diamonds, which become superconductors when cooled to ultra-low temperatures, allowing limitless current flow.

Yet diamonds are most famous for their extraordinary toughness. Created in intense heat and pressure about 150 kilometres down in the Earth's mantle, their crystal structure is maintained by strong bonds between their carbon atoms.

This has put them at the sharp end of attempts to recreate conditions inside the Earth.

Using so-called diamond anvil presses, scientists have achieved crushing pressures of 6 million atmospheres – about 6,000 tonnes per square centimetre.

With so many potential applications, the ways of creating diamonds to order have long been the focus of research.

The first artificial diamonds were made more than half a century ago, and since then the aim has been to create artificial diamonds as large as possible.

But scientists have since achieved a breakthrough at the other end of the size spectrum.

In the process, they may have opened the way to something utterly mind-boggling in scale: the Space Elevator.

As its name suggests, this is something seemingly straight out of a science-fiction movie: a high-tech “stairway to heaven” whose final stop is geostationary orbit 36,000km above the equator.

Originally proposed in 1895 by the pioneering Russian space engineer Konstantin Tsiolkovsky, the basic idea has evolved over the decades, and is now generally envisaged to be a cable anchored to the Earth and kept aloft by a vast orbiting counterweight.

Electric-powered elevator “cars” then travel up and down into space at 200km/h or so, taking a few days to reach their destination.

As for the counterweight, engineers at Nasa have suggested using a small asteroid, nudged into stable Earth orbit and connected to the cable.

The biggest engineering challenge turns out to be creating a cable strong enough to cope with the colossal stresses created inside it as the counterweight whips round the Earth.

Now that material may finally have been created – from pure diamond.

Scientists have long tried to go beyond single crystals to make whole swathes of diamond-like material. The idea is that such material would be incredibly tough, held together by the same bonds that give diamond its strength.

Now a team led by researchers at Pennsylvania State University has created the very first samples of such a material.

To do it, they crushed a 6mm-wide sample of benzene – a liquid rich in carbon and hydrogen atoms – to the point where the atoms broke apart.

They then slowly released the pressure, giving the atoms space to re-form into carbon tetrahedrons, the classic four-sided pyramid shape that gives diamond its incredible strength.

The result was a thread of diamond-like material just a few atoms across, surrounded by a ring of hydrogen atoms.

Made in bulk, this “diamond nano-thread” is expected to be light in weight and stronger and stiffer than any other material.

Having reported their breakthrough in the research journal Nature Materials, the team is trying to find ways of scaling up the process, which has so far produced only a few cubic millimetres of the exotic material.

The hope is that by understanding the changes wrought by the simple use of brute force over tiny volumes, it may be possible to find chemical ways of mass-producing the stuff.

John Badding, a professor of chemistry at Penn State who led the research, believes there is a host of potential uses for such a material. For him, such uses include the Space Elevator, for which diamond nano-thread could form the ultra-strong cable.

The breakthrough is well-timed, given the growing concern about the expense and risks of making space travel routine.

Virgin Galactic, the British company striving to pioneer “space tourism”, suffered a major setback in October following the crash of its rocket-powered spacecraft and death of a test pilot.

In principle at least, the Space Elevator offers an almost leisurely means of getting into space.

Now that the final technological hurdle may have been overcome with the creation of diamond nano-thread, the biggest barrier to the Space Elevator becoming reality could simply be human imagination.

That was the view of the British science-fiction writer and futurist Arthur C Clarke, who mentioned the Space Elevator idea in The Fountains of Paradise, his 1979 novel.

He was sure that the Space Elevator would be built – and even gave a date: “About 50 years after everyone stops laughing.”

With the creation of diamond nano-thread, we may just have entered the era of the wry smile.

Robert Matthews is visiting reader in science at Aston University, Birmingham

Published: December 13, 2014 04:00 AM


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