PAge 58 MARch 2006 AUSTRALIA’S PAYDIRT

africa

PAge 58 MARch 2006 AUSTRALIA’S PAYDIRT

It is an exploration “tool” which is likely to be-come the envy of diamond hunters the world

over.Expectations are that the De Beers Group’s

Zeppelin airship, fitted with the full tensor gra-diometer (FTG), will be up to five times more efficient in finding kimberlites than conven-tional, fixed-winged aircraft.

The man behind the project is a geophysi-cist at De Beers’ headquarters in Johannes-burg, Dave Hatch. The Canadian-born senior

A new age of diamond exploration

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It is lift-off time, at sunset, for the De Beers airship at Jwaneng airport. The Zeppelin flights vary in length, but usually last more than five hours

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technical manager, Hatch has been in South Africa for the past eight years and, because of his closeness to the unusual project, has boundless enthusiasm for this extraordinary aircraft and its on-board high-tech equip-ment.

“We’re very lucky to pull a partnership like this off with other companies,” he said, refer-ring to Bell Geospace which operates the FTG, and Zeppelin, which operates the air-ship. Hatch points out that both the FTG and the Zeppelin cost about $US10 million each, and De Beers did not have to capitalise any major parts of the project. The unit is on lease to De Beers for the next two years.

“It’s quite fortuitous we were able to get the Zeppelin, as there are only three operating in the world.” The other two do tourist flights in Germany and Japan.

The De Beers Zeppelin is the prototype, built about eight years ago “but it is a fully functional, fully reliable aircraft”.

“The standard platform for collecting this kind of FTG data is the Cessna Grand Car-avan, so we had contracted Bell Geospace to do surveys for us in Botswana, using the Grand Caravan. And in analysing that data, it became apparent that although it is effective

Brad Pitts, left, is the on-site project manager for the De Beers Zeppelin exploration programme, seen here with Stefan Kuna of Bell Geospace, who operates the full tensor gradiometer equipment

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Joerg Straub, left, and Jurgen Wurtz are the Zeppelin pilots. They work for the German - based DRZ company

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for detecting the obvious big kimberlites with significant density contrasts, you miss poten-tially economic bodies that might be deeply buried. So there’s a real exploration risk that you’re going to miss economic bodies.

“So then the question came. ‘How can we improve the situation’ because having a good gravity instrument would give you huge com-petitive advantage.

“There were two ways to achieve this. Either you build a new instrument, which is better than the FTG; but that would take sev-eral years, a very difficult thing to do. Or, to do something more quickly, you find a more stable platform for it, which moves at a slower speed.”

The downside to conventional aircraft is that they fly fast, are noisy and vibrate. In the case of helicopters, noise and vibration are even greater while they do have the ad-vantage of being able to fly slowly. Light-duty helicopters, like the Bell Jet Ranger, are also unable to carry the heavy FTG equipment.

At a slower speed, geophysicists are able to take more readings along the line and cap-ture data of a higher resolution.

Looking at alternative aircraft – the Blimp which is just an elongated balloon without an internal frame – was discounted. “The ad-vantage of the internal frame is that you can mount the engines on the sides of the carbon fibre frame, well away from the gondola. You have to get the motors as far away from the instruments as possible.”

In the case of the De Beers Zeppelin, the engines are 12m away from the FTG, dimin-ishing noise and vibration. The engines are standard piston units which run on avgas. Hatch says that the use of conventional mo-tors was deliberate as the intention was to keep it as simple as possible, so that a good stock of spares could be kept in store to di-minish the aircraft’s downtime.

“So far, it has been fantastic. This time of year is a challenge in Botswana: it is stormy, windy but there’s been no downtime.”

The Zeppelin, which is 75m long, can do a top speed of 64 knots (110km/h) but travels about 33 knots (60km/h) when operational, 80m above the ground.

The engines on the helium-filled craft have to do no work when it comes to lift. The ini-tial operational area will be Botswana, but exploration priorities often change, Hatch is quick to point out. “We’ve signed a two-year contract to operate within Southern Africa. We want to minimise the technical risk, and operating in a country (like Botswana) where there’s good infrastructure makes it a lot more straightforward.”

Hatch says that the original plan to get the Zeppelin from Germany to Africa was to fly it out, but that option could have been fraught with complications. Areas of conflict and ob-taining overflight permits for the various ju-risdictions convinced De Beers that the best way would be to take it from Amsterdam to Cape Town in August last year was by dock ship. Because of the internal frame, it cannot be dismantled and rebuilt.

It requires specialist pilots to fly the aircraft, who have to obtain a “type” certificate and

complete 100 hours of flight time.During summer, exploration work is done

at night which requires two pilots, but during winter a single pilot is adequate. The FTG equipment requires only one geophysicist to operate.

At present, the Zeppelin is at the Jwaneng airport and brownfields exploration is being

done around the huge Jwaneng open cut. De Beers’ tenements extend for about 50km in each direction around the mine.

Jwaneng, says Hatch, has a very signifi-cant ground gravity anomaly in a basement high “so we’re looking for bodies which might be more deeply buried”.

The townsfolk of Jwaneng have come to accept the airship’s daily flights as part of the routine at the mine

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Dave Hatch, the De Beers man behind the Zeppelin project

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Joerg Straub at the controls while overflying Jwaneng

“It is very hard to walk away from this, the richest mine in the world, without having turned over every stone.

With the new aircraft, “we’d like to see a five-times improvement over the existing sys-tem” says Hatch. And it all comes down to the slower speed, less noise and virtually no vibration.

“That’s our goal. And the longer we have it, the further we can tweak it to effect improve-ments. It is very early days, but we already

have a four times improvement wrapped up,” said Hatch

The man now in charge of the project is Brad Pitts, who co-ordinates the efforts of all the parties involved.

Pitts is a seasoned geoscientist who has worked in some of the hardest destinations Africa has to offer – including Conakry in Guinea and Kinshasa in the Democratic Re-public of Congo. He shares Hatch’s enthusi-asm for the project and believes results are going to be good.

Pitts arranged a non-operational flight for

Paydirt at Jwaneng, a fairly remarkable ex-perience. It is almost eerily quiet in the craft’s gondola, which has been stripped down to bare essentials to comply with payload re-quirements.

Despite its size, it is unusually agile with a floaty feel to it … more like a boat than an aircraft.

– Barry Avery

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