The only man to break the sound barrier on land has done it again, this time with JCB

Dubai: Andy Green, the only person ever to break the sound barrier in a car on land, has set another world record. This time on hydrogen.

The 64-year-old retired RAF pilot averaged 406.320mph, or 653.908km/h, across two runs at the Bonneville Salt Flats in Utah on Tuesday. That is the fastest a hydrogen internal combustion car has ever travelled.

The previous record, set by a BMW H2R in 2004, was 185.5mph. It has been more than doubled.

The numbers

Run one: 400.623mph Run two: 412.135mph Average: 406.320mph Car: JCB Hydromax, 32 feet long, twin hydrogen combustion engines, 1,600bhp Where: Bonneville Salt Flats, near Wendover, Utah

The Fédération Internationale de l'Automobile officiated. The two runs were made in opposite directions, which is why the official figure is the average rather than the faster single pass. The speed remains provisional until the paperwork returns from the federation office, though the FIA has indicated an overturn at this stage would be highly unusual.

The run covered a full ten miles, close to the entire length of the flats, with the timed flying mile recorded between markers five and six. Green pulled the parachute at around mile seven.

He had packed it himself.

Where the engines came from

The Hydromax is powered by two hydrogen versions of a JCB engine originally built for excavators, the tracked digging machines found on construction sites everywhere. Not a bespoke racing powerplant. A digger engine, as they are known in Britain.

Ryan Ballard, JCB's engineering director, said in a statement: "This record belongs to the engineering team which took a hydrogen digger engine and made it the fastest of its kind on earth."

Prodrive ran the car on the salt, with chairman David Richards present.

Green's third record, on his third fuel

The comparison that matters is with himself.

In 1997 he drove the jet-powered ThrustSSC across Nevada's Black Rock Desert at 763mph, breaking the sound barrier on land. Nobody else has done it since, or before.

In August 2006 he set the diesel land speed record at 350.092mph in the JCB Dieselmax, on the same Bonneville flats.

Tuesday's hydrogen run beat that diesel figure by more than 56mph, twenty years on almost to the month.

"Setting a world land speed record with hydrogen power, 20 years after Dieselmax, is a huge privilege," Green said. "This record is a huge achievement by a world class team and superb technology."

He has previously called hydrogen the fuel of the future.

He nearly did not do it

Speaking to the BBC last month, Green said the decisive factor in accepting the challenge was his wife's encouragement, after a call from JCB chairman Lord Anthony Bamford.

Bamford was at Bonneville to watch, having flown in with his family.

"Twenty years ago we came to Bonneville with JCB Dieselmax and showed what British engineering could do with diesel power," he said. "Today we have done it again, this time with engines powered by hydrogen."

The record before the record

Tuesday was the second time in under a week the Hydromax rewrote a record book.

Earlier this month, during Bonneville Speed Week, it averaged 368.347mph across two consecutive days of running, with individual passes of 367.141mph and 369.554mph. That took a Southern California Timing Association record in the Blown Gas Streamliner class, beating the Spectre Streamliner's 348.342mph from 2010.

Between that and Tuesday, the team swapped an engine and turned the car up to its full 1,600bhp before FIA scrutineering.

The road here

JCB unveiled the Hydromax at its global headquarters in May. In testing at RAF Wittering in Cambridgeshire that same month, it reached 208mph.

Three months later it hit 412mph.

Bonneville flats

The flats are the remains of a prehistoric lake bed, about 100 miles west of Salt Lake City, and they sit on a shallow aquifer that cools the tyres from underneath.

The surface is low-friction, the desert air is dry, and the combination has drawn drivers since the first race there in 1914.

Hydrogen combustion

Hydrogen combustion has spent years being treated as the less promising sibling of hydrogen fuel cells and battery electric power, largely because nobody had demonstrated it doing anything spectacular.

An engine designed to move earth, converted to run on hydrogen, has just gone faster than any hydrogen combustion car in history, by a margin of more than 200mph.

With reporting from AP, the BBC and PistonHeads.