Suppose you discovered a new fuel that packed the energy from 10 tonnes of coal into something weighing no more than a pea. And suppose that the magical fuel in question was readily available in sea water, with known reserves sufficient to last for millions of years.
Such a fuel sounds completely impossible, but researchers hope to show this morning that the impossible can be made to happen. They are attempting to reproduce the energy system which drives the Sun and the stars - fusion - here on Earth.
The work is being carried out at the Joint European Torus (JET), near Oxford. JET is a joint undertaking involving 15 countries, including Ireland, established in 1978 to develop the science behind fusion.
"Fusion is what happens in the Sun," explained Mr Frank Turvey, deputy chief executive of the Radiological Protection Institute of Ireland, and a former chairman of the JET executive committee.
It is nature's own energy source, a completely natural form of nuclear power. Nuclear energy as we understand it from facilities such as Sellafield or Sizewell is based on fission, the breaking up of big, heavy atoms as a source of heat energy. Fusion is a different process and involves the joining of lightweight atoms of hydrogen to form helium, a reaction which releases a great deal of energy recoverable as heat.
The fusion fuel is provided by two hydrogen forms, deuterium and tritium; 500 litres of sea water would yield 10 grams of deuterium, enough fuel to provide a year's electricity to 200,000 homes. Tritium does not occur naturally but can be manufactured from lithium metal, and 15 grams would be enough to supply a person's lifetime electricity needs.
Bonded together the two form helium but the reaction also releases a very energetic leftover particle called a neutron. The neutron is picked up on a target which converts the energy to heat. In a fusion reactor, this heat would be used to create steam which in turn would drive turbines. The aim would be to achieve a sustained fusion reaction, with hydrogen continuously converted into helium and energetic neutrons.
Unfortunately, fusion is disarmingly simple on paper but notoriously difficult if you aren't on the Sun. Two hydrogen atoms, when they get too close, will repel one another with the most powerful force known in the universe, and this force can only be overcome by packing them into a confined space and heating them up to spectacular temperatures, at least 100 million C or more than twice the temperature at the Sun's core. "We cannot achieve the high densities that occur in the centre of the Sun. You have to make up for that with higher temperatures," Mr Turvey explained.
These are achieved using a range of techniques from microwave and radio wave heating, to sending electric currents of up to seven million amperes through the hydrogen gas, which is contained within a ring-shaped device called a tokamak. As the temperatures soar, the atoms lose their electrons and become what is known as a plasma.
On November 9th, 1991, the JET tokamak produced 1.7 million watts of fusion power for about two seconds using 90 per cent deuterium and 10 per cent tritium, which proved that the reaction could be achieved. The problem was that more than 1.7 million watts of energy were used up heating the plasma, not much use if you want an energy source.
All this could change today, however, as a new series of fusion experiments begin at JET using a 50/50 deuterium/tritium fuel mix, the optimum blend for the reaction. Researchers hope to achieve a 10-million watt output sustained for several seconds, which should smash the "break-even" barrier, with energy output exceeding energy input.
"I expect we will get to break even on Monday and that would be a great achievement, a milestone on the road to success," Mr Turvey said. He believes that the work at JET during the next six weeks will enter the history books. "What we are achieving with fusion will be seen to be as significant as what the Wright brothers did in 1903."