He3 is one of the rarest substances in the solar system, but it holds the key to commercially successful fusion. The first fusion stations came on-line in 2041, burning a mix of deuterium and tritium; second-generation stations employed a straight deuterium–deuterium reaction. Those combinations have a number of advantages: ignition is easy, the energy release is favourable, and the fuels are available in abundance. The major drawback is that both reactions are neutron emitters. Although you can use this effect to breed more tritium, by employing lithium blankets, it's a messy operation, requiring more complex (read: expensive) reactors, and a supplementary processing facility to handle the lithium. Without lithium blankets the reactor walls become radioactive, then have to be disposed of; and you require additional shielding to protect the magnetic confinement system. The costs in both monetary and environmental terms weren't much of an improvement on fission reactors.

Then in 2062 the JSKP dropped its first aerostat into Jupiter's atmosphere, and began extracting He3 in viable quantities. There are only minute amounts of the isotope present in Jupiter. But minute is a relative thing when you're dealing with a gas giant.

The fusion industry—if you'll pardon the expression—went critical. Stations burning a deuterium–He3 mix produced one of the cleanest possible fusion reactions, a high-energy proton emitter. It also proved an ideal space drive, cutting down costs of flights to Jupiter, which in turn reduced the costs of shipping back He3 , which led to increased demand.

An upward spiral of benefits. He3 was every economist's fantasy commodity.

Bob Parkinson was the man charged with ensuring a steady supply was maintained; a senior JSKP vice-president, he ran the entire mining operation. It wasn't the kind of responsibility I would ever want, but he appeared to handle it stoically. A tall fifty-year-old, with a monk's halo of short grizzled hair, and a heavily wrinkled face.

«I was wondering when you were going to get round to me,» he said.

«They told me it would have to be today.»

«God, yes. I can't delay the lowering, not even for Penny. And I have to be there.» A finger flicked up to one of the screens showing a small rugby-ball-shaped asteroid which seemed to be just skimming Jupiter's cloud tops. Fully half of its surface was covered with machinery; large black radiator fins formed a ruff collar around one conical peak. A flotilla of industrial stations swarmed in attendance, along with several inter-orbit transfer craft.

«That's the cloudscoop anchor?» I asked.

«Yes. Quite an achievement; the pinnacle of our society's engineering prowess.»

«I can't see the scoop itself.»

«It's on the other side.» He gave an instruction to his desk, and the view began to tilt. Against the backdrop of salmon and white clouds I could see a slender black line protruding from the side of the asteroid which was tide-locked towards the gas giant. Its end was lost somewhere among the rumbustious cyclones of the equatorial storm band.

«A monomolecule silicon pipe two and a half thousand kilometres long,» Bob Parkinson said with considerable pride. «With the scoop head filters working at full efficiency, it can pump a tonne of He3 up to the anchor asteroid every day. There will be no need to send the shuttles down to the aerostats any more. We just liquify it on the anchor asteroid, and transfer it straight into the tanker ships.»