Daedalus once invented a red-hot boat. The water could never touch its hull, which was insulated by a thin layer of steam. So it had extremely low skin-friction, and no trouble with fouling weeds or barnacles either. But its fuel costs were high, and its insulation problems severe.

He now returns to the field with a converse scheme. He wants to coat a ship with ice. He argues that ice must have the lowest skin-friction against water of any solid. Furthermore, in its flow past the ice, the water would tend to melt away preferentially those features that obstructed the stream lines. The hull would shape itself into the perfect streamline form for minimum drag. But again, the idea suffers from heat-transfer problems. This time, Daedalus has a way out. He wants to coat his ship with foamed ice.

Foamed ice, like foamed polystyrene, would be an excellent thermal insulator. DREADCO engineers are now exploring ways of making it. The simplest idea is just to make the surface of the cooled hull porous, and pump air out of the holes as the water freezes onto it. Another is to saturate the surrounding water with a gas such as carbon dioxide, which is expelled by water as it freezes. It might even be possible to generate the gas electrolytically, using electrodes integral with the hull. But whichever way proves best, the ship will build up its primary ice-coating in port, and only have to maintain it against melting at sea. A good refrigerator can pump heat at several times its own power-drain. Daedalus estimates that a few tens of kilowatts of refrigeration could maintain a foamed ice-sheet over the wetted surface of even a sizeable freighter. Its slippery coating, proof against fouling organisms, should save many hundreds of kilowatts of propulsive power. And in a maritime accident, the ship could make instant rafts and lifeboats of foamed ice, to support the crew until help arrived.

Foamed ice should have many other uses too. The DREADCO team hopes to develop a generator to make it in quantity on land. A given volume of water would make a much larger volume of foamed ice. Unlike snow, it would have a closed-cell structure, impermeable and very rigid; and its low thermal conductivity would limit its rate of melting. It would be ideal for temporary structures such as crash barriers, fire breaks, scaffolding, ski- ramps and foamed igloos for emergency shelter.