Even in a well-insulated vessel, a cryogenic liquid such as oxygen slowly evaporates as heat leaks into it by all possible routes. One route is usually impossible — conduction or convection from the vapour above the liquid. The steady upward flow of evaporated vapour prevents heat being conducted downwards.

Daedalus is now generalizing this idea. Imagine, he says, a spherical droplet of a liquefied gas, evaporating outwards evenly in all directions. Both conduction and convection would be frustrated, pushed away by the radial outflow. Only radiation would remain to be countered.

So DREADCO technicians are fabricating little spheres of microporous carbon aerogel, and fluorinating their outer surface to limit its wettability to liquefied gas. An outer coating of reflective metallized foam completes the DREADCO ‘cryogenic bull's-eye’. A bull's-eyes can be loaded with liquefied gas simply by dipping it deeply in the liquid. But when it is removed, only its outer metallized coating drains dry. The liquid in the microporous core is trapped by its non-wetting outer boundary. It evaporates very slowly, its radial passage outwards preventing heat from leaking in. Each bull's-eye can hold many times its own weight of liquid.

The first application will be an update of an old DREADCO invention, a pill to be swallowed in case of fire. It reacted chemically in the swallower's stomach, releasing oxygen for him to ‘digest’. He could stop breathing, and walk to safety through the thickest and most toxic smoke.

An edible oxygenated cryogenic bull's-eye, exhaling oxygen at a steady rate, would do the job far more neatly. Similarly, a bull's-eye loaded with liquefied anaesthetic gas might be swallowed as a ‘knockout pill’. Its reliable, automatic delivery would make surgery much safer. But Daedalus hopes to perfect cryogenic bull's-eyes with even lower loss-rates. They will at last tame methane and hydrogen for automotive use. Safely and almost permanently liquefied inside a charge of bull's-eyes, these tricky fuels could be poured and stored like so much coal. Once in the vehicle's fuel tank, they would be evaporated by a microwave heater, acting on the bull's-eyes' carbon aerogel cores and controlled from the accelerator. When the bull's-eyes had boiled dry, they could simply be exchanged at a filling station for full ones. Smelly, polluting petrol would at last be replaced by its clean and ecologically virtuous rivals.