The ramjet is an appealingly simple engine, with no moving parts. Its sheer forward velocity compresses the air entering its intake; fuel is burnt in it, and the resulting hot gas expands in the exhaust nozzle to generate thrust. Sadly, it only works at very high speeds. Daedalus once invented a more tractable variant. This was a ground-effect ramjet, or gramjet, which skimmed over a prepared smooth track. As it sped along, its sloping underside compressed the air beneath it against the track. Downward-firing burners raised its temperature, and the hot exhaust gases expanded against its upwardly sloping rear surface to drive it along. Ground-effect compression works at quite moderate speeds, and the upward pressure of entrainment and combustion levitated the craft in hovercraft fashion. Inevitably, however, the fierce unshielded flame beneath it tended to damage its track.

Daedalus now wants his gramjet to travel over water. He sees it as the ideal way of cleaning up oil slicks. Not only would the intense flame from the vehicle burn the oil; the heat of its combustion would help to drive it along. Indeed, a fresh, thick slick loaded with volatile hydrocarbons might even burn fiercely enough to drive the gramjet for free.

Sadly, most aged slicks are too thin and tenuous to burn as strongly as this. In any case, a thin slick is water-cooled too well to burn completely. But Daedalus is undismayed. He recalls that a flame passed over a polyethylene sheet oxidizes its surface (this makes it easier to glue). Even if a slick is only partly oxidized by flame, the resulting oxygenates and fatty acids will act as detergents, emulsifying and dispersing the unburnt portions. So DREADCO engineers are now devising the most chemically active flame for the slick-burning gramjet. Ozone will enhance its reactivity; an electric discharge through the flame will generate active free radicals; oxidants such as sodium peroxide will be sprayed in to encourage the combustion reaction and form detergent from its residues.

Thus a powerful new broom will sweep our polluted seas and waterways. Waterborne gramjets will zoom over oceanic slicks, around dirty harbours and along fouled industrial canals, leaving a sparkling wake behind them. Unless, of course, it is more profitable to keep the water thickly covered in oil, and run slick-fuelled gramjet services over it.