Unmanned Future

How small drones can revolutionise warfare once battery life is improved. An extract

David Hamling

There is an old, pre-smartphone-era joke about a man who meets his inventor friend carrying two suitcases down the street. The inventor shows off the wristwatch he has built, which as well as indicating the time anywhere in the world, also shows the tides, phases of the moon, and position of the stars. His friend is duly impressed. The only problem, says the inventor picking up the suitcases, is the size of the batteries.

That about describes the present situation of small drones. What they do is great; the only problem is the batteries. Whatever small drones can do, they cannot do it for long because of their limited battery life. The smallest only fly for ten minutes or so. Quadrotors may manage half an hour, and the Raven, our gold standard for capability, keeps flying for about ninety minutes.

The situation is better the larger the drone. The RQ-20 Puma, the Raven’s big brother with twice the wingspan and three times the weight, has an endurance of three hours. Scaling means that, other things being equal, bigger drones carry proportionately more batteries or fuel.

Switching from battery power to liquid fuel extends the range of small drones dramatically. In 2003, a drone weighing eleven pounds with a wingspan of six feet flew across the Atlantic, from Cape Spear in Newfoundland to Mannin Beach in Ireland. The drone, known as TAM 5, took thirty-eight hours to make a crossing of almost two thousand miles, at a steady speed of around fifty miles an hour. Small drones can cross oceans and continents.

Unfortunately, the internal combustion engine has disadvantages. For one thing, it is very noi