America’s navy is developing an antenna made of seawater

A BIG American warship bristles with more than 100 large copper antennae that send and receive signals for its weapons, its radar and its voice and data communications. A lot of aerials, then, but still not enough. The navy wants its ships to carry even more of them. Fulfilling that desire has, however, stymied experts for decades. If placed too close together, antennae interfere with each other’s signals. They also get in the way of aircraft and weapons. And, crucially, naval antennae—many of them more than 20 metres tall—make warships more easily visible to enemy radar.

At the American navy’s Space and Naval Warfare Systems Command (known as SPAWAR for short), in San Diego, a team of more than 30 engineers is trying to solve such problems. In 2007 the team’s leader, Daniel Tam, thought of a possible answer, appropriately enough, while taking his morning shower. The sodium and chloride ions in salt water conduct electricity. Could a spout of seawater, he mused, replace a metal antenna? …