In the vast expanse of the ocean, a streak of white light pierces the sky. It’s not a natural phenomenon, but a weapon — a high-energy laser fired from the deck of a U.S. Navy destroyer.

The Helios weapon, which uses a 60 kW high-energy laser that can engage targets at the speed of light, is an advanced directed energy system developed for the US by Lockheed Martin. It obliterates ...