NASA was due on Friday to launch a spacecraft from Florida on its way to Psyche, a distant, metal-rich asteroid that is the solar system's largest-known metallic object and is thought to be the remnant core of an ancient protoplanet. The Psyche probe, folded inside the cargo bay of a SpaceX Falcon Heavy rocket, was slated for blastoff at 10:19 a.m. EDT (1419 GMT) from NASA's Kennedy Space Center in Cape Canaveral on a planned journey 2.2 billion miles (3.5 billion km) through space. Propelled by a system of solar-electric ion thrusters being used for the first time on an interplanetary mission, the spacecraft - about the size of a small van - is expected to reach its target on the outer fringes of the main asteroid belt between Mars and Jupiter nearly six years from now.