CAPE CANAVERAL, Florida: Two pieces of the space shuttle Challenger washed ashore near Cape Canaveral, almost 11 years after the explosion that killed all seven aboard. A beachcomber named Spider dragged both bits of wreckage out of the surf near Cocoa Beach, 20 miles south of Kennedy Space Center. By identifying the serial numbers on pieces of attached thermal tile, NASA was able to confirm the two pieces of metal, one 6 by 15 feet, the other 1 by 5 feet, were from the doomed shuttle. Challenger flew for 73 seconds after lifting off the pad at the Cape when a leak in one of the shuttle's solid fuel rockets caused the explosion. A sobering reminder, at a time when the U.S. space program is looking ahead to the construction of the international space station, of just how dangerous space exploration can be.