Photos: America’s 100th EELV blasts off

Pioneering spacecraft from NASA and the Japanese space agency promise to reveal two unexplored asteroids later this year, officials said Wednesday, beginning surveys that will culminate in daring descents to capture samples for return to Earth, where eager scientists await a hands-on look at the specimens.

Riding a half-million pounds of thrust, a Minotaur 4 rocket fired off a launch pad in Virginia, surpassed the speed of sound in less than 20 seconds, and vaulted into orbit Wednesday with four classified payloads for the National Reconnaissance Office.

Near the end of a ground-shaking test firing of Northrop Grumman’s solid-propellant Castor 600 rocket motor — the first stage of a new booster being designed to launch spy satellites and other national security payloads — a major part of the rocket’s big nozzle appeared to break apart, littering the test site with shards of debris.