Northrop Grumman’s first big test of its future OmegA rocket seems to have ended in a small explosion. Today, the company fired up the main engine on the rocket during a ground test in Utah. Toward the end of the test, part of the vehicle’s engine burst apart, sending pieces of hardware flying. Today’s test is what is known as a static fire, when the engine of a rocket is ignited while the vehicle is held firmly to the ground. Northrop Grumman was conducting the very first static fire test of the OmegA’s first stage — the main body of...