Boeing, Lockheed Martin rocket Vulcan inches toward its first launch

Building a rocket is difficult. Preparing a new rocket for its first flight is even more difficult.

That has proved true for the Vulcan, a new rocket developed by the United Launch Alliance, a joint venture between Boeing and Lockheed Martin. The first Vulcan was supposed to launch in May, but a propellant tank cracked during testing in March. Hydrogen leaking from the tank ignited in a fireball, destroying the Vulcan’s upper stage and damaging the test stand.