By Joey Roulette WASHINGTON (Reuters) – A lot is riding on the first launch of the new Vulcan rocket by the United Launch Alliance, a joint venture of Boeing and Lockheed Martin. A successful launch at Cape Canaveral next week will allow ULA to fulfill a deep backlog of missions worth hundreds of millions of dollars and establish a competitive footing with Elon Musk’s SpaceX. And it could prove vital to plans by the two U.S. aerospace firms to sell their joint venture. “It’s a very nervous time for them,” said George Sowers, ULA’s former chief scientist, who was key to Vulcan’s creation. “It’s…