The launch was pushed back two minutes to avoid an object in space that could have been in the path of the rocket, said Michael J. Rein, spokesman for United Launch Alliance, the joint venture of rocket builders Lockheed Martin Corp. and Boeing Co.
It was the fifth launch of the Delta IV Heavy, but the first from Vandenberg, and the most powerful rocket ever to lift off from the West Coast. The other four launches were at Cape Canaveral, Fla.
The rocket, launched at 1:10 p.m. PST, is believed to be carrying a spy satellite.
Officials said the rumble of the liftoff may be heard as far as 50 miles away. Lompoc residents were alerted so they won't think it's an earthquake.
"This launch marks a significant milestone in our nation's space capability" said Lt. Col. Brady Hauboldt, launch director. "We've really restored a national capability for heavy lift on the Western Range, something we have not had since the last of the Titan IV-Bs flew out of Vandenberg."
Preparing for the launch took three years and $100 million in infrastructure upgrades at Vandenberg, 130 miles northwest of Los Angeles.
The Associated Press contributed to this story.
