US launches its largest rocket, likely carrying spy satellite (VIDEO)

The United States launched its biggest rocket from the central California coast Wednesday, carrying what is likely to be a spy satellite.

The mission is classified, but it is known that the satellite belongs to the National Reconnaissance Office, which oversees US intelligence-gathering satellites.

The unmanned rocket, which took off from Vandenberg Air Force Base, about 150 miles northwest of Los Angeles, is a Delta IV Heavy rocket.

Delta IV Heavy rockets are 23 stories tall and propelled by three pickup-truck-sized hydrogen-fueled engines. They’re able to carry up to 24 tons into low Earth orbit.

It’s the 364th flight of a Delta rocket overall, and the 24th for a vehicle in the Delta IV group.

The Delta IV Heavy is manufactured by United Launch Alliance, a joint venture of Lockheed Martin Corp. and Boeing Co.

Massive rockets will play an even more important role in the near future, with NASA at work on building a giant rocket called the Space Launch System to hurl astronauts toward asteroids and Mars, Space.com noted.

The first version of SLS will be 321 feet tall and be able to carry up to 70 metric tons into space. A later version will stretch 384-foot-tall and carry up to 130 metric tons.