The first Boeing Delta 4 rocket destined to fly from California came ashore Sunday, bringing closer a new era in launching critical national security satellites from the West Coast.

The Delta 4 rocket is backed off the Delta Mariner vessel at Vandenberg on Sunday. Photo: Boeing/Thom Baur

After a five-week trek from its Alabama manufacturing plant to Vandenberg Air Force Base aboard the Delta Mariner transport ship, including passage through the Panama Canal, the first stage of the rocket was unloaded and driven to the new processing hangar built at Space Launch Complex-6.

"I feel like I just gave birth to a child. It's probably one of the most exciting days of my career," Ken Liptak, Boeing's site manager, told reporters Sunday afternoon.

"Obviously, this is a big deal today because it's a major milestone toward achieving the first launch at the end of the year."

With the Atlas 2AS and Titan 4 heritage rockets having just two launches left from Vandenberg, the foreseeable future of lofting large spy satellites from California will be in the hands of the next-generation Delta 4.

Vandenberg is America's prime launch site for placing satellites into orbits around Earth's poles to cover most of the planet's surface.

The Delta 4 rocket travels from the warf to the Slick Six hangar. Photo: Boeing/Thom Baur

The California home of Delta 4 is commonly referred to as "Slick Six" -- an infamous site that has a star-crossed legacy. It was originally constructed in the 1960s for the Air Force's Manned Orbiting Laboratory and then rebuilt in the 1980s for space shuttle launches. However, both projects were cancelled before any liftoffs occurred.

The pad was used for a handful of launches by Lockheed Martin's small Athena booster in the 1990s.

Three years ago, Boeing took over the sprawling complex, giving it a new lease on life for the Delta 4 fleet. The rocket family is designed to provide affordable and reliable delivery of government and commercial satellite cargos into orbit over the next 20 years.

The Delta 4 and Lockheed Martin's Atlas 5 were developed as part of the Air Force's Evolved Expendable Launch Vehicle Program. The rival rockets flew successful inaugural flights from Cape Canaveral last year.

Atlas 5 was once envisioned to fly from Vandenberg as well. But Lockheed Martin scrapped those plans due to the relatively small number of launches from the West Coast and the cost of building a new pad.

That decision gave Boeing all of the government's Vandenberg satellite launches in the first batch of EELV missions.

The Delta 4 takes a scenic route to Slick Six. Photo: Boeing/Thom Baur

Slated for launch in mid-December carrying a classified payload for the National Reconnaissance Office, the first Delta 4 rocket will spend the next two months in the Horizontal Integration Facility hangar at Slick Six. The rocket's upper stage was not shipped on the Delta Mariner; it will be trucked to California, officials said.

With construction activities nearly finished, Boeing is turning its attention to exhaustive testing of the launch complex in support of the first flight.

"Most of the major construction is done. We've got the Fixed Pad Erector in and the modifications to the old shuttle facility to accommodate the Delta 4," Rich Murphy, Boeing's director of launch sites, said in a recent interview.

"We are just completing our (ground support equipment) installation and checkout," added Jim Boyle, the company's Vandenberg site director. "By March we will finish all of the final testing of the swing arms. We will go into some pathfinder activity with the booster. Then a little later in the year there will be a spacecraft pathfinder with the customer. Once that is done, we basically roll right into the processing for the first launch. That will bring us to the December time frame."

With the launch pad in the background, the Delta 4 rocket makes its way to the Horizontal Integration Facility. Photo: Boeing/Thom Baur

Like at the Cape, the Delta 4 stages are connected together in the hangar. The assembled rocket is then transported horizontally to the pad and lifted vertically by an erector arm.

Boeing plans to roll the rocket to the Slick Six launch pad for the first time in late-March for use in completing the activation of the complex and mechanical fit-checks.

The vehicle will be returned to its hangar after the initial pad tests are completed, then head back to the pad in late-May or early-June where it will remain through launch.

A pair of countdown dress rehearsals are slated to fully fuel the rocket for simulated launch day activities.

Also during its long stay on the pad, crews will attach two strap-on solid motors and the satellite cargo to the rocket.

An on-pad engine firing like the one performed at the Cape last October is not planned at Vandenberg.

Delta 4 arrives at the HIF. Photo: Boeing/Thom Baur