Sea Launch engineers say the three-week round-trip journey across the Pacific Ocean is the most rewarding part of their jobs.

The cruise is the culmination of nearly two months of work preparing the rocket, payload and launch teams for the mission. Prior to operations at Home Port, about 18 months goes into the planning, flight design and logistics.

"It's really nice to know most of the reviews are over and we're finally ready to launch," said Bill Rujevcan, mission director for the company's next flight later this month.

A pair of Zenit 3SL rockets in the assembly bay of the Sea Launch Commander ship are being prepared for the company's next two flights. Credit: Chris Miller/Spaceflight Now SEE MORE IMAGES HERE

More than 300 people take the trip to the company's equatorial launch site about 1,400 miles south of Hawaii. The crew includes workers from several nations, including: Ukraine, Russia, Norway, the Philippines, and the United States.

Ukraine-based Yuzhnoye and Yuzhmash build the Zenit 3SL rocket's first and second stages, while Energia of Russia manufactures the Block DM-SL upper stage for the rocket.

Norwegian ship officers manage marine operations, and Filipino deckhands work on both the Sea Launch Commander and the Odyssey launch platform.

U.S. employees from the Boeing Co. fill management roles and provide the flight design, payload fairing and satellite adapter. Astrotech, a contractor, oversees processing of customer payloads inside a clean room at the company's Payload Processing Facility at Home Port in Long Beach, Calif.

After 27 missions in nine years of business, Sea Launch is thriving in the do-or-die commercial launch industry.

The company's Zenit 3SL rocket has suffered three setbacks in that time. Two were total failures.

The rocket's success rate places it among the top tier of heavy-lift launchers on the commercial market, and the company's launch backlog seems to confirm that.

Sea Launch is already booking payloads for launch in 2010. Next year is sold out, according to company officials.

Sea Launch Home Port is a decommissioned U.S. Navy facility on the tip of a manmade peninsula at the Port of Long Beach. The Sea Launch buildings are all left over from the Navy except for the Payload Processing Facility, which the company built in the late 1990s.

The company's pier is home to two one-of-a-kind vessels - the Sea Launch Commander and the Odyssey launch platform.

The Sea Launch Commander carries about 240 people, ranging from rocket technicians and corporate leaders to chefs and helicopter pilots. The Commander houses a state-of-the-art launch control center divided between two sections designed for Ukrainian and Russian engineers and American engineers and managers.

Inside the Sea Launch Commander, the Block DM-SL upper stage (far right) is poised for attachment to the Zenit rocket's second stage. Credit: Chris Miller/Spaceflight Now

The cavernous rocket assembly and checkout hall is located on the command ship's lower deck and stretches nearly the entire length of the vessel. The facility is capable of supporting two simultaneous launch campaigns using staging and integration compartments and a fueling cell.

Giant cranes inside the high bays lift rocket stages, which sits on Russian-gauge rails on the floor integration room floor.

The rocket's ground support equipment inside the Sea Launch Commander is virtually identical to hardware used for Zenit launches at the Baikonur Cosmodrome in Kazakhstan, according to Sea Launch officials.

The Sea Launch Commander was specially constructed for Sea Launch at a Scotland shipyard by the maritime unit of Kvaerner, then a leading Norwegian industrial company. Measuring 656 feet long and 105 feet wide, the command ship was outfitted with more than 600 tons of rocket support equipment in Russia before sailing to Long Beach in 1998.

The massive ship's crew quarters are home to Sea Launch's international employees during their stay in the United States.

As Ukrainian and Russian engineers complete work to ready the Zenit rocket, technicians inside Sea Launch's Payload Processing Facility are busy preparing the booster's satellite payload down the road from the docked vessels.

The Sea Launch Commander and the Odyssey platform are seen here docked at Home Port. Credit: Chris Miller/Spaceflight Now

When both groups are ready, the spacecraft is transported about 1,000 feet and loaded into the Sea Launch Commander's final assembly hall on the roll-on, roll-off vessel. Already enclosed in the payload fairing, the satellite is attached to the Zenit-3SL's upper stage to complete the rocket's construction.

EchoStar 11, the payload for Sea Launch's mission this month, was rolled from the clean room to the command ship hangar June 25. The 12,150-pound satellite was bolted to the Block DM-SL upper stage a day later.

The rocket was next moved to the Odyssey Launch Platform. The launcher, which weighs about 100,000 pounds without propellant, is transferred in a high-precision operation more 200 feet above the waters of Long Beach Harbor.

The Sea Launch Commander first pulls in front of Odyssey and the rocket is rolled out of the integration hall. The rocket is then hoisted into Odyssey's hangar, where it stays during the transit from Long Beach to the launch site.

Sea Launch then lifts the 200-foot-tall rocket upright on its launch pad for a final series of tests to make sure all systems are ready to set sail for the equator.

"That's our last big test before we leave," Rujevcan said.

Odyssey, the slower of the company's two ships, usually leaves Long Beach a few days before the Sea Launch Commander. The launch platform left port for the EchoStar 11 campaign last week.

With a top speed of about 12 knots, Odyssey's crew of 70 sailors and engineers serve as caretakers of the Zenit rocket during the 2,882-mile transit to the launch site along the equator at 154 degrees west longitude.

Odyssey is a converted North Sea oil drilling platform built in Japan in 1983. Kvaerner's maritime division modified the vessel between 1995 and 1997 to support rocket launches, according to Sea Launch.

The Zenit's hangar extends off the forward end of the mammoth Odyssey platform. Credit: Chris Miller/Spaceflight Now

The changes included adding two extra vertical support columns, effectively extending the length of the platform to 436 feet. The deck extension was needed to make room for the Zenit launch pad, an immense hole in Odyssey's deck with a gas diffuser directly beneath it, said Paula Korn, Sea Launch spokesperson.

Workers replaced more than 20 miles of wiring on Odyssey after Sea Launch suffered a failure on the launch pad during a liftoff last year. The platform underwent a slate of repairs, including the replacement of a destroyed gas deflector and the repainting of the ship, Korn said.

The Sea Launch Commander pulled out of port this weekend to begin its trek to the equatorial Pacific. The ship will rendezvous with Odyssey at sea later this week.

Officials keep busy during the trip by completing a handful of final prelaunch reviews, two countdown rehearsals and several other meetings, Rujevcan said.

The ships also offer a number of recreational activities for the launch team. The Sea Launch Commander carries basketball and volleyball courts, a swimming pool, and a movie theater, not to mention opportunities to play pool, foosball and air hockey.

Crews also enjoy access to DirecTV programming and XM Satellite Radio, two regular customers for Sea Launch.

The Sea Launch Commander is furnished with a full-service cafeteria and bar, but the booze stops flowing soon after the ships arrive at the launch site.

Odyssey's ballast tanks are filled with seawater to submerge the platform's pontoons to a depth of about 65 feet to help keep the vessel stable.

The command ship pulls alongside Odyssey and technicians move between the vessels using a 115-foot-long link bridge. The team begins the launch countdown three days prior to liftoff.

The Sea Launch Commander sails three-and-a-half miles away from Odyssey a day before launch. A helicopter transfers final personnel and equipment between the vessels.

As viewed from the aft end of Odyssey, this is the launch pad where the Zenit rockets are erected. The closed doors of the hangar are seen in the background. Credit: Chris Miller/Spaceflight Now

The Zenit 3SL rocket is rolled out of its hangar and erected on the pad about 27 hours before the scheduled launch.

Pneumatic pistons power the erector during the 10-minute lifting operation, and technicians torque four hold-down bolts to firmly attach the rocket to the launch pad. The bolts automatically retract from the booster at liftoff.

The countdown enters an automated sequence five hours before launch, and the team serves as watchdogs to ensure no preset parameters are breached. The final workers are evacuated from Odyssey about three hours prior to launch.

During the final countdown, Odyssey's marine crew occupies a remote control station on the bridge of the Sea Launch Commander. The consoles give the marine officers full control of the launch platform three-and-a-half miles away, Sea Launch officials told Spaceflight Now.

Fueling of the Zenit 3SL's three stages with kerosene and liquid oxygen begins two hours and 40 minutes before liftoff. Fuel and oxidizer tanks aboard Odyssey hold enough propellant for three launch attempts, according to Rujevcan.

Managers hold their final poll 36 minutes before launch, and the rocket's umbilical arm detaches from the rocket at the 17-minute point.

The Zenit's automated sequence reaches a last milestone with one minute to go.

"At that point, we are committed to launch unless the sequence tells us to stop," Rujevcan said.

Now on his 18th mission to the equator, Rujevcan is one of three certified Sea Launch mission directors. The mission director is the final authority on whether the launch occurs.

"I am the ultimate go guy," he said.

Rujevcan oversees a team of about 50 engineers inside the Launch Control Center. The launch team typically conducts three launch rehearsals during each campaign to hone their skills.

The launch team monitors the rocket, weather, ship systems, and ground stations to ensure they are all ready for launch.

Notices of the launch are issued for vessels traveling in the area to keep at least 25 miles from Odyssey during the final countdown. Sea Launch helicopters and ship-based radar keep tabs on nearby ocean traffic.

A file image shows a Zenit rocket on the pad ready for flight and the Commander ship overseeing the countdown nearby. Credit: Sea Launch

Officials closely watch Odyssey's exact location during the final moments before launch. Managers allow a tolerance of two kilometers, or about 1.2 miles, from the standard launch site at the intersection of the equator and 154 degrees west longitude.

Powerful underwater azimuth thrusters hold Odyssey's heading at launch time. The platform must be within one degree of the expected orientation for launch.

A Sea Launch campaign in November was plagued by persistent strong ocean currents and high winds. The underwater thrusters were not enough to match the unruly conditions, and the platform constantly drifted out of position.

Officials eventually ordered the ships to return to California after more than two weeks on station at the mid-Pacific launch site.

Engineers have since installed extra generators on Odyssey to increase the amount of time the vessel can stay at sea.

The unusual experience with ocean currents is an example of how Sea Launch continues to encounter challenges and learn from experience, Korn said.

Rujevcan agreed.

"After 27 missions, you just see a little bit of everything," Rujevcan said. "It's never really routine to the point of complacency."