With four months left until its crucial maiden voyage, the first Boeing Delta 4 rocket was moved to the launch pad at Cape Canaveral's Complex 37 on Tuesday to begin an extensive campaign of testing and final pre-flight preparations.

Riding on its side atop a motorized transporter, the two-stage rocket was rolled out of the hangar early in the morning for the 20-minute, half-mile trip to launch pad 37B at edge of the Atlantic Ocean. By late afternoon, a hydraulic lifting arm had erected the rocket upright on the pad's launch table.

The Delta 4 rocket heads up the ramp to the launch pad Tuesday. Photo: Carleton Bailie/Boeing

The rocket's placement on the pad not only marks a major achievement on the road to launch, but also a morale booster for workers.

"We have had several launch crew meetings where you could feel the excitement and almost electricity in respect to the launch operations and the moving off of Delta 4 from development stage and transitioning to operational," Joy Bryant, Boeing's Delta 4 launch site director at the Cape, said in an interview Tuesday. "The guys here are ecstatic. We are chomping at the bit."

Liftoff is scheduled for August 31 when a commercial telecommunications satellite for Paris-based Eutelsat will be carried into Earth orbit.

But before the launch, technicians will put the rocket through multiple fueling tests, countdown demonstrations and other exercises.

Over the coming days the two strap-on solid rocket motors are slated to be hoisted onto the pad and attached to the base of the Delta 4. In mid-May "power-on" testing of the rocket will be performed. Both activities, Bryant said, are standard for a Delta 4 after reaching the pad.

With those "routine" events completed, technicians will turn their attention to pathfinder work.

In late-May, a satellite payload simulator encapsulated in a rocket nose cone fairing will be delivered to the pad and mounted atop the Delta 4's second stage. This will give crews the chance to check out ground handling equipment and get some practice attaching payloads to the rocket at the new launch pad in the same fashion to be employed with real satellites in the future.

June through early July will be spent conducting four fueling tests in which the rocket is loaded with super-cold cryogenics:

• The first test will load liquid oxygen into the first and second stages.
• The second test will have liquid hydrogen pumped into the stages.
• The third test will feature the stages being filled with both oxygen and hydrogen like on launch day, but no time limits will be placed on the team.
• The final test will run on the countdown timeline with both stages fully fueled per the launch day script.

With the successful demonstration of fueling the rocket, two so-called "Wet Dress Rehearsals" will be on the agenda later in July. The WDRs, as the name suggests, involves fueling the rocket while running an entire countdown so the team can rehearse a full launch day scenario.

But the second WDR, expected in late July, has a dramatic twist. A five-second firing of the Rocketdyne-built RS-68 main engine is planned at the culmination of the countdown.

The rocket begins to rotate vertical at Complex 37 on Tuesday. Photo: Carleton Bailie/Boeing

The hydrogen/oxygen powerplant, the first new liquid-fueled rocket engine developed in the U.S. in a quarter-century, will fire to life and build up to full thrust. The engine cutoff command then will be given immediately.

A test version of a Delta 4 first stage and RS-68 engine underwent a series of firings at NASA's Stennis Space Center in Mississippi last year. But there were differences in those tests and Boeing wants to prove out the actual sequence on the launch pad before the first liftoff.

"There is a terminal count sequence that we use here that is slightly different than that used for the static fire at Stennis. So we want to check not only that complex system there at the pad but also our countdown sequence in the (launch control center)," Bryant explained. "We are going to check the (ground support equipment) associated with the RS-68 and the pad configuration of the launch table."

The Flight Readiness Firing also presents the chance to gather true-life acoustics measurements during ignition, engineers have said.

One the engine test is completed, refurbishment of the pad will commence.

By mid-August, the "standard" launch processing, which was stopped after the solid motors were attached and "power-on" testing was performed so the pathfinder exercises could be run, will resume for the final push to the planned liftoff day. The Eutelsat payload, already encapsulated in the nose cone, will be brought to the pad from an off-site preparation facility and mated to the rocket.

The normal series of pre-launch checks will follow in advance of starting the real countdown.

The Delta 4 is nearly vertical in this image from Tuesday's rollout to the launch pad. Photo: Carleton Bailie/Boeing

Boeing and Eutelsat officials recently opted to bump the target launch date from July 15 to August 31. The decision was based on delays getting the launch site ready and when the satellite would be set to go.

Bryant said the new schedule includes a few weeks worth of slack, giving time to resolve any problems that could arise over the next four months.

"We actually have a good amount of contingency in (the schedule), so I'm pretty comfortable with that," Bryant said.

"As you process a vehicle you want to have weeks of contingency to respond to any questions...You take one step, you cautiously look for safety and mission success, then take another step, and have all those planned pathfinders and time for data review."

"We took into consideration the spacecraft's request, looked at the schedule and put back in the schedule the contingency time."

Following the inaugural launch, Boeing has two more Delta 4 missions scheduled this year. A Defense Satellite Communications System spacecraft for the Air Force is now scheduled for launch on November 13. Another commercial launch rounds out the year on December 21 when the Brazilian Estrela do Sul 1 communications satellite is lofted for Loral.