The two stages of Boeing's inaugural Delta 4 rocket have been joined together inside a massive hangar at Cape Canaveral's newly refurbished Complex 37 as preparations continue for a targeted July 15 blastoff carrying a communications satellite for Eutelsat.

The second stage is attached to the Common Booster Core inside the HIF. Photo: Boeing

With the help of a precision laser alignment system derived from Boeing's commercial aircraft production line, technicians mated the upper stage to the Common Booster Core first stage at the Horizontal Integration Facility last weekend.

After a couple of weeks of electrical tests, the rocket will be rolled to the launch pad on a special transporter and erected upright by a hydraulic lifter.

The milestone half-mile move to the pad is expected in mid-February, said Dave Herst, Boeing's director of Delta 4 launch sites.

Once at the pad, the the twin strap-on solid boosters will be attached to the rocket as a three-month series of tests kick off to ready for the maiden flight of Delta 4. Activities will include countdown simulations, fueling exercises, tests with a dummy satellite cargo and an engine firing.

A testing rocket, not built to fly, was used in pathfinder exercises at Complex 37 last summer, allowing engineers to ensure tools, handling equipment and other hardware worked with the Delta 4's Common Booster Core first stage. All five versions of the Delta 4 launch vehicle use the common core.

In late August it was erected on the pad to verify the tower and service structure all fit together properly.

The test rocket is rotated upright to sit atop the pad's launch table in August. Photo: Carleton Bailie

But the test booster wasn't designed to be hooked up to the launch pad's fuel lines and other umbilicals. That's where the first flight rocket comes in.

In the coming months technicians will mate the tail service mast and swing arm umbilicals to the rocket and conduct multiple fueling tests.

The process will begin with partial loading of super-cold liquid oxygen and liquid hydrogen into the first and second stages. Ultimately, a complete countdown dress rehearsal, with the rocket fully fueled, will be performed to simulate launch day activities until just prior to engine ignition, Herst explained in a recent interview.

A second countdown rehearsal, now slated for late May, will see the rocket fueled again, but this time the countdown clock will continue into the final seconds.

The RS-68 main engine, the Rocketdyne-developed 650,000-pound thrust hydrogen/oxygen powerplant, will roar to life for a "Flight Readiness Firing," similar to tests performed on space shuttles before their maiden launches.

The RS-68 if the first large liquid-fueled rocket engine developed in the United States in nearly three decades. Photo: Boeing

After taking a few seconds to build up thrust, the engine will fire at full thrust for one second before shutting down. The rocket will be firmly bolted to the launch pad for the dramatic test.

The purpose of the engine firing is to measure the acoustics and pressure levels at the new launch pad that will be experienced at liftoff. That is crucial to ensure engineers' predictions for such conditions are correct before bringing the Eutelsat payload to the pad for launch.

Complex 37 has been intended as a "dry pad" with no water deluge flooding the flame trench to suppress the sound proceeded at launch like other pads. The plumbing is in place, however, to turn the water on if needed to dampen the acoustics.

The engine test will occur about six weeks prior to launch, allowing time to refurbish the pad, retest systems and mount the real Eutelsat spacecraft atop the rocket.

Over the past couple of months the payload fairing -- rocket's nose cone -- and payload adapter for the first launch have been put through a pathfinder exercise with a dummy satellite at a military facility at the Cape.

The pretend payload was attached to the adapter and then enclosed within the two-halves of the fairing. It is now ready to go to the pad for mating with the Delta 4, giving technicians a payload to practice lifting into the tower and attaching to the rocket before handling the real payload. The satellite simulator will remain atop the rocket through the engine firing test before being removed.

An artist's concept of a payload, encapsulated in the rocket's nose cone, being lifted into the launch pad for attachment to the Delta 4. Photo: Boeing

The encapsulation work has been performed at a government site where an Air Force satellite will be processed for launch aboard the second Delta 4 flight this fall.

"The government wants to make sure when we do that first payload encapsulation in the government facility we are ready," Herst said.

Once the pad exercises with the dummy satellite are completed in a few months, it will be taken to the commercial AstroTech facility in nearby Titusville for removal of the fairing and detachment from the payload adapter, thus testing out both types of processing sites, Herst explained.

The launch date for the first Delta 4 has been pushed back a couple of times by development delays. Most recently, the liftoff had been targeted for April 30. However, Eutelsat requested postponing the mission until mid-July.

"The major driver for July 15 was the request from our first commercial customer," Herst said. "However, obviously that gives us additional time to do additional pad checkout as well as vehicle checkout. We did have some impacts from the base here due to all additional security that reduced the efficiency of our construction contractor testing systems."

The exact identity of the Eutelsat payload has not been announced, but is rumored to be the repaired W1 satellite that was damaged a few years ago in a factory accident.

The Delta 4 family has five different configurations, capable of launching between 9,300 to 29,000 pounds of cargo to geosynchronous transfer orbit. The first launch will use a Delta 4 Medium+ 4,2 -- which means it will have one Common Booster Core and upper stage, a four-meter payload fairing and two strap-on solid rocket motors.

The second Delta 4 launch, with the Defense Satellite Communications System spacecraft for the Air Force using a plain Delta 4 Medium rocket with a four-meter fairing and no solid strap-on motors, is now targeted for around October 15. Boeing plans to spend about three months analyzing data from the maiden flight before launching the second Delta 4.

The third and final Delta 4 of 2002 is targeted for November 20 when the Brazilian Estrela do Sul 1 communications satellite is launched for Loral. The rocket configuration for this launch will be the same as the inaugural flight.