America's new heavy-lifting rocket takes its much-anticipated test flight Saturday, if Mother Nature cooperates. The Boeing Delta 4-Heavy rocket was supposed to launch today, but the forecast for strong winds and stormy weather at Cape Canaveral postponed the liftoff by 24 hours.

The Delta 4-Heavy rocket is ready for its inaugural flight. Credit: Boeing photo by Carleton Bailie

Launch is scheduled for 2:31 p.m. EST (1931 GMT) at the opening of a two-hour, 56-minute window. Saturday's weather is iffy with a 60 percent chance of violating the launch rules.

When the rocket does fly it will cap a six-year development effort that produced this massive vehicle designed to loft large payloads into space.

"It really has been a labor of love over the past six years to get to this point, which has taken the efforts of thousands and thousands of people from the U.S. Air Force, The Boeing Company and from all of our suppliers from far-flung reaches to make all of this happen. It's really the start of a great era in space launch with the Delta 4-Heavy," said Dan Collins, the Boeing vice president of expendable launch systems.

"I'm very proud to be able to lead this organization on the eve of this historic launch and look forward to watching the Delta 4-Heavy demo zoom over the horizon on its way to geosynchronous orbit -- as soon as the weather permits."

The rocket, which takes three hydrogen-fueled booster stages and mounts them together, is a technical marvel. Each Common Booster Core has its own Rocketdyne RS-68 main engine generating over 650,000 pounds of thrust at liftoff.

"We've had a lot of independent folks look at this launch vehicle and the conclusion that's been come to, by all of the people, is we have a very robust launch system. In fact...it's much more robust than they had anticipated going in. But even that said, there is a recognition that this launch system is the most complex to come to the pad ...since the space shuttle," Collins said.

The Heavy's main customer -- the U.S. government -- has purchased two missions, including next year's launch of a missile-warning satellite and a later classified reconnaissance cargo. This demonstration flight serves as a dress rehearsal for the rocket before the costly national security missions go forward.

"We're confident this mission is ready for flight, and will serve as the foundation for the first operational launch of Delta 4-Heavy next year," said Col. Mark Owen, the 45th Space Wing commander.

"It is tough to communicate to you the level of excitement that I feel and the 45th Space Wing team feels as we stand on the verge of history as the U.S. Air Force joins Boeing and its other mission partners preparing to launch the first Delta 4-Heavy from Cape Canaveral Air Force Station."

The Delta 4-Heavy can loft payloads comparable in weight to the Titan 4 rocket that has been in service since 1989. But that Lockheed Martin-built booster is being retired after two more flights next year Florida and California. The Delta promises to provide launches far cheaper than Titan.

"This is somewhat similar to a baton pass in a race. With a sense of history, I note that the last heavy-lift Titan 4B from the Cape is stacked out at Launch Complex 40 at the same time we've got the first of the next-generation, we've got the Delta 4-Heavy out at SLC-37B," said Col. John Insprucker, the EELV system program director.

The Air Force's Evolved Expendable Launch Program has backup capabilities between the rival Boeing Delta 4 and Lockheed Martin Atlas 5 families. But the two future operational Delta 4-Heavy missions have been awarded to Boeing and there are no plans to use Atlas 5.

"The Delta 4-Heavy is their ride to space," Col. Insprucker said, referring to the two cargos relying on the new rocket.

The first operational Delta 4-Heavy, presently scheduled for next August, will carry the final Defense Support Program craft that detects enemy missile launches and nuclear weapon detonations from space. If things go seriously wrong Saturday and the U.S. military was in a pinch to find alternate launch options, that particular satellite could fly aboard a Lockheed Martin Atlas 5-551 configuration rocket, company officials said. That version of Atlas 5 uses five strap-on solid boosters. A two-booster configuration launches next week.

The Air Force says the second operational Delta 4-Heavy launch currently booked, carrying a secret National Reconnaissance Office payload, could not fly on existing Atlas 5 configurations available today. The power of an Atlas 5-Heavy would be required to lift that cargo into space.

Lockheed Martin's heavy-lift vehicle is proceeding through development and would be ready to fly its inaugural flight 30 months from the time it's ordered.

The long-range military outlook for Heavy missions is sparse.

"The NRO still has another heavy satellite that will be ready to launch in about 2008," Col. Insprucker said. "After that we've got a little hiatus, I think, until probably the Transformational Communication Satellite architecture comes forward."

Meanwhile, NASA's launch needs for its proposed exploration initiatives to the moon and Mars could provide new business opportunities for both rocket builders.

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