It is America's largestunmanned space booster. Its level of complexity causes engineers to liken it tolaunching three rockets at one time. And its fiery blastoffs create a dazzlingyet heart-in-your-throat sight.
Now, the mammoth Delta4-Heavy has enteredoperational service with Saturday night's successfulascent carrying a critical surveillance satellite.
The Delta 4-Heavy'scharacteristics make it well suited for launching a Defense Support Program(DSP) missile warning satellite into geosynchronous orbit 22,300 miles abovethe planet.
"It's always better tofind a problem than to have a latent and yet-to-be-discovered (problem). That'spart of why we considered the Heavy demo such a success. It was a very subtleproblem, but we found it and we fixed it," said Col. Jim Planeaux, theDelta group commander at the Space and Missile Systems Center.
"We took a lot ofreadings on accelerations, vibrations, acoustics in the various compartments ofthe vehicle. In a few cases (we) determined that they were higher than weexpected and we either modified the hardware slightly or moved some of thecomponents to a more benign environment. We finished all of those(modifications) late last year, and we're very comfortable with the vehiclewe've got."
The Delta 4-Heavy iscreated by taking three Common Booster Cores -- the liquid hydrogen-fueledmotor that forms a Delta 4-Medium's first stage -- and strapping them togetherto form a three-wide rocket, and then adding the powerful upper stage.
"We've done a lot ofthinking about it since (the test). It does get pretty hot up around even thepayload vents. So to mitigate that, we've added some modifications to thisparticular payload fairing to essentially keep the plume out as the vehiclerises and still allow the payload compartment to vent properly," Planeauxsaid.
"When you've got apayload that's very sensitive to contamination, we had to go through somefairly elaborate measures to ensure we were well protected there."
The three identical mainengines, the world's largest hydrogen-fueled rocket engine and each capable ofgenerating 17 million horsepower, propelled the vehicle into a clear night skywith three distinct red-hot plumes trailing more than 200 feet long.
- Launch photo gallery 1
- Launch photo gallery 2
- Launch photo gallery 3
- Tower rollback gallery 1
- Tower rollback gallery 2
About 50 seconds intoflight, the center Common Booster Core's engine was throttled back to itsminimum power level of 57 percent thrust to conserve fuel that became importantlater. The starboard and port boosters continued firing at full throttle -- 102percent thrust -- through the launch's first four minutes before emptying theirliquid hydrogen and liquid oxygen propellant tanks and shutting down the RS-68engines. The boosters peeled away and plummeted into the Atlantic Ocean.
Once the outer boosterswere shed, the center stage finally throttled back up to 102 percent for morethan a minute of propulsion, consuming that fuel supply saved during the periodof reduced thrust. The stage was jettisoned about five minutes, 40 secondsafter liftoff, leaving the rocket's upper stage and payload to continue thejourney to orbit.
About 13 minutes intoflight, the upper stage completed its first burn to achieve an initial parkingorbit above Earth and entered an hour-long coast mode until it reached theextreme western Pacific Ocean northeast of Australia. That is where the RL10engine was re-ignited to reach a geosynchronous transfer orbit with a highpoint stretching 22,000 miles at its high point.
The stage then coasted inthis orbit, eventually reaching the apogee where the RL10 engine was fired fora third time starting at T+plus 6 hours, 10 minutes. The three-minute burncircularized the orbit over the equator off the western coast of South America.
At 3:09 a.m. EST, the5,179-pound DSP satellite was released from the Delta 4-Heavy rocket tocomplete the launch.
"Lastnight's successful countdown and flight culminate a tremendous amount of hardwork by the entire Air Force launch team and our industry partners.Congratulations to all who made this challenging and spectacular launch of theDSP 23 satellite a reality," Planeaux said.
"As the firstoperational launch of a Delta 4 Heavy Lift Vehicle, it marks a major milestoneaccomplishment for the EELV program and for assured access to space."
Bringing the Heavy versionof the Air Force's Evolved Expendable Launch Vehicle family into operationalservice, the military has now successfully replaced the retired Titan rocketfleet for deploying large satellite payloads.
"This successhighlights the continued maturization of our EELV program," said Brig.Gen. Susan Helms, 45th Space Wing commander at Cape Canaveral.
Another Heavy is next up onthe Delta 4's launch schedule. An April liftoff is planned from Cape Canaveralto deliver a classified spy satellite into orbit for the U.S. NationalReconnaissance Office.
Officials plan a five-monthgap between Saturday's flight and the subsequent launch while engineerscomplete a thorough review of data.
"That has a five-monthstandoff to digest all of the analysis and redo all of the loads for thepayload. But we look forward to not taking any more time than that to launchNROL-26," said Mark Wilkins, United Launch Alliance vice president forDelta Programs.
Another secret NRO launchusing a Heavy from the Cape is planned in 2009, followed no sooner than 2010the first Heavy flight from California's Vandenberg Air Force Base with anotherNRO payload. Outfitting of that West Coast pad to install equipment for thelarger rocket has begun.
For more on Defense SupportProgram 23 satellite launched Saturday night, see our separate story here.
- Looking Back on 50 Years of Spaceflight
- IMAGES: 20 Great Rocket Launches
- All About Satellites
Copyright2007 SpaceflightNow.com, all rights reserved.
