The Heavy: Triple-sized Delta 4 rocket to debut
BY JUSTIN RAY
Posted: December 7, 2004
After years of development and 366 days standing on the launch pad, Boeing's behemoth Delta 4-Heavy rocket flies its maiden mission Friday to showcase its proficiency and character in hauling hefty cargos to space.
What's more, a successful debut is crucial to establishing a solid first impression of the heavy-lifter that may one day launch astronauts in NASA's proposed Crew Exploration Vehicle.
The 23-story rocket is scheduled for liftoff at 2:31 p.m. EST (1931 GMT) from pad 37B at Cape Canaveral Air Force Station, Florida. The day's available launch window extends two hours and 56 minutes to 5:27 p.m. EST (2227 GMT).
The rocket was erected on the seaside pad last December where it has since undergone an exhaustive program of tests and countdown rehearsals that built a database of knowledge for engineers and the launch team.
The Cape's Complex 37 is the same site used in the 1960s to fly unmanned Saturn 1 and 1B rockets that helped prepare for mankind's voyage to the moon. The site was rebuilt for the Delta 4 era, successfully supporting the previous three liftoffs in the next-generation vehicle family.
Those initial missions in 2002 and 2003 all flew in the Delta 4-Medium configuration with two stages. The lower stage, called the Common Booster Core, features the Rocketdyne RS-68 main engine that generates 650,000 pounds of thrust. The cryogenic upper stage has the Pratt & Whitney RL10B-2 powerplant.
The Delta 4-Heavy debuting this week is engineered from the foundation built by the Medium models, but is much larger and far more complex.
"The Delta 4-Heavy launch represents a remarkable American technological achievement," said Dan Marin, Boeing's director of Delta 4 Air Force programs.
The Heavy is created by taking three Common Booster Cores -- the liquid hydrogen-fueled motor that forms the Medium's first stage -- and strapping them together to form a triple-body rocket, and then adding the powerful upper stage.
The Delta 4-Heavy is capable of delivering 48,000 pounds of cargo into low-Earth orbits, including that of the International Space Station, 28,000 pounds into geosynchronous transfer orbit used by communications satellites, 22,000 pounds for Trans Lunar Injection routes to the moon and 17,600 pounds on Mars-bound trajectories.
The Air Force has ordered two Heavy rockets that will loft the final Defense Support Program missile-launch detection satellite next fall and sometime later a classified payload for the National Reconnaissance Office, which is the government agency responsible for the U.S. fleet for spy satellites.
During creation of the Delta 4 under the military's Evolved Expendable Launch Vehicle program, a healthy commercial satellite market was supposed to help offset development costs for the Air Force. But that dream fizzled and the potential to launch the first Heavy with a commercial cargo financing the trip went nowhere, prompting the government to purchase a test flight before the DSP and NRO craft are entrusted to the booster.
"The original strategy for demonstrating the Heavy capability was to utilize the perceived burgeoning commercial market. In 1998, this vehicle would have been a big player in what was projected back in those times. So the Air Force was in a great position. They were going to be able to benefit from the commercial launches," Collins said.
"When that commercial launch market started to go away and signs that it wasn't going to allow the demonstration to happen, the Air Force stepped in and said 'hey, we've got some important payloads to go. We want to get data before we put those on top of the rocket.' So they came in and purchased an amendment to the development of the contract for this mission."
In December 2000, the Air Force awarded a $141 million contract for the Delta 4-Heavy demonstration launch.
The Air Force is preparing another batch of launch orders to be competed between Delta 4 and Lockheed Martin's Atlas 5. But program manager Lt. Col. James Planeaux says it is not yet known how many, if any, Heavy missions will be up for grabs.
Lockheed Martin, which had skipped plans to field its version of the Atlas 5-Heavy, changed course and is developing the vehicle that will resemble the Delta 4-Heavy with three booster cores tied together.
NASA is studying the Delta 4, Atlas 5, space shuttle-derived concepts and completely new space vehicles to launch missions in the agency's Vision for Space Exploration that aims to return astronauts to the moon and ultimately send the first humans to Mars.
"The biggest help we're being at this point is by providing (NASA) information about the system, what its growth possibilities are, where its limitations are, so that they have the best set of data to match up with planning an overall exploration program," Collins said of Boeing's ongoing discussions with NASA.
"We're working hard with them but really in an information exchange situation and helping them get educated and smart on what the existing Delta capabilities are and then how Delta can grow."
Collins said a key aspect in selecting a launch vehicle is the infrastructure -- manufacturing factories, processing hangars and pads -- already available to support the exploration vision.
"The reason that's a key is a big part of the job ahead of NASA is making the exploration program fit within a budget."
Boeing designers foresee a host of engine, upper stage and other upgrades to the existing Delta 4-Heavy design that would increase the rocket's payload-carrying capacity into low-Earth orbit for NASA. One configuration would ferry 100,000 pounds -- that's double the ability of the current system.
Futuristic Delta 4 ideas that would require construction of new launch pad and ground infrastructure envision monster rockets with five-to-seven Common Booster Cores strapped together in a cluster. Some concepts built with lightweight materials and sporting an advanced main engine could loft upwards of 200,000 pounds of cargo.
But the current focus is proving the Delta 4-Heavy is trustworthy and reliable. Friday's demonstration flight will last nearly six hours from liftoff until deployment of the instrumented satellite mockup into geosynchronous orbit.
"It is tuned to demonstrate capabilities of the rocket," Collins said. "The Air Force and the Delta team have gotten together and designed the generic DemoSat to answer questions for many missions. It will do a very good job of that, but it isn't tied specifically to one certain payload. It is really tied to a broader sense of demonstrating the capabilities and getting data points from some of the critical aspects of the environment within the payload fairing."
Sensors placed throughout the rocket will obtain the crucial information on the vehicle's actions during launch.
"(There is) a huge amount of telemetry and special instrumentation on this vehicle, being the inaugural mission, looking to get all of the data that we can in order to understand exactly how the rocket has performed," Collins added.
Hitching a ride on the side of DemoSat will be a pair of 35-pound, six-sided nanosatellites nicknamed Ralphie and Sparky. Built in collaboration between Arizona State University, New Mexico State University and the University of Colorado at Boulder, the canister-like nanosats were originally supposed to launch aboard a space shuttle mission in 2003. But the Columbia accident and grounding of the shuttle fleet led to the Air Force proposing an alternate route to orbit on Delta 4.
The missions of Ralphie and Sparky to conduct imaging, micropropulsion and intersatellite communications experiments will last a few days, controlled via ground stations linked by the Internet, before the craft tumble into the atmosphere.
About 50 seconds into flight, the center Common Booster Core's engine is throttled back to its minimum power level of 58 percent thrust to conserve fuel that becomes important later. The starboard and port boosters continue firing at full throttle -- 102 percent thrust -- through the launch's first four minutes before emptying their liquid hydrogen and liquid oxygen propellant tanks and shutting down the RS-68 engines. The 15-story boosters will peel away and plummet into the Atlantic Ocean.
"A lot of the risk is burnt down at that point in time when we get back the single-core flying," Collins said, noting that the rocket will resemble a Delta 4-Medium from this point forward.
Once the outer boosters are shed, the center stage finally throttles back up to 102 percent for more than a minute of propulsion, consuming that fuel supply saved during the period of reduced thrust. The stage is jettisoned five minutes, 41 seconds after liftoff, leaving the rocket's upper stage and payload to continue the journey to orbit.
The upper stage is a bit larger than ones flown previously on Delta 3 and Delta 4-Medium missions. It features wider liquid hydrogen and lengthened liquid oxygen tanks to carry additional propellants, enabling the RL10 engine to fire longer.
About 12 minutes, 48 seconds into flight, the upper stage completes its first burn to achieve a low-altitude parking orbit of 100 by 135 nautical miles above Earth. It is here that Ralphie and Sparky are deployed, each testing low-shock separation systems for possible future applications.
The stage will coast in this orbit, eventually reaching the apogee where the RL10 engine is fired for a third time starting at T+plus 5 hours, 37 minutes. This three-minute burn circularizes the orbit and lowers the inclination to 10 degrees.
About five hours and 50 minutes after leaving Cape Canaveral, DemoSat is released from the Delta 4-Heavy rocket to fly 19,623 nautical miles above the planet, completing the launch.
"It takes quite a while to get there. It is a long mission for us," Collins said.
"It ends up a pretty good long day by the time it takes us about six hours to get everything (fueled for launch) and ready to go, and then it takes another six hours to go run the mission. But I'm sure when we get to successful (DemoSat) separation, everybody will not feel tired at all!"
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