BY JUSTIN RAY

Follow the countdown and launch of the first operational Delta 4-Heavy rocket and the final Defense Support Program missile warning satellite. Reload this page for the very latest on the mission.

Additional coverage for subscribers:
VIDEO: WIDESCREEN MOVIE OF LAUNCH SHOT FROM PRESS SITE PLAY
VIDEO: DELTA 4-HEAVY ROCKETS LAUNCHES WITH DSP 23 PLAY

VIDEO: PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: ANIMATION OF DSP SATELLITE PLAY
VIDEO: DSP 23 SATELLITE IS TRANSPORTED TO PAD 37B PLAY
VIDEO: THE DSP 23 SPACECRAFT MOUNTED ATOP ADAPTER PLAY
VIDEO: FIRST DELTA 4-HEAVY FROM LIFTOFF TO BOOSTER SEP. PLAY
VIDEO: ONBOARD CAMERA RECORDS FIRST HEAVY LAUNCH PLAY
VIDEO: ONBOARD CAMERA SEES BOOSTER SEPARATION PLAY
VIDEO: ONBOARD CAMERA CAPTURES FAIRING JETTISON PLAY
SUBSCRIBE NOW

SUNDAY, NOVEMBER 11, 2007

It is America's largest unmanned space booster. Its level of complexity causes engineers to liken it to launching three rockets at one time. And its fiery blastoffs create a dazzling yet heart-in-your-throat sight. Now, the mammoth Delta 4-Heavy has entered operational service with Saturday night's successful ascent carrying a critical surveillance satellite.

Read our launch story.

For more on Defense Support Program 23 satellite, see our separate story here.

0828 GMT (3:28 a.m. EST)

"Following the Delta 4-Heavy test flight three years ago, the hard work and dedication of the team to prepare to launch our first operational mission was phenomenal," said Mark Wilkins, United Launch Alliance vice president for Delta Programs. "We appreciate the support from our Air Force customer in achieving this milestone, and ULA is pleased to welcome the Delta 4-Heavy as a member of our operational vehicle family."

0825 GMT (3:25 a.m. EST)

Spectacular photos of tonight's liftoff taken with sound-activated cameras at the launch pad are posted here.

0822 GMT (3:22 a.m. EST)

The Air Force confirms tonight's launch has been a complete success!

0809 GMT (3:09 a.m. EST)

T+plus 6 hours, 19 minutes, 57 seconds. SPACECRAFT SEPARATION! The Defense Support Program 23 satellite has been deployed into geosynchronous orbit from the Delta 4-Heavy rocket, completing tonight's first operational launch of America's largest unmanned space booster.

0807 GMT (3:07 a.m. EST)

T+plus 6 hours, 17 minutes, 30 seconds. The upper stage has achieved the payload release orientation.

0805 GMT (3:05 a.m. EST)

T+plus 6 hours, 15 minutes. The stage will be reorienting to the proper attitude for releasing the DSP spacecraft a few minutes from now. The relative separation velocity will be about 1.3 feet per second as the 5,179-pound satellite is cast free from the upper stage rocket motor.

0803 GMT (3:03 a.m. EST)

T+plus 6 hours, 13 minutes, 23 seconds. Engine cutoff No. 3. The upper stage has finished this third and final firing of the night.

0802 GMT (3:02 a.m. EST)

T+plus 6 hours, 12 minutes, 15 seconds. Chamber pressures are reported normal.

0801 GMT (3:01 a.m. EST)

T+plus 6 hours, 11 minutes. A good, stable burn is in progress.

0800 GMT (3:00 a.m. EST)

T+plus 6 hours, 10 minutes, 28 seconds. The Delta 4-Heavy rocket's upper stage has just ignited for the third time of the night. While flying over the Pacific Ocean near the equator just west of South America, this three-minute burn circularizes the orbit at geosynchronous altitude and lowers the inclination to 4.0 degrees.

0315 GMT (10:15 p.m. EST Sat.)

T+plus 85 minutes. The rocket has begun a five-hour coast through space to reach the high point of this egg-shaped orbit about 22,000 miles above Earth. That is where the upper stage engine will ignite again at T+plus 6 hours, 10 minutes. That three-minute burn circularizes the orbit and lowers the inclination to 4.0 degrees.

About six hours and 20 minutes after leaving Cape Canaveral, DSP 23 will be released from the Delta 4-Heavy rocket in geosynchronous orbit, completing the launch.

0312 GMT (10:12 p.m. EST Sat.)

T+plus 82 minutes, 5 seconds. Engine shutdown! Two firings complete, one more to go for the Delta 4-Heavy rocket's upper stage tonight to place the Defense Support Program 23 spacecraft into geosynchronous orbit.

0310 GMT (10:10 p.m. EST Sat.)

T+plus 80 minutes, 10 seconds. Engine chamber pressures still looking good.

0308 GMT (10:08 p.m. EST Sat.)

T+plus 78 minutes, 45 seconds. Pitch and yaw steering is nominal.

0308 GMT (10:08 p.m. EST Sat.)

T+plus 78 minutes. The Pratt & Whitney Rocketdyne RL10B-2 cryogenic rocket engine continues to burn well.

0307 GMT (10:07 p.m. EST Sat.)

T+plus 77 minutes, 15 seconds. The vehicle is more than 500 miles in altitude over the extreme western Pacific, northeast of Australia as it travels 24,900 feet per second.

0305 GMT (10:05 p.m. EST Sat.)

T+plus 75 minutes, 45 seconds. Chamber pressures have stablized after ignition.

0305 GMT (10:05 p.m. EST Sat.)

T+plus 75 minutes, 36 seconds. Ignition! The RL10B-2 powerplant is firing again for a seven-minute burn.

0300 GMT (10:00 p.m. EST Sat.)

T+plus 70 minutes. The upper stage is about five minutes away from re-igniting its engine. This second of three planned firings will raise one side of the rocket's orbit to geosynchronous altitude around 22,000 statute miles.

0255 GMT (9:55 p.m. EST Sat.)

Our gallery of launch images is posted here.

0240 GMT (9:40 p.m. EST Sat.)

Spaceflight Now Plus subscribers can watch a movie of tonight's spectacular liftoff here.

You can learn more about this service here.

0204 GMT (9:04 p.m. EST Sat.)

T+plus 14 minutes. The vehicle will be coasting in this initial orbit for about an hour before the upper stage engine is restarted.

0203 GMT (9:03 p.m. EST Sat.)

T+plus 13 minutes, 12 seconds. Engine cutoff. The upper stage has completed the first of three burns tonight to haul the DSP 23 satellite into the planned geosynchronous orbit.

0201 GMT (9:01 p.m. EST Sat.)

T+plus 11 minutes. The duration of the burn is governed by the rocket's guidance system. The engine will be commanded to shut down once the desired orbit is obtained.

0200 GMT (9:00 p.m. EST Sat.)

T+plus 10 minutes. The upper stage is firing at full thrust to accelerate the upper stage into orbit. It will take another three minutes to reach the initial parking orbit around the planet.

0159 GMT (8:59 p.m. EST Sat.)

T+plus 9 minutes, 15 seconds. The rocket is 147 miles in altitude and 1,039 miles downrange from the launch pad.

0158 GMT (8:58 p.m. EST Sat.)

T+plus 8 minutes, 15 seconds. Chamber pressure reported normal on the RL10 engine as it continues to fire.

0157 GMT (8:57 p.m. EST Sat.)

T+plus 7 minutes, 30 seconds. No problems have been reported during the upper stage engine firing. The RL10B-2 is burning consuming its mixture of liquid hydrogen and liquid oxygen.

0156 GMT (8:56 p.m. EST Sat.)

T+plus 6 minutes, 20 seconds. The payload fairing showing the DSP satellite has been jettisoned in three pieces halves.

0156 GMT (8:56 p.m. EST Sat.)

T+plus 6 minutes, 1 second. Engine start! The Pratt & Whitney Rocketdyne RL10B-2 cryogenic rocket engine is up and burning for the first of three firings during tonight's launch of the Delta 4-Heavy.

0155 GMT (8:55 p.m. EST Sat.)

T+plus 5 minutes, 45 seconds. Pyrotechnics have detonated to jettison the spent center Common Booster Core. The rocket's upper stage and attached payload are now flying free.

0155 GMT (8:55 p.m. EST Sat.)

T+plus 5 minutes, 35 seconds. Main engine cutoff! The center booster's RS-68 engine has finished its job.

0154 GMT (8:54 p.m. EST Sat.)

T+plus 4 minutes, 55 seconds. The rocket is 59 miles in altitude, traveling at 16,800 feet per second as it flies 228 miles downrange from the launch pad.

0154 GMT (8:54 p.m. EST Sat.)

T+plus 4 minutes, 30 seconds. The center Common Booster Core's RS-68 engine has revved up to full throttle for the Delta 4-Heavy rocket's on-going journey to space. The booster is identical to the outer strap-on stages, carrying the same propellant supply and engine package, but it employed a more conservative fuel consumption strategy over the past three minutes. That has left enough cryogenic fuel to fire nearly 90 seconds longer.

0154 GMT (8:54 p.m. EST Sat.)

T+plus 4 minutes, 20 seconds. The 15-story tall starboard and port Common Booster Cores that provided the vast majority of thrust during the first four minutes of flight have expended their fuel and peeled away from the center stage. Tiny solid-fueled motors on the discarded boosters gave helpful nudges to ensure a clean separation. The boosters will tumble into the Atlantic Ocean below.

0154 GMT (8:54 p.m. EST Sat.)

T+plus 4 minutes, 10 seconds. Engine cutoff!

0153 GMT (8:53 p.m. EST Sat.)

T+plus 3 minutes, 35 seconds. Coming up in about 20 seconds, the outer Common Booster Cores will throttle down as a precursor to engine shutdown and jettison of the stages. It will take five seconds to ease the power setting to 58 percent. The boosters will operate at that throttle for another five seconds before the RS-68s are shut down.

0153 GMT (8:53 p.m. EST Sat.)

T+plus 3 minutes, 15 seconds. All three main engines can't and won't burn identically in respect to precise performance and fuel consumption. The rocket was designed with that fact in mind. The vehicle is programmed to accommodate and react to the differences during flight. In the event one of the outer boosters depletes its fuel tanks sooner than the other, a simultaneous engine cutoff will be commanded to prevent an unstable situation.

0153 GMT (8:53 p.m. EST Sat.)

T+plus 3 minutes. The center engine remains at 58 percent thrust while the starboard Common Booster Core's engines are firing at 102 percent. The outer boosters have just over one minute remaining in powered flight.

0152 GMT (8:52 p.m. EST Sat.)

T+plus 2 minutes, 20 seconds. The vehicle 17 miles in altitude.

0152 GMT (8:52 p.m. EST Sat.)

T+plus 2 minutes. The 8-foot diameter bell-shaped nozzles on the three main engines gimbal during flight, allowing the rocket to steer itself on the intended trajectory to space.

0151 GMT (8:51 p.m. EST Sat.)

T+plus 1 minute, 40 seconds. The outer Common Booster Cores and their RS-68 main engines continue to consume the supply of super-cold liquid hydrogen and liquid oxygen rocket fuel while firing at full throttle. The RS-68 is considered the world's largest hydrogen-fueled rocket engine. Each powerplant is capable of generating 17 million horsepower.

0151 GMT (8:51 p.m. EST Sat.)

T+plus 1 minute, 20 seconds. The vehicle is ascending through the flight regime that provides the maximum aerodynamic pressures on the rocket. This period is called Max-Q. And in the next few seconds, the Delta 4-Heavy will break the sound barrier as its speed reaches Mach 1.

0151 GMT (8:51 p.m. EST Sat.)

T+plus 60 seconds. All appears normal one minute into the flight. The Delta 4-Heavy is slowly and thunderously rising away from Earth with three distinct red-hot main engine plumes trailing 20 stories long, backdropped against clear night sky.

0150 GMT (8:50 p.m. EST Sat.)

T+plus 51 seconds. The center Common Booster Core's main engine is throttling back to 57 percent thrust as a fuel conservation effort. The starboard and port boosters continue to operate at their maximum power setting of 102 percent thrust.

0150 GMT (8:50 p.m. EST Sat.)

T+plus 30 seconds. All three Pratt & Whitney Rocketdyne RS-68 main engines are firing at full throttle, gulping three tons of propellant per second to produce 1.9 million pounds of thrust.

0150 GMT (8:50 p.m. EST Sat.)

T-minus 10, 9, 8, sequencer now controlling, T-minus 6, 5, 4, 3, 2, engine ignition, 0, and LIFTOFF! Liftoff of Delta 4-Heavy rocket, America's largest unmanned rocket enters operational service to launch the final Defense Support Program missile warning satellite.

0149 GMT (8:49 p.m. EST Sat.)

T-minus 30 seconds. The terminal countdown sequencer will take control at T-minus 8.5 seconds. Ignition of the three RS-68 powerplants will follow at T-minus 5.5 seconds. The engines power up to the 102 percent level of thrust for a computer-controlled checkout before liftoff.

0149 GMT (8:49 p.m. EST Sat.)

T-minus 40 seconds. Upper stage liquid hydrogen tank is ready.

0149 GMT (8:49 p.m. EST Sat.)

T-minus 1 minute and counting. The ignition parameters for the RS-68 main engine are met.

0148 GMT (8:48 p.m. EST Sat.)

T-minus 70 seconds and counting. The Eastern Range has given its "go" for launch.

0148 GMT (8:48 p.m. EST Sat.)

T-minus 2 minutes and counting. The three Common Booster Core liquid hydrogen tanks have reached flight level and pressure. The rocket's liquid oxygen tanks are being secured.

0147 GMT (8:47 p.m. EST Sat.)

T-minus 3 minutes and counting. The Common Booster Core propellant topping is being secured. And pressurization of the tanks has started.

0146 GMT (8:46 p.m. EST Sat.)

T-minus 4 minutes and counting. Vehicle ordnance is being armed.

0145 GMT (8:45 p.m. EST Sat.)

T-minus 4 minutes, 30 seconds. The systems of the Common Booster Cores and upper stage of the Delta 4-Heavy rocket are switching from ground-fed power to internal batteries for launch.

0145 GMT (8:45 p.m. EST Sat.)

T-minus 5 minutes and counting! The final phase of today's countdown has commenced for launch of Delta 4-Heavy rocket and the Defense Support Program 23 satellite. Liftoff is set to occur at 8:50 p.m. EST (0150 GMT) from pad 37B at Cape Canaveral Air Force Station, Florida.

0144 GMT (8:44 p.m. EST Sat.)

The launch director has given final approval to resume the countdown. Clocks will start ticking again in one minute.

0141 GMT (8:41 p.m. EST Sat.)

Launch team members have been polled again to re-verify all systems are "go" to proceed with the count.

0140 GMT (8:40 p.m. EST Sat.)

NEW LAUNCH TIME. Liftoff has been rescheduled for 8:50 p.m. EST.

0138 GMT (8:38 p.m. EST Sat.)

Tentatively, launch is being targeted for 8:50 p.m. EST, pending resolution of this minor issue.

0135 GMT (8:35 p.m. EST Sat.)

There's no immediate estimate of how long this extra hold will last. But all indications point to a brief delay of only a matter of minutes.

0134 GMT (8:34 p.m. EST Sat.)

The clocks remain holding at T-minus 5 minutes while the launch team discusses what appears to be a minor issue.

0132 GMT (8:32 p.m. EST Sat.)

HOLD! Countdown clock will not resume due to a problem just reported.

0132 GMT (8:32 p.m. EST Sat.)

This has been an incredibly smooth countdown, and clocks will resume in two minutes. Launch of the Delta 4 rocket is just seven minutes away from Cape Canaveral.

0131 GMT (8:31 p.m. EST Sat.)

The launch pad swing arm retraction system pins are being pulled. The three arms will be rotated away from the Delta 4 rocket at liftoff.

0130 GMT (8:30 p.m. EST Sat.)

All systems are reported "ready" by the launch team. There are no technical problems standing in the way of liftoff tonight.

0129 GMT (8:29 p.m. EST Sat.)

Launch team polling is underway.

0124 GMT (8:24 p.m. EST Sat.)

The DSP 23 spacecraft is confirmed to be running on internal battery power for flight.

0119 GMT (8:19 p.m. EST Sat.)

T-minus 5 minutes and holding. The countdown has just entered a planned hold point. Clocks will remain here for 15 minutes to give the launch team members a chance to finish any work running behind schedule and mission officials to conduct final readiness checks. Liftoff is still targeted for 8:39 p.m. EST.

0109 GMT (8:09 p.m. EST Sat.)

T-minus 15 minutes. The countdown clocks will be going into a planned hold at the T-minus 5 minute mark.

0053 GMT (7:53 p.m. EST Sat.)

Now 45 minutes from launch. All systems remain "go" for a liftoff of the Delta 4-Heavy rocket at 8:39 p.m.

0051 GMT (7:51 p.m. EST Sat.)

The Defense Support Program spacecraft payload atop the Delta 4-Heavy rocket is switching to internal power for launch.

0048 GMT (7:48 p.m. EST Sat.)

The three Common Booster Core main engines slew tests are now finished. There were no problems reported in any of the checks, which confirm the rocket will be able to steer itself properly during ascent.

0042 GMT (7:42 p.m. EST Sat.)

The upper stage RL10 engine steering checks have been completed. The Common Booster Core tests are coming up next.

0034 GMT (7:34 p.m. EST Sat.)

The team is now preparing to conduct steering checks of the Delta 4 rocket's engines.

0025 GMT (7:25 p.m. EST Sat.)

The Range Safety checks have been completed.

0014 GMT (7:14 p.m. EST Sat.)

The Air Force-controlled Eastern Range is preparing to run inhibited command destruct receiver checks. This ensures safety personnel can destroy the Delta 4 rocket if it veers off course or experiences a problem during launch.

0006 GMT (7:06 p.m. EST Sat.)

Radio frequency link checks have been completed.

0005 GMT (7:05 p.m. EST Sat.)

The upper stage liquid oxugen tank has entered topping mode, putting all eight propellant tanks in topping to replenish the cryogenics that naturally boil away.

2346 GMT (6:46 p.m. EST)

All remains fairly quiet in the countdown as clocks continue to tick toward an on-time liftoff at 8:39 p.m. EST this evening. The eight cryogenic propellant tanks aboard the Delta 4-Heavy rocket are now full as pre-flight activities proceed smoothly.

2330 GMT (6:30 p.m. EST)

Check out this gallery of remarkable images taken by United Launch Alliance photographer Pat Corkery this morning during rollback of the mobile service tower. The photos are posted here.

2315 GMT (6:15 p.m. EST)

Fast-fill loading of the upper stage liquid hydrogen supply just concluded.

2305 GMT (6:05 p.m. EST)

Topping of the Common Booster Core liquid hydrogen tanks is beginning. And the filling of the upper stage liquid oxygen tank is finishing.

2239 GMT (5:39 p.m. EST)

Three hours and counting.

2225 GMT (5:25 p.m. EST)

Weather continues to look excellent for launch, fueling operations remain underway at pad 37B and mission managers say there are no significant technical issues being worked in the countdown.

2215 GMT (5:15 p.m. EST)

Filling of the upper stage liquid oxygen is beginning.

2159 GMT (4:59 p.m. EST)

The launch team is preparing to start chilldown thermal conditioning of the upper stage liquid oxygen system.

2151 GMT (4:51 p.m. EST)

The loading of liquid oxygen into the Common Booster Cores has been completed. The launch team will be performing vent and relief checks following tanking and begin chilldown procedures for the upper stage liquid oxygen system.

2149 GMT (4:49 p.m. EST)

With the CBC liquid hydrogen tanking continuing, the launch team has been given approval to begin chilldown conditioning of the upper stage liquid hydrogen system. This is a precursor to fueling the upper stage.

2139 GMT (4:39 p.m. EST)

Now four hours till launch. The Delta 4 rocket's three Common Booster Cores are currently being loaded with super-cold liquid oxygen and liquid hydrogen propellants.

Complex 37 has two giant sphere-shaped fuel tanks to store the cryogenic liquid oxygen and liquid hydrogen. The LOX tank holds 250,000 gallons and LH2 sphere about 850,000 gallons. Complex 37 has two giant sphere-shaped fuel tanks to store the cryogenic liquid oxygen and liquid hydrogen. The LOX tank holds 250,000 gallons and LH2 sphere about 850,000 gallons.

The cryogenics are fed from the storage tanks through pipelines to the pad. For the three Common Booster Cores, the propellants are routed up to the launch table upon which the rocket sits. Tail service masts, the large box-like structures at the base of the vehicle, feed the oxygen and hydrogen to the boosters via separate umbilicals. The upper stage receives its cryos from the middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

2137 GMT (4:37 p.m. EST)

The liquid hyrogen loading is switching to the "fast-fill" mode now.

2123 GMT (4:23 p.m. EST)

The cold gas chilldown for the hydrogen side has been completed and the launch team is beginning the slow pumping of liquid hydrogen propellant into the three Common Booster Core stages. This "slow-fill" will be sped up to "fast-fill" after a small portion of each tank is loaded.

Chilled to Minus-423 degrees Fahrenheit, the liquid hydrogen will be consumed by the RS-68 main engines along with liquid oxygen during the early minutes of launch.

2109 GMT (4:09 p.m. EST)

We're now four-and-a-half-hours from launch. The launch team has not reported any problems and the Cape Canaveral weather remains excellent for tonight's liftoff of the Delta 4-Heavy rocket.

2044 GMT (3:44 p.m. EST)

With the Common Booster Cores' liquid oxygen systems properly conditioned for cryogenic temperatures, the loading of Minus-298 degree LOX into the Delta 4-Heavy rocket is about to begin. The liquid oxygen tanks in all three Common Booster Cores will be filled over the next hour or so. The oxidizer will be consumed by the RS-68 main engines during launch.

2035 GMT (3:35 p.m. EST)

The cold gas chilldown conditioning of the Common Booster Cores for liquid hydrogen fueling is beginning.

2034 GMT (3:34 p.m. EST)

The liquid oxygen chilldown is starting in advance of feeding the cryogenic oxidizer into the Delta 4-Heavy rocket this afternoon.

2029 GMT (3:29 p.m. EST)

The "go" has been given for fueling operations. The launch team will start thermal conditioning steps to ready equipment for pumping the super-cold liquid oxygen and liquid hydrogen propellants into the Delta 4-Heavy rocket today. Loading of liquid oxygen into the Common Booster Cores begins first.

2009 GMT (3:09 p.m. EST)

T-minus 5 hours, 15 minutes and counting! The Terminal Countdown has commenced for this first operational launch of the Delta 4-Heavy rocket and the final Defense Support Program missile warning satellite. With one planned hold at T-minus 5 minutes, liftoff is still targeted for 8:39 p.m. EST. The launch window extends two hours and two minutes, meaning liftoff could occur as late as 10:41 p.m. EST.

The multi-step process of loading all eight cryogenic propellant tanks in the rocket was scheduled to begin in the next half hour and continue into the early evening.

1955 GMT (2:55 p.m. EST)

Launch team members have just been polled to ensure everyone is ready to begin Terminal Count at the end of this built-in hold. No constraints were reported.

1945 GMT (2:45 p.m. EST)

Our gallery of images taken this morning showing the mobile service tower rolling back to reveal the Delta 4-Heavy rocket is posted here.

1940 GMT (2:40 p.m. EST)

"A great day out there," launch weather officer Joel Tumbiolo says.

1924 GMT (2:24 p.m. EST)

The call to "man stations for Terminal Count" just went out to the launch team.

1909 GMT (2:09 p.m. EST)

T-minus 5 hours, 15 minutes and holding. Countdown clocks are entering a planned one-hour hold in today's launch operation at Cape Canaveral's Complex 37. During this hold, the full launch team will be seated at their consoles, the launch pad will be verified clear of workers and readiness polls will be conducted by mission management to ensure everyone is ready to proceed with the count.

The Terminal Countdown begins when the clocks resume ticking at 3:09 p.m. EST.

1730 GMT (12:30 p.m. EST)

Preparations are continuing at Complex 37 for tonight's Heavy launch. The weather outlook is calling for clear skies, good visibility, a northerly wind of 8 gusting to 12 knots and a temperature around 61 degrees F.

1422 GMT (9:22 a.m. EST)

The 330-foot tall mobile service tower is slowly beginning to roll away from the Delta 4-Heavy rocket at Cape Canaveral's launch pad 37B in preparation for tonight's liftoff at 8:39 p.m. EST.

The wheeled mobile service structure moves along rail tracks to its launch position about the length of a football field from the rocket's mount.

The 9-million pound tower shields the Delta 4 from the weather, provides workers 360-degree access to the various areas on the vehicle and is needed to hoist the payload atop the upper stage during the launch campaign. The tower is 90-feet wide and 40-feet deep.

Once the tower is fully retracted, crews will secure the complex for launch before leaving the danger area around the pad. All workers must be clear of the area in preparation for the start of hazardous operations, including fueling the vehicle later this afternoon.

FRIDAY, NOVEMBER 9, 2007

Nearly three years after the highly complex Delta 4-Heavy rocket flew a test launch to demonstrate its capabilities for hauling hefty cargos to space, the giant booster will enter service Saturday night with a fiery blastoff carrying a national security satellite.

The massive rocket towering more than 230 feet tall is scheduled for liftoff from Cape Canaveral's Complex 37 at 8:39 p.m. EST (0139 GMT). The evening's launch window will extend 122 minutes to 10:41 p.m. EST (0341 GMT).

The 23rd and final Defense Support Program satellite will ride the rocket all the way to geosynchronous orbit, a trip that will take six-and-a-half-hours from liftoff until deployment.

"As we close the book on one era with the launch of the final DSP satellite, we're also beginning a new era with this first operational launch of the Delta 4-Heavy and taking another significant step forward toward assured access to space," said Col. Jim Planeaux, the Delta group commander at the Air Force's Space and Missile Systems Center.

The Heavy is the biggest booster -- in size and stature -- for the Air Force's Evolved Expendable Launch Vehicle family of rockets. It is capable of carrying the military's largest and heaviest payloads that once relied upon the now-retired Titan rocket fleet.

The Delta 4-Heavy is created by taking three Common Booster Cores -- the liquid hydrogen-fueled motor that forms a Delta 4-Medium's first stage -- and strapping them together to form a triple-body rocket, and then adding an upper stage.

It is the most powerful all-liquid propellant American rocket in use today. And its level of complexity makes it a challenge to launch.

"It's a big rocket -- it's got three booster cores, it's got a lot more hardware," Planeaux said.

Each booster core features a Pratt & Whitney Rocketdyne RS-68 main engine that generates 650,000 pounds of thrust while burning supercold liquid hydrogen and liquid oxygen propellants. The cryogenic upper stage has the Pratt & Whitney Rocketdyne RL10B-2 powerplant.

The December 2004 demonstration launch of the Delta 4-Heavy lacked a real satellite payload -- fitted instead with an instrumented dummy craft. The launch's purpose was gathering flight experience and engineering data on the vehicle's performance before critical satellites began riding on the rocket.

The Air Force's decision to pay for a test flight proved to be a wise decision. All three main engines experienced early shutdowns because of a phenomenon called cavitation. Vapor bubbles in the booster cores' liquid oxygen fuel lines fooled sensors into thinking the oxidizer tanks were running dry and triggered the engines to cut off despite plenty of propellant still aboard. The early extinctions resulted in the rocket failing to achieve the intended orbit.

"We're very fortunate and happy that we found this, as with any problem. In my opinion, it's always better to find a problem than to have a latent and yet-to-be-discovered (problem). That's part of why we considered the Heavy demo such a success," Planeaux said.

"It was a very subtle problem but we found it and we fixed it. The interesting thing about that one was if we had throttled the engines down about a second earlier than happened, we might not have ever seen it in the demo flight. It might not necessarily have occurred on DSP flight but it's kind of a moot argument in my opinion. We do demos to find these things. We found it and were able to fix it."

Hardware and computer software changes were implemented to increase the pressure in the liquid oxygen system and the time in which the rocket's computer brain will begin accepting "dry" signals from the fuel lines was moved.

"We increased the pressure in the tanks, had a pretty straightforward fix to ensure we're not going to see that again. We've actually flown the modifications on NROL-22 and DMSP 17 last year," Planeaux said, referring to a pair of Delta 4-Medium-type rocket missions successfully launched from Vandenberg Air Force Base, California.

"There's lots of challenges and even with the demo flight there's still lots of firsts on (Saturday's) mission," Planeaux said. "It's been very challenging to get here. But I'm very confident."

The $400 million DSP 23 satellite is counting on the Heavy to showcase its proficiency Saturday evening. The craft will need three firings by the rocket's upper stage to reach a circular geosynchronous orbit above Earth during a lengthy and complicated trek.

It all begins with 1.9 million pounds of thrust powering the Delta 4-Heavy rocket ever so slowly off the ground, taking more than 15 seconds for the vehicle to clear the launch pad tower on three pillars of flame from the hydrogen-fueled engines.

"It's a spectacular ascent...It has a thrust-to-weight ratio of about 1.2-to-1 coming off the pad. So you get a lot time to watch it as it rises up above the umbilical tower," Planeaux said.

About 50 seconds into flight, the center Common Booster Core's engine is throttled back to its minimum power level of 57 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.

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, 40 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.

The shiny white metallic nose cone, originally developed to shroud payloads on Titan 4 rockets, is jettisoned in three pieces about six minutes into flight to reveal the DSP satellite to space.

About 12 minutes, 55 seconds into the launch, the upper stage completes its first burn to achieve an initial parking orbit of 117 by 851 nautical miles above Earth.

After a 62-minute coast, the upper stage is re-ignited northeast of Australia to reach a geosynchronous transfer orbit with a high point of 19,614 nautical miles, low point of 496 nautical miles and inclination of 26.6 degrees north and south of the equator.

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 6 hours, 10 minutes while flying over the Pacific Ocean near the equator just west of South America. This three-minute burn circularizes the orbit and lowers the inclination to 4.0 degrees.

About six hours and 20 minutes after leaving Cape Canaveral, the 5,179-pound DSP satellite is released from the Delta 4-Heavy rocket to fly 19,386 nautical miles above the planet, completing the launch.

"Part of the reason we have this Heavy vehicle is because we have these very complex missions. We're lifting big satellites, so we need a lot of thrust off the pad and a lot of overall impulse for the mission, and we're taking them out to geostationary orbit and we're injecting them directly into the orbit without the help of a kick motor as you might have on some other satellites," Planeaux said.

"We believe we've got a great rocket, a great ride and a great satellite that we'll soon place on-orbit and really deliver the capability our nation needs," said Col. Roger Teague, the Air Force's Space Based Infrared Systems group commander.

DSP satellites form an orbiting surveillance system that detects enemy missile launches and nuclear weapon detonations. Built by Northrop Grumman, the spacecraft use infrared telescopes to spot the heat from missile and booster plumes against the Earth's background, giving the U.S. and allies early warning of impending attacks.

"The DSP program has provided over 37 years of vigilant service detecting the launch of ballistic missiles and threats against our great nation," Teague said.

Watch this page for live countdown reports beginning Saturday morning with rollback of the mobile service tower from around the rocket shortly before 10 a.m. EST.