BY JUSTIN RAY

Follow the preparations and maiden launch of Boeing's Delta 4 rocket carrying the Eutelsat W5 communications satellite. Reload this page for the very latest on the mission.

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

T-minus 3 hours and counting. A smooth countdown thus far on a beautiful day. After a planned hold at T-minus 5 minutes for 15-minutes, liftoff is set to occur at 5:39 p.m. EST.

Approval has been given for performing the events leading up to filling the upper stage liquid oxygen tank. The first stage liquid oxygen tanking is nearing completion. The first stage liquid hydrogen fast-fill continues.

1910 GMT (2:10 p.m. EST)

The link checks to ensure the flow of telemetry from the rocket have been completed. Also, the launch team has received a "go" to start activities for loading the upper stage liquid hydrogen tank as the countdown rolls on.

1900 GMT (2:00 p.m. EST)

Steady tanking of the first stage with super-cold liquid hydrogen and liquid oxygen continues. In the next few minutes, telemetry RF link checks will be performed.

1841 GMT (1:41 p.m. EST)

Fueling of the first stage continues with no problems reported.

Complex 37 has two giant sphere-shaped fuel tanks to store the super-cold liquid oxygen and liquid hydrogen for Delta 4. The LOX tank holds 250,000 gallons and LH2 sphere about 850,000 gallons. The tanks' large supplies should allow for at least three consecutive launch attempts before having to be replenished.

The cryogenics flow from the storage tanks, through pipes to the base of the pad. For the first stage, 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 stage in separate umbilicals. The second stage receives its cryos from the middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

1830 GMT (1:30 p.m. EST)

The loading of -298 degree liquid oxygen into the Delta 4 rocket's first stage is beginning.

1822 GMT (1:22 p.m. EST)

A "go" have been given to start slowly pumping liquid hydrogen propellant into the first stage. This "slow-fill" will be sped up to "fast-fill" after a small portion of the tank is loaded. Chilled to Minus-423 degrees Fahrenheit, the hydrogen will be guzzled by the RS-68 main engine along with liquid oxygen, to be loaded shortly.

1809 GMT (1:09 p.m. EST)

Now 4 1/2 hours from today's 5:39 p.m. EST launch time. Countdown activities are marching along at Complex 37, including the early portions of fueling work for the first stage of the Delta 4 rocket.

To put a final period on the issue that ultimately scrubbed yesterday's launch opportunity, there was a computer error that resulted in the failure of a first stage liquid oxygen valve to close. Without the valve's closure, the oxygen tank wouldn't pressurize for launch. Seeing the valve was not closed, the countdown was aborted. The glitch has been reviewed and cleared.

1732 GMT (12:32 p.m. EST)

The launch team is now starting the work to load the first stage liquid hydrogen tank. And the liquid oxygen pump chilldown conditioning is beginning.

1720 GMT (12:20 p.m. EST)

The dressing of some cables on one of the pad's swing arms has been completed and the special crew has departed the pad. With the Blast Danger Area cleared, the "go" has been given for fueling operations today.

1639 GMT (11:39 a.m. EST)

T-minus 5 hours, 45 minutes and counting! The Terminal Countdown has begun for the second attempt to launch Boeing's debut Delta 4 rocket. With one planned hold at T-minus 5 minutes, liftoff is still targeted to occur at 5:39 p.m. EST. There are no significant technical or weather constraints being reported at this time. All of last night's issues have been put to rest. The forecast for today calls for an 80 percent chance of good weather.

As the count moves into the early afternoon, the launch team will be focused on re-loading the liquid hydrogen and liquid oxygen into both stages of the rocket.

1627 GMT (11:27 a.m. EST)

With liftoff just over six hours away, the launch team is now seated on console. A poll of the various team members was performed to ensure everyone was "ready" for continuing today's countdown. No issues were announced.

There are still some workers at the launch pad doing some clean-up chores with cabling. They should be clear of the area in time to start fueling as scheduled.

1550 GMT (10:50 a.m. EST)

The countdown has entered a planned hour-long hold at T-minus 5 hours, 45 minutes. Once clocks start ticking again, the Terminal Count will begin. A little while ago, the Range Safety hold-fire checks were performed to ensure the countdown can be stopped in the final seconds if a problem is detected. And the initial work to turn on the rocket's avionics has started.

The weather forecast for today is calling an 80 percent chance of acceptable conditions for liftoff. See the full report here.

1440 GMT (9:40 a.m. EST)

The Boeing team is gearing up for another attempt to launch the first Delta 4 rocket. Countdown activities are getting underway this morning here at Cape Canaveral. Terminal Count will start 11:39 a.m., followed by loading of the first and stage stages with liquid hydrogen and liquid oxygen propellants. The available launch window extends for 70 minutes from 5:39 to 6:49 p.m. EST.

We have not heard how last night's liquid oxygen valve issue was resolved. But we'll post the information here when it becomes available from Boeing officials.

0100 GMT (8:00 p.m. EST Tues.)

The official reason for the launch scrub has been traced to the failure of a first stage Common Booster Core liquid oxygen valve to properly close, according to Boeing spokeswoman Madonna Walsh. That prompted the countdown software package to stop the clocks. Without the valve closed, the tank wouldn't be able to pressurize for launch.

Initial reports that it was an upper stage liquid oxygen issue have proven erroneous.

Boeing is still targeting another launch attempt Wednesday at 5:39 p.m. EST.

We'll update this page in the morning when more information should be available.

TUESDAY, NOVEMBER 19, 2002
2350 GMT (6:50 p.m. EST)

The launch team will be draining the liquid hydrogen and liquid oxygen from the first and second stages tonight. The mobile service tower will be left in its current launch position, meaning it won't be rolled back around the vehicle.

Troubleshooting is continuing to determine if the "Scripts" abort was caused a software problem or a hardware issue. The issue appears related to the upper stage liquid oxygen system. But again, it isn't clear yet if the problem is with the software or vehicle.

The weather forecast is calling for an 80 percent chance of acceptable weather tomorrow. Ground winds and coastal showers are the main threats.

2341 GMT (6:41 p.m. EST)

A Boeing spokesman says the problem is related to the "Scripts" countdown software.

Another attempt is being tentatively scheduled for Wednesday during a window of 5:39 to 6:49 p.m. EST. That would be the last opportunity before the planned Friday attempt to launch shuttle Endeavour from nearby Kennedy Space Center. All launches from the Cape require safety, tracking and communications services from the Eastern Range, which can only support one mission per 48 hours.

2338 GMT (6:38 p.m. EST)

There is no further detail from Boeing yet on the problem that forced the countdown to be halted and this launch attempt scrubbed. But liftoff won't happen today.

2334 GMT (6:34 p.m. EST)

There was a technical-related problem with the "Scripts" system. Safing of the Delta 4 rocket and pad systems is underway.

2333 GMT (6:33 p.m. EST)

SCRUB. That call has been announced the launch team. A tentative plan to try again tomorrow is being put into place.

2333 GMT (6:33 p.m. EST)

This abort of the countdown effectively scrubs tonight's launch attempt. There won't be enough time to work the issue, recycle the clock and count down before the close of the window at 6:49 p.m. EST.

2333 GMT (6:33 p.m. EST)

HOLD! Countdown clock has been stopped at T-minus 2 minutes, 22 seconds.

2332 GMT (6:32 p.m. EST)

T-minus 3 minutes and counting. The first stage liquid hydrogen replenishment is being secured again. And pressurization of the tank for launch has started.

2331 GMT (6:31 p.m. EST)

T-minus 4 minutes and counting. Ordnance on the rocket is being re-armed for launch.

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

T-minus 4 minutes, 30 seconds. The systems of the first and second stages of the Delta 4 rocket have switched to internal power.

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

T-minus 5 minutes and counting! Clocks are ticking once again at Cape Canaveral for another attempt to launch Boeing's first Delta 4 rocket. Liftoff is set to occur at 6:35 p.m. EST (2335 GMT).

2329 GMT (6:29 p.m. EST)

Countdown will resume in one minute.

2326 GMT (6:26 p.m. EST)

Another poll of the launch team for a "go" to resume the countdown again has been performed with no problems reported. Clocks set to pick up at 6:30 p.m.

2325 GMT (6:25 p.m. EST)

Now 10 minutes from the new launch time.

2323 GMT (6:23 p.m. EST)

High-altitude winds have been verified acceptable through tonight's launch window. However, the surface-level winds are the key.

2322 GMT (6:22 p.m. EST)

Propellant conditioning of the first stage liquid hydrogen and liquid oxygen tanks reported "go" by the team.

2320 GMT (6:20 p.m. EST)

The current wind measurement at the pad is 15 knots. The limit for launch is 16 knots. Winds were noted at 17 knots earlier, forcing a cutoff of the countdown.

2318 GMT (6:18 p.m. EST)

Launch team reports the pad's swing arm system is re-verified ready. Clocks are now set to resume from T-minus 5 minutes at 6:30 p.m. for liftoff at 6:35 p.m. EST. A 14-minute window will be available to work any other issues tonight.

2317 GMT (6:17 p.m. EST)

Eutelsat's W5 communications satellite, the cargo atop the Delta 4 rocket, has remained on internal power and in a "go for launch" condition.

2314 GMT (6:14 p.m. EST)

NEW LAUNCH TIME! Boeing is targeting a new liftoff time of 6:35 p.m. EST (2335 GMT). There is a COLA, or Collision Avoidance cutout period, that prohibits liftoff between 6:16 and 6:25 p.m. because the rocket would be launched on a course that would pass too close to an object already in orbit. Today's launch window extends to 6:49 p.m. EST.

2310 GMT (6:10 p.m. EST)

The wind limit tonight's launch is 16 knots. The weather team measured a 17-knot gust, forcing a cutoff of the countdown.

2307 GMT (6:07 p.m. EST)

The countdown clocks appeared to have been stopped at T-minus 2 minutes, 51 seconds. Again, they are being recycled to T-minus 5 minutes. The launch team is currently safing the vehicle and returning it to the configuration it was in at T-minus 5 minutes.

2306 GMT (6:06 p.m. EST)

Launch Weather Officer Joel Tumbiolo called the hold in the countdown when the ground-level winds exceeded the acceptable limit. Clocks are being recycled to T-minus 5 minutes and holding.

2306 GMT (6:06 p.m. EST)

HOLD! Countdown clock has been stopped by the Launch Weather Officer!

2306 GMT (6:06 p.m. EST)

T-minus 3 minutes and counting. The first stage liquid hydrogen replenishment is being secured. And pressurization of the tank for launch has started.

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

T-minus 4 minutes and counting. Ordnance is being armed.

2304 GMT (6:04 p.m. EST)

T-minus 4 minutes, 30 seconds. The systems of the first and second stages of the Delta 4 rocket have switched to internal power.

2304 GMT (6:04 p.m. EST)

T-minus 5 minutes and counting! The maiden voyage of Boeing's Delta 4 rocket is now just minutes away. Liftoff is set to occur at 6:09 p.m. EST (2309 GMT) from pad 37B at Cape Canaveral Air Force Station in Florida.

2303 GMT (6:03 p.m. EST)

Standing by for the release of the hold in one minute. Launch Director Joy Bryant has given her final approval.

2301 GMT (6:01 p.m. EST)

Launch team has given a "go" to continuing the countdown at 6:04 p.m. EST for liftoff five minutes later.

2259 GMT (5:59 p.m. EST)

It appears this latest issue was an alarm associated with topping the upper stage. But it has now been cleared. Another poll of the launch team is underway.

2258 GMT (5:58 p.m. EST)

NEW LAUNCH TIME. Liftoff is now scheduled for 6:09 p.m. EST.

2257 GMT (5:57 p.m. EST)

There is no word on what the problem is. But once the team is ready to launch, five minutes will be needed to prepare for picking up the clock, then the five minutes of the countdown to liftoff.

2254 GMT (5:54 p.m. EST)

HOLD EXTENDED! With less than a minute from resuming the countdown, a launch team member announced "hold, hold, hold" due to a problem.

2251 GMT (5:51 p.m. EST)

The Boeing launch team, Range and weather officer have been polled for a "go" to resume the countdown from T-minus 5 minutes at 5:55 p.m. and everyone gave their approval.

2250 GMT (5:50 p.m. EST)

Now 10 minutes from the launch. Standing by for a readiness poll of the launch team.

2247 GMT (5:47 p.m. EST)

NEW LAUNCH TIME. The remaining technical issue has been put to rest. So liftoff is now "go" for 6:00 p.m. EST (2300 GMT).

2242 GMT (5:42 p.m. EST)

Launch conductor reports the issue with C-band beacon on the second stage is almost resolved. Still awaiting for a new liftoff time. Today's window extends until 6:49 p.m. EST, so there is no particular rush.

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

Boeing reports the upper stage C-band system alarm is understood. Final discussions are underway before the new launch time is selected.

2235 GMT (5:35 p.m. EST)

The pins on the swing arms have been successfully retracted with no problems reported this time around. So that problem has been resolved. However, the current level on the C-band system of the upper stage remains unresolved. It appears the launch will be delayed further, beyond the 5:44 p.m. EST target.

2232 GMT (5:32 p.m. EST)

A red alarm has been sounded due to a C-band current constraint on the upper stage.

2232 GMT (5:32 p.m. EST)

A new time of 5:44 p.m. EST has been scheduled.

2230 GMT (5:30 p.m. EST)

HOLD EXTENDED. The countdown will remain in this hold by an extra five minutes, at least. That will delay the launch accordingly. During retraction of the pins in the pad's swing arm retraction system a few minutes ago, a fault was indicated. The pins are being cycled back into position and retracted again in hopes of clearing the issue.

2226 GMT (5:26 p.m. EST)

Troubleshooting of the swing arm pin-pull indication continues.

2226 GMT (5:26 p.m. EST)

The W5 spacecraft is now on internal power.

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

The launch conductor reports that an issue is being worked with the pulling of pins on the swing arm retraction system. The launch team is working the issue.

2223 GMT (5:23 p.m. EST)

A "go" has been given to configure the satellite payload for launch. This is the call to switch the Eutelsat W5 communications satellite to internal battery power for flight.

2220 GMT (5:20 p.m. EST)

Boeing reports the ground winds have eased to within limits for today's launch attempt.

2219 GMT (5:19 p.m. EST)

T-minus 5 minutes and holding. Today's countdown has entered a planned 15-minute pause. This hold gives the launch team the opportunity to catch up on work running behind schedule and discuss any outstanding issues.

Currently all four cryogenic tanks on the rocket -- the liquid hydrogen and liquid oxygen tanks on both the first and second stages -- are being topped off. Also, the pad's swing arm retraction system is being readied. The three arms will be swung away at liftoff.

2214 GMT (5:14 p.m. EST)

T-minus 10 minutes and counting. The countdown clock is nearing the built-in hold at T-minus 5 minutes.

2209 GMT (5:09 p.m. EST)

T-minus 15 minutes and counting. The Range Safety checks were completed a short time ago. Countdown clocks are heading to the T-minus 5 minute mark were a 15-minute hold is planned. Boeing says there are no major technical issues standing in the way of launch.

2156 GMT (4:56 p.m. EST)

The Air Force-controlled Eastern Range is now performing 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.

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

Liftoff of the first Delta 4 is just 50 minutes away as the countdown continues very smoothly and on schedule.

With the memory of the stinging failures of the first two Delta 3 rockets, Boeing officials have used outside reviews of the Delta 4 rocket and systems to ensure a successful introduction of the next-generation launcher.

"We've have reviewed this rocket, we've tested, gone back reviewed results of the tests. We've really have gone over it nine ways to Sunday," Boeing's Delta programs vice president Dan Collins said.

"We have gone through, very systematically, and looked at all the systems on Delta 4 that we could not test on the ground. We took those systems and then went outside of the Delta program, and outside The Boeing Company, and brought in independent reviewers to make sure we have done this right. We identified 61 totally analyses that we could not go run a credible test on the ground."

The independent reviewers included engineers from across the aerospace community and even space shuttle program personnel.

"They are people who really understand spaceflight but don't have 40 years of 'that's how Delta does it.' So by being able to bring those people over, they were able to challenge us. They were able to bring a different perspective and we were able to really make sure what we've done with Delta 4 is the right way to go, we've got good strong margins and that we are ready for flight."

Boeing also had a "blue-ribbon" panel of distinguished space leaders review the Delta 4 program.

"They were an enormous help to us. They brought a lot of experience and lessons learned. What they were focused on was our processes. They couldn't be at every test or everywhere we go, but they wanted to make sure we were running the program with strong processes that focus on mission assurance."

The group was chaired by Sheila Widnall, retired secretary of the Air Force.

"She gave a very glowing report, very, very confident that the processes we have used on Delta 4 are the right processes and the team is really focused on mission success," Collins said.

2142 GMT (4:42 p.m. EST)

The first stage steering checks have been performed. No problems reported in any of the slew tests.

2134 GMT (4:34 p.m. EST)

The slew tests of the RL-10B-2 upper stage engine is now completed. Solid motor steering checks are next.

2128 GMT (4:28 p.m. EST)

The engine steering checks are now underway at launch pad 37B.

2125 GMT (4:25 p.m. EST)

Prep work is now beginning to run the steering, or slew, checks on the rocket's engine nozzles. This is a standard pre-launch event during a countdown.

2114 GMT (4:14 p.m. EST)

Now 85 minutes from launch.

Will Trafton, president of Boeing Launch Services that which markets the Delta and Sea Launch rockets, recently spoke to reporters about a variety of topics at the pre-flight news briefing for today's debut of Delta 4.

Today's mission is about a year behind the original schedule due to delays experienced in the development of the new RS-68 hydrogen-fueled first stage main engine and activation of the pad 37B.

"There have been challenges, as one would expect. You just do not start with a new RS-68 engine and build a brand new launch vehicle and do it without some major challenges. The team has faced those challenges and I think they have done a wonderful job tackling them and getting us ready for first launch."

Delta 4 is the second of the two Evolved Expendable Launch Vehicles to fly. EELV was developed by the U.S. Air Force to reduce the cost of launching satellites into orbit and to improve reliability over the heritage Titan, Delta and Atlas rocket families. The first EELV rocket to launch was Lockheed Martin's Atlas 5, which successfully came online in August by lifting off at the opening of the window on the first attempt.

"We do not feel pressure because Lockheed Martin has launched the Atlas 5...our focus is on a successful first flight and that takes priority over anything else," Trafton said.

So what will a successful inaugural launch of Delta 4 mean?

"Success means that the EELV program is off and running and that the Air Force's desire for two competitive vehicles be available to them is successful. On the commercial side, it means now our commercial customers have another choice in the marketplace."

2053 GMT (3:53 p.m. EST)

Ground winds at the launch pad are being closely monitored. The winds have been blowing above the allowable launch limit this afternoon. But meteorologists say the conditions should be within limits by launch time.

There have been handful of minor nits worked by the launch team during the count. At this point, there are no significant technical problems that appear to be a constraint for flight.

Overall, countdown activities have been running ahead of the timeline throughout the day.

2039 GMT (3:39 p.m. EST)

Now two hours away from liftoff time. The countdown is ticking along very quietly at this point.

The launch team and management are guiding the countdown from the Delta Operations Center, located about 9,200 feet from the pad. The engineers overseeing the rocket and ground systems are located on the third floor; the Mission Directors Center room is on the fourth floor. Both rooms have a view of pad 37B and the Delta 4 rocket out their windows, which are covered with shatter-proof film. Other rooms are also set up for engineering support.

The DOC was formerly built to support the Titan-Centaur program, but has since been refurbished to support Delta 4.

2015 GMT (3:15 p.m. EST)

To recap, there are no significant technical issues being worked on the Delta 4 rocket or the Range. The winds have kicking up this afternoon here at the Cape. However, forecasters remain optimistic that the breezy conditions will ease by launch time.

With filling of the rocket's fuel tanks completed, the topping off will continue until very late in the countdown. The next major event in the count will be steering checks of engine nozzles, expected to start in just over an hour.

2006 GMT (3:06 p.m. EST)

The pressurized chill conditioning of the RS-68 main engine has been completed, so the topping of first stage hydrogen tank has started. All four cryo tanks of the Delta 4 rocket are now in replenishment following fueling operations this afternoon.

1952 GMT (2:52 p.m. EST)

Topping off is underway of the liquid oxygen tanks on both stages of the Delta 4 and upper stage liquid hydrogen tank. The first stage hydrogen tank topping will resume shortly after some activities associated with the RS-68 main engine are completed.

1939 GMT (2:39 p.m. EST)

Liftoff of the inaugural Delta 4 rocket is just three hours away. Launch time is 5:39 p.m. EST from pad 37B at Cape Canaveral Air Force Station, Florida.

Complex 37B has been completely rebuilt over the past four years. The site, which helped put America on the path to the moon in the 1960s, has been transformed into the East Coast home of Boeing's Delta 4 rocket family.

Between 1964 and 1968, pad 37B served as the launching pad for eight Saturn 1 and 1B rockets, including the first unmanned flight of an Apollo lunar module. After sitting idle for couple decades, Boeing leased the complex from the Air Force to build a brand new pad from the ground up.

In addition to the mobile service tower, fixed umbilical tower and launch table at the pad, the Horizontal Integration Facility was constructed a half-mile away to act as the Delta 4's hangar where the first and second stages are joined together.

Riding on a special motorized transporter, the rocket is driven to the pad and erected vertically by a hydraulic lifting arm. Once on the pad, the rocket is fitted with the satellite cargo and strap-on solid motors -- if that specific mission is using them.

Boeing ultimately plans to reduce the amount of time a Delta 4 spends on the pad to 7-10 days, speeding up the time between launches.

The horizontal processing of the stages in the HIF is designed to make workers' jobs easier and more efficient.

"One of the key advantages in the horizontal, you've got everything at one level," said Boeing's Delta programs vice president Dan Collins. "All of your workers tool are at one level and you can create a good work environment.

"We felt by keeping it horizontal, we could reduce the cost of the building it is in, it was better for workers to be working on it in a horizontal position and that we would be able to have greater throughput -- both through our processing facility and through the launch pad. That's just what our analysis showed for our particular situation."

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

T-minus 3 hours and counting. The countdown continues very smoothly with no significant technical problems being reported. After a planned hold at T-minus 5 minutes for 15-minutes, liftoff is set to occur at 5:39 p.m. EST.

1918 GMT (2:18 p.m. EST)

The final update to today's Collision Avoidance period has been announced. Due to the rocket's path and another orbiting object, liftoff can't occur during a 9-minute period of today's overall 70-minute launch window. So that means Boeing will have two windows in which to launch the Delta 4 today:

• 5:39 to 6:16 p.m. EST (2239-2316 GMT)
• 6:25 to 6:49 p.m. EST (2325-2349 GMT)

1911 GMT (2:11 p.m. EST)

Boeing reports the countdown activities are still running ahead of the schedule. Both the first and second stage liquid hydrogen tanking operations are now in the topping off phase. The first stage liquid oxygen tank was filled earlier; the upper stage LOX loading is still ongoing. All of the cryogenic tanks will be replenished through the final minutes of the countdown to replace the supplies that naturally boil away.

The launch team has also completed the C-band beacon interrogation with the Range and the RF link checks.

1902 GMT (2:02 p.m. EST)

Chilldown for the upper stage liquid oxygen system has been completed, clearing the way for loading of the stage's tank.

1843 GMT (1:43 p.m. EST)

The filling of the first stage liquid oxygen tank has been completed, the launch team reports. After some checks, preparations will start to load liquid oxygen into the upper stage. Liquid hydrogen loading to both stages remains in work.

1835 GMT (1:35 p.m. EST)

The chilldown thermal conditioning of the upper stage liquid hydrogen side has been completed. The launch team is now "go" to begin loading the hydrogen tank, which is the top orange foam-covered area of the rocket.

Also in the countdown, the beacon checks between the rocket and Eastern Range have been completed. The RF link checks are upcoming.

1824 GMT (1:24 p.m. EST)

T-minus 4 hours and counting. Clocks remain on track for liftoff at 5:39 p.m. EST today. There is one planned hold at T-minus 5 minutes for 15-minutes, leading to the opening of the 70-minute launch window.

Tanking continues on the first stage, and work to chill the upper stage hydrogen system has started.

1810 GMT (1:10 p.m. EST)

Fueling of the first stage continues with no problems reported.

Complex 37 has two giant sphere-shaped fuel tanks to store the super-cold liquid oxygen and liquid hydrogen for Delta 4. The LOX tank holds 250,000 gallons and LH2 sphere about 850,000 gallons. The tanks' large supplies should allow for at least three consecutive launch attempts before having to be replenished.

The cryogenics flow from the storage tanks, through pipes to the base of the pad. For the first stage, 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 stage in separate umbilicals. The second stage receives its cryos from the middle swing arm that extends from the Fixed Umbilical Tower to the front-side of the rocket.

1754 GMT (12:54 p.m. EST)

Running a bit ahead of schedule, the loading of liquid hydrogen and liquid oxygen rocket fuel into the Delta 4 rocket's first stage is underway.

Chilled to Minus-423 degrees Fahrenheit, the liquid hydrogen and the -298 degree liquid oxygen will be consumed from the stage's Rocketdyne RS-68 main engine during the first four minutes of the launch.

The first stage hydrogen tank is the largest of the orange foam-covered areas of the rocket, accounting for about two-thirds of the first stage. The oxygen tank is the middle orange band on the vehicle.

1739 GMT (12:39 p.m. EST)

The launch team is now entering the final five hours of the countdown to today's debut launch of Boeing's Delta 4 rocket from Cape Canaveral Air Force Station's Complex 37B. The "go" has been given to start fueling the first stage. There are no significant problems being addressed and forecasters remain hopeful on the weather.

1710 GMT (12:10 p.m. EST)

The chilldown procedures are underway to thermally condition the first stage liquid hydrogen and liquid oxygen systems in advance of loading the cryogenics into the vehicle. The stage, called the Common Booster Core, and its RS-68 main engine are the key new parts of Delta 4.

1639 GMT (11:39 a.m. EST)

T-minus 5 hours, 45 minutes and counting! The Terminal Countdown has begun for the first launch of Boeing's Delta 4 rocket. With one planned hold at T-minus 5 minutes, liftoff is still targeted to occur at 5:39 p.m. EST. There are no technical or weather concerns being worked.

As the count moves into the early afternoon, the launch team will be focused on loading the liquid hydrogen and liquid oxygen into both stages of the rocket.

Today's available launch window extends for 70 minutes to 6:49 p.m. EST. However, a preliminary Collision Avoidance period has been reported by the Air Force that would prohibit liftoff between 6:15:54 and 6:25:01 p.m. EST. The COLA launch window cutouts ensure the rocket isn't launched at a time that would allow it to pass too close to another orbiting object.

1630 GMT (11:30 a.m. EST)

The full launch team has reported on console and ready for continuing today's countdown. A poll of the various team members concluded with no issues announced. The weather remains "go" as well. Standing by to end this planned hold in about nine minutes.

1539 GMT (10:39 a.m. EST)

Countdown clocks have entered a planned 60-minute built-in hold at the T-minus 5 hour, 45 minute mark. When the clocks resume ticking, the Terminal Count phase of today's launch operation will commence. One further hold is planned -- for 15 minutes -- at the T-minus 5 minute point.

Liftoff remains scheduled for 5:39 p.m. EST (2239 GMT), the opening of a 70-minute launch window.

1515 GMT (10:15 a.m. EST)

Hold-fire checks have been completed successfully. And word has been received that clearing of workers from the pad is nearing completion.

Today's updated launch weather forecast can be seen here.

1500 GMT (10:00 a.m. EST)

Activation of the Delta 4 rocket's avionics is underway at this hour as the countdown continues for today's 5:39 p.m. EST liftoff. In the next few minutes, the Range will perform hold-fire checks to ensure safety personnel can halt the countdown in the final seconds if a problem arises.

1245 GMT (7:45 a.m. EST)

The 9-million pound mobile service tower has been slowly rolled away from the Boeing Delta 4 rocket this morning at Cape Canaveral's launch pad 37B.

The wheeled structure moved along European-style tracks to a position about the length of a football field from the launch table.

The 330-foot tall tower shields the rocket from the weather, provides workers access to the various areas on the vehicle and serves the vital role in mounting the strap-on solid rocket motors to the first stage and hoisting the payload atop the upper stage.

Crews will spend part of the morning securing the tower in the launch configuration. After the final chores to ready the complex for launch have been completed, all workers will clear the area in preparation for the start of hazardous operations.

The Terminal Countdown is scheduled to begin at 11:39 a.m. EST (1639 GMT), exactly six hours before liftoff time. Fueling of the rocket with liquid hydrogen and liquid oxygen will follow in the early afternoon.

Keep watch on this page for countdown status updates as the day rolls on!

1221 GMT (7:21 a.m. EST)

The mobile service tower is in motion at launch pad 37B, driving back from the Delta 4 rocket in preparation for today's liftoff attempt.

0115 GMT (8:15 p.m. EST Mon.)

Boeing's next-generation Delta 4 rocket will take the ultimate test today, blasting off from Cape Canaveral on its debut launch during a window of 5:39 to 6:49 p.m. EST (2239-2349 GMT).

"Our whole team is very, very excited," said Dan Collins, Boeing's vice president of Delta programs. "I would also like to publicly thank the thousands of people who have worked so hard on Delta 4 the past five years to get us to this point. It is a labor of love. I don't think there is a better team in the world. I am very, very excited about getting to Tuesday and watching our baby fly. It's a beautiful rocket. It's a great team. Go Delta!"

On Monday, Boeing formally closed out the remaining technical review of the Pratt & Whitney RL-10 upper stage engine. The recent test incident with an RL-10B-2 engine built this year was determined to be no concern for the powerplant on the first Delta 4, which was manufactured four years ago.

"We took the time we needed to ensure mission success," Collins said. "We are ready to launch and that sentiment was echoed throughout the Launch Readiness Review."

Countdown activities will get underway before sunrise as workers at launch pad 37B prepare the towering mobile service structure for retraction from around the Delta 4 rocket.

We'll be out at the Cape bright and early. Watch this page for confirmation of tower rollback and our continuing live reports throughout the day as Boeing counts down to liftoff.

MONDAY, NOVEMBER 18, 2002
2055 GMT (3:55 p.m. EST)

Mission officials held the Launch Readiness Review today and gave approval to continue with preparations for tomorrow's countdown and liftoff of the first Delta 4 rocket. There are no outstanding problems being reported and the weather forecast calls for a 90 percent chance of acceptable conditions.

1600 GMT (11:00 a.m. EST)

Today's updated launch weather forecast can be seen here.

SUNDAY, NOVEMBER 17, 2002
2300 GMT (6:00 p.m. EST)

Boeing exonerated the RL-10 upper stage engine during reviews Sunday, clearing the way for Monday's Launch Readiness Review that will formally put to rest an issue that prompted officials to cancel Saturday's liftoff attempt.

The Delta 4 rocket uses one RL-10B-2 cryogenic engine, which is built by Pratt & Whintey. But a recent incident with an RL-10 test engine caused lengthy analysis to ensure the powerplant installed on the first Delta 4 is fit to fly.

Although the extra time needed to study the problems forced a launch delay, Boeing officials said the precautionary move was necessary to leave no doubt that the Delta 4's RL-10 will fire properly to propel the Eutelsat W5 telecommunications satellite into the proper orbit during Tuesday evening's mission.

The inaugural Delta 4's engine passed all of its key pre-flight tests, officials said.

The weather forecast for Tuesday's 5:39 to 6:49 p.m. EST (2239-2349 GMT) launch window is near-perfect with a 90 percent chance of acceptable conditions. The only slight concern is for gusty ground-level winds.

News from the Launch Readiness Review is expected by mid-to-late afternoon Eastern Time. We will update this page with confirmation that all systems are "go" for liftoff.

And watch this page for comprehensive live updates throughout the day Tuesday during the countdown and 37-minute flight of the Delta 4.

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

Today's updated launch weather forecast can be seen here.

SATURDAY, NOVEMBER 16, 2002

Launch Weather Officer Joel Tumbiolo has issued an updated weather forecast for Tuesday's launch attempt. See the forecast and the weather rules here.

FRIDAY, NOVEMBER 15, 2002

Boeing won't send its first Delta 4 rocket into space Saturday as planned after a last-minute engine issue was raised and meteorologists predicted virtually no hope of favorable weather conditions. Read our full story.

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

Although Boeing spokespeople still have not released any details on why tomorrow's launch has been scrubbed, sources say the continued work to formally resolve a concern with the Pratt & Whitney RL-10 engine test and the bad weather forecast prompted to postponement to Tuesday.

An RL-10 engine suffered a turbopump problem during a recent test. Although Boeing is confident the RL-10 on the Delta 4 rocket's upper stage for this inaugural launch is just fine, the paperwork and analysis has taken time to put to rest. With all the late hours Boeing engineers have logged this week, coupled with the awful weather expected Saturday, the decision was made to stand down till next week.

We'll have a full story later tonight.

1735 GMT (12:35 p.m. EST)

Boeing officials are planning a 3 p.m. EST news conference today at which time more information will be provided on the reason for postponing the debut launch of Delta 4. A potential concern has been raised with the rocket, which sources say involves the RL-10 engine.

"The launch team is working to resolve a potential issue at this time, and will determine by Monday the launch readiness for Tuesday, November 19," Boeing said in a statement today.

At the request of this launch's customer, Eutelsat, no launch attempts were possible on Sunday and Monday. In addition, the weather forecast gave little hope of acceptable conditions on Saturday.

We'll update this page as soon as more info becomes available.

1635 GMT (11:35 a.m. EST)

SCRUB - Boeing has called off Saturday's planned maiden flight of the Delta 4 rocket. Launch is has been delayed until at least Tuesday. The weather forecast called for little hope of acceptable conditions Saturday and an issue with the RL-10 second-stage engine appears to have been a factor.

1235 GMT (7:35 a.m. EST)

The weather forecast has worsened for Saturday's launch attempt. Meteorologists now predicting a 90 percent chance of bad weather. See the latest forecast and the weather rules here.

2330 GMT (7:30 p.m. EST Thurs.)

The final launch readiness reviews will be held Friday to give approval for Saturday's scheduled countdown and liftoff of the inaugural Delta 4 rocket.

Expected lousy weather conditions at the Cape remain the major threat to an on-time launch. Launch Weather Officer Joel Tumbiolo is predicting only a 20 percent chance of meeting the strict weather rules during Saturday's 5:38 to 6:49 p.m. EST launch window. He is calling for gusty winds, rain and unacceptable clouds.

If the Delta 4 can't launch on Saturday, the next attempt is not expected before Tuesday evening due to the Leonids meteor shower. Paris-based satellite operator Eutelsat, which is launching its W5 spacecraft on the Delta 4, doesn't want to attempt liftoff on Sunday or Monday.

A pre-launch news conference in Cocoa Beach is scheduled for 3 p.m. EST Friday. We'll be there and file a complete update and preview of the countdown on this page later.

And when the launch does occur, watch the page for comprehensive live reports throughout the countdown and 37-minute flight of the rocket!

MONDAY, OCTOBER 14, 2002

Belching flame and roaring like a lion, Boeing's inaugural Delta 4 rocket did everything but lift off during a successful countdown rehearsal Monday that was capped by a dramatic engine firing on Cape Canaveral's launch pad 37B. Read our full story.

2330 GMT (7:30 p.m. EDT)

We have posted video clips above for our Spaceflight Now Plus subscribers of the final countdown, engine ignition and the post-shutdown fireball. Very dramatic! A couple images of are posted to the right.

Boeing is calling this test a success.

"We are about to launch a new family of rockets that will have a long-term impact on the space launch, telecommunications and defense industries," said Dan Collins, vice president and Delta program manager. "Our team did a fantastic job of completing this rehearsal. The test firing serves as a steppingstone and positions us to obtain our goal of providing the U.S. government and the commercial world the best value, performance-driven launch vehicle for satellite deployment.

"We planned a rigorous test program focused on assuring mission success and we've completed every test in the plan. Now it's time to go launch."

We'll have a wrap-up story later this evening.

2141 GMT (5:41 p.m. EDT)

We'll have a video clip of the engine firing and some pictures shortly. The firing was extremely dramatic with a whole lot of fire.

2138 GMT (5:38 p.m. EDT)

The Boeing Delta 4 rocket's new RS-68 main engine, the first large all-American liquid-fueled rocket engine built in 25 years, has been fired for a few seconds at Cape Canaveral Air Force Station's launch pad 37B. Today's Flight Readiness Firing was designed to prove the rocket, engine, launch pad and software will work together properly for next month's inaugural voyage of the Delta 4.

Safing of the rocket and pad has been completed with no significant issues reported.

2136 GMT (5:36 p.m. EDT)

With a lot of fire, smoke and roar, the Flight Readiness Firing has occurred.

2135 GMT (5:35 p.m. EDT)

Engine cutoff confirmed! The RS-68 engine has completed its brief firing. Safing is in progress.

2134 GMT (5:34 p.m. EDT)

T-minus 3 seconds. Main engine ignition!

2134 GMT (5:34 p.m. EDT)

T-minus 8 seconds. The terminal countdown sequencer has been activated. Standing by for main engine start at T-minus 5.5 seconds.

2134 GMT (5:34 p.m. EDT)

T-minus 30 seconds. Launch team is passed the point when the problem occurred before.

2134 GMT (5:34 p.m. EDT)

T-minus 1 minute and counting. Simulated "go" from the range.

2133 GMT (5:33 p.m. EDT)

T-minus 2 minutes and counting. First stage liquid hydrogen tank is at flight level and pressure.

2132 GMT (5:32 p.m. EDT)

T-minus 3 minutes and counting.

2131 GMT (5:31 p.m. EDT)

T-minus 4 minutes and counting. Ordnance is being armed once again.

2130 GMT (5:30 p.m. EDT)

T-minus 4 minutes, 30 seconds. The systems of the first and second stages of the Delta 4 rocket have switched to internal power.

2130 GMT (5:30 p.m. EDT)

T-minus 5 minutes and counting! The earlier problem with a pressure limit setting has been resolved, and Boeing has restarted the countdown for a second try at performing the Flight Readiness Firing at Cape Canaveral's pad 37B. The RS-68 engine will be ignited at T-minus 5.5 seconds.

2126 GMT (5:26 p.m. EDT)

The launch team has been polled and all was reported "go" to resume the countdown for another attempt. Clock will pick up at 5:30 p.m.

2125 GMT (5:25 p.m. EDT)

Now 10 minutes away from the rescheduled engine firing of the Delta 4 rocket.

2121 GMT (5:21 p.m. EDT)

A new engine start time has been set for 5:35 p.m. EDT. So the countdown will resume from the T-minus 5 minute mark at 5:30 p.m.

The abort was caused by a gaseous nitrogen pressure limit. The launch team has a workaround plan so an alarm and cutoff of the count does not occur again.

2119 GMT (5:19 p.m. EDT)

The launch team is being told that a resumption of the countdown is quickly approaching. So they are picking up with the final tasks before restarting the clock -- including preparing the pad's swing arm system and performing the simulated transfer of the payload to internal power.

2117 GMT (5:17 p.m. EDT)

While work continues to resolve the problem that caused the alarms and countdown abort, Boeing has been able to arrange for an extension of today's test window from 6 until 6:39 p.m. EDT.

2112 GMT (5:12 p.m. EDT)

A Boeing spokesman says a parameter apparently was incorrectly entered into a computer system, which caused the abort. That parameter is being changed for the next countdown attempt. There is still hope of getting this work done and still performing the engine firing today.

2106 GMT (5:06 p.m. EDT)

Engineers in the launch control room are going to perform some more recycle activities. This will shorten the amount of time needed from the point the "go" is given to resume the count and when the clock can actually start ticking.

A new T-0 time has not been set, nor has the issue been put to rest.

2100 GMT (5:00 p.m. EDT)

The launch team reports the four cryogenic tanks are being topped off in support of another attempt at today's Flight Readiness Firing. Boeing managers and engineers are still working to understand and resolve the problem that aborted the first countdown around T-minus 38 seconds. The count has been recycled back to T-minus 5 minutes.

2052 GMT (4:52 p.m. EDT)

A Boeing spokesman says the issue could be resolved shortly, allowing the countdown to resume in 10-15 minutes. But the company spokespeople still have not said provided any detail on the problem.

2038 GMT (4:38 p.m. EDT)

It's now beginning to sprinkle some rain at the Cape press site.

2025 GMT (4:25 p.m. EDT)

The Boeing management and engineering teams are still assessing the situation to understand what triggered some alarms and a cutoff of the countdown. The launch team will be ready to pick up a fresh countdown from T-minus 5 minutes if this issue can be resolved today. There is no estimation on when the count will resume. Boeing has a two-hour window, extending to 6 p.m. EDT, to perform the engine firing today.

We'll pass along the information as it becomes available.

2012 GMT (4:12 p.m. EDT)

We're still awaiting word from Boeing with details on what prompted clocks to stop around T-minus 38 seconds.

2002 GMT (4:02 p.m. EDT)

There is no word yet on what the problem was that caused the countdown to be stopped today. Boeing has a two-hour window to perform today's engine firing. So if the glitch can be resolved, the test could occur by 6 p.m. EDT.

2000 GMT (4:00 p.m. EDT)

The launch team is going through safing and recycle steps following an abort of the countdown around T-minus 40 seconds. Clocks will be reset to T-minus 5 minutes.

1959 GMT (3:59 p.m. EDT)

HOLD! Countdown clock has been stopped.

1959 GMT (3:59 p.m. EDT)

T-minus 1 minute and counting. Final "go" calls for simulated launch have been made.

1958 GMT (3:58 p.m. EDT)

T-minus 2 minutes and counting. First stage liquid hydrogen tank is at flight level and pressure.

1957 GMT (3:57 p.m. EDT)

T-minus 3 minutes and counting. The propellant flow to the first stage is being secured.

1956 GMT (3:56 p.m. EDT)

T-minus 4 minutes and counting. Ordnance is being armed.

1955 GMT (3:55 p.m. EDT)

T-minus 5 minutes and counting! The countdown has resumed for the five-second firing of the Delta 4 rocket's main engine. The rocket is switching to internal power.

1951 GMT (3:51 p.m. EDT)

The Boeing launch team has been polled for a "go" to resume the countdown at 3:55 p.m. and everyone gave their approval.

1950 GMT (3:50 p.m. EDT)

Now 10 minutes from the engine firing. Standing by for a readiness poll of the launch team.

1945 GMT (3:45 p.m. EDT)

As part of today's countdown simulation, a mock "go" has been given to configure the satellite payload for launch. On the real launch day, this will be the call to switch the Eutelsat W5 communications satellite to internal battery power.

1940 GMT (3:40 p.m. EDT)

T-minus 5 minutes and holding. Today's countdown has entered a planned 15-minute pause. This hold gives the launch team the opportunity to catch up on work running behind schedule and discuss any outstanding issues. But at this point everything appears to be going very smoothly for the Flight Readiness Firing.

Currently all four cryogenic tanks on the rocket -- the liquid hydrogen and liquid oxygen tanks on both the first and second stages -- are being topped off. Also, engineers have verified the pad's swing arm retraction system is ready. The top arm will be swung away during today's test.

1935 GMT (3:35 p.m. EDT)

T-minus 10 minutes and counting. The countdown clock is headed to T-minus 5 minutes when a 15-minute planned built-in hold will occur.

1930 GMT (3:30 p.m. EDT)

Thirty minutes away from ignition. There are no problems are being reported that would stand in the way counting down to engine start at 4:00 p.m.

The launch team and management are guiding the countdown from the Delta Operations Center, located about 9,200 feet from the pad. The engineers overseeing the rocket and ground systems are located on the third floor; the Mission Directors Center room is on the fourth floor. Both rooms have a view of pad 37B and the Delta 4 rocket out their windows.

The DOC was formerly built to support the Titan-Centaur program, but has since been refurbished to support Delta 4.

1925 GMT (3:25 p.m. EDT)

Range Safety command destruct receiver checks have been performed over the past few minutes. Results were acceptable for today's countdown.

1915 GMT (3:15 p.m. EDT)

The engine steering tests have been completed with no problems reported.

Today's Flight Readiness Firing has three main objectives:

• Verify the RS-68 main engine, Delta 4 vehicle and launch pad design work together properly
• Verify countdown auto sequences through engine start and thrust to full power
• Verify launch abort capability

1900 GMT (3:00 p.m. EDT)

Now one hour away from the brief ignition of the Boeing Delta 4 rocket's main engine at the conclusion of today's countdown dress rehearsal. It has been raining at the launch pad this afternoon as some weather moves through the area. But the countdown has continued and the launch team is still targeting a T-minus 0 seconds at 4:00 p.m. EDT.

Currently the team is running steering, or slew, checks on the rocket's engine nozzles. This is a standard pre-launch event during a countdown.

Boeing is running today's test very close to the timeline that will be used on the real launch day. Today's mock liftoff time is 4 p.m. and the T-0 on November 14 will be around 5:30 p.m. EDT.

1705 GMT (1:05 p.m. EDT)

The second stage liquid hydrogen and liquid oxygen tanks have been filled. Topping of the tanks is still to be completed.

Boeing is still targeting 4:00 p.m. EDT for today's Flight Readiness Firing of the Delta 4 rocket's RS-68 main engine.

We'll pause our updates for now while we get into position to cover the FRF. Watch this page for live updates during the final countdown!

1645 GMT (12:45 p.m. EDT)

T-minus 3 hours and counting. With a 15-minute planned hold at T-minus 5 minutes, today's countdown continues on track for engine ignition at 4:00 p.m. EDT (2200 GMT).

The first stage has been loading and topping is underway. Second stage liquid hydrogen and liquid oxygen filling is currently being performed in parallel.

Activities appear to be going very well with no problems reported. In fact, some events are occurring ahead of the timeline.

1630 GMT (12:30 p.m. EDT)

The first stage hydrogen loading has reached the topping phase. And the Boeing launch team has started upper stage fueling operations.

1615 GMT (12:15 p.m. EDT)

First stage tanking operations continue to progress smoothly with no issues reported. The liquid oxygen tank has been filled. Topping to flight level has now started. Liquid hydrogen loading is still in work.

The chilldown conditioning of the upper stage liquid hydrogen and liquid oxygen tanks will be completed momentarily to be followed by tanking.

1530 GMT (11:30 a.m. EDT)

The loading of Delta 4 rocket's first stage with liquid hydrogen and liquid oxygen is now underway at launch pad 37B. The upper stage is scheduled to be filled later today.

Clocks stand at T-minus 4 hours, 15 minutes and counting. One hold is planned for 15 minutes at T-minus 5 minutes. That will lead to ignition of the RS-68 main engine at 4:00 p.m. EDT today.

1430 GMT (10:30 a.m. EDT)

The countdown is continuing at Complex 37 this morning with no reports of any significant problems. Fueling of the rocket with liquid hydrogen and liquid oxygen cryogenics is scheduled to start a little later.

MONDAY, OCTOBER 14, 2002

Boeing's first Delta 4 rocket won't blast off today but its brand new liquid hydrogen-fueled main engine will fire to life for a few seconds on Cape Canaveral's rebuilt pad 37B at the culmination of a crucial countdown rehearsal.

As its name suggests, today's Flight Readiness Firing, or FRF, is aimed at giving Boeing the proof that the next-generation rocket, launch pad, ground systems and software are ready for the inaugural Delta 4 liftoff next month.

The Delta 4 is the second new American rocket being fielded this year. Lockheed Martin successfully flew its Atlas 5 booster in August from the Cape. Both rockets were designed as part of the U.S. Air Force's Evolved Expendable Launch Vehicle program that seeks to provide affordable and reliable access to space for the next two decades.

Today's test will see the Boeing launch team conduct a full-up countdown dress rehearsal to practice the activities to occur on the real launch day, including retracting the protective 330-foot tall service gantry, fueling the rocket's two stages with liquid hydrogen and liquid oxygen propellants and running standard pre-liftoff checks.

But what sets this test apart from several performed over the past few months is the ignition of the rocket's RS-68 main engine. It will be the first FRF on Florida's Space Coast since NASA fired space shuttle Endeavour's three main engines in April 1992 before that ship's maiden voyage.

Developed by Rocketdyne over the past five years, the RS-68 is the first large all-American liquid-fueled rocket engine built since the shuttle main engine a quarter-century ago. The new power-plant was created to be simple and cheap to produce. It can generate 650,000 pounds of sea-level rated thrust.

"Nobody has ever developed an engine like this and done it in the amount time that Rocketdyne did. This is a great success and really the heart and soul of Delta 4 and what we are going to build our future on as far as our propulsion system," said Dan Collins, Boeing's vice president of Delta programs.

If all goes well, today's countdown will progress to a planned T-minus 0 seconds at 4 p.m. EDT (2000 GMT). Boeing has scheduled a two-hour window, extending to 6 p.m. EDT, to perform the firing if any problems crop up.

After a planned hold at T-minus 5 minutes, countdown clocks will resume at 3:55 p.m. EDT. The last seconds of the count will go like this:

• At T-minus 8.5 seconds, the computer-controlled sequencing of the countdown takes over.
• At T-minus 5.5 seconds, the command is issued to ignite the RS-68 engine.
• At T-minus 3.3 seconds, the engine begins to produce thrust.
• At T-minus 1 second, the RS-68 reaches full power and computers check key parameters to ensure the engine is operating normally.
• At T+plus 0.2 seconds, the engine starts shutting down.
• At T+plus 1.3 seconds, the thrust level reaches zero.

"The sequence that is required for FRF is to get the terminal countdown initiation at 8.5 seconds to engine start commit at 5.5 seconds and roll down to minus 1 second with all the valves in the right place, the right firing and we will call that perfect," Delta 4 Launch Director Joy Bryant said.

"What we really want to do is to prove out that we can send all the commands to the engine and get through that sequence. Anything from minus 1 second to plus 1 second is gravy. We are just going to go through the sequence and then shut it down."

The rocket's two strap-on solid rocket motors won't be able to receive an accidental ignition command. But the command path to the motors will be checked to ensure the start order is sent and received correctly.

"We will have them wired to testers. We will send the command through the cables and receive it and validate it comes at the right time, right place, right command," said Bryant.

Throughout the event, the bottom two swing arms extending from the launch pad's umbilical tower to the rocket's first and second stages will remain attached to the vehicle. But the top arm, which serves the purpose of providing conditioned air to the rocket's satellite payload inside the nose cone, will be swung away. Since the cargo hasn't been mounted to the rocket yet, the arm isn't attached to anything and will be free to move back.

In addition, the tail service masts providing the liquid hydrogen, liquid oxygen and other umbilicals from the ground to the first stage won't be retracted from the base of the rocket.

So what will be seen during the test?

"You will get a full flame as that first wave of the hydrogen comes all the way out," Bryant said, adding that a small fireball around the engine at ignition is normal with the RS-68.

"I would expect some lateral motion but there will be zero vertical motion. But much like when we do just tank ventings we'll get some oscillations in the upper stage."

The rocket will remain firmly bolted to the launch table.

A dust cloud is expected from the flame trench. But since the trench was engineered to suppress the acoustics of launch without the use of a water deluge system, there won't be a massive billowing cloud of steam like the space shuttle FRFs produced. However, there is a mist-like spray of water that is activated at T-minus 2 seconds for engine cooling.

With liftoff just a month away -- currently booked on the Eastern Range for November 16 but could move up to November 14 if a scheduling conflict is cleared -- today's firing will give Boeing a real-life simulation of how the Delta 4, the pad and software will get along on launch day.

Countless earlier tests over the past couple years have proven the various parts of the system. The FRF will put it all together.

"We're ready to go put some fire underneath the rocket out on the launch pad," Collins said.

"We are focused on mission success. This is a test. (It) will give us data and I can, with some confidence, say we are going to learning from this test. That is why we run it.

"When we get the data back, we will go through it. We are essentially all a bunch of engineers and we can't wait to get our hands on the data and see how good our system works. We will make sure that we go through every bit of data that comes out of the test and build towards a successful first launch. It is important. It is part of the incremental building of confidence and reliability in our rocket."

Collins said the rocket and launch pad systems are covered with sensors and data-gathering instruments.

"We got instrumentation all over the rocket and pad to make sure we understand the ignition overpressure, everything that's going on -- the vibration, the acoustic environments -- really to make sure we get first-launch success.

"It will give an enormous amount of data from the ground systems, the vehicle, the RS-68, and the whole integrated system. So that is very important."

After the engine shuts down, drying purges will be started to remove moisture from the power-plant.

Later, post-test inspections will be performed at the pad to ensure the internal workings of the engine came through the firing without damage. Technicians also will torque the engine's turbomachinery to ensure everything rotates freely and reload ignitors for launch.

Watch this page for live updates on today's firing!