Boeing is planning to run a crucial Delta 4 countdown test this week to check ground software, which officials hope will clear the way for a dramatic engine firing on the launch pad early next month.

Aerial view of Delta 4 rocket on pad 37B. Photo: Boeing

Late last month, during the first full-up countdown simulation known as a Wet Dress Rehearsal, engineers uncovered trouble with software designed to automate some activities during the countdown.

Debugging of that software has been completed and officials want to prove the problems are fixed by conducting a "tanking test" in which the rocket is fully fueled at Cape Canaveral's Complex 37B. Boeing had initially envisioned performing that test a week-and-a-half ago but new concerns were raised with the timing of computer software.

"We have resolved all of problems on the automation," Delta 4 Launch Director Joy Bryant said in an interview Friday. "And in our last validation in front of the tanking test we said 'you know, I'm not sure about this timing.' So we decided to be a little bit more cautious and work on it...and push off the tanking test."

Officials say they will take as much time as necessary to correct any glitches to ensure the Delta 4 rocket is successful on its maiden voyage. The new rocket was developed as part of the Air Force's Evolved Expendable Launch Vehicle program aimed at affordable and reliable access to space.

"We had multiple issues and we were ticking those and we resolved all of those. The residual one is this timing. We want the guys to go look at it and validate that they are comfortable with the timing sequence," Bryant said. "I want to make sure they are happy before we move forward."

Bryant said various contractors have been looking at their ground systems to see what is causing latency in the software timing.

"One of the routines that we do is to monitor engine position. The sample rate for monitoring that engine position was up around 300 samples per second -- extremely high. It doesn't need to be that high. And the timing of all of those samples being handled by the ground system is slowing down the latency of that sub-routine such that its timing is longer than we expected," Bryant explained in citing an example of the timing issue.

Officials considered running the tanking test over the weekend but instead opted to shuffle the schedule of activities and slip the event a few more days to give technicians a chance to rest up.

"It's been slow but we are seeing good results. We were setting up to do a tanking test this weekend, having resolved two of those timing issues and I'm still comfortable that we've resolved those. But we've got a tired set of ground engineers," Bryant said.

"What we decided to do is pull (some engine firing preparations) to the left in the schedule, those things that we can do ahead of time such as ordnance installation, loading up our software for the vehicle, stuff that needs to be done and we had sequenced later.

"That will allow the software guys for the ground system to take a deep breath, look at all their data, their sequences, look at the configuration that they are in and make sure that they're happy going into the tanking test."

The tanking test could happen around the middle of this week.

The engine test, called the Flight Readiness Firing, is now expected to occur after the planned October 2 space shuttle launch. Both the FRF and shuttle liftoff require support from the Air Force-controlled Eastern Range, which needs time to reconfigure its systems from one event to the next.

The five-second engine firing is planned to show the computer software governing the final seconds of the countdown will work properly with the rocket and ground equipment. The liquid hydrogen/liquid oxygen-fed RS-68 engine, which has never flown before, will be ignited and build to 100 percent thrust before shutting down.

For now, Delta 4 remains slated for launch on November 3. Whether that date will hold will depend on how well activities proceed through the engine firing, Bryant said.

"We are burning our contingency time...By the time we get to FRF we will have done all of the procedures that go between FRF and launch. So we will be well practiced in each of those and we will have a good feel how much contingency time we should put in the schedule and how much we need.

"Right now I am comfortable that can meet the 3rd (of November)...But if we continue to be concerned with timing or if we have longer refurb after FRF, any of those things would tell me I need to put more contingency time in. There is not enough for significant impacts with FRF."

The inaugural Delta 4 flight will carry a commercial telecommunications satellite into orbit for Paris-based operator Eutelsat. The craft has arrived in Florida to begin its launch campaign.

The launch window on November 3 extends from 5:34 to 6:38 p.m. EST (2234-2338 GMT).