Steam and smoke billows around the second Delta 3 moments before liftoff last May at Cape Canaveral's pad 17B. Photo: Boeing

Boeing's new, more powerful Delta 3 rocket is ready for its third attempt at launching a satellite into space now that engine trouble which doomed the last flight a year ago has been fixed, officials said this week.

But when that launch will occur is not yet clear, nor has it been decided if the rocket will carry a paying customer or just a dummy satellite.

The Delta 3 is capable of lifting twice the payload weight as the older Delta 2 vehicle, allowing the new booster to enter the lucrative commercial satellite launch market. However, Delta 3 has failed in its first two launches in August 1998 and May 1999.

The first malfunction was related to a guidance software error that ultimately caused the rocket's steering system to run out of hydraulic fluid. The two-stage rocket lost control and exploded 72 seconds into flight.

The second try made it to space but the RL-10B2 liquid-fueled second engine, built by Pratt & Whitney of West Palm Beach, Fla., exploded due to faulty manufacturing of the powerplant's combustion chamber. The Asian telecommunications satellite carried by the rocket was released into space, but in a worthless orbit.

On Tuesday, Boeing told members of the satellite industry that the Delta 3 rocket was ready to resume operations at the end of this month, having completed a major engine test recently at Pratt.

"The final test looked at the stresses and temperatures the engine experiences at ignition under worst-case conditions," said Dave Crosse, leader of Boeing's Delta 3 return-to-flight effort. "The engine, with a new combustion chamber, passed with flying colors."

Extensive testing and analysis ruled out the possibility that the predicted structural loads the engine would experience in flight were wrong, thus clearing the modeling as a potential cause last May's failure.

Boeing says Pratt & Whitney has refined its process for building the RL-10B2 combustion chambers, as well as the methods employed to check the quality of each chamber, including using ultrasonic inspection techniques.

Pratt & Whitney has produced 16 "near-perfect" RL-10 combustion chambers for both Lockheed Martin's Atlas and Delta programs to date. Atlas rockets' Centaur upper stages use an older version of the RL-10 engine.

An RL-10B2 upper stage engine like the one used on Delta 3. Photo: Pratt & Whitney

The hour-glass-shaped combustion chamber is comprised of four sections with strengthener strips brazed, or soldered, over the seams.

A 67-square-inch, diamond-shaped breach of its combustion chamber during the failed launch last May was caused by a rupture at a reinforcement strip.

The brazing technique used to attach the strips, started in 1997, was found to be faulty during the subsequent failure investigation because it could leave voids, or gaps, that make the joints weakened and susceptible to breaking from the stresses of launch.

The investigation found inspection records of the failed engine that indicated the quality of the brazing by Pratt did not meet requirements.

However, Pratt & Whitney workers did not recognize there was a problem because of poor translation of brazing coverage requirements from design engineers to the screening criteria used by quality inspectors.

Boeing and Pratt & Whitney engineers have successfully completed acceptance testing on the RL-10B2 engine that will be used in the return-to-flight launch. That powerplant has been already mounted to the Delta 3's second stage at Cape Canaveral Air Force Station and is ready for launch, Boeing said.

Company officials acknowledge they are in discussions with a potential commercial customer that would use the next Delta 3 rocket, launching sometime later this summer.

The next firm Delta 3 flight is not scheduled until October 5 to place a satellite into orbit for the ICO mobile communications system.

Under pressure to demonstrate the Delta 3 is reliable, including the second stage and RL-10B2 to be used on the next generation Delta 4, Boeing is also considering flying the rocket with a dummy payload in the next few months if a commercial satellite is not found soon.

The company, however, would eat the $85 million cost of the launch if satellite mockup is flown.