WASHINGTON — Having had more than two weeks to analyze data from the shaky debut of Boeing Co.’s Delta 4 heavy-lift rocket, U.S. Air Force officials remain confident that the vehicle will be able to successfully launch two critical national security satellites later this year.

The first of those payloads is the only remaining satellite of the Air Force’s Defense Support Program (DSP) missile-warning system, whose replacement is already about six years behind schedule. The second is owned by the U.S. National Reconnaissance Office (NRO), which buys and operates the nation’s spy satellites.

Officials with both organizations reiterated their trust in the Delta 4 Heavy despite the fact that the vehicle failed to place its payload into a sustainable orbit in a Dec. 21 demonstration launch from Cape Canaveral Air Force Station, Fla. After the launch, Boeing and the Air Force issued press releases declaring success, with the Air Force asserting that it had no plans to conduct a second demonstration flight.

Maj. Karen Finn, a spokeswoman for the Air Force, said Jan. 7 the service is sticking with its plan to launch the DSP satellite on a Delta 4 Heavy . That mission currently is scheduled for September.

NRO spokesman Art Haubold likewise said Jan. 6 plans to launch a classified satellite aboard a Delta 4 Heavy in December are unchanged. “The Air Force did the demonstration launch so that Boeing could get the lessons learned and determine what issues they would have to work before launching our satellite, and I think they are doing that,” he said.

But some analysts and congressional staffers suggested that the Air Force should take time and review its options before going forward with the missions.

If analysis of the post-flight telemetry indicates that a relatively minor software glitch caused the main-stage propulsion system of the rocket to shut down early, that’s one thing, said Phil McAlister, program manager for the space and telecommunications analysis unit at Futron Corp. of Bethesda, Md. But if the analysis turns up something more significant, the Air Force should consider another test flight, he said.

Several congressional sources concurred, noting that a loss of the final DSP satellite would raise the possibility of a gap in the nation’s missile warning capability in the years ahead. In fact, the Defense Appropriations Act for 2005, which was signed into law in August directs the Air Force to conduct an analysis of the current and projected health of the DSP system in light of repeated delays to the follow-on Space Based Infrared System High.

Conducting a second Delta 4 Heavy demonstration would make it difficult if not impossible to keep the DSP and NRO missions on schedule, although the Air Force does have a potential alternative in the case of the missile warning satellite. Just over a year ago, the Air Force asked Boeing rival Lockheed Martin Corp. to determine whether its Atlas 5 rocket might be able to handle the DSP mission if there were a problem on the Delta 4 Heavy demonstration, according to Julie Andrews, a spokeswoman for Bethesda, Md.-based Lockheed Martin.

Like the Delta 4, the Atlas 5 was developed under the Air Force’s Evolved Expendable Launch Vehicle program. Although there are no firm plans to date for a heavy-lift Atlas 5, a medium-lift variant of the vehicle that has already flown twice could do the DSP job, Andrews said.

Lockheed Martin believes it can launch the satellite aboard its Atlas 5 521 variant, which includes a 5.4-meter payload fairing and two solid-fuel strap-on boosters, Andrews said. That vehicle launched a commercial communications satellite in December 2004 and in 2003, she said.

Andrews said it would take at least six months to make an Atlas 5 521 available in general, but declined to be specific about how long it might take to produce one for a DSP mission.

Andrews also said Lockheed Martin, at the Pentagon’s request, evaluated using the Atlas 5 to launch the NRO satellite, but concluded that a heavy-lift version of the vehicle would be needed. It would take roughly 30 months to produce a heavy-lift Atlas 5, she said.

Finn said the Air Force is not looking at alternatives to the Delta 4 Heavy at this time.

The Air Force is still in the early stages of a planned two-month demonstration mission review that includes engineers from Boeing, based in Chicago, and The Aerospace Corp. of El Segundo, Calif. In a press release issued Jan. 7, the Air Force shed no new light on why the rocket’s core-stage boosters shut down prematurely but reiterated its belief that the issue will be resolved in time for the rocket’s first operational flight.

The heavy-lift variant of the Delta 4 consists of three core-stage boosters, each powered by a Boeing-developed RS-68 engine, in a side-by-side configuration. The center core is topped with a second stage powered by a Pratt & Whitney-supplied RL10 engine, whose job is to take the payload on the last leg of its journey to the designated orbit.

The Air Force press release said the three core boosters shut down before they were able to propel the vehicle to its designated velocity but had sufficient fuel on board to have done so. The RL10 compensated properly, firing for a record total of 1,115 seconds in three burns, but ran out of fuel before it could achieve the velocity required to put the payload into the proper orbit, the press release said.

The Delta 4 Heavy was carrying an instrumented test payload and a pair of university-built nano-satellites, and dropped them off in an orbit that was not high enough to be sustained. The press release made no mention of where they wound up.

The RS-68 engines performed as designed, and aside from their premature shutdown all aspects of the six-hour mission went as planned, the Air Force said.

“The overall purpose of this mission was to demonstrate the capability of the Delta 4 Heavy ground and flight systems,” Col. John Insprucker, the Air Force’s Evolved Expendable Launch Vehicle program director, said in a prepared statement. “The mission profiles were selected to stress the system and reduce the risk to flying an operational mission. This is as close as space systems come to a flight test.”

The press release concluded by saying that given the “repetitive nature of the anomaly on all three common booster cores” the Delta 4 team is confident the issue “will be resolved prior to an operational heavy mission.”

In a telephone interview Dec. 23, Boeing spokesman Robert Villanueva said many of the Delta 4 Heavy flight demonstration objectives were achieved but stopped short of calling the mission a success. “We do have an outstanding issue we need to work on before our first operational launch next year,” he said.

Villanueva said that Boeing officials were unavailable for additional comment.

Comments: jsinger@space.com