WASHINGTON -- The early shutdown of the Delta 4 Heavy's propulsion system during the Boeing-built rocket's demonstration launch Tuesday prevented three satellites on board from reaching orbit.

The rocket's main payload, a sensor-equipped dummy satellite called DemoSat, was dropped too low to achieve orbit due to a shorter than expected first stage burn. Also lost were two experimental nanosatellites provided by the U.S. Air Force Research Laboratory.

The Air Force Space & Missiles Systems Center released a statement Wednesday saying that primary objectives of the Delta 4 Heavy demonstration were achieved despite the problems with the rocket's main stage propulsion system. Boeing and the Air Force will spend the next two months reviewing the launch data, according to the statement. Air Force spokesman Joe Davidson could not be reached at his office Dec. 23 and did not immediately return a call placed to his cell phone.

Preliminary analysis indicates that the rocket's two strap-on Common Core Booster burned out and separated several seconds early, forcing the rocket's upper stage engine to compensate for the premature shutdown.

Boeing spokesman Robert Villanueva said that many flight objectives were achieved but stopped short of calling the demonstration a success.

"We do have an outstanding issue we need to work on before our first operational launch next year," Villanueva said Dec. 23.

The Delta 4 Heavy is slated to carry the final Defense Support Program missile launch detection satellite to orbit in August. A classified National Reconnaissance Office payload is scheduled to fly aboard the second operational Delta 4 Heavy launch currently scheduled to liftoff next December.

The 23-story Delta 4 Heavy rocket, a heavy-lift variant of the Delta 4 family, lifted off from its launch pad at Cape Canaveral Air Force Station in Florida on Dec. 21 at 4:50 p.m. (2150 GMT). The flight had been delayed three times this month due to weather and technical glitches.