The engine, known to NASA engineers as No. F-6049, was supposed to help propel Apollo 11 into orbit in 1969, when NASA sent Neil Armstrong and two other astronauts to the moon for the first time.

The flight went off without a hitch, but no thanks to the engine it was grounded because of a glitch during a test in Mississippi and later sent to the Smithsonian Institution, where it sat for years.

Now, young engineers who weren't even born when Armstrong took his one small step are using the bell-shaped motor in tests to determine if technology from Apollo's reliable Saturn V design can be improved for the next generation of US missions back to the moon and beyond by the 2020s.

They're learning to work with technical systems and propellants not used since before the start of the space shuttle program, which first launched in 1981.

Nick Case, 27, and other engineers at NASA's Marshall Space Flight Center on Thursday completed a series of 11 test-firings of the F-6049's gas generator, a jet-like rocket which produces 30,000 pounds (13,600 kilograms) of thrust and was used as a starter for the engine. They are trying to see whether a second-generation version of the Apollo engine could produce even more thrust and be operated with a throttle for deep-space exploration.