Pratt & Whitney Rocketdyne, of West Palm Beach, Florida has successfully completed the third round of its Common Extensible Cryogenic Engine (CECE) testing for the National Aeronautics and Space Administration (NASA). CECE is a new deep throttling engine designed to reduce thrust and allow a spacecraft to land gently on the moon, Mars, or some other non-terrestrial surface.

The CECE engine is being designed under a joint development project involving Pratt & Whitney Rocketdyne, NASA’s Marshall Space Flight Center in Huntsville, Alabama, and NASA’s Glenn Research Center in Cleveland, Ohio. It’s based on the existing Pratt & Whitney Rocketdyne RL10 upper stage rocket engine and uses a combination of liquid oxygen and liquid hydrogen to generate 13,800 pounds of thrust.

The liquid oxygen is used at about 90 degrees Kelvin (approximately -297 degrees Fahrenheit) and the liquid hydrogen at 20 degrees Kelvin (approximately -423 degrees Fahrenheit). The two propellants super cool the engine components and generate a gas made of hot steam that’s pushed out of the nozzle to create the thrust. As the steam passes through the cold nozzle, condensation occurs and the resulting water eventually freezes into icicles as it exits.

This third round of testing throttled the engine from 104 percent of its expected potential thrust down to 8 percent. This is a record for an engine of this type and beats the expected 100 percent to 10 percent change.

Previous testing induced chugging, or pressure oscillations, at lower levels of throttling. Careful adjustments of the injector and propellant feeding systems to better control the flow of the liquid oxygen and liquid hydrogen into the engine have eliminated the chugging in the latest tests.

The CECE engine is expected to be a prototype design rather than an engine actually used in spaceflight. However, NASA expects the technology used to solve problems with CECE will be incorporated into another cryogenic engine and eventually used in the Altair Lunar Lander that’s part of the current Constellation program . Thus, CECE represents an important step in the lunar lander design.