This is one of the coolest demonstrations ever: NASA's new Common Extensible Cryogenic Engine for the lunar lander gets icicles on its rim while burning at 2760 degrees Celcius. How is this stunning feat possible?
The CECE—developed by Pratt & Whitney Rocketdyne and NASA—is fuelled by liquid oxygen and liquid hydrogen. All the engine components are super-cooled, so when vapour comes out of the burning of the oxygen and the hydrogen and touches the rim of the cryogenic engine, it transforms into ice instantly.
The engine architecture allows it to smoothly throttle from top power levels—it was tested up to 108 percent—down to very-low power: 8 percent, which apparently is a new record in these kind of engines. Its performance allows it to smoothly land on the Moon while carrying a bigger load. [Pratt & Whitney via Universe Today]