English: An RS-68 engine undergoing hot-fire testing at NASA's Stennis Space Center during its developmental phase. RS-68 being tested at NASA's Stennis Space Center. The nearly transparent exhaust is due to this engine's exhaust being mostly superheated steam (water vapor from its propellants, hydrogen and oxygen)
The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use. [2]
An RS-68 engine undergoing hot-fire testing at NASA's Stennis Space Center during its developmental phase. '''Source''': http://www.nasa.gov/images/content/148709main_d4_testing_08.jpg