Three vintage bipropellant engines from the space race. Each of them was used for maneuvering in space, and each has a simple solenoid valve assembly, which allows the fuel and oxidizer to spray into the combustion chamber. These particularly noxious hypergolic chemicals have the valuable property that they ignite spontaneously upon contact, in a vacuum, with no spark required.
From left to right:
• Gemini SE-6, provided attitude and maneuvering control for the Gemini spacecraft. Pitch, roll, and yaw torques were obtained by firing these engines in pairs. Sixteen SE-6 engines made up the Reentry Control System (RCS) in the nose of the Gemini spacecraft. Made of steel and an ablative nozzle by Rocketdyne, these engines produced 25 pounds of thrust.
• Apollo Command Module SE-8: A set of 12 of these Rocketdyne RCS engines provided the Command Module with rotation control, rate damping, and attitude control after separation from the Service Module and during re-entry. The engine has had several test firings. Described in detail when it first arrived. 93 lbs. of thrust.
• Apollo Lunar Module R-4D: The most difficult to find, clusters of four of these engines were an iconic external feature of the Lunar Module and Service Module. I’ll post some photos below from the moon. This one is still fully functional and came directly from the manufacturer (Marquardt Corp.), where it was test fired. Molybdenum nozzle, radiation cooled, 100 lbs of thrust. Part Number 228686-501. Test fired four times in Apollo LM testing. I posted a detailed writeup on this particular R4D, and some pretty pictures, in the comments below
The fuels are similar, but the valves become more complex for the main Lunar Module Descent Engine and Ascent Engine.
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