By “native engines” we refer to engines made strictly from Lunar materials.   These are engines that produce mechanical motion.  Native production of rocket motor propellants, and of rocket motors will be handled separately.

Native engines implies implies solar powered.  Possible variations are:

• Steam engines
• Stirling (air cycle) engines
• Solid expansion and contraction engines

Stirling engines, or engines that create mechanical force by simply heating up air and using it to move a piston, predate steam engines.

 

They were used in industry, but steam engines were far more powerful and practical.  Just as internal combustion engines were far better than steam engines.

But in Lunar applications, things may be different.  The gravity is six times less, implying that something like six times less energy is needed to move a rover around or power a machine.  And the solar energy is four times stronger on the Lunar surface.

 

 

Curiosity – 1.5 inches per second – 145 meters/hour

Lunokhod – 2,000 meters/hour

Apollo LRV – >18,000 meters/hour

The high speed of the Apollo rover was to assist in getting as much done as possible by the humans during their limited stay time (max 72 hours).

The Stirling engine may be presumed to be dependent on a temperature difference, which in turn would limit it’s utility in certain Lunar conditions, times and places.  At the Equator at “lunar high noon”, there are no shadows, therefore there are no natural temperature differences.   More precisely, within 20 degrees of latitude of the Equator and for two or three days before and after high lunar noon, these conditions exist.