One of the second stage engines on the Saturn V rocket at Johnson Space Center in Houston, Texas.
Five Rocketdyne J-2 engines, powered by liquid hydrogen and liquid oxygen powered the second stage of the rocket. They had the unusual (at the time) property of being designed to allow them to be stopped and restarted once during use. The engine was used during ascent then stopped for a time and restarted to power trans-lunar insertion.
I like your placement of the repetitive circular elements Dave. Really nice shot.
Great capture and processing, Dave. I love techno/mechanical images like this.