I made these for Ultra Safe Nuclear’s website. It’s a relatively simple process of exploding the parts in the right order with the right natural motion and coordination so that things just snap into place.
This shows the component hierarchy of the Micro Modular Reactor starting with the large pressure vessels, to the fuel blocks and cylindrical fuel pellets, and finally down to the tiny millimeter-sized spherical fuel particles.
Nuclear Thermal Propulsion (NTP) is one of those sci-fi technologies that has been previously demonstrated by a previous more advanced civilization than our own - the USA from the 1960s. This particular NTP is the one pursued by USNC which uses low enriched uranium and has remarkably low mass.