Fascinating article, I wish they could publish some design examples. I would love to see some examples of clockwork mechanisms operating in a 500° C oven, a temperature where the blackbody radiation coming off the structure will almost* be visible to the human eye. Even just finding lubricants that can last in that environment without slowly degrading the metals they're there to protect is probably a struggle.
*the threshold is 524° C, it's close but not quite there
I'm sure if you email them, they can direct you to the reports. The are usually hosted on the NIAC site, but there was some dustup over accessibility concerns, I think.
Tbc, if the structure is at the same temperature as its surroundings (which is the point of these proposals -- no refrigeration required), then this radiation cannot be used to visually distinguish the structure from its surroundings. The reason is that all blackbody radiation is the same, regardless of the surface it's coming off of. The inside of every closed and equilibrated oven looks identical, regardless of shape and contents: a uniform glow in all directions.
In other words, if there was a human down on the surface who could somehow survive and look around from a nuclear-powered refrigerated spacesuit, they would only be able to distinguish the robot structure by the radiation it was reflecting/emitting other than the blackbody radiation associated with the ambient temperature.
*the threshold is 524° C, it's close but not quite there