The free piston stirling engines required also operate via magic and few people understand them well enough to make one suitable for this purpose. The engines required for a reactor like this haven’t been designed yet and it would take years of effort before They would be designed and approved for flight use.
For this test they used a couple of undersized (<100W) stirling engines and the rest were just thermal simulators.
Stirling Engines exceed their competition by percentage points. Nuclear energy exceeds its competition by orders of magnitude. I stand by my statement that the magic comes from the nuclear half of this relationship -- so long as we accept a definition of magic related to, you know, energy production, rather than effort or hipster points.
