I was reading about Stirling Generators having potential applications for power generation in outer space. Have Stirling engines ever been sent into space?
Stirling Engine powered refrigeration units were first tested on STS-60 (on this trip the astronauts had ice-cream)
Have a look at this document from Sunpower for more information.
Now, I see the link you have is more around the use of Stirling Engines to provide high levels of output power from the heating from radioisotopes, but the principle is the same.