This site describes a matchbox sized gas turbine capable of producing 100W at 500,000rpm. It says that it could be used in dental drills or portable heart-lung machines.

Sounds interesting.

500,000 RPM for ten hours at a stretch? That's impressive! Nice bearings, at least.

Hope you're having an enjoyable long weekend, Jonathan. And regards to your Dad.

Your link reminds me of the alternator turbines in Vickers Vigilant anti-tank missiles. Made in the mid 1950's, if I remember rightly. As the missile fired up, a mere puff of the gases was squirted onto the turbine, which spun sufficiently to power the electronics for the duration of the flight (about 12.5 seconds). You could hear the "puff" and the turbine run up just before the the missile flew (crawled) out of its box (the "container-launcher" ... man-portable, by two blokes that is). Those were the days!

Meanwhile, I didn't realise that Sir Clive had been talking to NASA.