I met a guy at an airport here in SOCAL few years ago who was kinda an
expert on pulse jets. I ws skeptical so he shoed me into his hangar and
sre enough amog his other treasures were pulse jets in various sizes.
The largest one was about 6 feet long and was made of some exotic metal
he had imported from germany.
His experiments mostly led to meltdowns until he got this metal. He and
a friend
actually took one of the 3 foot size and mounted it to a gokart and
tethered it to a post with a cable. His buddy climbed in and ran a few
fast laps until the valve melted.
He had also built an electric car most out of wood and the most
beautiful 7 cylinder radial model engine I have ever seen. .
No airplane in that hangar so he rarely opened it for fear of losing his
lease