Gene Middlebrooks had a dream. Working for a defense contractor in Florida making ballistic missiles, he wondered why the technology couldn't somehow be adapted for civilian use, sort of a rocket fuel for the masses idea. He started a now legendary company by the name of Turbonique and designed the mother of all power adders, well, three different versions, actually, a supercharger, a drag axle and a thrust engine, selling them all by mail order. The various versions all required the use of his magic ingredient, Thermolene, or N-propyl-nitrate, which was essentially rocket fuel and they sold it by the drum. Try doing that today! It's a story far too long and exciting to tell here, but the supercharger and drag axle were capable of instantly producing an extra 1000 horsepower or more at the push of a button! Ah, those were the days.
What we have here offered for sale are a pair of Turbonique thrust engines, or more accurately, the combustion chambers, but identified in the Turbonique materials as the "combustor." You'll still need to find, buy or build the rest of the necessary components and then get hold of some Thermolene, though the tech manual says other fuels can be used as a substitute with some modifications to the engine.
The combustor is an integral part of both the supercharger and the microturbine engine, as well as being used as a thrust engine alone. In turbine applications, the exhaust spins a turbine wheel which is geared down for use in the drive mechanism and was the more frequent configuration in comparison to pure thrust applications.
An interesting side note: According to a racer who worked with these turbines, those big exhaust cones often seen in stationary photos of these little engines were strictly for visual effect and were never used in actual operation, since the high temperature of the exhaust gases would melt the aluminum the cones were made of, just one more thing they learned along the way.
To be clear, these are not the complete engines, they are only a part of two engines, in fact, one of the contributing factors to the downfall of Turbonique was the difficulty of building the various pieces. Customers bought what they thought was a ready to build kit, but "some assembly required" was an understatement of considerable proportions.
Middlebrooks eventually found himself in court over what were considered misrepresentations in his advertisements and some other financial problems and afterwards the company went under. He went off the radar and was reportedly running some motel or resort in Florida until his death in 2005. What's interesting is he was brought down by charges of mail fraud, not because of anything to do with the dangers of the Turbonique rocket engines themselves. How times have changed.
How many of these parts still exist is hard to say, but here are two to get you started. They're for sale on eBay.