Robert Maddox goes by the nickname Rocketman, and it's not because he's an astronaut or really loves the classic Elton John song. Maddox builds pulsejet engines and installs them in motorcycles and go-karts. In this video, he and a buddy take two of these wild machines for a high-speed blast through a dry lake bed.

Both machines are something to behold. The rider straddles the blue one like a motorcycle, but it has four wheels. A massive exhaust chimney sticks up from the back. The red kart has three stacked pulsejets that make the vehicle look like something out of a cartoon. reached out to Maddox for more details about these builds. The blue vehicle uses his Maddoxjets 250-pound-thrust pulsejet engine running on petrol. It has a reed valve that allows air into the combustion chamber but closes off during the explosion. "The valved engine requires a lot of air blown in it to start it, and a big leaf blower is easier to use in the field than compressed air," Maddox told us.

The red kart uses a valve-less design that has no moving parts. It makes a total of 150 pounds (68 kilograms) of thrust from the three pipes. "If I made a single engine that made 150 pounds of thrust, the engine would be way too large to fit on a kart," he said.

This vehicle uses liquid propane to get started and then runs on diesel. It's "my own fuel injection that I should patent," Maddox said. "Diesel has more power than the propane and runs cooler and is easy to just pour into a fuel tank, so I use both because I can run longer without filling the propane tank, which is a pain." 

The video above provides an idea of how Maddox constructs these pulsejet engines because he's assembling a larger one for his red kart. He uses a waterjet cutter to create each of the components. Then, he rolls them into tubes and welds everything together.

If you really want to get into the science behind pulsejets, check out this senior project by California Polytechnic State University students. They created a design using a dual intake and a single exhaust.