Pulsejets use the forward speed of the engine and the inlet shape to compress the incoming air,
then shutters at the inlet close while fuel is ignited in the combustion chamber and the
pressure of the expanding gasses force the jet forward. The shutters then open and the process
starts again at a high frequency. This results in the buzzing drone for which the experimental
pulsejet missile is named the "BuzzBomb". People have pointed out that pulsejets can be cooled
which would solve the heating problem of the ramjets. They could also, theoretically, generate
"donut-on-a-rope" contrails due to the engine's
operational design.
The known advantages of the Pulsejet engine are:
- Theoretically it has a higher fuel efficency than a normal engine that keeps constant
pressure.
- Engines can be produced in many sizes with many different thrust ouputs ranging from a few
pounds to thousands of pounds.
- They have a very high thrust-to-weight ratio, which means a lighter engine producing more
pounds of thrust than it's weight.
- They are mechanically very simple and have very little moving parts.
- They do not depend on the oxygen in the atmosphere to provide as an oxidizer, which means it
could go in or out of the atmosphere.