I think my mother would have had flashbacks galore over this...

 

I was interested to see that a new unmanned aerial vehicle, or drone, has just flown using pulsejet technology - the same used to power the Nazi V1 flying bomb during World War II.

The pulsejet actually stops and starts many times per second in order to generate thrust, opening a series of valves to let in air and push the exploding fuel out the back of the engine, then shutting them again to detonate the next dollop of fuel.  You'll find a detailed explanation at Wikipedia.  The result is a loud buzzing sound, as the explosions follow each other in very rapid succession.  Here's a recording of a World War II V-1 in flight.

My mother endured months of bombardment by V-1's during 1944.  She said that as long as one heard the engine, one knew one was safe, because it was still flying;  but if it suddenly cut out, one knew it had begun its "death dive" to explode on the ground, and one hunted for cover as fast as possible.

The new pulsejet-powered drone is much smaller than its infamous predecessor, but it's only a prototype.  Future versions will doubtless be much larger and heavier.  However, it still sounds very like the V1.

If my mother was still alive, I wouldn't dare send her a link to that video.  She'd have all sorts of things to say to me (none of them polite) if she heard that sound again . . .

Interestingly, the V1's engine was not powerful enough (i.e. did not generate enough thrust) for the flying bomb to take off under its own power.  It had to be launched up a long ramp using a rocket booster, shown in the first part of the video clip below.

Once airborne, the pulsejet engine produced enough power to keep it flying.  The new drone's engine is much less powerful than the V1's, but the drone itself is much smaller, so it can take off under its own power.  I daresay that by the time they develop it into a production version, the engine will have been scaled up to cope with the additional bulk and weight.

Peter