BETA
This is a BETA experience. You may opt-out by clicking here

More From Forbes

Edit Story

Why Doesn't The Military Use Pulse Jet Engines?

Following
This article is more than 7 years old.

Why isn't the pulse jet used in military applications? originally appeared on Quora - the knowledge sharing network where compelling questions are answered by people with unique insights.

Answer by Tom Farrier, retired USAF command pilot; expert in aviation safety, on Quora:

A pulse jet is as inefficient as the dickens in comparison with internal combustion or turbine engines, although a good one can squeeze a lot of flying out of its fuel load. It's also incredibly loud (the reason why V-1s were referred to as "buzz bombs").

I've seen conflicting information and opinions regarding a pulse jet's "efficiency" -- different people look at that term through different prisms. If you get one fired up, it'll burn pretty much every drop of consumable fuel available to it, which means it's "efficient" at obtaining and delivering as much energy as possible from what it's been fed. However, since pulse jets are a pretty much straight conversion of fuel into thrust (and noise), you don't have the ability to meter it very well ... it's on, or it's off.

Also, there are two products of pulse jet operation (three counting noise): thrust and heat. The heat is evidence that a lot of energy is being wasted. Add to that the difficulty of getting one started (and the need to get the heck out of its way once you do), and you can see that they really aren't worth investing in by any military forces with access to better options.

Of course, pulse jets do have a few virtues. They're extremely simple and cheap to build, and the flip side of their inefficiency from a fuel consumption perspective is that they can sustain ignition on almost any kind of petroleum-based or biofuel you'd care to name. So, from time to time, various designers and entrepreneurs look for ways of improving on the basic concept. Here's a link to a pretty well-written exploration of that general topic: Increasing Pulsejet Efficiency.

This question originally appeared on Quora - the knowledge sharing network where compelling questions are answered by people with unique insights. You can follow Quora on Twitter, Facebook, and Google+. More questions:​