"Everyman's Jet Engine" - Why  Valveless  Pulsejets? An "impractical" engine? In 2007, I sent an audio recording describing the valveless pulsejet hobby to National Public Radio's "Soundclips" project. While NPR's Art Silverman did a superb job of editing this into a usable two-minute audio clip (aired on NPR on October 2, 2007), whoever did the text for the online access page decided to give it the title Sounds from an Impractical Homemade Engine! (You can find it here: NPR Soundclips - click on "Listen now" to hear the audio clip exactly as it was aired, right after a little promotional blurb.) Most people you talk to about propulsion systems either don't know about valveless pulsejets or will simply offer the opinion that no such engine can exist (without bothering to do any research or seriously think about the possibilities, of course). The few who have given these engines due consideration will generally point out some honestly felt objections: Valveless pulsejets are awkward and bulky; the radiated heat is a big problem; the high noise level makes them undesirable; the engines are hard to start; throttling capability is limited. However, most of these objections will apply equally to ordinary valved pulsejets, and the claims of hard starting and throttling problems are basically just not true for well-designed and well-built engines (or show up as temporary setbacks just because careful engine tuning hasn't been accomplished). But, as with most all-negative appraisals, these claims don't begin to tell the whole story. Decide for yourself if you think anyone should be interested in engines with characteristics like these: Light weight Very low materials and construction cost Reasonable thrust/weight ratio Reasonable fuel consumption at low subsonic airspeeds Reasonable throttleability Instantaneous throttle response Built without any use of exotic materials No moving parts of any kind Built without machining of any kind No replaceable parts except fuel nozzle (and optionally, spark plug) No lubrication of any kind needed No ignition system needed after startup All-weather operation without special care or modifications Immediately ready to run even after being completely flooded with water Essentially zero maintenance for continued operation over its useful life With fuel nozzle replacement, can be set up for almost any known combustible fuel Extremely easy to repair if damaged Does that sound to you like an engine that's too "impractical" to use? (Ha! I didn't think so.) Go back to select another topic     Larry Cottrill Director of Product Development Cottrill Cyclodyne Corporation Questions? Comments? email larrycottrill@cottrillcyclodyne.com