# Pulsejet > A jet engine that burns in a rapid string of puffs - Date: 1865 - Era: Industrial age - Domain: [Aeronautics](https://lastcodex.org/en/domains/aviation/) - Rebuild stage: V (Electric age) - Difficulty: 4/5 - URL: https://lastcodex.org/en/inventions/pulsejet/ A pulsejet is a jet engine with very few moving parts: a tube in which combustion takes place in a rapid string of puffs, each one driving hot gas out of the rear and pushing the engine forward. The French inventor Charles de Louvrié described such an engine in 1865, and its best-known use was in the German Fi 103 flying bomb of 1944, nicknamed the buzz bomb for its noise. ![Pulsejet · A jet engine that burns in a rapid string of puffs](https://lastcodex.org/_astro/plate.By4EiS9b_9rhzp.webp) ## Legend 1. Air intake grille at the front 2. Head of the tube 3. Long tail pipe 4. Open exhaust at the rear ## What it is A pulsejet is a jet engine that works by intermittent combustion. It is a tube, open at the rear, in which combustion starts again and again in quick succession. Each burst drives a gust of hot gas out of the rear, and the reaction pushes the tube forward. Unlike a turbojet, it has no compressor or turbine, and unlike a ramjet, in which combustion is continuous, it works in pulses. ![A Fi 103 flying bomb on display in a museum hall, hanging on chains from a timber roof truss: a slender body with straight wings and a pulsejet tube mounted above the rear of the fuselage, with the tail fin standing under its rear end, the tube projecting behind the tail; below, three visitors look up beside an information panel](https://lastcodex.org/_astro/v3.DddklHGS_1DIa1.webp) _The Argus pulsejet rides above the tail of a Fi 103 on display in a museum._ Its appeal was its simplicity. A pulsejet could be made cheaply from sheet steel, and it has no rotating parts. Its drawbacks are as marked: it is very loud, it shakes whatever it is mounted on, and the engines of the Second World War were built to last only for a short flight. Because of these limits it saw little use, mostly on pilotless craft. The Argus engine of the German Fi 103 was built in large numbers during the war. At the front a round grille, set back in the wider head of the tube, takes in the air. Behind the head the tube narrows into a long tail pipe that ends in an open exhaust. On the missile the engine was mounted above the rear of the fuselage. A running pulsejet is dangerous to stand near: its noise is extreme, its tube becomes very hot and its exhaust is a flame. Testing such engines is work for specialist test facilities. ## How it works The engine breathes in through the front, burns, and blows out through the rear, in a swift succession of pulses rather than a steady flow. In valved designs, such as the Argus engine, a set of light flaps behind the intake grille lets air in and closes when the burst comes, so that the hot gas can escape only towards the rear. Each pulse throws a mass of gas backwards, and the engine is pushed forward in reaction, as a gun recoils. The pulses follow one another fast enough for the push to feel steady. ![A Fi 103 flying bomb in flight over a countryside of fields and hedges under a grey sky, a short flame and a trail of smoke at the exit of its tube; tiny figures on the ground look up](https://lastcodex.org/_astro/v1.CFZRJYy8_1MGpC1.webp) _People on the ground heard the pulsejet of the Fi 103 long before they saw it._ The pulses are what make the engine so loud. Each one is a small explosion, and the string of them makes a harsh, rasping buzz that can be heard from far away, which earned the Fi 103 its English nicknames of buzz bomb and doodlebug. The same pulses shake the engine and its mounting. In Germany the Argus engine was tried on gliders and other aircraft, and the vibration made it unsuitable for them. On an expendable missile with a flight of about half an hour, roughness and a short life mattered little. A pulsejet can in principle push even when it stands still. In practice the Fi 103's engine worked well only once the missile was already moving fast, so the missile was launched by a catapult or from an aircraft. Pulsejets also work poorly at great heights and high speeds, which is why other engines soon replaced them for most purposes. ## History and evolution In 1863 the French inventor Charles de Louvrié patented a flying machine, the Aéronave, to be driven by a propeller or by the reaction of gas expelled under pressure. In November 1865 he added to the patent a design for a reaction engine: a tube closed at the front by a valve, in which each combustion shut the valve and drove the burnt gases out at the rear. On 9 April 1906 Victor de Karavodine applied in Paris for a patent on a pulsejet, which was granted in 1907. Its title calls the device a generator of explosion gases with a pulsating jet. In 1909 the inventor Georges Marconnet patented a similar device, which he meant for aeroplanes and airships. Over the following years the French engineer René Lorin published proposals for jet-propelled pilotless aircraft driven by pulsating or continuous combustion. In Germany the engineer Paul Schmidt patented a pulsejet in 1931. In 1939 the German Air Ministry started a second programme at the engine firm Argus in Berlin under Fritz Gosslau, whose team adopted Schmidt's flap valves. The Argus engine was then chosen to power the Fi 103 flying bomb, an Argus and Fieseler project begun in 1942. From June 1944 and into 1945 thousands of these missiles were launched against London, Antwerp and other targets, killing and injuring many civilians. Air defences brought down many of them, and their inaccuracy limited what they could achieve. ![The small XH-26 Jet Jeep helicopter of the 1950s in a low hover over grassland: a glazed single-seat cockpit with its pilot, a two-bladed rotor carrying at the tip of each blade a small pulsejet tube set crosswise to the blade in the plane of the rotor, the left one pointing its glowing exit towards the viewer and the right one facing away, a small two-bladed tail rotor with a round weight beside its hub, and skids](https://lastcodex.org/_astro/v2.QxOb1Qw3_ZcY3dF.webp) _The XH-26 Jet Jeep spun its rotor with pulsejets at the blade tips, so it needed no engine or transmission in the fuselage._ After the war the pulsejet was used for some years as a cheap power plant for target drones and subsonic missiles in the United States and other countries, until faster and higher-flying craft made it obsolete. It also found an unusual use on helicopters. In the early 1950s the American Helicopter Company built the XH-26 Jet Jeep for the US Army and Air Force, a small observation helicopter with a pulsejet at the tip of each rotor blade. The jets spun the rotor directly, so the craft needed no engine or transmission in its body. The prototypes flew, but they were extremely loud and could not stay up long, and the Army abandoned the type. ## Key facts - Charles de Louvrié's design: Addition of November 1865 to his French patent of 1863 - Karavodine's patent: Victor de Karavodine, French patent applied for on 9 April 1906 - Best-known pulsejet: Argus engine of the Fi 103 flying bomb, Second World War - Nickname of the Fi 103: Buzz bomb, from the noise of its pulsejet - Pulsejet helicopter: American Helicopter XH-26 Jet Jeep, early 1950s, with pulsejets at the rotor-blade tips ## Requires - [Steel](https://lastcodex.org/en/inventions/steel/): Iron with just enough carbon (c. 1,000 BCE) ## Sources - [L'invention du premier réacteur par Charles de Louvrié (patent 60 712 of 3 November 1863 for the Aéronave; third certificate of addition of 4 November 1865 describing a pulsating combustion tube closed at the front by an automatic valve), Lettre 3AF no. 50, January 2022, pp. 102-105](https://charlesdelouvrie.fr/AACDL_documents/AACDL_lettre-3af-Charles%20de%20Louvri%C3%A9.pdf), Gérard Pujol, Association aéronautique et astronautique de France (3AF) - [V1, arme du désespoir, Collection Histoire de l'Aviation no. 29 (Lela Presse, 2011), p. 23: de Louvrié's third improvement memoir of 3 November 1865 describing a "propulseur-réacteur" with a front valve and rear exhaust; Karavodine patent of 1907; Marconnet 1909](https://www.aircraft-navalship.com/uploads/attachment/produit/produit_1570_078e099b449665c9b894f96924106d9b.pdf), Yannick Delefosse, Lela Presse (extract) - [Propulsion aéronautique: la propulsion à réaction (first patent describing a jet propulsion system attributed to Charles de Louvrié; Aéronave presented to the Académie des sciences in 1863)](https://www.universalis.fr/encyclopedie/propulsion-aeronautique/2-la-propulsion-a-reaction/), Jean Calmon, Encyclopædia Universalis - [Progress in Flying Machines (de Louvrié's proposal of 1863, driven by a screw or by the reaction of an explosive substance), The Railroad and Engineering Journal, September 1892](https://invention.psychology.msstate.edu/i/Chanute/library/Prog_Aero_Sep1892.html), Octave Chanute, via Mississippi State University - [The Defence of the United Kingdom, chapter XXIII: The Flying Bomb, Part One (B. Collier, HMSO, 1957)](https://www.ibiblio.org/hyperwar/UN/UK/UK-Defence-UK/UK-DefenseOfUK-23.html), HyperWar Foundation - [FR374124A: Générateur de gaz d'explosion à jet pulsatoire](https://patents.google.com/patent/FR374124A/fr), Google Patents - [DE523655C: Verfahren zum Erzeugen von Antriebskräften (Reaktionskräften) an Luftfahrzeugen (German patent no. 523 655, filed 24 April 1930, published 1931; Schmidt's pulsejet patent per the Smithsonian NASM record)](https://patents.google.com/patent/DE523655C/de), Google Patents - [Missile, Cruise, V-1 (Fi 103, FZG 76) (Karavodine 1906/1907; Schmidt patent no. 523 655 of 1931; Argus 1939)](https://www.si.edu/object/missile-cruise-v-1-fi-103-fzg-76:nasm_A19600341000), Smithsonian National Air and Space Museum - [Fieseler Fi 103 "V1"](https://www.museumofflight.org/aircraft/fieseler-fi-103-v1), The Museum of Flight - [Museum's XH-26 provides view into Aviation experimentation](https://www.army.mil/article/199046/museums_xh_26_provides_view_into_aviation_experimentation), U.S. Army - [XH-26 Jet Jeep (two pulse jets at the ends of the two main rotor blades, 1-bladed counter-weighted tail rotor, no engine or transmission)](https://www.armyaviationmuseum.org/get-involved/restoration/), Army Aviation Museum - [American Helicopter XH-26 Jet Jeep (narrow pyramidal cockpit with four large windows at the front, sides and rear)](https://aviationsmilitaires.net/v3/kb/aircraft/show/1509/american-helicopter-xh-26-jet-jeep), Aviationsmilitaires.net - [The Jet Jeep (XH-26 with a plexiglass cockpit, five prototypes evaluated by the Army and Air Force), Vertical, vol. 19, no. 2 (2020)](https://assets.verticalmag.com/digital/2020/V19I2/V19I2-LOW.pdf), Vertical Magazine, MHM Publishing Fact-checked on 2026-10-21. --- The Last Codex · https://lastcodex.org/en/inventions/pulsejet/ · © The Last Codex. 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