3D Printed Pulsejet Uses Tesla Valve

For most people, a jet is a jet. But there are several different kinds of jet engines, depending on how they operate. You frequently hear about ramjets, scramjets, and even turbojets. But there is another kind — a very old kind — called a pulsejet. [Integza] shows how he made one using 3D printed parts and also has a lot of entertaining background information. You can see the video below. (Beware, there is a very little bit of off-color language and humor in the video, so you might not want to watch this one at work.)

They are not ideal from a performance standpoint, but they are easy to make. How easy? A form of pulsejet was accidentally discovered by a young Swiss boy playing with alcohol in the early 1900s. Because of their simplicity, they’ve been built by lots of different people, including rocket pioneer Robert Goddard, who mounted one to a bicycle.

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US Air Force Says They’re Developing An Open Source Jet Engine; We Say Show Us The Design

The economies of scale generally dictate that anything produced in large enough numbers will eventually become cheap. But despite the fact that a few thousand of them are tearing across the sky above our heads at any given moment, turbine jet engines are still expensive to produce compared to other forms of propulsion. The United States Air Force Research Laboratory is hoping to change that by developing their own in-house, open source turbine engine that they believe could reduce costs by as much as 75%.

The Responsive Open Source Engine (ROSE) is designed to be cheap enough that it can be disposable, which has obvious military applications for the Air Force such as small jet-powered drones or even missiles. But even for the pacifists in the audience, it’s hard not to get excited about the idea of a low-cost open source turbine. Obviously an engine this small would have limited use to commercial aviation, but hackers and makers have always been obsessed with small jet engines, and getting one fired up and self-sustaining has traditionally been something of a badge of honor.

Since ROSE has been developed in-house by the Air Force, they have complete ownership of the engine’s intellectual property. This allows them to license the design to manufacturers for actual production rather than buying an existing engine from a single manufacturer and paying whatever their asking price is. The Air Force will be able to shop ROSE around to potential venders and get the best price for fabrication. Depending on how complex the engine is to manufacture, even smaller firms could get in on the action. The hope is that this competition will serve to not only improve the design, but also to keep costs down.

We know what you’re thinking. Where is the design, and what license is it released under? Unfortunately, that aspect of ROSE seems unclear. The engine is still in development so the Air Force isn’t ready to show off the design. But even when it’s complete, we’re fairly skeptical about who will actually have access to it. Open Source is in the name of the project and to live up to that the design needs to be available to the general public. From a purely tactical standpoint keeping the design of a cheap and reliable jet engine away from potential enemy states would seem to be a logical precaution, but is at cross purposes to what Open Source means. Don’t expect to be seeing it on GitHub anytime soon. Nuclear reactors are still fair game, though.

[Thanks to Polymath99 for the tip.]

Building A Turbocharger Turbojet

Jet engines are known to be highly demanding machines, requiring the utmost attention to tolerances, material specifications, and operating regimes. If any of these parameters are ignored, failures can be catastrophic and expensive. Despite these exacting requirements, it is possible to build a jet engine in the home workshop – and using a turbocharger is a great way to do that. (Video also embedded after the break.)

[Tech Ingredients] does a great job of discussing the basic concepts behind the turbocharger jet engine build, and how various parameters impact performance and efficiency. Through the use of various rules of thumb, developed over years of experimentation by home builders and engineers alike, it’s possible to whip up a functioning engine without too much trial and error. The video breaks down and discusses the thermodynamics at play, as well as practical considerations like cooling and lubrication, in several easy to digest steps.

Jet engines are a popular high-octane build, and we’ve seen it pulled off before by makers like [Colin Furze]. The trick is to pull it off without causing yourself serious injury.

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Building The World’s Smallest Jet Turbine By Hand

There are very few machines as complex to build as a turbojet engine. The turbine blades on a commercial airliner are grown from a single crystal of metal. The engineering tolerances are crazy, and everything spins really, really fast. All of these problems aren’t a concern for [Igor], who’s building what will probably end up being the world’s smallest turbojet engine. He’s doing it in his home shop, and a lot of the work is being done by hand. We don’t know the Russian translation for ‘hold my beer’, but [Igor] certainly does.

The design of this turbojet — as far as we can tell — is a centrifugal flow turbine, or something that’s not terribly different than the projects we’ve seen that turn the turbocharger from a diesel engine into a jet. The innovation here is using a lathe to machine the compressor stages by mounting an end mill to the headstock and the compressor blank on the cross slide, in a rotary table. It’s weird, but you really can’t argue with something that looks like it’ll work.

[Igor] has made a name for himself by creating some crazy contraptions. The most impressive, by far, is a gigantic remote controlled plane, powered by a handmade jet engine. This is an enormous fiberglass plane with a homebrew engine that spins at 90,000 RPM and doesn’t fly apart. That’s impressive by any measure.

[Igor] is posting a lot of his build process on YouTube and Instagram, including heat treating the compressor stages with a blowtorch. This is an amazing project, and even if this tiny turbine will be able to self-sustain, that’s an amazing accomplishment. You can check out a few more videos from [Igor] below.

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Plug Your Ears And Hop On This Jet-Powered EBike

Ah, the simple pleasures of a bike ride. The rush of the wind past your ears, the gentle click of the derailleurs as you change gears, the malignant whine of the dual electric jet turbines pushing you along. Wait, what?

Yes, it’s a jet bike, and its construction was strictly a case of “Why not?” for [Tech Ingredients]. They recently finished up a jet engine build using a hybrid design with electric ducted fans as compressors and fueled with propane. It was quite a success, and pretty spectacular, but left an embarrassment of riches upon its passing in terms of spare parts. The ducted fans, monstrous 90-mm 12s beasts, along with dual 150A ESCs found their way onto a mountain bike by way of a rear luggage rack. Pannier bags on each side hold the batteries, and a quick control panel went on the handlebar. The video below shows the build details and a couple of test rides, which show just how fast you can go with this setup. It may not be very practical compared to a more traditional hub motor, but it’s nowhere near as cool. Just be sure to wear your hearing protection.

Is this the first jet engine on a bike we’ve featured? Of course not. But for an impromptu build, it’s pretty impressive. Continue reading “Plug Your Ears And Hop On This Jet-Powered EBike”

GE’s Engine To Reignite Civil Supersonic Flight

On October 24th, 2003 the last Concorde touched down at Filton Airport in England, and since then commercial air travel has been stuck moving slower than the speed of sound. There were a number of reasons for retiring the Concorde, from the rising cost of fuel to bad publicity following a crash in 2000 which claimed the lives of all passengers and crew aboard. Flying on Concorde was also exceptionally expensive and only practical on certain routes, as concerns about sonic booms over land meant it had to remain subsonic unless it was flying over the ocean.

The failure of the Concorde has kept manufacturers and the civil aviation industry from investing in a new supersonic aircraft for fifteen years now. It’s a rare example of commercial technology going “backwards”; the latest and greatest airliners built today can’t achieve even half the Concorde’s top speed of 1,354 MPH (2,179 km/h). In an era where speed and performance is an obsession, commercial air travel simply hasn’t kept up with the pace of the world around it. There’s a fortune to be made for anyone who can figure out a way to offer supersonic flight for passengers and cargo without falling into the same traps that ended the Concorde program.

With the announcement that they’ve completed the initial design of their new Affinity engine, General Electric is looking to answer that call. Combining GE’s experience developing high performance fighter jet engines with the latest efficiency improvements from their civilian engines, Affinity is the first new supersonic engine designed for the civil aviation market in fifty five years. It’s not slated to fly before 2023, and likely won’t see commercial use for a few years after that, but this is an important first step in getting air travel to catch up with the rest of our modern lives.

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3D Printed Variable Area Jet Nozzle

If you’ve ever seen the back end of a military jet, you’ve likely seen variable area nozzles. They’re used to adjust the exhaust flow out of the rear of a jet engine during supersonic flight and while the afterburner is engaged. Commercial aircraft, with the exception of the Concorde, don’t need such fancy hardware since a static exhaust nozzle works well enough for the types of flying they’ll be doing. For much the same reasons, RC aircraft don’t need variable area nozzles either, but it doesn’t keep builders from wanting them.

Which brings us to this utterly gorgeous design by [Marco Colucci]. Made up of 23 individual PETG parts, this variable area nozzle is able to reduce its diameter by 50% with just a twist of the rotating collar. When paired with a hobby servo, this mechanism will allow the operator to adjust the nozzle aperture with an extra channel on their RC transmitter. The nozzle hasn’t flown yet, but a test run is being planned with a 40mm Electric Ducted Fan (EDF) motor. But thanks to the parametric design, it shouldn’t be a problem to scale it up to larger motors.

But the big question: does it have an effect on the EDF’s performance? The answer is, of course, no. This doesn’t actually do anything. An EDF motor has no need for this sort of nozzle, and even if you tried to fit this on a scale jet engine, it would melt in seconds from the exhaust temperature. This is purely a decorative item, to give the plane a more accurate scale look. To that end, it looks fantastic and would definitely be impressive on the back of a large scale RC military fighter.

If anything, [Marco] says he expects performance to be worse with the nozzle fitted. Not only is it adding dead weight to the plane, but restricting the air coming out of the back of the fan isn’t going to do anything but reduce thrust. But on the bright side: if it’s flying slower, it will be easier to see how awesome your adjustable nozzles look.

This isn’t the first time somebody’s tried to make an electric RC plane look like it’s packing a proper turbine, but it certainly might be one of the slickest. Only way to top this is to build an actual jet engine for the thing.

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