model rocketry

Retrotechtacular: Junior Missile Men Of The 1960s

Just like the imaginative kids depicted in “Junior Missile Men in Action,” you’ll have to employ a fair bit of your own imagination to figure out what was going on in the original film, which seems to have suffered a bit — OK, a lot — from multiple rounds of digitization and format conversion. [GarageManCave] tells us he found the film on a newsgroup back in the 1990s, but only recently uploaded it to YouTube. It’s hard to watch, but worth it for anyone who spent hours building an Estes model rocket and had that gut-check moment when sliding it onto the guide rail and getting it ready for launch. Would it go? Would it survive the trip? Or would it end up hanging from a tree branch, or lost in the high grass that always seemed to be ready to eat model rockets, planes, Frisbees, or pretty much anything that was fun?

Model rocketry was most definitely good, clean fun, even with the rotten egg stink of the propellant and the risk of failure. To mitigate those risks, the West Covina Model Rocket Society, the group the film focuses on, was formed in the 1960s. The boys and girls pictured had the distinct advantage of living in an area where many of their parents were employed by the aerospace industry, and the influence of trained engineers shows — weekly build sessions, well-organized range days, and even theodolites to track the rockets and calculate their altitude. They even test-fired rockets from miniature silos, and mimicked a Polaris missile launch by firing a model from a bucket of water. It was far more intensive and organized than the early rocketry exposure most of us got, and has the look and feel of a FIRST robotics group today.

Given the membership numbers the WCMRS boasted of in its heyday, and the fact that model rocketry was often the “gateway drug” into the hacking lifestyle, there’s a good chance that someone in the Hackaday community got their start out in that park in West Covina, or perhaps was even in the film. If you’re out there, let us know in the comments — we’d love to hear a first-hand report on what the club was like, and how it helped you get started.

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3D printed rocket laying on grass

3D Printed Rocket’s Features Are Out Of This World

We’re delighted to see the progress on [Foaly]’s 3D-printed Cortex 2 rocket, and the latest build log is full of beautiful pictures and design details. Not only is this rocket jam-packed with an efficiency of electronics and smart design, but it almost seems out to single-handedly prove that 3D-printing is far from the novelty some think it is.

Electronics and wires packing the fuselage of a model rocket
Cable management and component layout is far from a trivial task in a rocket like this.

There is so much going on in the Cortex 2 that it simply wouldn’t be possible to do everything it does without the ability to make one’s own parts exactly to specification. In fact, there is so much going on that cable management is its own challenge.

Everything in the build log is interesting, but the design of the parachute system is of particular note. [Foaly]’s original Cortex rocket met it’s end when the parachute failed to deploy, and Cortex 2 is determined to avoid that fate if it can. For the parachute and any cords and anchors, a careful layout maximizes the chances of a successful deployment without anything tangling, but there are some extra features as well. The panel covering the parachute is mounted with the help of four magnets, which are mounted with opposing polarities. This provides an initial repulsing force when the door is unlocked by a servo, which should help wind immediately rush in to the opening to blow the panel away. The recovery system even has its own dedicated microcontroller and can operate autonomously; even if software for everything else crashes, the parachute will still get deployed. Locking connectors for all cables also ensure that acceleration forces don’t dislodge any contacts.

Everything about the rocket looks great, and the amount of work that has gone into the software is particularly evident. The main controller even has an interactive pre-flight checklist, which is a fantastic feature.

The last time we saw the Cortex 2 it was still only about half built, and we can’t wait to see how it performs. Rocketry is a field that has benefited greatly from things like 3D printing, the availability of highly-integrated electronics, and even such things as a rocket design workbench for FreeCAD. Better tools enable better work, after all.

Image of detonation engine firing

Japanese Rocket Engine Explodes: Continuously And On Purpose

Liquid-fuelled rocket engine design has largely followed a simple template since the development of the German V-2 rocket in the middle of World War 2. Propellant and oxidizer are mixed in a combustion chamber, creating a mixture of hot gases at high pressure that very much wish to leave out the back of the rocket, generating thrust.

However, the Japan Aerospace Exploration Agency (JAXA) has recently completed a successful test of a different type of rocket, known as a rotating detonation engine. The engine relies on an entirely different method of combustion, with the aim to produce more thrust from less fuel. We’ll dive into how it works, and how the Japanese test bodes for the future of this technology.

Deflagration vs. Detonation

Humans love combusting fuels in order to do useful work. Thus far in our history, whether we look at steam engines, gasoline engines, or even rocket engines, all these technologies have had one thing in common: they all rely on fuel that burns in a deflagration. It’s the easily controlled manner of slow combustion that we’re all familiar with since we started sitting around campfires. Continue reading “Japanese Rocket Engine Explodes: Continuously And On Purpose”

3D Printing Steel Parts At Home Via Special Filaments

Rocket engines are great for producing thrust from fire and fury, but they’re also difficult to make. They require high-strength materials that can withstand the high temperatures involved. [Integza], however, has tried for a long time to 3D print himself a working rocket engine. His latest attempt involves printing an aerospike design out of metal.

Even steel couldn’t hold up to the fury of the rocket exhaust!

The project relies on special metal-impregnated 3D printer filaments. The part can be printed with a regular 3D printer and then fired to leave just the metal behind. The filament can be harsh, so [Integza] uses a ruby nozzle to handle the metal-impregnated material. Processing the material requires a medium-temperature “debinding” stage in a kiln which removes the plastic, before a high-temperature sintering process that bonds the remaining metal particles into a hopefully-contiguous whole. The process worked well for bronze, though was a little trickier for steel.

Armed with a steel aerospike rocket nozzle, [Integza] attempts using the parts with his 3D printed rocket fuel we’ve seen before. The configuration does generate some thrust, and lasts longer than most of [Integza]’s previous efforts, though still succumbs to the intense heat of the rocket exhaust.

Overall, though, it’s a great example of what it takes to print steel parts at home. You’ll need a quality 3D printer, ruby nozzles and a controllable kiln, but it can be done. If you manage to print something awesome, be sure to drop us a line. Video after the break.

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A High Power Wood Rocket In 5 Days

Getting started with model rocketry is relatively cheap and easy, but as you move up in high power rocketry, there are a few hoops to jump through. To be able to buy rocket motors larger than H (160 N·s / 36 lbf·s impulse) in the US, you need to get certified by the National Association of Rocketry. The main requirement of this certification involves building, flying, and recovering a rocket with the specific motor class required for the certification level. [Xyla Foxlin] had committed to doing her Level 2 certification with a couple of friends, thanks to the old procrastination monster, was forced to build a rocket with only 5 days remaining to launch data.

For Level 2 certification, the rocket needs to fly with a J motor, which is capable of producing more than 640 N·s of impulse. Fortunately [Xyla] had already designed the rocket in OpenRocket, and ordered the motor and major body, nosecone, and parachute components. The body was built around 2 sections of 3″ cardboard tubes, which are covered in a few layers of fiberglass. The stabilizing fins were laser cut from cheap plywood and were epoxied to the inner tube which holds the motor and passes through the sides of the outer tube. The fins are also fibreglassed to increased strength. For a unique touch, she covered the rocket with a real wood veneer, with the rocket’s name, [Fifi], inlaid with darker wood. The recovery system is a basic parachute, connected to the rocket body with Kevlar rope.

[Xyla] finished her rocket just in time for the trek out to the rocket range. She successfully did the certification flight and recovered [Fifi] in reusable condition, which is a requirement. There was nothing groundbreaking about [Fifi], but then again, reliability the main requirement. You don’t want to do a certification with a fancy experimental rocket that could easily fail. Continue reading “A High Power Wood Rocket In 5 Days”

FreeCAD Takes Off With A Rocket Design Workbench

Here’s how FreeCAD works: the program’s design space is separated into different “workbenches”, each of which is intended for a particular set of operations, and a piece of work can be moved between them as needed. There is a sketching workbench, a part design workbench, and now a Rocket workbench has been added to the healthy ecosystem of FreeCAD add-ons. There’s even a series of video tutorials; ain’t open source grand?

It all started when [concretedog] posted on the FreeCAD forums, making a strong case for a Rocket-themed workbench. People got interested, and a short while later [DavesRocketShop] had some useful tools up and running. Here’s a blog post by [concretedog] which goes into detail and background, and while the Rocket workbench is available via FreeCAD’s add-on manager, the very latest experimental builds are available for manual installation on [Dave]’s GitHub repository.

This sort of development and utility is exactly the kind of thing our own Elliot Williams was describing when he made the point that one of open source’s greatest strengths is in the little things, like the FreeCAD ecosystem letting people scratch strange and specific itches, and the ability to share those solutions with others.

Experimenting With 3D Printed Rocket Nozzles

Rocketry is an exacting science, involving a wide variety of disciplines, encompassing everything from fluid mechanics to thermodynamics and materials engineering. As complex as it sounds, that doesn’t mean it’s beyond the purview of the average maker. [Sciencish] demonstrates this with a series of experiments on rocket nozzles in the home lab. (Video, embedded below.)

The video starts with an amusing analogy about nozzle design based on people fleeing a bad pizza. From there, [Sciencish] 3D prints a wide variety of nozzle designs for testing. The traditional bell nozzle is there, of course, along with the familiar toroidal and linear aerospikes and an expansion deflection design. Of course, 3D printing makes it easy to try out fun, oddball geometries, so there’s also a cowbell nozzle , along with the fancy looking square and triangular aerospikes too. Testing involves running the nozzles on a test stand instrumented with a load cell. A soda bottle is filled with rubbing alcohol vapour, and the mixture is ignited, with each nozzle graded on its thrust output. The rockets are later flown outside, reaching heights over 40 feet.

[Sciencish] notes that the results are a rough guide only, as the fuel/air mixture was poorly controlled. Despite this, it’s a great look at nozzle design and all the science involved. It also wouldn’t be too hard to introduce a little more rigour and get more accurate data, either. However, if solid fuels are more your jam, consider brewing up some rocket candy instead.

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