A Look Inside A DIY Rocket Motor

September 11, 2024 by 6 Comments

[Joe Barnard] made a solid propellant rocket motor, and as one does in such situations, he put it through its paces on the test stand. The video below is not about the test, nor is it about the motor’s construction. Rather, it’s a deconstruction of the remains of the motor in order to better understand its design, and it’s pretty interesting stuff.

Somewhere along the way, [Joe], aka “BPS.Space” on YouTube, transitioned from enthusiastic model rocketeer to full-fledged missile-man, and in the process stepped up his motor game considerably. The motor that goes under the knife — or rather, the bandsaw — in this video is his “Simplex V2,” a completely DIY build of [Joe]’s design. For scale, the casing is made from a 6″ (15 cm) diameter piece of aluminum tubing over a meter in length, with a machined aluminum forward closure and a composite nozzle assembly. This is a pretty serious piece of engineering.

The closure and the nozzle are the focus of the video, which makes sense since that’s where most of the action takes place. To understand what happened during the test, [Joe] lopped them off and cut them roughly in half longitudinally. The nozzle throat, which was machined from a slug of graphite, fared remarkably well during the test, accumulating only a little slag from the propellant, a combination of powdered aluminum, ammonium perchlorate, and HTBP resin. The lower part of the nozzle, made from phenolic-impregnated linen, did pretty well too, building up a pyrolyzed layer that acted much like a space capsule’s ablative heat shield would. The forward closure, whose sole job is to contain the inferno and direct the exhaust anywhere but up, took more of a beating but stood up to the challenge. Especially interesting was the state of the O-rings and the way that the igniter interfaced with the closure.

Post mortems like these are valuable teaching tools, and while it must be heartbreaking to destroy something you put so much work into, you can’t improve what you can’t measure. Hats off to [Joe] for the peek inside his world. Continue reading “A Look Inside A DIY Rocket Motor” →

Why Have Seven Segments When You Can Have 21?

September 10, 2024 by 35 Comments

IO user [monte] was pointed towards an 1898 display patent issued to a [George Mason] and liked the look of the ‘creepy’ font it defined. The layout used no less than 21 discrete segments to display the complete roman alphabet and numerals, which is definitely not possible with the mere seven segments we are all familiar with. [monte] then did the decent thing and created a demonstration digit using modern parts.

For the implementation, [monte] created a simple PCB by hand (with an obvious mistake) and 3D-printed an enclosure and diffuser to match. After a little debugging, a better PCB was ordered from one of the usual overseas factories. There isn’t a schematic yet, but they mention using a CH32V003 Risc-V micro, which can be seen sitting on the rear of the PCB.

Maximum flexibility is ensured by storing every glyph as a 32-bit integer, with each LED corresponding to a single bit. It’s interesting to note the display incorporates serifs, which are definitely optional, although you could display sans-serif style glyphs if you wanted to. There is now a bit of a job to work out how to map character codes to glyph codes, but you can have a go at that yourself here. It’s still early doors on this project, but it has some real potential for a unique-looking display.

We love displays—every kind. Here’s a layout reminiscent of a VFD digit but done purely mechanically. And if you must limit yourself to seven digits, what about this unique thing?

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Mobile Coffee Table Uses Legs To Get Around

September 10, 2024 by 22 Comments

For getting around on most surfaces, it’s hard to beat the utility of the wheel. Versatile, inexpensive, and able to be made from a wide array of materials has led to this being a cornerstone technology for the past ten thousand years or so. But with that much history it can seem a little bit played out. To change up the locomotion game, you might want to consider using robotic legs instead. That’s what [Giliam] designed into this mobile coffee table which uses custom linkages to move its legs and get itself from place to place around the living room.

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Assessing The Energy Efficiency Of Programming Languages

September 10, 2024 by 66 Comments

Programming languages are generally defined as a more human-friendly way to program computers than using raw machine code. Within the realm of these languages there is a wide range of how close the programmer is allowed to get to the bare metal, which ultimately can affect the performance and efficiency of the application. One metric that has become more important over the years is that of energy efficiency, as datacenters keep growing along with their power demand. If picking one programming language over another saves even 1% of a datacenter’s electricity consumption, this could prove to be highly beneficial, assuming it weighs up against all other factors one would consider.

There have been some attempts over the years to put a number on the energy efficiency of specific programming languages, with a paper by Rui Pereira et al. from 2021 (preprint PDF) as published in Science of Computer Programming covering the running a couple of small benchmarks, measuring system power consumption and drawing conclusions based on this. When Hackaday covered the 2017 paper at the time, it was with the expected claim that C is the most efficient programming language, while of course scripting languages like JavaScript, Python and Lua trailed far behind.

With C being effectively high-level assembly code this is probably no surprise, but languages such as C++ and Ada should see no severe performance penalty over C due to their design, which is the part where this particular study begins to fall apart. So what is the truth and can we even capture ‘efficiency’ in a simple ranking?

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A Look At The Small Web, Part 1

September 10, 2024 by 62 Comments

In the early 1990s I was privileged enough to be immersed in the world of technology during the exciting period that gave birth to the World Wide Web, and I can honestly say I managed to completely miss those first stirrings of the information revolution in favour of CD-ROMs, a piece of technology which definitely didn’t have a future. I’ve written in the past about that experience and what it taught me about confusing the medium with the message, but today I’m returning to that period in search of something else. How can we regain some of the things that made that early Web good?

We All Know What’s Wrong With The Web…

It’s likely most Hackaday readers could recite a list of problems with the web as it exists here in 2024. Cory Doctrow coined a word for it, enshitification, referring to the shift of web users from being the consumers of online services to the product of those services, squeezed by a few Internet monopolies. A few massive corporations control so much of our online experience from the server to the browser, to the extent that for so many people there is very little the touch outside those confines. Continue reading “A Look At The Small Web, Part 1” →

Hard Lessons Learned While Building A Solar RC Plane

September 9, 2024 by 17 Comments

Although not the first to try and build a DIY solar-powered remote control airplane, [ProjectAir]’s recent attempt is the most significant one in recent memory. It follows [rctestflight]’s multi-year saga with its v4 revision in 2019, as well as 2022’s rather big one by [Bearospace]. With so many examples to look at, building a solar-powered RC airplane in 2024 should be a snap, surely?

The first handicap was that [ProjectAir] is based in the UK, which means dealing with the famously sunny weather in those regions. The next issue was that the expensive, 20% efficient solar panels are exceedingly fragile, so the hope was that hot-gluing them to the foam of the airplane would keep them safe, even in the case of a crash. During the first test flights they quickly found that although the airplane few fairly well, the moment the sun vanished behind another cloud, the airplane would quite literally fall out of the sky, damaging some cells in the process.

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DOOM On A Volumetric Display

September 9, 2024 by 15 Comments

There’s something magical about volumetric displays. They really need to be perceived in person, and no amount of static or video photography will ever do them justice. [AncientJames] has built a few, and we’re reporting on his progress, mostly because he got it to run a playable port of DOOM.

Base view of an earlier version showing the motor drive and PSU

As we’ve seen before, DOOM is very much a 3D game viewed on a 2D display using all manner of clever tricks and optimizations. The background visual gives a 3D effect, but the game’s sprites are definitely very solidly in 2D land. As we’ll see, that wasn’t good enough for [James].

The basic concept relies on a pair of 128 x 64 LED display matrix modules sitting atop a rotating platform. The 3D printed platform holds the displays vertically, with the LEDs lined up with the diameter, meaning the electronics hang off the back, creating some imbalance.

Lead, in the form of the type used for traditional window leading, was used as a counterbalance. A Raspberry Pi 4 with a modified version of this LED driver HAT is rotating with the displays. The Pi and both displays are fed power from individual Mini560 buck modules, taking their input from a 12 V 100 W Mean-Well power supply via a car alternator slip ring setup. (Part numbers ABH6004S and ASL9009  for those interested.) Finally, to synchronise the setup, a simple IR photo interrupter signals the Pi via an interrupt.

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