The Moment A Bullet Turns Into A Flashlight, Caught On Film

July 22, 2023 by Donald Papp 14 Comments

[The Slo Mo Guys] caught something fascinating while filming some firearms at 82,000 frames per second: a visible emission of light immediately preceding a bullet impact. The moment it occurs is pictured above, but if you’d like to jump directly to the point in the video where this occurs, it all starts at [8:18].

The ability to capture ultra-slow motion allows us to see things that would otherwise happen far too quickly to perceive, and there are quite a few visual spectacles in the whole video. We’ll talk a bit about what is involved, and what could be happening.

Spotting something unusual on video replay is what exteme slo-mo filming is all about.

First of all, the clear blocks being shot are ballistic gel. These dense blocks are tough, elastic, and a common sight in firearms testing because they reliably and consistently measure things like bullet deformation, fragmentation, and impact. It’s possible to make homemade ballistic gel with sufficient quantities of gelatin and water, but the clear ones like you see here are oil-based, visually clear, and more stable (they do not shrink due to evaporation).

We’ve seen the diesel effect occur in ballistic gelatin, which is most likely the result of the bullet impact vaporizing small amounts of the (oil-based) gel when the channel forms, and that vaporized material ignites due to a sudden increase in pressure as it contracts.

In the video linked above (and embedded below), there is probably a bit more in the mix. The rifles being tested are large-bore rifles, firing big cartridges with a large amount of gunpowder igniting behind each bullet. The burning powder causes a rapid expansion of hot, pressurized gasses that push the bullet down the barrel at tremendous speed. As the bullet exits, so does a jet of hot gasses. Sometimes, the last bits of burning powder are visible as a brief muzzle flash that accompanies the bullet leaving the barrel.

A large projectile traveling at supersonic velocities results in a large channel and expansion when it hits ballistic gel, but when fired at close range there are hot gasses from the muzzle and any remaining burning gunpowder in the mix, as well. All of which help generate the kind of visual spectacles we see here.

We suspect that the single frame of a flashlight-like emission of light as the flat-nosed bullet strikes the face of the gel is also the result of the diesel effect, but it’s an absolutely remarkable visual and a fascinating thing to capture on film. You can watch the whole thing just below the page break.

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Who’s Afraid Of Assembly Language?

July 22, 2023 by Elliot Williams 109 Comments

This week, [Al Williams] wrote a great thought piece about whether or not it was worth learning an assembly language at all anymore, and when. The comments overflowed, and we’re surprised that so many people basically agree with us: yes. Of course, it’s a Hackaday crowd, but I still didn’t expect the outpouring of love for the most primitive of languages.

Assembly language isn’t really one language, though. Every chip speaks its own dialect. Of course there are similarities: every CPU has an add function, right? But almost no CPU has just one add – there are variants with and without carry, storing and reading from working registers or RAM. And once you start talking about memory access, direct or indirect, the individual architectures of the chips demand different assembly languages.

But still, although the particular ways that CPUs do what they do can be incompatible from a strictly language perspective, they are a lot more similar in terms of the programming idioms that you’ll pick up along the way. Just as learning a set of solid algorithms will help you no matter which higher-level language you use, learning the concepts behind crafting loops and simple memory structures out of raw assembly language will serve you no matter which CPU you choose.

I have only written assembly language for a handful of CPUs, and not much of it at that, but I’ve found the microcontrollers to be the friendliest. So if you want to dip your toes in that water, pick up an AVR or an MSP430. Or maybe even the new hotness – a RISC-V. You’ll find the instruction sets small enough that you have to do most of the work yourself. And that is, after all, the point of learning an assembly language: learning to think like the silicon. If you treat it like a fun puzzle to solve, you’ll probably even enjoy the experience.

[Al]’s original question was when you should learn an assembly language: before or after a higher-level language. For 99% of our readers, I’d say the answer is right now.

That Ultra-White Paint That Helps Cool Surfaces? Make Your Own!

July 22, 2023 by Donald Papp 53 Comments

It started with [KB9ENS] looking into paints or coatings for passive or radiative cooling, and in the process he decided to DIY his own. Not only is it perfectly accessible to a home experimenter, his initial results look like they have some promise, as well.

[KB9ENS] read about a type of ultra-white paint formulation that not only reflects heat, but is able to radiate it into space, cooling the painted surface to below ambient temperature. This is intriguing because while commercial paints can insulate and reflect heat, they cannot make a surface cooler than its surroundings.

Anecdotally speaking, this painted battery section of a solar recharger gets too hot to touch in full sunlight. But when painted over, it was merely warm.

What really got [KB9ENS] thinking was that at its core, the passively-cooling paint in the research is essentially a whole lot of different particle sizes of barium sulfate (BaSO₄) mixed into an acrylic binder. These two ingredients are remarkably accessible. A half-pound of BaSO₄ from a pottery supply shop was only a few dollars, and a plain acrylic base is easily obtained from almost any paint or art supplier.

[KB9ENS] decided to mix up a crude batch of BaSO₄ paint, apply it to some things, and see how well it compared to other paints and coatings. He wetted the BaSO₄ with some isopropyl alcohol to help it mix into the base, and made a few different concentrations. A 60% concentration by volume seemed to give the best overall results.

There’s no indication of whether any lower-than-ambient cooling is happening, but according to a non-contact thermometer even this homemade mixture does a better job of keeping sunlight from heating things up compared to similarly-applied commercial paints (although it fared only slightly better than titanium dioxide-based white paint in the initial test.)

[KB9ENS] also painted the battery section of a solar recharger with his homemade paint and noted that while under normal circumstances — that is to say, in full sunlight — that section becomes too hot to touch, with the paint coating it was merely warm.

Actual passive cooling can do more than just keep something less warm than it would be otherwise. We’ve seen it recently used to passively and continuously generate power thanks to its ability to create a constant temperature differential, day and night.

Behold A Gallery Of Sony’s PS VR2 Prototypes

July 22, 2023 by Donald Papp 3 Comments

Every finished product stands at the end of a long line of prototypes, and Sony have recently shared an interview and images of their PlayStation VR2 prototypes.

Many of the prototypes focus on a specific functionality, and readers who are not familiar with building things might find it a bit wild to see just how big and ungainly un-optimized hardware can be.

Finished product (bottom) contrasted with functionally-identical prototype (top).

The images are definitely the best part of that link, but the interview has a few interesting bits. For example, one prototype was optimized for evaluating and testing camera placement with a high degree of accuracy, and it hardly looks like a VR headset at all.

The controllers on the other hand seem to have gone though more iterations based on the ergonomics and physical layout of controls. The VR2 controllers integrate the adaptive triggers from the PlayStation 5, which are of a genuinely clever design capable of variable resistance as well as an active force feedback effect that’s not quite like anything that’s come before.

There’s a lot of work that goes into developing something like a VR headset, as we see here and we’ve seen with Facebook’s (now Meta) VR research prototypes. But even when one can leverage pre-made modules as much as possible and doesn’t need to start entirely from scratch, making a VR headset remains a whole heap of work.

An Amiga 500 with a blue case and blue accessories

Restored Amiga 500 Is Blue – And Glows In The Dark

July 21, 2023 by Robin Kearey 5 Comments

Few things are as satisfying to watch as a good retrocomputer restoration project – we’re always happy to see someone bring a rusty old Commodore, Apple or Atari back to life. The goal is typically to get the machine as close to its original state as possible, except for perhaps a few non-intrusive mods like memory upgrades. [Drygol] however, had already done this so many times that he thought it was time to take a different route for once, and apply some creativity to an old Amiga 500 case. Originalists may shudder, but we quite like his funky blue-and-yellow A500 mod.

An Amiga 500 with a poor blue-and-yellow paint job — Missing keys, random stickers and an ugly paint job: the A500 wasn’t looking great at the beginning

To be fair, [Drygol] wasn’t the first one to modify this specific Amiga’s case: one of its previous owners had already applied a rather shoddy blue paint job and defaced it with some stickers. [Drygol] decided to stick with the basic idea, but do it right this time. First he removed the old paint using concentrated lye, then gave it a fresh coat of blue. He also applied glow-in-the-dark paint to the Amiga logo embossed in the case and added a fluorescent yellow laser-cut circuit board ornament. It took a bit of experimenting to get all these elements just right, but the end result definitely looks the part.

The insides of the Amiga also needed some TLC: [Drygol] competely cleaned and lubricated the floppy drive, gave the motherboard a good ultrasonic scrub, and replaced dodgy capacitors all over. He expanded the RAM from 512 kB to 1 MB and added a Gotek floppy emulator, which can work in parallel with the original disk drive. To make the Gotek easy to operate, [Drygol] placed its OLED screen and a pair of touch-sensitive buttons in a cutout on the front of the case.

A matching blue mouse and gamepad, both connected through the MouSTer adapter, complete the setup. The result is a good-looking A500 with some modern conveniences that’s perfect for exploring the Amiga’s extensive software library. If custom colors aren’t your thing, you’ll be happy to know that the original shade of grey or beige might be available for your retro console, too.

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When Is Open Source AI Not Open Source AI?

July 21, 2023 by Jenny List 18 Comments

The world of AI is abuzz, or at least parts of it are, at the news of Meta’s release of Llama 2. This is an AI text model which is thought to surpass ChatGPT in capabilities, and which the social media turned VR turned own all your things company wants you to know is open to all. That’s right, the code is open source and you can download the model, and Meta want you to feel warm and fuzzy about it. Unfortunately all is not as it seems, because of course the model isn’t open-source and is subject to a licensing restriction which makes it definitely not free of charge for larger users. This is of course disappointing to anyone hoping for an AI chatbot without restrictions, but we’re guessing Meta would prefer not to inadvertently enable a competitor.

Happily for the open source user large or small who isn’t afraid of a little work there’s an alternative in the form of OpenLLaMA, but we understand that won’t be for all users. Whichever LLM you use though, please don’t make the mistake of imagining that it possesses actual intelligence.

Thanks to the CoupledAI team for the tip!

RoboPianist Is A Simulation For Advancing Robotic Control

July 21, 2023 by Lewin Day 10 Comments

Researchers at Google have posed themselves an interesting problem to solve: mastering the piano. However, they’re not trying to teach themselves, but a pair of simulated anthropomorphic robotic hands instead. Enter RoboPianist.

The hope is that the RoboPianist platform can help benchmark “high-dimensional control, targeted at testing high spatial and temporal precision, coordination, and planning, all with an underactuated system frequently making-and-breaking contacts.”

If that all sounds like a bit much to follow, the basic gist is that playing the piano takes a ton of coordination and control. Doing it in a musical way requires both high speed and perfect timing, further upping the challenge. The team hopes that by developing control strategies that can master the piano, they will more broadly learn about techniques useful for two-handed, multi-fingered control. To that end, RoboPianist models a pair of robot hands with 22 actuators each, or 44 in total. Much like human hands, the robot hands are underactuated by design, meaning they have less actuators than their total degrees of freedom.

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