Underwater Jetpack Is Almost Practical

December 17, 2025 by Tyler August 1 Comment

The jet pack is one of those pre-war sci-fi dreams that the cold light of rational consideration reveals to be a terrible idea. Who wants to cook their legs with hot exhaust while careening out of control? Nobody. Yet it’s such an iconic idea, we can’t get away from it. What if there was a better environment, one where your jetpack dreams could come true? [CPSdrone] has found one: the world’s oceans, and have taken that revelation to build the world’s fastest underwater jetpack.

Underwater? Yeah, water drag is worse than air drag. But there are two big advantages: one, humans are fairly buoyant, so you don’t need fight gravity with rocket thrust, and two, the high density of water makes small, electric props a reasonable proposition. The electric ducted fans on this “jetpack” each produce about 110 pounds of thrust, or just over 490 N. The first advantage is helped further by the buoyancy provided by the air-filled “hull” of the jetpack. That’s necessary because while the motors might be rated for submersion, but the rest of the electronics aren’t.

Alas, wearing the device on the back is considerably less hydrodynamic than hanging on behind in the standard ‘water scooter’ configuration. While they’re able to go faster than a swimming human, the ESCs weren’t able to handle the motors full power so we can’t tell you if this device would allow [CPSdrone] to outrun a shark with those 220 lbf on tap, which was the design goal. Apparently they’re working on it.

From the testing done on-screen, it’s safe to say that they’d at least need to hang on behind to get their desired speed goals, and abandon their jet pack dreams just as we landlubbers were forced to do long ago. Well, some of us, anyway.

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WiFi Menorah For Eight Nights Of Bandwidth

December 17, 2025 by Tyler August 18 Comments

Hanukkah is upon us, and if that’s your jam [Brian] has you covered with this stylish WiFi menorah. While we can’t say if it’ll stretch your last gigabyte of connectivity into eight, it’s certainly going to provide awesome signal with all those antennae.

You could perhaps coax us to make one of these.

[Brian] was inspired by the enterprise version of the Hak5 “WiFi Pineapple”, a high-powered pentesting device. Seeing its plethora of antennae, he was struck with the idea of mounting them all onto a menorah, so he did. The menorah itself is 3D printed (of course) with lots of coax running through it down to the base, where presumably it would be connected to a Pineapple or high-powered router.

The project is presented as more of an art piece than a functional device, as there’s no evidence that [Brian] has actually hooked it up to anything yet. But consider the possibilities — along with the traditional candles, you could “light” one WiFi antenna each night, bringing the holiday glow to 2.4 GHz or 5 GHz. If you prefer more visible wavelengths, perhaps this LED menorah would be more to your tastes.

If you’ve got a hack for your culturally-relevant holiday festival, be it Christmas, Hanukkah, or Festivus, we’d love to see it. The tips line is open all year round.

One of four MDF half-tone blocks coming off the laser cutter.

Laser Cutter Plus CYMK Spraypaint Equals Full-Color Prints

December 16, 2025 by Tyler August 13 Comments

This is one of those fun hacks that come about from finding a product and going “I wonder if I could…” — in this case, artist/YouTuber [Wesley Treat] found out his favourite vendor makes spray cans in CYMK colours– that is the Cyan, Yellow, Magenta and blacK required for subtractive printing. Which got him wondering: can I make full-colour prints with this paint?

MDF block print — The MDF-based print, with naive half-tone dots.

His answer was “yes”, and the process to do so is fairly simple. First, split the image into colour channels, generate a half-tone pattern for each one, and carve it out of MDF on the laser. Then spray the MDF with the appropriate colour spray paint. Press the page against each block in turn, and voila! A full colour print block print, albeit at very low DPI compared to your average inkjet.

Now, you might be wondering, why half-tone instead of mixing? Well, it turns out that these CYMK paints are too opaque for that to work in a block-printing process. At least with a naive spray technique; [Weseley] does admit a very fine mist might be able to make that work. The second question is why not just hook the rattle cans into a CNC machine for a paint-based mega inkjet? That’s a great question and we hope someone tries it, but [Weseley] evidently likes block-printing so he tried that first.

The Mylar stencil print, with a more artistic half-tone pattern.

Laser-ablating enough MDF away to make decent print blocks took too long for [Weseley]’s tastes, however, so he switched to using mylar stencils. Instead of spraying a block and pressing onto it, the paint is sprayed through the stencil. The 10 mil Mylar not only cuts faster, but can support finer detail. Though the resulting prints lose some of the artistic flair the inconsistencies block printing brings, it probably looks better.

If you prefer to skip the manual paint-can-handling, perhaps we can interest you in a spray-can plotter. If you do like manually flinging paint, perhaps you could try this dot-painting spray can attachment, for a more self-directed half-tone.

Thanks to [Keith Olson] for the tip.

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A graph showing the poisoning success rate of 7B and 13B parameter models

It Only Takes A Handful Of Samples To Poison Any Size LLM, Anthropic Finds

December 14, 2025 by Tyler August 98 Comments

It stands to reason that if you have access to an LLM’s training data, you can influence what’s coming out the other end of the inscrutable AI’s network. The obvious guess is that you’d need some percentage of the overall input, though exactly how much that was — 2%, 1%, or less — was an active research question. New research by Anthropic, the UK AI Security Institute, and the Alan Turing Institute shows it is actually a lot easier to poison the well than that.

We’re talking parts-per-million of poison for large models, because the researchers found that with just 250 carefully-crafted poison pills, they could compromise the output of any size LLM. Now, when we say poison the model, we’re not talking about a total hijacking, at least in this study. The specific backdoor under investigation was getting the model to produce total gibberish.

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Condensing Diesel Heater Hack Is Dripping With Efficiency

December 13, 2025 by Tyler August 13 Comments

Not a huge percentage of our readers probably get their heat from diesel fuel, but it’s not uncommon in remote areas where other fuels are hard to come-by. If you’re in one of those areas, this latest hack from [Hangin with the Hursts] could save you some change, or keep you ̶2̶0̶%̶ ̶c̶o̶o̶l̶e̶r̶ 25% warmer on the same fuel burn.

It’s bog simple: he takes his off-the-shelf hydronic diesel heater, which is already 71% efficient according to a previous test, and hooks its exhaust to a heat exchanger. Now, you don’t want to restrict the exhaust on one of these units, as that can mess with the air fuel mix, but [Hurst] gets around that with a 3″ intercooler meant for automotive intake. Sure, it’s not made for exhaust gas, but this is a clean-burning heater, and it wouldn’t be a hack if some of the parts weren’t out of spec.

Since it’s a hydronic heater, he’s able to use the exhaust gas to pre-heat the water going into the burner. The intercooler does a very good job of that, sucking enough heat out of the exhaust to turn this into a condensing furnace. That’s great for efficiency — he calculates 95%, a number so good he doesn’t trust it — but not so good for the longevity of the system, since this intercooler isn’t made to deal with the slightly-acidic condensation. The efficiency numbers are combustion efficiency, to be clear. He’s only accounting for the energy in the diesel fuel, not the energy that heats the water in his test, for the record; the electrical power going into the blower is considered free. That’s fair, since that’s how the numbers are calculated in the heating industry in general — the natural gas furnace keeping this author from freezing to death, for example, is a condensing unit that is also 95% efficient.

Another thing you can do to get the most from your diesel heating fuel is add some brains to the operation. Since this is a hydronic system, the cheapest option, long-term, might be to add some solar energy to the water. Sunlight is free, and diesel sure isn’t getting any cheaper.

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A biohacker with her lactose-rich slurry

Biohack Your Way To Lactose Tolerance (Through Suffering)

December 13, 2025 by Tyler August 49 Comments

A significant fraction of people can’t handle lactose, like [HGModernism]. Rather than accept a cruel, ice cream free existence, she decided to do something you really shouldn’t try: biohacking her way to lactose tolerance.

The hack is very simple, and based on a peer reviewed study from the 1990s: consume lactose constantly, and suffer constantly, until… well, you can tolerate lactose. If you’re lactose intolerant, you’re probably horrified at the implications of the words “suffer constantly” in a way that those milk-digesting-weirdos could never understand. They probably think it is hyperbole; it is not. On the plus side, [HGModernism]’s symptoms began to decline after only one week.

The study dates back to the 1980s, and discusses a curious phenomenon where American powdered milk was cluelessly distributed during an African famine. Initially that did more harm than good, but after a few weeks mainlining the white stuff, the lactose-intolerant Africans stopped bellyaching about their bellyaches.

Humans all start out with a working lactase gene for the sake of breastfeeding, but in most it turns off naturally in childhood. It’s speculated that rather than some epigenetic change turning the gene for lactose tolerance back on — which probably is not possible outside actual genetic engineering — the gut biome of the affected individuals shifted to digest lactose painlessly on behalf of the human hosts. [HGModernism] found this worked but it took two weeks of chugging a slurry of powdered milk and electrolyte, formulated to avoid dehydration due to the obvious source of fluid loss. After the two weeks, lactose tolerance was achieved.

Should you try this? Almost certainly not. [HGModernism] doesn’t recommend it, and neither do we. Still, we respect the heck out any human willing to hack the way out of the limitations of their own genetics. Speaking of, at least one hacker did try genetically engineering themselves to skip the suffering involved in this process. Gene hacking isn’t just for ice-cream sundaes; when applied by real medical professionals, it can save lives.

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Iteration3D Is Parametric Python In The Cloud

December 11, 2025 by Tyler August 14 Comments

It’s happened to all of us: you find the perfect model for your needs — a bracket, a box, a cable clip, but it only comes in STL, and doesn’t quite fit. That problem will never happen if you’re using Iteration3D to get your models, because every single thing on the site is fully-parametric, thanks to an open-source toolchain leveraging 123Dbuilds and Blender.

Blender gives you preview renderings, including colors where the models are set up for multi-material printing. Build123D is the CAD behind the curtain — if you haven’t heard of it, think OpenSCAD but in Python, but with chamfers and fillets. It actually leverages the same OpenCascade that’s behind everyone’s other favorite open-source CAD suite, FreeCAD. Anything you can do in FreeCAD, you can do in Build123D, but with code. Except you don’t need to learn the code if the model is on Iteration3D; you just set the parameters and push a button to get an STL of your exact specifications.

The downside is that, as of now, you are limited to the hard-coded templates provided by Iteration3D. You can modify their parameters to get the configuration and dimensions you need, but not the pythonic Build123D script that generates them. Nor can you currently upload your own models to be shared and parametrically altered, like Thingiverse had with their OpenSCAD-based customizer. That said, we were told that user-uploads are in the pipeline, which is great news and may well turn Iteration3D into our new favorite.

Right now, if you’re looking for a box or a pipe hanger or a bracket, plugging your numbers into Iteration3D’s model generator is going to be a lot faster than rolling your own, weather that rolling be done in OpenSCAD, FreeCAD, or one of those bits of software people insist on paying for. There’s a good variety of templates — 18 so far — so it’s worth checking out. Iteration3D is still new, having started in early 2025, so we will watch their career with great interest.

Going back to the problem in the introduction, if Iteration3D doesn’t have what you need and you still have an STL you need to change the dimensions of, we can help you with that.

Thanks to [Sylvain] for the tip!