Wacky Science: Using Mayonnaise To Study Rayleigh-Taylor Instability

Sometimes a paper in a scientific journal pops up that makes you do a triple-take, case in point being a recent paper by [Aren Boyaci] and [Arindam Banerjee] in Physical Review E titled “Transition to plastic regime for Rayleigh-Taylor instability in soft solids”. The title doesn’t quite do their methodology justice — as the paper describes zipping a container filled with mayonnaise along a figure-eight track to look at the surface transitions. With the paper paywalled and no preprint available, we have to mostly rely the Lehigh University press releases pertaining to the original 2019 paper and this follow-up 2024 one.

Rayleigh-Taylor instability (RTI) is an instability of an interface between two fluids of different densities when the less dense fluid acts up on the more dense fluid. An example of this is water suspended above oil, as well as the expanding mushroom cloud during a explosion or eruption. It also plays a major role in plasma physics, especially as it pertains to nuclear fusion. In the case of inertial confinement fusion (ICF) the rapidly laser-heated pellet of deuterium-tritium fuel will expand, with the boundary interface with the expanding D-T fuel subject to RTI, negatively affecting the ignition efficiency and fusion rate. A simulation of this can be found in a January 2024 research paper by [Y. Y. Lei] et al.

As a fairly chaotic process, RTI is hard to simulate, making a physical model a more ideal research subject. Mayonnaise is definitely among the whackiest ideas here, with other researchers like [Samar Alqatari] et al. as published in Science Advances opting to use a Hele-Shaw cell with dyed glycerol-water mixtures for a less messy and mechanically convoluted experimental contraption.

What’s notable here is that the Lehigh University studies were funded by the Lawrence Livermore National Laboratory (LLNL), which explains the focus on ICF, as the National Ignition Facility (NIF) is based there.

This also makes the breathless hype about ‘mayo enabling fusion power’ somewhat silly, as ICF is even less likely to lead to net power production, far behind even Z-pinch fusion. That said, a better understanding of RTI is always welcome, even if one has to question the practical benefit of studying it in a container of mayonnaise.

Ryobi Battery Pack Gives Up Its Secrets Before Giving Up The Ghost

Remember when dead batteries were something you’d just toss in the trash? Those days are long gone, thankfully, and rechargeable battery packs have put powerful cordless tools in the palms of our hands. But when those battery packs go bad, replacing them becomes an expensive proposition. And that’s a great excuse to pop a pack open and see what’s happening inside.

The battery pack in question found its way to [Don]’s bench by blinking some error codes and refusing to charge. Popping it open, he found a surprisingly packed PCB on top of the lithium cells, presumably the battery management system judging by the part numbers on some of the chips. There are a lot of test points along with some tempting headers, including one that gave up some serial data when the battery’s test button was pressed. The data isn’t encrypted, but it is somewhat cryptic, and didn’t give [Don] much help. Moving on to the test points, [Don] was able to measure the voltage of each battery in the series string. He also identified test pads that disable individual cells, at least judging by the serial output, which could be diagnostically interesting.  [Don]’s reverse engineering work is now focused on the charge controller chip, which he’s looking at through its I2C port. He seems to have done quite a bit of work capturing output and trying to square it with the chip’s datasheet, but he’s having trouble decoding it.

This would be a great place for the Hackaday community to pitch in so he can perhaps get this battery unbricked. We have to admit feeling a wee bit responsible for this, since [Don] reports that it was our article on reverse engineering a cheap security camera that inspired him to dig into this, so we’d love to get him some help.

Original Game Boy Gets Display “Upgrade”

Before LCD and LED screens were ubiquitous, there was a time when the cathode ray tube (CRT) was essentially the only game in town. Even into the early 2000s, CRTs were everywhere and continuously getting upgrades, with the last consumer displays even having a semi-flat option. Their size and weight was still a major problem, though, but for a long time they were cutting edge. Wanting to go back to this time with their original Game Boy, [James Channel] went about replacing their Game Boy screen with a CRT.

The CRT itself is salvaged from an old video conferencing system and while it’s never been used before, it wasn’t recently made. To get the proper video inputs for this old display, the Game Boy needed to be converted to LCD first, as some of these modules have video output that can be fed to other displays. Providing the display with power was another challenge, requiring a separate boost converter to get 12V from the Game Boy’s 6V supply. After getting everything wired up a few adjustments needed to be made, and with that the CRT is up and running.

Unfortunately, there was a major speed bump in this process when [James Channel]’s method of automatically switching the display to the CRT let the magic smoke out of the Game Boy’s processor. But he was able to grab a replacement CPU from a Super Game Boy, hack together a case, and fix the problem with the automatic video switcher. Everything now is in working order for a near-perfect retro display upgrade. If you’d like to do this without harming any original hardware, we’ve seen a similar build based on the ESP32 instead.

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Possible Discovery Of Liquid Water In Mars’ Mid-Crust By The Insight Lander

One of the most sought after substances in the Universe is water – especially in its liquid form – as its presence on a planet makes the presence of life (as we know it) significantly more likely. While there are potentially oceans worth of liquid water on e.g. Jupiter’s moon Europa, for now Mars is significantly easier to explore as evidenced by the many probes which we got onto its surface so far. One of these was the InSight probe, which was capable of a unique feat: looking inside the planet’s crust with its seismometer to perform geophysical measurements. These measurements have now led to the fascinating prospect that liquid water may in fact exist on Mars right now, according to a paper published by [Vashan Wright] and colleagues in PNAS (with easy-read BBC coverage). Continue reading “Possible Discovery Of Liquid Water In Mars’ Mid-Crust By The Insight Lander”

Maker [Dala] showing powerwall statistics

From Vehicle-to-Grid To DIY Home Powerwalls

As battery-to-grid and vehicle-to-home technologies become increasingly mainstream, the potential for repurposing electric vehicle (EV) batteries has grown significantly. No longer just a niche pursuit, using retired EV batteries for home energy storage has become more accessible and appealing, especially as advancements in DIY solutions continue to emerge. Last year, this project by [Dala] showcased how to repurpose Nissan Leaf and Tesla Model 3 battery packs for home energy storage using a LilyGO ESP32, simplifying the process by eliminating the need for battery disassembly.

In the past few months, this project has seen remarkable progress. It now supports over 20 different solar inverter brands and more than 25 EV battery models. The most exciting development, however, is the newly developed method for chaining two EV packs together to create a single large super-battery. This breakthrough enables the combination of, for example, two 100kWh Tesla packs into a massive 200kWh storage system. This new capability offers an accessible and affordable way to build large-scale DIY home powerwalls, providing performance that rivals commercial systems at a fraction of the cost.

With these advancements, the possibilities for creating powerful, cost-effective energy storage solutions have expanded significantly. We do however stress to put safety first at all times.

Hungry for more home powerbanks? We’ve been there before.

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Cheap DIY Button Pad Uses Neat Punchcard Trick

A StreamDeck is effectively a really cool box full of colorful buttons that activate various things on your PC. They’re fun and cool but they’re also something you can build yourself if you’re so inclined. [Jason] did just that for his sim racing setup, and he included some nifty old-school tech as well.

An ESP32 is at the core of the build, listening to button presses and communicating with the PC. However, the build doesn’t actually use regular buttons. Instead, it uses infrared sensors wired up in a matrix. This was an intentional choice, because [Jason] wanted the device to be reconfigurable with different paper card overlays. There are ways to do this with regular buttons too, but it works particularly well with the infrared technique. Plus, each button also gets a Neopixel allowing its color to be changed to suit different button maps.

What’s really neat is that the button maps change instantly when a different overlay card is inserted. [Jason] achieved this with an extra row of infrared sensors to detect punched holes in the bottom of the overlay cards.

Once upon a time, even building your own keyboard was an uphill battle. Today, it’s easier than ever to whip up fun and unique interface devices that suit your own exact needs. That’s a good thing! Video after the break.

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Stemfie, The 3D-Printable Construction Set

Construction kit toys are cited by many adults as sparking great creativity and engineering talent in their youth. LEGO, Meccano, K’NEX, Lincoln Logs—these are all great commercial options. But what about printing your very own construction kit at home? Meet Stemfie.

Fundamentally, Stemfie isn’t that different from any other construction kit you might have seen before. It has various beams and flat plates that are full of holes so they can be assembled together in various ways. It also uses bolts, spacers, and small plastic nuts that can be tightened using a special hand tool. Think of a mixture between LEGO Technic and Meccano and that will get you in the ballpark. It includes neat motion components too, including gears, wheels, and even a large flat spring!

What can you build with it? Well, as every construction kit toy says, you’re only limited by your imagination! However, if your imagination is especially small, you can just use the Stemfie 3D YouTube channel for inspiration. It features everything from a ping pong ball catapult to a rubber-band driven car. Plus, since it’s all 3D printed, you can simply scale up the parts and build even bigger designs. Like a giant catapult that can hurl entire water jugs. Fun!

We’ve seen other projects in this vein before. One of our favorites is [Ivan Miranda]’s giant 3D printed assembly kit that he uses to build big monster toys.

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