Day: May 18, 2025

In Memory Of Ed Smylie, Whose Famous Hack Saved The Apollo 13 Crew

May 18, 2025 by 30 Comments

Some hacks are so great that when you die you receive the rare honor of both an obituary in the New York Times and an in memoriam article at Hackaday.

The recently deceased, [Ed Smylie], was a NASA engineer leading the effort to save the crew of Apollo 13 with a makeshift gas conduit made from plastic bags and duct tape back in the year 1970. [Ed] died recently, on April 21, in Crossville, Tennessee, at the age of 95.

This particular hack, another in the long and storied history of duct tape, literally required putting a square peg in a round hole. After an explosion crippled the command module the astronauts needed to escape on the lunar excursion module. But the lunar module was only designed to support two people, not three.

The problem was that there was only enough lithium hydroxide onboard the lunar module to filter the air for two people. The astronauts could salvage lithium hydroxide canisters from the command module, but those canisters were square, whereas the canisters for the lunar module were round.

[Ed] and his team famously designed the required adapter from a small inventory of materials available on the space craft. This celebrated story has been told many times, including in the 1995 film, Apollo 13.

Thank you, [Ed], for one of the greatest hacks of all time. May you rest in peace.

Header: Gas conduit adapter designed by [Ed Smylie], NASA, Public domain.

Two clear phials are shown in the foreground, next to a glass flask. One phial is labelled “P,” and the other is labelled “N”.

Designing A Hobbyist’s Semiconductor Dopant

May 18, 2025 by 3 Comments

[ProjectsInFlight] has been on a mission to make his own semiconductors for about a year now, and recently shared a major step toward that goal: homemade spin-on dopants. Doping semiconductors has traditionally been extremely expensive, requiring either ion-implantation equipment or specialized chemicals for thermal diffusion. [ProjectsInFlight] wanted to use thermal diffusion doping, but first had to formulate a cheaper dopant.

Thermal diffusion doping involves placing a source of dopant atoms (phosphorus or boron in this case) on top of the chip to be doped, heating the chip, and letting the dopant atoms diffuse into the silicon. [ProjectsInFlight] used spin-on glass doping, in which an even layer of precursor chemicals is spin-coated onto the chip. Upon heating, the precursors decompose to leave behind a protective film of glass containing the dopant atoms, which diffuse out of the glass and into the silicon.

After trying a few methods to create a glass layer, [ProjectsInFlight] settled on a composition based on tetraethyl orthosilicate, which we’ve seen used before to create synthetic opals. After finding this method, all he had to do was find the optimal reaction time, heating, pH, and reactant proportions. Several months of experimentation later, he had a working solution.

After some testing, he found that he could bring silicon wafers from their original light doping to heavy doping. This is particularly impressive when you consider that his dopant is about two orders of magnitude cheaper than similar commercial products.

Of course, after doping, you still need to remove the glass layer with an oxide etchant, which we’ve covered before. If you prefer working with lasers, we’ve also seen those used for doping. Continue reading “Designing A Hobbyist’s Semiconductor Dopant” →

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Hackaday Links: May 18, 2025

May 18, 2025 by 8 Comments

Say what you want about the wisdom of keeping a 50-year-old space mission going, but the dozen or so people still tasked with keeping the Voyager mission running are some major studs. That’s our conclusion anyway, after reading about the latest heroics that revived a set of thrusters on Voyager 1 that had been offline for over twenty years. The engineering aspects of this feat are interesting enough, but we’re more interested in the social engineering aspects of this exploit, which The Register goes into a bit. First of all, even though both Voyagers are long past their best-by dates, they are our only interstellar assets, and likely will be for centuries to come, or perhaps forever. Sure, the rigors of space travel and the ravages of time have slowly chipped away at what these machines can so, but while they’re still operating, they’re irreplaceable assets.

Continue reading “Hackaday Links: May 18, 2025” →

Speed Up Arduino With Clever Coding

May 18, 2025 by 57 Comments

We love Arduino here at Hackaday; they’ve probably done more to make embedded programming accessible to more people than anything else in the history of the field. One thing the Arduino ecosystem is rarely praised for is its speed. That’s where [Playduino]  comes in, with his video (embedded below) that promises to make everyone’s favourite microcontroller run 50x faster.

You might be expecting an unstable overclocking setup, with swapped crystals, tweaked voltages and a hefty heat sink, but no! This is stock hardware. The 50x speedup comes from one simple hack: don’t use digitalWrite();

If you aren’t familiar, the digitalWrite() function is one of the key functions Arduino gives you to operate its boards– specify the pin and the value (high or low) to drive it. It’s very easy, but it’s also very slow. [Playduino] takes a moment to show just how much is going on under the hood when you call digitalWrite(), and shows you what you can do instead if you have a need for speed. (Hint: there’s no Arduino-provided code involved; hardware registers and the __asm keyword show up.)

If you learned embedded programming in an earlier era, this will probably seem glaringly obvious. If you, like so many of us, got started inside of the Arduino ecosystem, these closer-to-the-metal programming techniques could prove useful tools in your quiver. Big thanks to [Stephan Walters] for the tip.

Of course if you prefer to speed things up by hardware rather than software, you can overclock an Arduino– with liquid nitrogen, even.

Continue reading “Speed Up Arduino With Clever Coding” →

Christmas Comes Early With AI Santa Demo

May 18, 2025 by 6 Comments

With only two hundred odd days ’til Christmas, you just know we’re already feeling the season’s magic. Well, maybe not, but [Sean Dubois] has decided to give us a head start with this WebRTC demo built into a Santa stuffie.

The details are a little bit sparse (hopefully he finishes the documentation on GitHub by the time this goes out) but the project is really neat. Hardware-wise, it’s an audio-enabled ESP32-S3 dev board living inside Santa, running the OpenAI’s OpenRealtime Embedded SDK (as implemented by ExpressIf), with some customization by [Sean]. Looks like the audio is going through the newest version of LibPeer and the heavy lifting is all happening in the cloud, as you’d expect with this SDK. (A key is required, but hey! It’s all open source; if you have an AI that can do the job locally-hosted, you can probably figure out how to connect to it instead.)

This speech-to-speech AI doesn’t need to emulate Santa Claus, of course; you can prime the AI with any instructions you’d like. If you want to delight children, though, its hard to beat the Jolly Old Elf, and you certainly have time to get it ready for Christmas. Thanks to [Sean] for sending in the tip.

If you like this project but want to avoid paying OpenAI API fees, here’s a speech-to-text model to get you started.We covered this AI speech generator last year to handle the talky bit. If you put them together and make your own Santa Claus (or perhaps something more seasonal to this time of year), don’t forget to drop us a tip!

Two rings of magnets are shown encasing a circular channel in a white plastic piece. The channel is filled with liquid metal, and a loop of wire is about to be lowered into the metal.

Magnetohydrodynamic Motors To Spin Satellites

May 18, 2025 by 18 Comments

Almost all satellites have some kind of thrusters aboard, but they tend to use them as little as possible to conserve chemical fuel. Reaction wheels are one way to make orientation adjustments without running the thrusters, and [Zachary Tong]’s liquid metal reaction wheel greatly simplifies the conventional design.

Reaction wheels are basically flywheels. When a spacecraft spins one, conservation of angular momentum means that the wheel applies an equal and opposite torque to the spacecraft, letting the spacecraft orient itself. The liquid-metal reaction wheel uses this same principle, but uses a loop of liquid metal instead of a wheel, and uses a magnetohydrodynamic drive to propel the metal around the loop.

[Zach] built two reaction wheels using Galinstan as their liquid metal, which avoided the toxicity of a more obvious liquid metal. Unfortunately, the oxide skin that Galinstan forms did make it harder to visualize the metal’s motion. He managed to get some good video, but a clearer test was their ability to produce torque. Both iterations produced a noticeable response when hung from a string and activated, and achieved somewhat better results when mounted on a 3D-printed air bearing.

Currently, efficiency is the main limitation of [Zach]’s motors: he estimates that the second model produced 6.2 milli-newton meters of torque, but at the cost of drawing 22 watts. The liquid metal is highly conductive, so the magnetohydrodynamic drive takes high current at low voltage, which is inconvenient for a spacecraft to supply. Nevertheless, considering how hard it is to create reliable, long-lasting reaction wheels the conventional way, the greatly improved resilience of liquid-metal reaction wheels might eventually be worthwhile.

If you’re curious for a deeper look at magnetohydrodynamic drives, we’ve covered them before. We’ve also seen [Zach]’s earlier experiments with Galinstan.

Continue reading “Magnetohydrodynamic Motors To Spin Satellites” →

Casting Shade On “Shade-Tolerant” Solar Panels

May 18, 2025 by 32 Comments

Shade is the mortal enemy of solar panels; even a little shade can cause a disproportionate drop in power output. [Alex Beale] reviewed a “revolutionary” shade-tolerant panel by Renology in a video embedded below. The results are fascinating.

While shading large portions of the panels using cardboard to cut off rows of cells, or columns of cells, the shade tolerant panel does very well compared to the standard panel– but when natural, uneven shading is applied to the panel, very little difference is seen between the standard and active panels in [Alex]’s test.  We suspect there must be some active components to keep power flowing around shaded cells in the Renology panel, allowing it to perform well in the cardboard tests. When the whole panel is partially shaded, there’s no routing around it, and it performs normally.

It’s hard to see a real-world case that would justify the extra cost, since most shading doesn’t come with perfect straight-line cutoffs. Especially considering the added cost for this “shade tolerant” technology (roughly double normal panels).

You might see a better boost by cooling your solar panels. Of course you can’t forget to optimize the output with MPPT. It’s possible that a better MPPT setup might have let the Renology panel shine in this video, but we’re not certain. Whatever panels you’re using, though, don’t forget to keep them clean.

Continue reading “Casting Shade On “Shade-Tolerant” Solar Panels” →