Mysterious Files PH

Sometimes claimed to give you wings, energy drinks can, at the very least, be used to make rockets fly. This is what [Nate Scovill] did in a recent video, where cans of the sugary stuff are processed to give a rocket its proverbial wings.

The basic concept is so-called rocket candy, which uses the fact that sugar is a pretty decent fuel type that — when combined with an oxidizer like potassium nitrate — can be turned into solid rocket fuel. Naturally it’d be easiest to start off with a pure source of sucrose or sorbitol for the sugar, but what if you only have access to cans of sugary soda?

Removing the moisture from the energy drink was the obvious first step, as water and rocket fuel aren’t a great mix. Adding and mixing potassium nitrate to the resulting thick syrup created the fuel-oxidizer mixture, also known as rocket fuel. This did take a detour involving removing the carbonation using a vacuum chamber, as CO₂ and fire do not really like each other either.

We previously covered making your own rocket candy, though it’s far from the only rocket fuel that can be made at home using products bought at the local supermarket. Obviously, doing so comes with a whole heap of risks, not least of which is the notion that the difference between a rocket and a bomb is a pretty thin and fuzzy line that you do not want to accidentally cross.

Steam power is a staple of the steampunk aesthetic, thermodynamics, and a checkpoint for the budding mechanical engineer studying heat cycles. But because food is largely made of water, steam is also common in the culinary arts. So it’s no surprise that when thermodynamics is applied to cooking, exciting things can happen. 

This particular example of steam-powered culinary happenings is inspired by industrial potato-peeling machines. By adding high-pressure, high-temperature steam to a pressure vessel with potatoes inside, heat can transfer more easily to the inside of the potatoes. Because the pressure is so high, however, the water in the skin won’t boil. This is fundamentally the same concept as a pressure cooker. However, what’s different is that instead of a pressure cooker’s slow release, these industrial peeling machines rely on explosive decompression, flash boiling the water underneath the potato’s skin. This rapidly expanding steam rips away the skin in a nice clean sheet.

But, to [Stuff Made Here’s] disappointment, there were no videos of the process on the internet. But, fortunately for us, being an engineer of complicated machines means that there is one now that you can watch below.

The machine itself is, on paper at least, fairly simple. It consists of a boiler, connected to a fruit chamber by a valve, and another valve to vent the steam out of the fruit chamber. However, engineering a pressure vessel that can safely withstand over 1,000 kPa of steam with a window for filming when you can’t weld very well is another matter entirely. The boiler is two stainless steel plates with a cylinder in the middle, with face seals used to keep the chamber steam-tight. A custom jig was needed to machine the pipe ends flat enough to mate with the seals. It’s held together with threaded rods. However, because the rods and the vessel body have different thermal expansion coefficients, Belleville washers are used as expansion joints in the system.

The fruit chamber is welded together because it experiences lower pressures. This also allows for a less sensitive O-ring seal on the door, reducing the work required to use the door. A glass piece inlaid into the steel door provides a view, held in place by pressure and 3D-printed brackets. A stand holds the fruit centered within the window for our viewing pleasure!

The results speak for themselves, though operation is complicated and dangerous, and it can only peel one fruit at a time; the skin of nearly every example placed inside is perfectly removed. Experiments include apples, potatoes, grapes, lemons, strawberries, blackberries, and (pictured above) popcorn on the cob. It’s quite a fun demonstration of the thermodynamic principles at play!

Thanks [DjBiohazard] for the tip!

It’s a sci-fi trope that you can ‘scan for life signs’ and detect if there are humans — or suspiciously human-shaped aliens — present, but in real life it’s harder than that. [The Masked Bear]’s wifisense-pi project isn’t really scanning for signs of life, either, unless you happen to consider breathing a sign of life. Even then, it’s not detecting breathing per se, but the subtle motion that goes with it: it’s a very sensitive motion detector that relies on the fact that we fleshy bags of goo disturb WiFi signals with our presence, and motion alters those disturbances.

The device uses an ESP32-S3 to measure the radio channel 100 times per second, while a Raspberry Pi 4 provides the signal processing muscle. It can detect the slightest motions, and even determine the presence of a perfectly still human by their breathing, though you can hide your presence for as long as you can hold your breath. A single sensor, no matter how sensitive, cannot give position information, and while multiple humans will distort WiFi more than a single one, [The Masked Bear] reports you cannot reliably extract that signal. So this project answers the question: “are there humans in this room?” Or, even more likely, “are there any large breathing animals in this room?” We can’t imagine a 50 kg Mastiff looking any different to this sensor than an equivalent mass of quivering human flesh.

Before you dismiss this as just another motion sensor, keep in mind that it is sniffing the signals already present on the 2.4 GHz band, and, like the WiFi signals themselves, it can work through walls. So we think it’s pretty nifty. Of course, there are many other ways to detect humans, from machine-learning cameras to millimeter-wave sensors to a simple PIR. This isn’t the first project we’ve seen that uses WiFi like this. It isn’t even the first with an ESP32, but it’s an interesting implementation worth checking out.

[The Modern Rouge] found an old childhood friend in a closet: a Radio Shack 200-in-1 electronic kit. Along with [Josh Nass], he put it through its paces and made a few repairs along the way. As you might expect, the batteries had long ago leaked out their magic juice.

If you missed these, they were a host of real electronic components with springs connected to the leads. To make a circuit, you bend the spring over, insert a wire, and let go of the spring. By changing the wiring, you could make radios, alarms, computer circuits, and more

There were dozens of these kits, some more capable than others. This was a particularly nice one with a loaded front panel and several exotic components. In the end, they made a code practice oscillator, and it worked.

While you can’t find kits exactly like these anymore, you can make your own. Or try Snap Circuits and print your own modules. You take solderless breadboards for granted today, but they haven’t always been around or affordable.

Any parent with a baby and deep pockets– or friends with deep pockets– will probably sing the praises of the BabyBjorn rocking sling chair. A simple spring-loaded sling seat allows you to rock a child to sleep like magic– but you do have to rock the child. In the tradition of fathers everywhere since the stone age, [Ceyhun Karataş] saw that as something to tinker around, creating his Automatic BabyBjorn Bouncer/Rocker with a servo, an Arduino, and some 3D printed parts.

You still can’t leave your child unattended with this hack, [Ceyhun] takes pains to point out, but it will free a hand so you can keep junior happy while tinkering up other toys for him or her. Music players are a popular staple, for example.

You should have plenty of time for such projects, because it won’t take long for you to replicate [Ceyhun]’s invention– it’s only as complicated as it needs to be, which is not very. The servo, a Futaba S3003 which is mounted to the bottom of the rocker in a 3D printed case, reels the baby in with a string tied to the bouncing seat portion.  The BabyBjorn’s built-in spring bounces junior back up. As stated, Arduino Nano controls the servo, with two potentiometers in the build allowing you to control the speed and amplitude of the bounce independently to get the perfect naptime ratio. Everything you need to get started — aside from the hardware and the child– is available at the link above. You can see it in action in the video below, which in spite what you may fear from the Turkish thumbnail, does have authentic English audio, not AI auto-dubbing.

If you’ve got the baby but not the bouncy chair, have a gander at this mechatronic crib that does something similar on a much larger budget.

Thanks to [Ceyhun] for overcoming the new-parent sleep deprivation to document this project and send in a tip.

These days, most of us interface with our computing devices in the same old-fashioned ways—via keyboards, mice, and touchscreens. The idea of a more direct brain-to-machine interface remains appealing to many. [Ildar Rakhmatulin] and [Youssef El Abbass] have been working on just such a device, with an eye to using it for gaming.

The device is referred to as Octopus 16, so named because it combines sixteen EEG electrodes into a single compact package, along with the required common reference and ground. The contacts themselves are pogo pins, assembled into a coin-sized cluster. The device is strapped to the head, pushing the contacts against the scalp, and data from the electrodes is then siphoned off to a host machine via Bluetooth Low Energy. The EEG signals are picked up with a pair of Texas Instruments ADS131M08 ADCs, each with 8 channels, with a resolution of 24-bits to capture fine detail in whatever the brain is doing. An ESP32 microcontroller is responsible for grabbing the ADC output and trucking it out over Bluetooth.

The rig is designed for use with the PiEEG software platform. The team have experimented with the device, showing it off by using the EEG signals to detect an individual’s focus state and using that to feed into simple game environments.

Ultimately, what has been shown so far is not so different from the old Force Trainer toy, but the design might prove useful if you’re looking into doing EEG experiments on a budget. Just do your due diligence to make sure you’re getting more signal than noise out of those lovely 24-bit ADCs. Video after the break.

It’s still hot on both sides of the Atlantic, but Kristina has a new secret weapon for staying cool without making noise. Will Elliot and the others follow suit? Time will tell.

In Hackaday news, well, there’s a lot of it. For starters, Supercon Ten tickets went on sale Thursday morning, but chances are good that by the time you read this, the early bird offering will be all pecked out. But, never fear! More tickets will be released soon enough.

Don’t want to buy a ticket, but still want to go? Submit a talk proposal that gets accepted, and you’ll be welcomed in free of charge. Lucky for you, we just extended the deadline by two weeks to August 26th.

After exhausting the news, Elliot reached into the ol’ Mailbag and found a funny anecdote from [Vik Olliver]. (Funny in that it’ll make you go ‘hmm’.) A brief discussion about imperial vs. metric ensued, but then it was on to the hacks.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Download in lovely MP3.

Episode 382 Show Notes:

News:

• Supercon Ten Tickets On Sale Now
• Procrastineers Rejoice! 2026 Supercon Call For Participation Extended
• Have Scientists Stuck The Landing On The Glueball Discovery?
• Watch Today’s Eclipse At Home

Mailbag:

• This week, we have a head-scratcher from [Vik Olliver] and well, you’ll just have to listen!

Interesting Hacks of the Week:

• Hacking Fiber To The Home
• FlipBuddy Is Borg, You Will Be Assimilated
• Creating A Supersonic Trebuchet
  • Trebucheting Tennis Balls At 124 MPH
  • Make Physics Fun With A Trebuchet
  • Flywheel Trebuchet Spins Right Round
• Track Bird Visitors With A Raspberry Pi And A USB Mic
• Lighting 3D Printed Parts On Fire For Science
• Wrist Welcomes Wii Nunchuk As Gloriously Ergonomic Macropad

Quick Hacks:

• Elliot’s Picks:
  • Retrotechtacular: A View Of The Moon From 1964
  • The Chernobyl NPP And Forty Years Of Robots For High Radiation Environments
  • Read A USB Logitech Racing Wheel On An ESP32‑S3
• Kristina’s Picks:
  • Your Laptop Keyboard, On Another Device
  • Titanic-esqe Telegraph Keeps Relationship Afloat
  • The PiShot Is Ready For Your Snaps

Can’t-Miss Articles:

• Bladerunners And The Mother Of Invention
• FitzRoy’s Glass: Victorian Weather Marvel Or Glorified Thermometer?