TechyMagThings

Although for many decades the planet Mars has been prodded, poked, driven upon, flown over and especially orbited by various spacecraft, landers and rovers sent over by a certain humanoid species on Earth, the two moons that orbit Mars have featured significantly more in science-fiction and video games than in scientific literature. This is now about to change when the Martian Moons eXploration (MMX) mission launches on October 19th, which will include a sample return from Phobos.

So far these two moons of Mars – Phobos and Deimos – have only received a few cursory glances by passing spacecraft, leaving many fundamental questions surrounding their formation and composition very much open. With the MMX mission this should change dramatically, with this spacecraft intended to perform detailed measurements of both moons.

In addition a rover – called Idefix – will perform a landing on Phobos for observations of its surface. This will be quite a feat as despite this lander coming in at 25 kg, on Phobos’ surface it will weigh only 15 grams due to the low gravity, or even less than the diminutive dog companion of Obelix, with potential bouncing as we have seen with previous landing attempts on such small bodies.

After launch, the MMX mission will take a year to arrive at Mars, in August of 2027, with Idefix being released in early 2029 for its hopefully soft paws-down on the surface of Phobos where it can scurry about for a while until the main MMX spacecraft lands later for its sample retrieval and return part of the mission. If everything goes well, this would mean that a sample of Phobos should be landing in Australia in 2031.

An engineer’s greatest tool is the writing utensil. Be it pen or pencil, we use them for everything from making diagrams to marking out cuts. But as with any practitioner of an art, we can tend to become rather particular about the details. [Choronva Engineering] is not different, and to that end set out to re-invent the pencil sharpener. 

In this case, [Chronova]’s ideal pencil tip shape is a concave cone. This is a shape quite trivial to make by using a knife, but rather impossible with a traditional twisting motion. But what if one automatized the knife whittling motion? This is actually a very old idea, with examples dating back to at least 1910. In this example, the blade is guided along two tracks with a particular curvature to enable the concave cone. This is driven by a cam shaft connected to a little cranking mechanism. Initial tests showed the mechanism works quite well at producing a cutoff of the desired shape, but lacks a pencil rotation mechanism.

Inspired by the Geneva wheel, [Chronova] developed a fresh intermittent mechanism for improved satisfaction in the sharpener’s operation. Instead of two gear-like mechanisms on a flat plane, the input and output can sit at a 90 degree offset from each other giving room for the blade’s motion. Rotation is input on a part called the indexing pinion which outputs on a lantern pinion.

At every full rotation of the indexing pinion, it interfaces with the lantern pinion moving it two teeth. Because of this quirk, by making the lantern with an odd number of teeth, twice the number of indexing positions are available in the output. At all other points in the pinion’s rotation the lantern is locked in place.

The pencil is held in place with a collect chuck and mounted on a screw coupled to the lantern pinion’s rotational output. This enables the pencil to move forward slightly with every turn of the crank. The project is topped of neatly with a shavings catcher and handle.

It works rather well, but a practical pencil sharpener that does not make. It takes a rather long time, and is fairly laborious to use. But over-engineering machines to do simple tasks is still quite fun!

One of the often made claims about plastics is that they are chemically inert under most conditions, such as when exposed to water. This long-held belief has also challenged the notion that micro- and nanoplastics (MNPs) are dangerous to organisms such as us human animals. A hitherto unknown mechanism between common plastics as investigated by [Naixin Qian] et al. and published in Nature serves to generate highly reactive hydroxyl radicals when exposed to water.

Hydroxyl radicals (HO^•) are the neutral form of the hydroxide ion (OH^–). It’s a free radical that tends to be extremely short-lived due to its reactivity, much like the singular oxygen molecule that is freed at the plastic-water interface. The energy provided for this reactivity comes from the electrostatic effect, itself highly correlated with many plastics, with the six types of microplastics used in the experiment showing varying levels of free radicals, particularly for the more hydrophobic types.

This high reactivity of free radicals is a well-known problem in cellular biology, with evolution having developed many tools over the years to deal with capturing these radicals as well as repair the (DNA) damage that they can cause. The effect of these microplastics and their generated free radicals was thus studied as well.

Of note here is that the electrostatic effect itself already serves to draw charged biomolecules to it, before the impact of free radicals is considered. By using mouse red blood cells and exposing them to polystyrene (PS) microplastics fatal damage was observed to the red blood cells.

This indicates that there are at least three possible ways in which MNPs can be harmful to organisms. It also provides another clue to how this may affect the ageing of plastics, among other implications.

Currently there is still ongoing debate on whether MNPs are truly harmful and just how prevalent they may be in e.g. our bodies. Reliably detecting them in e.g. biological tissues remains a challenge, which this new study may also be helpful with, since one of our biggest blind spots is that we lack solid knowledge of how MNPs may behave inside an organism.

Classic DOS games never ran from within stand-up arcade cabinets in dollhouses, but [Juha Lilja] imagines a world in which they did. His Micro DOS arcade cabinet is described as a device that “runs nothing” because the tiny unit is actually streaming the games over Wi-Fi from a nearby PC. That doesn’t mean it’s just a glorified movie player, though — the cabinet is playable, if a bit awkward to do so.

The core of the micro arcade cabinet is a M5Stack AtomS3R running as an embedded remote terminal. One tilts the whole cabinet as if it were a virtual joystick to send up, down, left, and right. Button presses are done by pushing on the physical screen; it supports single, double, and long-clicks. While in theory one could install a micro joystick and buttons instead, [Juha] aimed to keep everything self-contained and use only what was already built into the AtomS3R. In this case, that’s a motion sensor and the single button which is activated by pressing the screen.

The games themselves run on a PC, with screen contents being streamed wirelessly to the little display and inputs being sent back. The firmware on the AtomS3R doesn’t know or care what game is being played; all it does is display what it’s told, and send back input events. The back end does the rest. This makes it pretty flexible, and a tiny arcade cabinet is a handy way to demonstrate the whole system. It’s a pretty slick addition to his daughter’s dollhouse, too.

If streaming DOS games (or whatever else) to economical endpoints is giving you some ideas, the GitHub repository holds code and a fuller explanation of how it works. There’s a deeper discussion on some of the finer technical points, as well. Watch it in action in the video embedded just below the page break.

Technically all that you need in order to make a drone fly is a single motor and single propeller, but realistically it becomes basically impossible to fly it at that point. In the case of helicopters you therefore need a second rotor somewhere to provide counterbalance to the first and to be able to steer.

There are of course a number of ways to make a drone fly with a single helicopter, but the compromise usually is to use very large propellers, as well as other mechanisms that make for a very large drone. This wasn’t good enough for [Joshua Bird] who wanted to have a very small, single propeller drone.

Key to making it work is not only a very high RPM, but also a hinged propeller hub that manipulates the  angle of the blades in such a way that both pitch and roll can be controlled if you react quickly enough. This turned out to be impossible using standard motor ESCs that do not directly measure the motor’s speed and position but rely on back EMF.

In the final prototype of the drone such details had to be measured directly, with super-fast adjustments to the motor’s speed only possible with custom controller code and a lot of trial and error. Even then the drone would often lose track of its position and crash once more. The solution there was to add an infrared beacon in the room and a sensor on the drone, to give it a fixed reference point.

You can find the project files so far on the GitHub project page, with upcoming changes to the drone design involving improvements like adding a scanner to the drone so that it can autonomously use features in its environment as fixed reference points. That way it might conceivably be able to fly outside as well, which would be quite exciting to see.

On the face of it, making an event badge should be an easy process. After all, most of us can hand-assemble a microcontroller, some buttons, a battery, and a screen. But anyone who has been involved in producing one will tell you, the difference between producing one or two, and making sure hundreds or even thousands appear on day one of the event fully working is enormous. [Nicholas Ficara] produced 1750 of his first badge for Canada’s Hack The North hackathon, and he’s shared the full story.

We’ve been involved with the gestation of more than one badge here at Hackaday, so we recognise some of his learning moments only too well. He approached it with a well-planned series of prototype and release candidate steps to catch the problems, which came in handy as there certainly were a few. Wrong footprints, misplaced components, power supply issues, and rotated parts were fixed, and eventually they were delivered in time. It’s good to see that they were well received and well used at the event.

If you’re thinking of doing a badge we can certainly recommend that you give this a read. A few years ago we wrote up the story of another badge whose creators put in some hard work to save it from a more serious part error.

[Bob the Science Guy] remembers how to use a slide rule. Even after all these years, it is pretty easy to remember how to multiply and divide. If you can’t remember, you can usually work it out, as long as you understand how slide rules work. But what about sine, cosine, and quadratics? [Bob’s] been making videos about topics like this, and if you’ve wanted to put your slide rule collection to practical use, you’ll enjoy these videos. You can see one below.

The trick to the slide rule is that it is deceptively simple. You are in effect adding logarithms and then taking an antilog. The issue is that you still have to have some intuition about the scale of the answer since 2×3 works out the same as 2×3000 or 200×300.

But it is even trickier than that. Adding and subtracting is not easy on the slide rule. [Bob] shows how to use your math skills to convert problems that might have been addition problems into trig problems. So while it might seem more complicated to use trig, it may help work the problem on the slide rule.

We like slide rules. If you don’t have one, try this one in your browser (hint: go full screen and show both sides).