Auto-Tracking Sentry Gun Gives Deer a Super Soaking

Things rarely go well when humans mix with wildlife. The problems are exacerbated in the suburbs, where bears dine on bird feeders and garbage cans, raccoons take up residence in attics, and coyotes make off with the family cat. And in the suburbs, nuisance wildlife can be an intractable problem because the options for dealing with it are so limited.

Not to be dissuaded in the battle to protect his roses, [dlf.myyta] built this motion-activated sentry gun to apply some watery aversion therapy to marauding deer. Shown in action below against a bipedal co-conspirator, the sentry gun has pretty much what you’d expect under the hood — Raspberry Pi, NoIR camera, a servo for aiming and a solenoid valve to control the water. OpenCV takes care of locating the intruders and swiveling the nozzle to center mass; since the deer are somewhat constrained by a fence, there’s no need to control the nozzle’s elevation. Everything is housed nicely in a plastic ammo can for portability and waterproofing. Any target that stands still for more than three seconds gets a hosing; we assume this is effective, but alas, no snuff films were provided.

We’re not sure if [dlf.myyta]’s code can discern friend from foe, and in this litigious world, hosing the neighbor’s kid could be a catastrophe. Perhaps version 2.0 can include image recognition for target verification.

Continue reading “Auto-Tracking Sentry Gun Gives Deer a Super Soaking”

Living On The Moon: The Challenges

Invariably when we write about living on Mars, some ask why not go to the Moon instead? It’s much closer and has a generous selection of minerals. But its lack of an atmosphere adds to or exacerbates the problems we’d experience on Mars. Here, therefore, is a fun thought experiment about that age-old dream of living on the Moon.

Inhabiting Lava Tubes

Lava tube with collapsed pits near Gruithuisen crater
Lava tube with collapsed pits near Gruithuisen crater

The Moon has even less radiation protection than Mars, having practically no atmosphere. The lack of atmosphere also means that more micrometeorites make it to ground level. One way to handle these issues is to bury structures under meters of lunar regolith — loose soil. Another is to build the structures in lava tubes.

A lava tube is a tunnel created by lava. As the lava flows, the outer crust cools, forming a tube for more lava to flow through. After the lava has been exhausted, a tunnel is left behind. Visual evidence on the Moon can be a long bulge, sometimes punctuated by holes where the roof has collapsed, as is shown here of a lava tube northwest from Gruithuisen crater. If the tube is far enough underground, there may be no visible bulge, just a large circular hole in the ground. Some tubes are known to be more than 300 meters (980 feet) in diameter.

Lava tubes as much as 40 meters (130 feet) underground can also provide thermal stability with a temperature of around -20°C (-4°F). Having this stable, relatively warm temperature makes building structures and equipment easier. A single lunar day is on average 29.5 Earth days long, meaning that we’ll get around 2 weeks with sunlight followed by 2 weeks without. During those times the average temperatures on the surface at the equator range from 106°C (224°F) to -183°C (-298°F), which makes it difficult to find materials to withstand that range for those lengths of time.

But living underground introduces problems too.

Continue reading “Living On The Moon: The Challenges”

This Drone Can Fly, Swim, and Explode….. Wait, What?

You’ve probably heard of micro-drones, perhaps even nano-drones, but there research institutions that shrink these machines down to the size of insects. Leading from the [Wiss Institute For Biologically Inspired Engineering] at Harvard University, a team of researchers have developed a miniscule robot that — after a quick dip — literally explodes out of the water.

To assist with the take off, RoboBee has four buoyant outriggers to keep it near the water’s surface as it uses electrolysis to brew oxyhydrogen in its gas chamber. Once enough of the combustible gas has accumulated — pushing the robot’s wings out of the water in the process– a sparker ignites the fuel, thrusting it into the air. As yet, the drone has difficulty remaining in the air after this aquatic takeoff, but we’re excited to see that change soon.

Looking like a cross between a water strider and a bee, the team suggest this latest version of the RoboBee series  — a previous iteration used electrostatic adhesion to stick to walls — could be used for search and rescue, environmental monitoring, and biological studies. The capacity to transition from aerial surveyor, to underwater explorer and back again would be incredibly useful, but in such a small package, it is troublesome at best. Hence the explosions.

Continue reading “This Drone Can Fly, Swim, and Explode….. Wait, What?”

3D Printed Tyres Let You Drive on Water

[Jesus] apparently walked on water, without any tools at all. But when you’ve got a 3D printer handy, it makes sense to use it. [Simon] decided to use his to 3D print some tyres for his R/C car – with awesome results.

[Simon] started this project with a goal of driving on water. Initial experiments were promising – the first design of paddle tyres gave great traction in the sand and were capable of climbing some impressive slopes. However, once aimed at the water, the car quickly sank below the surface.

Returning to the drawing board armed with the advice of commenters, [Simon] made some changes. The paddle tyres were reprinted with larger paddles, and a more powerful R/C car selected as the test bed. On the second attempt, the car deftly skipped along the surface and was remarkably controllable as well! [Simon] has provided the files so you can make your own at home.

It’s a great example of a practical use for a 3D printer. Parts can readily be made for all manner of RC purposes, such as making your own servo adapters.

Trike with Water-Rocket Engine

Many of us made soda bottle rockets for science class. Some of us didn’t have that opportunity, and made them in the backyard because that’s what cool kids do. Water rockets work on the premise that if water is evacuated from one side of a container, the container will accelerate away from the evacuation point. Usually, this takes the form of a 2-liter bottle, a tire pump and some cardboard fins. [François Gissy] modified the design but not the principle for his water trike which reached 261 kph or 162mph.

Parts for the trike won’t be found in the average kitchen but many of them could be found in a motorcycle shop, except for the carbon fiber wrapped water tank. There wasn’t a throttle on this rocket, the clutch lever was modified to simply open the valve and let the rider hold on until the water ran out. The front brake seemed to be intact, thank goodness.

Powering vehicles in unconventional ways is always a treat to watch and [François Gissy]’s camera-studded trike is no exception. If you like your water rockets pointed skyward, check out this launch pad for STEM students and their water rockets. Of course, [Colin Furze] gets a shout-out for his jet-powered go-kart.

Thank you, [Itay], for the tip.

Continue reading “Trike with Water-Rocket Engine”

The Illuminated Waterways of the United States

A recent convert to the ways of the laser cutter, redditor [i-made-a-thing] was in want of a project and — stumbling on some waterways maps on Etsy — launched into fabricating an illuminated map of all the waterways in the United States.

The map itself was laser-cut out of 1/4 inch plywood at his local makerspace. Thing is, smaller rivers and tributaries were too narrow at the scale [i-made-a-thing] wanted, so he ended up spending several hours in Photoshop preparing the image so larger rivers would be laser-cut — and not break off– while the rest would be etched onto the surface. After testing the process by making a few coasters, he was ready to get started on the real deal.

Continue reading “The Illuminated Waterways of the United States”

Living on Mars: the Stuff You Never Thought About

In The Martian we saw what kind of hacking was needed to stay alive for a relatively short while on Mars, but what if you were trying to live there permanently? Mars’ hostile environment would affect your house, your transportation, even how you communicate. So here’s a fun thought experiment about how you’d live on Mars as part of a larger community.

Not Your Normal House

Mars One living units under regolith
Mars One living units under regolith, Source video

Radiation on Mars comes from solar particle events (SPE) and galactic cosmic radiation (GCR). Mars One, the organization planning one-way trips to Mars talks about covering their habitats in several meters of regolith, a fancy word for the miscellaneous rocky material covering the bedrock. Five meters provides the same protection as the Earth’s atmosphere — around 1,000 g/cm2 of shielding. A paper from the NASA Langley Research Center says that the largest reduction comes from the top 15 to 20 cm of regolith. And so our Mars house will have an underlying structure but the radiation protection will come from somewhere between 20 cm to a few meters of regolith. Effectively, people will be living underground.

On Earth, producing water and air for your house is not something you think of doing, let alone disposing of exhaled CO2. But Mars houses will need systems for this and more.

Continue reading “Living on Mars: the Stuff You Never Thought About”