Hackaday Podcast 041: The “How Not To” Episode Of Rebreathers, Chain Sprockets, Hovercraft, And Data Logging

October 25, 2019 by 4 Comments

Hackaday Editors Mike Szczys and Elliot Williams shed some light on a true week of hacks. It seems as though all kinds of projects are doing this the “wrong” way this week and its delightful to see what they learn along the way. Hovercraft can work using the Coandă effect which uses the blowers on the outside. You can dump your Linux logs to soldered-on eMMC memory, and chain sprockets can be cut from construction brackets. If you really want to build your own rebreather you can. All of these hacks work, and seeing how to do something differently is an inspiring tribute to the art of hardware hacking… you can learn a lot by asking yourself why these particular techniques are not the most commonly used.

Plus, Mike caught up with Alessandro Ranellucci at Maker Faire Rome last weekend. In addition to being the original author of slic3r, Alessandro has been Italy’s Open Source lead for the last several years. He talks about the legislation that was passed earlier this year mandating that software commissioned by the government must now be Open Source and released with an open license.

Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

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Lessons Learned Building A DIY Rebreather

October 18, 2019 by 44 Comments

While the homebrew rebreather the [AyLo] describes on his blog looks exceptionally well engineered and is documented to a level we don’t often see, he still makes it very clear that he’s not suggesting you actually build one yourself. He’s very upfront about the fact that he has no formal training, and notes that he’s already identified several critical mistakes. That being said, he’s taken his rebreather out for a few dives and has (quite literally) lived to tell the tale, so he figured others might be interested in reading about his experiments.

For the landlubbers in the audience, a rebreather removes the CO2 from exhaled air and recirculates the remaining O2 for another pass through the lungs. Compared to open circuit systems, a rebreather can substantially increase the amount of time a diver can remain submerged for a given volume of gas. Rebreathers aren’t just for diving either, the same basic concept was used in the Apollo PLSS to increase the amount of time the astronauts could spend on the surface of the Moon.

The science behind it seemed simple enough, so [AyLo] did his research and starting designing a bare-minimum rebreather system in CAD. Rather than completely hack something together with zip ties, he wanted to take the time to make sure that he could at least mate his hardware with legitimate commercial scuba components wherever possible to minimize his points of failure. It meant more time designing and machining his parts, but the higher safety factor seems well worth the effort.

[AyLo] has limited the durations of his dives to ten minutes or less out of caution, but so far reports no problems with the setup. As with our coverage of the 3D printed pressure regulator or the Arduino nitrox analyser, we acknowledge there’s a higher than usual danger factor in these projects. But with a scientific approach and more conventional gear reserved for backups, these projects prove that hardware hacking is possible in even the most inhospitable conditions.

$100 Hot Water Bottle Pendulum Rebreather

March 25, 2006 by 23 Comments

swampfox

Humans exhale a lot of oxygen along with their waste carbon dioxide. Instead of throwing out this oxygen, a rebreather uses a scrubber to remove the CO2 and replace it with pure oxygen from a bottle. Tom Rose built this rebreather for $100. When you exhale air passes through the scrubbing material and is stored in hot water bottle counterlung until you inhale. The system is only 15 pounds; a great savings compared to most dive equipment. You are definitely putting your life in your own hands so this should not be used without plenty of “couch-diving” tests. Tom has a ton of other diving related projects on his site.

[via Divester]

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Skylab Under The Ocean

April 13, 2026 by 21 Comments

A crew lives on a station in a hostile environment. Leaving that environment requires oxygen tanks and specialized gear to deal with pressure differentials. A space station? Nah. A base built on the ocean floor. The US Navy was interested in such a base in the 1960s, and bases like this are a staple of science fiction. But today, we see more space stations than underwater bases. Have you ever wondered why?

Diving deep underwater is a tricky business. At a certain depth, the pressure forces gas like nitrogen to dissolve into your body. By itself, this isn’t a problem, but when you ascend, it is a big problem. If the gas all comes out at the same time, you get bubbles, which can cause decompression sickness, commonly called the bends. The exact problems vary, but the bends often cause extreme joint pain, fatigue, or a rash. Sometimes people die.

While you think of the bends as a deep-sea diver’s problem, it can also happen in airplanes and outer space. Any time you go from high pressure to low pressure quickly, you are subject to decompression sickness. Depending on what you are doing, there are different ways to mitigate the problem. For diving, traditionally, you simply don’t surface too quickly.

You dive, do your work, and then head towards the surface, stopping at preset stops to let the pressure equalize gradually. Physics is a bear, though. The longer you stay at a given depth, the longer you have to decompress.

That means you rapidly reach a point of diminishing returns. Suppose you dive to the ocean floor. You spend an hour working. Then you have to spend, say, eight hours gradually rising to the surface. That makes extended operations at significant depth impractical.

George Bond was thinking about all this and had an interesting idea. It is true that, in general, the longer you stay down, the more gas your body absorbs. But it is also true that, eventually, your tissues saturate, and then you don’t absorb any more.

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Diving With An Unlimited Air Supply

December 21, 2019 by 82 Comments

If you want to explore underwater, you have a few options. You can hold your breath. You can try to recycle your air. You can carry your breathing air with you as in SCUBA. You can stick a tube up like a snorkel, or you can have air sent down to you from the surface. EXOlung falls into this last category, but unlike many other surface solutions, it has a twist: it never runs out of power before you do. Watch the video below and you’ll see how it works.

A buoy puts a snorkel up out of the water, and a tube lets you dive up to 5 meters away. There’s a small tank on your chest, and your body’s motion serves to fill the tank from the outside air supply. As your legs extend and retract, you fill the tank and then put the tank’s air at ambient pressure so you can breathe. As a bonus, by varying how you inhale and exhale, you can control your buoyancy and, therefore, your depth.

The system does require you to strap your legs up to the apparatus. However, other similar systems have compressors or batteries which can fail or run down, meaning there can be a limit on how long you can stay under. EXOlung claims there is no limit to how long you can stay under.

The cost looks to be around 300 Euro, although for a bit more you can get one that uses different materials to withstand higher pressures. That one has a 7-meter hose.

Another approach is to just carry a little air and remove the CO2 from it and rebreathe it. We’ve also seen a risky surface air pump that uses wind power.

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Apollo’s PLSS And The Science Of Keeping Humans Alive In Space

August 19, 2019 by 13 Comments

Ever since humans came up with the bright idea to explore parts of the Earth which were significantly less hospitable to human life than the plains of Africa where humankind evolved, there’s been a constant pressure to better protect ourselves against the elements to keep our bodies comfortable. Those first tests of a new frontier required little more than a warm set of clothes. Over the course of millennia, challenging those frontiers became more and more difficult. In the modern age we set our sights on altitude and space, where a warm set of clothes won’t do much to protect you.

With the launch of Sputnik in 1957 and the heating up of the space race between the US and USSR, many firsts had to be accomplished with minimal time for testing and refinement. From developing 1945’s then state-of-the-art V-2 sounding rockets into something capable of launching people to the moon and beyond, to finding out what would be required to keep people alive in Earth orbit and on the Moon. Let’s take a look at what was required to make this technological marvel happen, and develop the Portable Life Support System — an essential component of those space suits that kept astronauts so comfortable they were able to crack jokes while standing on the surface of the Moon.

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