Welcome To SubTropolis: The Limestone Mine Turned Climate-Controlled Business Complex

November 10, 2024 by Maya Posch 32 Comments

After extracting all the useful stuff from a mine, you are often left with a lot of empty subterranean space without a clear purpose. This was the case with the Bethany Falls limestone mine, near Kansas City, Missouri, which left a sprawling series of caverns supported by 16′ (4.9 meter) diameter pillars courtesy of the used mining method. As detailed by [Benjamin Hunting] in a recent article on the Hagerty site, this made it a fascinating place for a business complex development now called SubTropolis that among other things is used for car storage by Ford and long-term stamp storage by the US Post Office. (Check out their cool period photos!)

The reason for this is the extremely stable climate within these man-made caverns, with relative humidity hovering around a comfortable 40% and temperatures stable year-round at about 21 °C (70 °F), making it ideal for storing anything that doesn’t like being placed outdoors, while saving a lot on airconditioning costs. With Ford one of the biggest companies in SubTropolis, this means that many companies providing customization services for vehicles have also moved operations inside the complex.

With the only negative being a lack of daylight, it seems like the perfect place for many businesses and (evil) lairs, assuming electrical power and constant air circulation are provided.

Featured image: “Subtropolis” by [ErgoSum88]

Building A Motor Feed For The UE1 Vacuum Tube Computer’s Paper Tape Reader

November 10, 2024 by Maya Posch 9 Comments

Building a paper tape reader by itself isn’t super complicated: you need a source of light, some photoreceptors behind the tape to register the presence of holes and some way to pull the tape through the reader at a reasonable rate. This latter part can get somewhat tricky, as Usagi Electric‘s [David Lovett] discovered while adding this feature to his vacuum tube-era DIY reader. This follows on what now seems like a fairly simple aspect of the photosensors and building a way to position said photosensors near the paper tape.

As the feed rate of the paper tape is tied to the reading speed, and in the case of [David]’s also contains the clock for the custom tube-based UE1 computer, it determines many of the requirements. With 8 bits per line, the tape forms the ROM for the system, all of which has to be executed and used immediately when read, as there is no RAM to load instructions into. This also necessitates the need to run the tape as an endless loop, to enable ‘jumping’ between parts of this paper-based ROM by simple masking off parts of the code until the desired address is reached.

For the motor a slot car motor plus speed-reduction gear was chosen, with a design to hold these then designed in FreeCAD. Courtesy of his brother’s hobby machine shop and a CAD professional’s help, producing these parts was very easy, followed by final assembly. Guides were added for the tape, not unlike with a cassette player, which allowed the tape to be pulled through smoothly. Next up is wiring up the photodiodes, after which theoretically the UE1 can roar into action directly running programs off paper tape.

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Excerpt from 1995 Stratasys patent, showing the drawings of FDM layers, including brick layers.

Brick Layers: The Promise Of Stronger 3D Prints And Why We Cannot Have Nice Things

November 9, 2024 by Maya Posch 87 Comments

It is a fact of life that 3D printed parts from an FDM (fused deposition modeling) printer have weaknesses where the layers join. Some of this is due to voids and imperfect layer bonding, but you can — as [Geek Detour] shows us — work around some of this. In particular, it is possible to borrow techniques from brick laying to create a pattern of alternating blocks. You can check out the video below.

The idea of ‘brick layers’ with FDM prints was brought to the forefront earlier this year by [Stefan] of CNC Kitchen. Seven months after that video you still can’t find the option for these layers in any popular slicers. Why? Because of a 2020 patent filed for this technique by a 3D printing company which offers this feature in its own slicer. But is this patent even valid?

It’s no surprise that prior art already exists in the form of a 1995 Stratasys patent. The above image shows an excerpt from the 1995 Stratasys patent, covering the drawings of FDM layers, including brick layers. This covered all such ways of printing, but the patent expired in 2016. In 2019, a PrusaSlicer ticket was opened, requesting this feature. So what happened? A second patent filed in 2020 assigned to Addman Intermediate Holdings: US11331848B2.

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Exploring The Physics Behind Cooling Towers

November 9, 2024 by Maya Posch 21 Comments

A characteristic of any thermal power plant — whether using coal, gas or spicy nuclear rocks — is that they have a closed steam loop with a condenser section in which the post-turbine steam is re-condensed into water. This water is then led back to the steam generator in the plant. There are many ways to cool the steam in the condenser, including directly drawing in cooling water from a nearby body of water. The most common and more efficient way is to use a cooling tower, with a recent video by [Practical Engineering] explaining the physics behind these.

For the demonstration, a miniature natural draft tower is constructed in the garage from sheets of acrylic. This managed to cool 50 °C water down to 20 °C by merely spraying the hot water onto a mesh that maximizes surface area. The resulting counter-flow means that no fan or the like is needed, and the hyperboloid shape of the cooling tower makes it incredibly strong despite having relatively thin walls.

The use of a natural draft tower makes mostly sense in cooler climates, while in hotter climates having a big cooling lake may make more sense. We covered the various ways to cool thermal plants before, including direct intake, spray ponds, cooling towers and water-free cooling solutions, with the latter becoming a feature of new high-temperature fission reactor designs.

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Ramsey Numbers And The Appearance Of Order In Random Numbers

November 8, 2024 by Maya Posch 25 Comments

Proof without words of the two-color case of Ramsey's theorem. (Credit: CMG Lee, Wikimedia) — Proof without words of the two-color case of Ramsey’s theorem. (Credit: CMG Lee, Wikimedia)

Generally when assuming a chaotic (i.e. random) system like an undirected graph, we assume that if we start coloring these (i.e. assign values) with two colors no real pattern emerges. Yet it’s been proven that if you have a graph with a certain set of vertices, coloring the resulting lines in this manner will always result in a clique forming. This phenomenon has been investigated for nearly a century now after its discovery by British mathematician [Frank P. Ramsey].

The initial discovery concerned a graph with 6 vertices, providing the lowest number of vertices required. Formally this is written as R(3, 3), with subsequent cases of these Ramsey numbers discovered. They are part of Ramsey theory, which concerns itself with the question of what the underlying properties are that cause this apparent order to appear, which requires us to discover more cases.

Finding the number for a particular instance of R(m, n) can be done the traditional way, or brute-forcing it computationally. Over the decades more advanced algorithms have been developed to help with the search, and people from different fields are mingling as they are drawn to this problem. So far the pay-off of this search are these algorithms, the friendships created and perhaps one day a deep insight in the causes behind this phenomenon that may have implications for physics, chemistry and other fields.

LEAF Mission Seeks To Grow Plants On The Moon

November 6, 2024 by Maya Posch 12 Comments

Space Lab's LEAF model crops & growth chamber. — Credit: Space Lab

We have seen a recent surge of interest in whether it’s possible to grow potatoes and other plants in Martian soil, but what is the likelihood that a future (manned) lunar base could do something similar? To that end [Space Lab] is developing the LEAF project that will be part of NASA’s upcoming Artemis III lunar mission. This mission would be the first to have Americans return to the Moon by about 2028, using the somewhat convoluted multi-system SLS-Starship-Lunar Gateway trifecta. The LEAF (Lunar Effects on Agricultural Flora) science module will feature three types of plants (rape (Brassica Rapa), duckweed and cress (Arabidopsis thaliana) ) in an isolated atmosphere.

The main goal of this project is to find out how the plants are affected by the lunar gravity, radiation and light levels at the landing site at the south pole. This would be the equivalent of a hydroponics setup in a lunar base. After about a week of lunar surface time the growth chamber will be split up into two: one returning back to Earth for examination and the other remains on the surface to observe their long-term health until they perish from cold or other causes.

This is not the first time that growing plants on the lunar surface has been attempted, with China’s Chang’e 4 mission from 2019. The lander’s Lunar Micro Ecosystem featured a range of seeds as well, which reportedly successfully sprouted, but the project was terminated after 9 days instead of the planned 100 due to issues with heating the biosphere during the brutal -52°C lunar night. Hopefully LEAF can avoid this kind of scenario when it eventually is deployed on the Moon.

Amazon Receives FAA Approval For MK30 Delivery Drone

November 6, 2024 by Maya Posch 23 Comments

It’s been about a decade since Amazon began to fly its delivery drones, aiming to revolutionize the online shopping experience with rapid delivery of certain items. Most recently Amazon got permission from the FAA to not only start flying from its new Arizona-based location, but also to fly beyond-visual-line-of-sight (BVLOS) missions with the new MK30 drone. We reported on this new MK30 drone which was introduced earlier this year along with the news of the Amazon Prime Air delivery service ceasing operations in California and moving them to Arizona instead.

This new drone has got twice the range as the old MK27 drone that it replaces and is said to be significantly quieter as well. The BLOS permission means that the delivery drones can service areas which are not directly visible from the warehouse with its attached drone delivery facility. With some people within the service range of the MK27 drones having previously complained about the noise levels, we will see quickly enough whether the MK30 can appease most.

As for the type of parcels you can have delivered with this service, it is limited to 2.27 kg (~5 lbs), which is plenty for medication and a range of other items where rapid delivery would be desirable.