Why NASA Only Needs Pi To So Many Decimal Places

December 17, 2024 by 53 Comments

If you’re new to the world of circular math, you might be content with referring to pi as 3.14. If you’re getting a little more busy with geometry, science, or engineering, you might have tacked on a few extra decimal places in your usual calculations. But what about the big dogs? How many decimal places do NASA use?

NASA doesn’t need this many digits. It’s likely you don’t either. Image credits: NASA/JPL-Caltech

Thankfully, the US space agency has been kind enough to answer that question. For the highest precision calculations, which are used for interplanetary navigation, NASA uses 3.141592653589793 — that’s fifteen decimal places.

The reason why is quite simple, going into any greater precision is unnecessary. The article demonstrates this by calculating the circumference of a circle with a radius equal to the distance between Earth and our most distant spacecraft, Voyager 1. Using the formula C=2pir with fifteen decimal places of pi, you’d only be off on the true circumference of the circle by a centimeter or so. On solar scales, there’s no need to go further.

Ultimately, though, you can calculate pi to a much greater precision. We’ve seen it done to 10 trillion digits, an effort which flirts with the latest Marvel movies for the title of pure irrelevance. If you’ve done it better or faster, don’t hesitate to let us know!

Tech In Plain Sight: Table Saw Safety

December 17, 2024 by 76 Comments

If you ask around a wood shop, most people will agree that the table saw is the most dangerous tool around. There’s ample evidence that this is true. In 2015, over 30,000 ER visits happened because of table saws. However, it isn’t clear how many of those are from blade contact and how many are from other problems like kickback.

We’ve seen a hand contact a blade in a high school shop class, and the results are not pretty. We’ve heard of some people getting off lucky with stitches, reconstructive surgery, and lifelong pain. They are the lucky ones. Many people lose fingers, hands, or have permanent disfiguration and loss of function. Surgeons say that the speed and vigor of the blade means that some of the tissue around the cut vanishes, making reconstruction very difficult.

Modern Tech

These days, there are systems that can help prevent or mitigate these kinds of accidents. The most common in the United States is the patented SawStop system, which is proprietary — that is, to get it, you have to buy a saw from SawStop.

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The Last Acorn BBC Computer Wasn’t A BBC Micro

December 17, 2024 by 27 Comments

For home computer users, the end of the 1980s was the era of 16-bit computers. The challenge facing manufacturers of 8-bit machines through the middle of the decade was to transfer their range and customers to the new hardware, and the different brands each did this in their own way. Commodore and Atari had 68000-based powerhouses, and Apple had their 16-bit-upgraded IIGS for the middle ground below the Mac, but what about Acorn, makers of the BBC Micro? They had the Archimedes, and [RetroBytes] takes us through how they packaged their 32-bit ARM processor for consumers.

The A3000 was the computer you wanted if you were a geeky British kid at the end of that decade, even if an Amiga or an ST was what you got. Schools had bought a few of the desktop Archimedes’, so if you were lucky you’d got to know Arthur and then RiscOS, so you knew just how fast these things were compared to the competition. The video below the break takes a dive into the decisions behind the design of this first ARM consumer product, and along the way it explains a few things we didn’t know at the time.  We all know what happened to Acorn through the 1990s and we all use ARM processors today, so it’s a fascinating watch. If only an extra two hundred quid had been in the kitty back then and we could have bought one ourselves.

If you have never used an Archimedes you can get pretty close today with another Cambridge-designed and ARM-powered computer. RiscOS never went away, and you can run it on a Raspberry Pi. As we found, it’s still pretty useful.

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Man Overboard Systems Aim To Increase Survival Rates At Sea

December 17, 2024 by 22 Comments

When you hear the cry of “Man Overboard!” on a ship, it’s an emergency situation. The sea is unkind to those that fall from their vessel, and survival is never guaranteed—even in the most favorable conditions. Raging swell and the dark of night can only make rescue more impossible.

Over the centuries, naval tradition has included techniques to find and recover the person in the water as quickly and safely as possible. These days, though, technology is playing an ever-greater role in such circumstances. Modern man-overboard (MOB) systems are designed to give crews of modern vessels a fighting chance when rescuing those in peril.

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See What ‘They’ See In Your Photos

December 17, 2024 by 46 Comments

Once upon a time, a computer could tell you virtually nothing about an image beyond its file format, size, and color palette. These days, powerful image recognition systems are a part of our everyday lives. They See Your Photos is a simple website that shows you just how much these systems can interpret from a regular photo.

The website simply takes your image submission, runs it through the Google Vision API, and spits back out a description of the image. I tried it out with a photograph of myself, and was pretty impressed with what the vision model saw:

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3D Printed Blaster Does It With Compliant Components

December 17, 2024 by 20 Comments

The ease of integrating bendy parts into designs is one of 3D printing’s strengths. A great example of this is [uhltimate]’s six-shot blaster which integrates several compliant mechanisms. The main blaster even prints in one piece, so there’s not even any assembly required.

The ergonomics are unconventional, but the design is pretty clever.

The blaster itself has three main parts: the trigger, the sear, and the striker. Each of them rely on compliant mechanisms in order to function. The user pulls back the trigger, which hooks into and pulls back the striker. When the trigger is pulled back far enough, the sear releases the striker. This zips forward and slams into a waiting projectile, sending it flying.

The other interesting part is the projectiles and magazine in which they sit. The magazine fits onto the front of the blaster and pulling the trigger allows the magazine to drop down, putting the next projectile into firing position. After the final round is fired, the empty magazine falls away. It’s a pretty clever design, even if the ergonomics are a little unusual and it relies on gravity in order to feed. Tilt it too far sideways or upside down, and it won’t load properly.

We’ve seen compliant mechanisms used for projectile firing before, but this design really raises the bar in the way it does more than just firing the striker.

3D printing allows rapid iteration of designs, which makes devices that rely on compliant mechanisms much easier to develop and fine-tune.

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Robot Air Hockey Player Predicts Your Next Move

December 16, 2024 by 21 Comments

Air hockey is a fun game, but it’s one you can’t play by yourself. That is, unless you have a smart robot hockey player to act as your rival. [Zeroshot] built exactly that.

The build is based around a small 27-inch air hockey table—not exactly arcade-spec, but big enough to demonstrate the concepts at play. The robot player moves its mallet in the X and Y axes using a pair of NEMA17 stepper motors and an H-belt configuration. To analyze the game state, there’s a Raspberry Pi 3B fitted with a camera, and it has a top-down view of the board. The Pi gives the stepper motors commands on how to move the mallet via an Arduino that communicates with the stepper drivers.  The Pi doesn’t just aim for the puck itself, either. With Python and OpenCV, it tries to predict your own moves by tracking your mallet, and the puck, too. It predicts the very-predictable path of the puck, and moves itself to the right position for effective defence.

Believe it or not, we’ve featured quite a few projects in this vein before. They’ve all got their similarities, and their own unique quirks. Video after the break.
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