Japanese Rocket Engine Explodes: Continuously And On Purpose

September 2, 2021 by Lewin Day 62 Comments

Liquid-fuelled rocket engine design has largely followed a simple template since the development of the German V-2 rocket in the middle of World War 2. Propellant and oxidizer are mixed in a combustion chamber, creating a mixture of hot gases at high pressure that very much wish to leave out the back of the rocket, generating thrust.

However, the Japan Aerospace Exploration Agency (JAXA) has recently completed a successful test of a different type of rocket, known as a rotating detonation engine. The engine relies on an entirely different method of combustion, with the aim to produce more thrust from less fuel. We’ll dive into how it works, and how the Japanese test bodes for the future of this technology.

Deflagration vs. Detonation

Humans love combusting fuels in order to do useful work. Thus far in our history, whether we look at steam engines, gasoline engines, or even rocket engines, all these technologies have had one thing in common: they all rely on fuel that burns in a deflagration. It’s the easily controlled manner of slow combustion that we’re all familiar with since we started sitting around campfires. Continue reading “Japanese Rocket Engine Explodes: Continuously And On Purpose” →

Perusing The People’s Computing Company

September 2, 2021 by Chris Lott 10 Comments

If you are a certain age, you might recall the People’s Computing Company (PCC) from the 1970s. It was not really a company, but rather a folksy computer newsletter in the visual style of the times. In the first issue, published in October 1972, founders Dennis Allison, Bob Albrecht and George Firedrake explained their reasons for starting the newsletter:

Computers are mostly used against people instead of for people, used to control people instead of to free them; time to change all that — we need a … People’s Computer Company

The Computer History Museum (CHM) in Mountain View CA has a print collection of these issues donated by [Jim Warren], spanning its ten-year publication run (it changed name to Recreational Computing in 1979). Despite the museum being closed to the public these days over Covid concerns, CHM supporter [Bob Zeidman] has scanned all the issues and they are available at the CHM collections archive.

It’s really fun to browse through these old issues, and see the kinds of topics which were of interest back then. Many would still be of interest today, and many others have become obsolete by advances in technology (but are still fun to read if you have an interest in retro-computing). For example, in the first issue you can read about why you might use different lenses on your Bell & Howell film projector, a comparison of DEC and HP computers as used in educational settings, and how to save money on your teleprinter maintenance contracts and consumables like TTY paper, ribbons, and punched paper tape. If you have some time to kill, check out these archives and take yourself back to a time when desktop publishing meant literally typing and drawing freehand with metal styli on special stencils which were mounted on drums in your mimeograph machine one page at a time.

The PCC was an early supporter of copyright-free software, teaching computer programming, using computer games as a learning tool, and encouraging computer literacy for everyone. They did this not only via the newsletter, but educational books, an organization called ComputerTown USA! for teaching kids, and spin-off periodicals like DragonSmoke and Dr. Dobb’s Journal of Computer Calisthenics & Orthodontia (edited by [Jim Warren] mentioned above) which went on to become the popular computer magazine Dr. Dobb’s Journal which stayed in publication until 2014. We wrote a piece a few years ago about a software-defined radio project from the PCC back in 1975. Do you have any favorite old journal archives that you like to peruse from time to time?

Pining For A De-Googled Smartphone

September 2, 2021 by Bryan Cockfield 89 Comments

Last summer in the first swings of the global pandemic, sitting at home finally able to tackle some of my electronics projects now that I wasn’t wasting three hours a day commuting to a cubicle farm, I found myself ordering a new smartphone. Not the latest Samsung or Apple offering with their boring, predictable UIs, though. This was the Linux-only PinePhone, which lacks the standard Android interface plastered over an otherwise deeply hidden Linux kernel.

As a bit of a digital privacy nut, the lack of Google software on this phone seemed intriguing as well, and although there were plenty of warnings that this was a phone still in its development stages it seemed like I might be able to overcome any obstacles and actually use the device for daily use. What followed, though, was a challenging year of poking, prodding, and tinkering before it got to the point where it can finally replace an average Android smartphone and its Google-based spyware with something that suits my privacy-centered requirements, even if I do admittedly have to sacrifice some functionality.

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Google Maps, Now On The NES

September 2, 2021 by Lewin Day 8 Comments

Many years ago, Google created one of its famous April Fools jokes suggesting it would make an 8-bit version of Google Maps for the original Nintendo Entertainment System. [ciciplusplus] decided it needed to become a reality, however, and set to work. (Video, embedded below.)

It’s a suitably blocky, low-resolution implementation, but it nevertheless is a mapping app running on an NES. Zooming in and out is via the A and B buttons, while the D-pad is used to scroll. Country and city labels are rendered on the map in the relevant areas in a charming old-school font.

The project uses a Raspberry Pi 3A+ and a Cypress Semiconductor FX2LP microcontroller, which fits inside a NES cartridge. It works the same way as the earlier NES Doom project which uses the Raspberry Pi to feed data to the NES’s Picture Processing Unit. It’s achieved with a simple bit of code burned on a ROM inside the cartridge, which boots up the NES and primes it to receive data from the Raspberry Pi via the FX2LP.

In current form, it’s not capable of doing much more than allowing the user to scroll around and zoom in on parts of the map. We’d love to see a fully-fledged version that could deliver driving directions or similar, however. If you end up achieving such a feat, be sure to let us know. Continue reading “Google Maps, Now On The NES” →

Neat Little Airboat Built From Old Drone Parts

September 2, 2021 by Lewin Day 3 Comments

Multirotor drones tend to need quality and well-matched parts in order to stay balanced and in the air. However, crash enough drones and you might find you’ve got plenty of mistmatched bits and pieces lying around. In just this vein, [Jason Suter] decided to raid his junk box and built himself a little FPV airboat using spare parts.

The airboat consists of a 3D printed hull, paired with a separate power module. The power module houses the flight controller, and mounts twin motors on the rear. Fitted with three-blade props, they propel the boat and allow it to be steered with differential thrust instead of a rudder. It’s then fitted with a camera to allow it to be piloted with an FPV headset.

Handling still isn’t perfect, and water on the FPV antenna causes some issues with video transmission. However, it’s a fun project that makes good use of old parts. Of course, if you’re having vibration problems with your own FPV projects, consider building a vibration-absorbing mount. Video after the break.
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Upgrade Board Adds GPIO Pins To Your Replica PDP-11

September 1, 2021 by Tom Nardi 10 Comments

Like many Hackaday readers, [Steven Stallion] has had his eyes on the replica PDP-11 created by [Oscar Vermeulen] for some time now, and this summer he finally got the opportunity to build one himself. But while most owners might be content to just watch the Raspberry Pi based faux-retro computer blink away on a shelf, he wanted to explore putting the machine to more practical use. The end result is the PiDP-11 I/O Expander, an add-on that lets the modern minicomputer interact with the world around it.

Developed after some discussion with [Oscar] himself, the Microchip MCP23016 based expander board fits neatly onto the PiDP-11 PCB, and [Steven] has made sure his installation guide meshes well with the replica’s documentation. The Pi’s I2C bus is actually broken out on the original PCB, so you just need to solder a header on and run some jumpers to where the expander is mounted. You’ll need to pull 5 V as well, and the installation guide has a few tips on convenient connection points.

Each expander board gives you 16 GPIO pins which can be accessed over I2C, including support for interrupts which has been connected to GPIO 19 on the Raspberry Pi. [Steven] notes that you should be able to stack multiples of his expander up should you need even more free pins, though some fiddling with pull-up resistors and I2C addresses will likely be necessary.

The PCBs for the expander have been released under the two clause BSD license, so you’re free to spin up your own copies however you see fit. But if you’d like to save some time, [Steven] is offering assembled boards on Tindie.

Since [Oscar] first teased it at the 2015 Hackaday Supercon, we’ve been enamored with his fantastic PDP-11 replica. We’re always glad to see when somebody has picked up one of these wonderful kits, and doubly so when they’ve figured out a way to expand it in unexpected ways.

Detect Lightning Strikes With An Arduino

September 1, 2021 by Bryan Cockfield 20 Comments

Lightning is a powerful and seemingly mysterious force of nature, capable of releasing huge amounts of energy over relatively short times and striking almost at random. Lightning obeys the laws of physics just like anything else, though, and with a little bit of technology some of its mysteries can be unraveled. For one, it only takes a small radio receiver to detect lightning strikes, and [mircemk] shows us exactly how to do that.

When lightning flashes, it also lights up an incredibly wide spectrum of radio spectrum as well. This build uses an AM radio built into a small integrated circuit to detect some of those radio waves. An Arduino Nano receives the signal from the TA7642 IC and lights up a series of LEDs as it detects strikes in closer and closer proximity to the detector. A white LED flashes when a strike is detected, and some analog circuitry supports an analog galvanometer which moves during lightning strikes as well.

While this project isn’t the first lightning detector we’ve ever seen, it does have significantly more sensitivity than most other homemade offerings. Something like this would be a helpful tool to have for lifeguards at a pool or for a work crew that is often outside, but we also think it’s pretty cool just to have around for its own sake, and three of them networked together would make triangulation of strikes possible too.

Continue reading “Detect Lightning Strikes With An Arduino” →