Retrotechtacular: The J-57 Afterburner Engine

July 14, 2015 by 15 Comments

The J-57 afterburner engine appeared in many airplanes of notable make, including the F-101, -102, and -103. This USAF training film shows the parts of the J-57, explains the complex process by which the engine produces thrust, and describes some maintenance and troubleshooting procedures.

The name of this game is high performance. Precision thrust requires careful rigging of the engine’s fuel control linkage through a process called trimming. Here, the engine fuel control is adjusted with regard to several different RPM readings as prescribed in the manual.

One of the worst things that can happen to a J-57 is known as overtemping. This refers to high EGT, or exhaust gas temperature. If EGT is too high, the air-fuel ratio is not ideal. Troubleshooting a case of high EGT should begin with a check of the lines and the anti-icing valve. If the lines are good and the valve is closed, the instruments should be checked for accuracy. If they’re okay, then it’s time for a pre-trimming inspection.

In addition to EGT, engine performance is judged by RPM and PP7, the turbine discharge pressure. If RPM and PP7 are within spec and the EGT is still high, the engine must be pulled. It should be inspected for leaks and hot spots, and the seals should be examined thoroughly for cracks and burns. The cause for high EGT may be just one thing, or it could be several small problems. This film encourages the user to RTFM, which we think is great advice in general.

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An Interview With Tesla Battery Hacker [wk057]

November 11, 2014 by 63 Comments

We covered [wk057] and his Tesla Model S battery teardown back in September. Since then we had some time to catch up with him, and ask a few questions.

You’ve mentioned that you have a (non hacked) Tesla Model S. What do you think of the car?

It’s the best car I’ve ever driven or owned, period. Not to get too into it, but, I love it. I’ve put almost 20,000 miles on it already in under a year and I have no real complaints. Software feature requests… but no complaints. After almost a year, multiple 1700-miles-in-a-weekend trips, and an overall great experience… I can never go back to a gas vehicle after this. It would be like going back to horses and buggies.

A salvage Tesla Lithium battery had to be expensive compared to a Lead Acid setup. What made you go with the Tesla?

Actually, if you consider that the Model S battery is already pre-setup as a high-capacity pack, contains the wiring to do so, and the modules are much more energy and power dense than any lead acid battery bank, it’s actually almost cheaper than a comparable lead acid bank and all the trimmings.

I haven’t officially weighed them, but the modules from the Model S battery are roughly 80 lbs. 80 lbs for a 5.3 kWh battery is around 15 lbs per kWh, which is impressive. For comparison, a decent lead acid battery will have a little over 1 kWh (of low-rate discharge capacity) and weigh almost the same.

Also, the Tesla pack is much more powerful than a lead acid bank of the same capacity.
Generally a lead acid battery bank would have a capacity that would only be realized with slow discharges, so, 1/20C. Much over that and you sacrifice capacity for power. 1/20C for an 85kWh pack is only 4.25kW, barely enough for a central air unit and some lights without losing capacity.

Now the Tesla pack can be discharged (based on how it does so in the vehicle) at up to 3.75C for short periods, and at 1/2C continuously without really affecting the overall capacity of the pack. That means I can run 10x more power than lead acid without a loss in overall charge capacity. Leads to a much more flexible battery solution since the loads will, in reality, always be so low that this will not even come into play with the Tesla pack, but would almost always be a factor with lead acid.

Charging is also somewhat better with the Tesla battery. Charge a lead acid battery at a 1/2C and it will boil. Charge the Tesla pack at 1/2C (42kW) and it might warm up a few degrees. Oh, and the charging losses at high rates are much less than lead acid also.
Overall, without continuing to yack about the technical aspects, it’s just a much better battery, takes up less space, weighs less, and has more power available.

There are likely decent arguments for other solutions, but the rest aside, this one won out because it was definitely more interesting.

Click past the break to read the rest of our interview with [wk057]!

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Hackaday 10th Anniversary: [1o57] And The Art Of Encryption

October 6, 2014 by 35 Comments

[Ryan] a.k.a. [1o57] comes from an age before anyone could ask a question, pull out their smartphone, and instantly receive an answer from the great Google mind. He thinks there’s something we have lost with our new portable cybernetic brains – the opportunity to ask a question, think about it, review what we already know, and reason out a solution. There’s a lot to be said about solving a problem all by yourself, and there’s nothing to compare to the ‘ah-ha’ moment that comes with it.

[1o57] started his Mystery Challenges at DEFCON purely by accident; he had won the TCP/IP embedded device competition one year, and the next year was looking to claim his title again. The head of the TCP/IP embedded competition had resigned from his role, and through a few emails, [1o57] took on the role himself. There was a miscommunication, though, and [1o57] was scheduled to run the TCP/IP drinking competition. This eventually morphed into a not-totally-official ‘Mystery Challenge’ that caught fire in email threads and IRC channels. Everyone wanted to beat the mystery challenge, and it was up to [1o57] to pull something out of his bag of tricks.

The first Mystery Challenge was a mechanical device with three locks ready to be picked (one was already unlocked), magnets to grab ferrous picks, and only slightly bomb-like in appearance. The next few years featured similar devices with more locks, better puzzles, and were heavy enough to make a few security officials believe [1o57] was going to blow up the Hoover dam.

With a few years of practice, [1o57] is turning crypto puzzles into an art. His DEFCON 22 badge had different lanyards that needed to be arranged to spell out a code. To solve the puzzle, you’ll need to talk to other people, a great way to meet one of [1o57]’s goals of getting all the natural introverts working together.

Oh. This talk has its own crypto challenge, something [1o57] just can’t get out of his blood:

We talked for a little bit, and 0x06 0x0a1 MFY YWXDWE MEOYOIB ASAE WBXLU BC S BLOQ ZTAO KUBDR HG SK YTTZSLBIMHB

Parts: 8bit IO Expander (PCF8574)

December 27, 2008 by 28 Comments

pcf8574

Sometimes a project has more sensors, buttons, or LEDs than your microcontroller has pins. The PCF8574 is an easy way to add 8 low-speed input or output pins to a microcontroller. A configurable address lets multiple PCF8574s exist on the same bus, so two microcontroller pins can control dozens of IO pins. We’ll show you how to use this chip below.

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View inside the vacuum vessel of Wendelstein 7-X in Greifswald, Germany. (Credit: Jan Hosan, MPI for Plasma Physics)

Wendelstein 7-X Sets New Record For The Nuclear Fusion Triple Product

July 15, 2025 by 17 Comments
Fusion product against duration, showing the Lawson criterion progress. (Credit: Dinklage et al., 2024, MPI for Plasma Physics)
Fusion product against duration, showing the Lawson criterion progress. (Credit: Dinklage et al., 2024, MPI for Plasma Physics)

In nuclear fusion, the triple product – also known as the Lawson criterion – defines the point at which a nuclear fusion reaction produces more power than is needed to sustain the fusion reaction. Recently the German Wendelstein 7-X stellarator managed to hit new records here during its most recent OP 2.3 experimental campaign, courtesy of a frozen hydrogen pellet injector developed by the US Department of Energy’s Oak Ridge National Laboratory. With this injector the stellarator was able to sustain plasma for over 43 seconds as microwaves heated the freshly injected pellets.

Although the W7-X team was informed later that the recently decommissioned UK-based JET tokamak had achieved a similar triple product during its last – so far unpublished – runs, it’s of note that the JET tokamak had triple the plasma volume. Having a larger plasma volume makes such an achievement significantly easier due to inherently less heat loss, which arguably makes the W7-X achievement more noteworthy.

The triple product is also just one of the many ways to measure progress in commercial nuclear fusion, with fusion reactors dealing with considerations like low- and high-confinement mode, plasma instabilities like ELMs and the Greenwald Density Limit, as we previously covered. Here stellarators also seem to have a leg up on tokamaks, with the proposed SQuID stellarator design conceivably leap-frogging the latter based on all the lessons learned from W7-X.

Top image: Inside the vacuum vessel of Wendelstein 7-X. (Credit: Jan Hosan, MPI for Plasma Physics)

2025 One Hertz Challenge: Valvano Clock Makes The Seconds Count

July 14, 2025 by 2 Comments

A man named [Jim Valvano] once said “There are 86,400 seconds in a day. It’s up to you to decide what to do with them.” — while we couldn’t tell you who [Jim Valvano] was without a google search*, his math checks out. The quote was sufficiently inspirational to inspire [danjovic] to create a clock count those seconds precisely.

It’s a simple project, both conceptually and electrically. All it does is keep time and count the seconds in the day– a button press switches between counting down, counting up, and HH:MM:SS. In every mode, though, the number displayed will change at one Hertz, which we appreciate as being in the spirit of the challenge. There are only four components:  an Arduino Nano, a DS3231 RTC module, a SSD1306 128×64 OLED module, and a momentary pushbutton. At the moment it appears this project is only on breadboard, which is a shame– we think it deserves to have a fancy enclosure and pride of place on the wall. Wouldn’t you be more productive if you could watch those 86,400 seconds ticking away in real time? We think it would be motivating.

Perhaps it will motivate you to create something for our One Hertz Challenge. Plenty of seconds to go until the deadline on August 19th, after all. If you’d rather while away the time reading, you can check out some of [danjovic]’s other projects, like this Cistertian-inspired clock, or this equally-inscruitable timekeeper that uses binary-coded octal.

2025 Hackaday One Hertz Challenge

 

*Following a google search, he was an American college basketball coach in the mid-20th century.

Hacking When It Counts: DIY Prosthetics And The Prison Camp Lathe

July 14, 2025 by 11 Comments

There are a lot of benefits to writing for Hackaday, but hands down one of the best is getting paid to fall down fascinating rabbit holes. These often — but not always — delightful journeys generally start with chance comments by readers, conversations with fellow writers, or just the random largesse of The Algorithm. Once steered in the right direction, a few mouse clicks are all it takes for the properly prepared mind to lose a few hours chasing down an interesting tale.

I’d like to say that’s exactly how this article came to be, but to be honest, I have no idea where I first heard about the prison camp lathe. I only know that I had a link to a PDF of an article written in 1949, and that was enough to get me going. It was probably a thread I shouldn’t have tugged on, but I’m glad I did because it unraveled into a story not only of mechanical engineering chops winning the day under difficult circumstances, but also of how ingenuity and determination can come together to make the unbearable a little less trying, and how social engineering is an important a skill if you want to survive the unsurvivable.

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