Project Orion: Detonating Nuclear Bombs For Thrust

Rockets with nuclear bombs for propulsion sounds like a Wile E. Coyote cartoon, but it has been seriously considered as an option for the space program. Chemical rockets combust a fuel with an oxidizer within themselves and exhaust the result out the back, causing the rocket to move in the opposite direction. What if instead, you used the higher energy density of nuclear fission by detonating nuclear bombs?

Detonating the bombs within a combustion chamber would destroy the vehicle so instead you’d do so from outside and behind. Each bomb would include a little propellant which would be thrown as plasma against the back of the vehicle, giving it a brief, but powerful push.

That’s just what a group of top physicists and engineers at General Atomic worked on between 1958 and 1965 under the name, Project Orion. They came close to doing nuclear testing a few times and did have success with smaller tests, exploding a series of chemical bombs which pushed a 270-pound craft up 185 feet as you’ll see below.

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Tariff Expansion Set To Hit 3D-Printing Right In The Filament

Mere weeks after tariffs were put into place raising the cost of many Chinese-sourced electronics components by 25%, a second round of tariffs is scheduled to begin that will deal yet another blow to hackers. And this time it hits right at the heart of our community: 3D-printing.

A quick scan down the final tariff list posted by the Office of the US Trade Representative doesn’t reveal an obvious cause for concern. In among the hundreds of specific items listed one will not spot “Filaments for additive manufacturing” or anything else that suggests that 3D-printing supplies are being targeted. But hidden in the second list of tariff items, wedged into what looks like a polymer chemist’s shopping list, are a few entries for “Monofilaments with cross-section dimension over 1 mm.” Uh-oh!

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Teardown: Queercon 15 Badge (and The Game Hidden Within)

Queercon is a conference within a conference. Taking place within DEF CON, Queercon is a social network of LGBT hackers that gathers each year to host events, talks, and a kickin’ pool party. Since 2012 they have also been building electronic badges as part of the fun and I can vouch that they’re contenders for most creative badge design every single year.

A total of 450 electronic badges were made this year, and the aesthetic is as close to a polished consumer product as I have ever seen in a badge, yet they also retain the charm and feel of unique electronics built for hardware geeks. With wireless communication that delivers a complex and clever game to the badges, the designers are encouraging interaction between people (not just between badges). I had the chance to do a teardown of one of these glorious badges, and also gathered quite a bit of info on the puzzles within during Friday’s badge talk in the QC suite.

Join me after the break as I tear down the Queercon 15 hardware badge. If you haven’t yet looked over my review of the official DC26 badge, check that out as well!

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Rediffusion Television: Early Cable TV Delivered Like Telephone

Recently I spent an enjoyable weekend in Canterbury, staying in my friend’s flat with a superb view across the rooftops to the city’s mediaeval cathedral. Bleary-eyed and in search of a coffee on the Sunday morning, my attention was immediately drawn to one of her abode’s original built-in features. There on the wall in the corner of the room was a mysterious switch.

Housed on a standard-sized British electrical fascia was a 12-position rotary switch, marked with letters A through L. An unexpected thing to see in the 21st century and one probably unfamiliar to most people under about 40, I’d found something I’d not seen since my university days in the early 1990s: a Rediffusion selector switch.

If you have cable TV, there is probably a co-axial cable coming into your home. It is likely to carry a VHF signal, either a series of traditional analogue channels or a set of digital multiplexes. “Cable ready” analogue TVs had wideband VHF tuners to allow the channels to be viewed, and on encrypted systems there would have been a set-top box with its own analogue tuner and decoder circuitry.

Your digital cable TV set-top box will do a similar thing, giving you the channels you have subscribed to as it decodes the multiplex. At the dawn of television transmission though, none of this would have been possible. Co-axial cable was expensive and not particularly high quality, and transistorised wideband VHF tuners were still a very long way away. Engineers designing the earliest cable TV systems were left with the technology of the day derived from that of the telephone networks, and in Britain at least that manifested itself in the Rediffusion system whose relics I’d found.

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First Look At DEF CON 26 Official Badge

To the delight of everyone, this year’s official DEF CON badge is an electronic badge chock full of entertainment. Of course there is blinky, the board is artistic, and everyone hopefully maybe gets one (it’s rumored 27,000+ were manufactured) if they don’t run out. But the badge contest at DEF CON is legendary — solve all the puzzles you are awarded the coveted black badge.

The creators of this badge are no strangers to the Hackaday community. Displayed proudly on the board and in the firmware, we discover that The Toymakers are the ones who have put it all on this line this year. Kudos to the dynamic hardware collective from Minnesota. There is no larger pressure cooker in the world of badges than this, and they pulled it off marvelously. Let’s take a look at all the goodies inside.

Most importantly, become a team member of the Hackaday.io DC26 badge solving project page to help discover all that’s involved in this badge. Okay, now let’s dive in!

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The VU Meter And How It Got That Way

Given its appearance in one form or another in all but the cheapest audio gear produced in the last 70 years or so, you’d be forgiven for thinking that the ubiquitous VU meter is just one of those electronic add-ons that’s more a result of marketing than engineering. After all, the seemingly arbitrary scale and the vague “volume units” label makes it seem like something a manufacturer would slap on a device just to make it look good. And while that no doubt happens, it turns out that the concept of a VU meter and its execution has some serious engineering behind that belies the really simple question it seeks to answer: How loud is this audio signal?

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Hackaday guide to Lathes

Lathe Headstock Alignment: Cutting A Test Bar

Let’s say you’ve recently bought a lathe and set it up in your shop. Maybe you’ve even gone and leveled it like a boss. You’re ready to make chips, right? Well, not so fast. As real machinists will tell you, you can use all the levels and lasers and whatever that you want, but the proof is in the cut. Precision leveling gets your machine in the ballpark (machinists have very small ballparks) but the final step to getting a machine to truly perform well is to cut a test bar. This is a surefire way to eliminate any last traces of twist in the bed.

There are two types of test bars. One is for checking headstock-to-ways alignment, which is what we’re doing here. There’s another type used for checking tailstock alignment, but that’s a subject for another day.

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