A parabolic antenna is a simple enough device, a curved reflector designed to focus all the radiation from the direction it’s pointed into a waveguide or antenna at its feedpoint. They’re easy enough to make for a radio amateur, but imagine making one for a spacecraft. It must fold into a minimal space and weigh almost nothing, both difficult to achieve. An engineering academic doing work for NASA, [Christopher Walker], has a new way to make the parabolic surface that solves the spacecraft designer’s problems at a stroke, it forms its parabolic reflector on the inside of an inflatable structure. In this way relatively huge reflectors can be built in space, with easy folding and very little weight. Continue reading “Need A Low-Mass Antenna In Space? Just Blow It Up!”→
In what reads somewhat like a convoluted detective story, the events unfolding at the Chornobyl Exclusion Zone (CEZ) in Ukraine during late February had the media channels lighting up with chatter about ‘elevated gamma radiation levels’, which showed up on the public CEZ radiation monitoring dashboard for a handful of gamma radiation sensors. This happened right before this reporting system went off-line, leaving outside observers guessing at what was going on. By the time occupying forces had been driven out of the CEZ, the gamma radiation levels were reported as being similar to before the invasion, yet the computer hardware which was part of the monitoring system had vanished along with the occupying forces. After considering many explanations, this left security researchers like [Ruben Santamarta] to consider that the high values had been spoofed.
The impacts of climate change continue to mount on human civilization, with warning signs that worse times are yet to come. Despite the scientific community raising an early warning as to the risks of continued air pollution and greenhouse gas output, efforts to stem emissions have thus far had minimal impact. Continued inaction has led some scientists to consider alternative solutions to stave off the worst from occurring.
Geoengineering has long been touted as a potential solution for our global warming woes. Now, the idea of launching a gigantic dust cloud from the moon to combat Earth’s rising temperatures is under the spotlight. However, this very sci-fi solution has some serious implications if pursued, if humanity can even achieve the feat in the first place.
Our homes are full of technological marvels, and, as a Hackaday reader, we are betting you know the basic ideas behind a microwave oven even if you haven’t torn one apart for transformers and magnetrons. So we aren’t going to explain how the magnetron rotates water molecules to produce uniform dielectric heating. However, when we see our microwave, we think about two things: 1) this thing is one of the most dangerous things in our house and 2) what makes that little turntable flip a different direction every time you run the thing?
First, a Little History
Westinghouse Powercaster which could, among other things, toast bread in six seconds
People think that Raytheon engineer Percy Spenser, the chief of their power tube division, noticed that while working with a magnetron he found his candy bar had melted. This is, apparently, true, but Spenser wasn’t the first to notice. He was, however, the first to investigate it and legend holds that he popped popcorn and blew up an egg on a colleague’s face (this sounds like an urban legend about “egg on your face” to us). The Raytheon patent goes back to 1945.
However, cooking with radio energy was not a new idea. In 1933, Westinghouse demonstrated cooking foods with a 10 kW 60 MHz transmitter (jump to page 394). According to reports, the device could toast bread in six seconds. The same equipment could beam power and — reportedly — exposing yourself to the field caused “artificial fever” and an experience like having a cocktail, including a hangover on overindulgence. In fact, doctors would develop radiothermy to heat parts of the body locally, but we don’t suggest spending an hour in the device.
When you’ve been a fact-sponge for electronics trivia for over four decades, it’s not often that an entire class of parts escapes your attention. But have you seen the Skiatron? It’s a CRT that looks like a normal mid-20th-century tube, until it’s switched on. Then its secret is revealed; instead of the glowing phosphor trace we’d expect, the paper-white screen displays a daylight-readable and persistent black trace. They’re invariably seen in videos of radar installations, with the 360 degree scans projected onto large table-top screens which show the action like a map. It’s like e-ink, but from the 1940s. What’s going on?
The tenebrescent mineral Hackmanite, before and after UV exposure. Leland Green…, CC BY-SA 2.0 and CC BY-SA 2.0.
The phosphor coating on a traditional CRT screen is replaced by a halide salt, and the property on which the display relies is called tenebrescence, changing colour under the influence of radiation. This seems most associated online with UV treatment of some minerals and gemstones to give them a prettier look, and its use a s a display technology is sadly forgotten.
A high-school physics understanding of the phenomenon is that energy from the UV light or the electron beam in the case of the tube, places some electrons in the crystal into higher energy levels, at which they absorb some visible light wavelengths. This is reversible through heat, in some substances requiring the application of heat while in others the heat of room temperature being enough. Of course here at Hackaday we’re hands-on people, so into the EPROM eraser went a small amount of table salt in a makeshift dish made of paper, but sadly not to be rewarded by a colour change.
On a real dark-trace CRT the dark trace would be illuminated from behind by a ring light round the glass neck of the tube. An interesting aside is that, unlike phosphor CRTs, they were more suitable for vertical mounting. It seems that small amounts of phosphor could detach themselves from a vertically mounted screen and drop into the electron gun, something that wasn’t a problem for tenebrescent coatings.
This display tech has shuffled off into the graveyard of obsolescence, we’re guessing because CRT technology became a lot better over the 1950s, and radar technologies moved towards a computerised future in which the persistence of the display wasn’t the only thing keeping the information on the screen. It seems at first sight to be a surprise that tenebrescent coatings have never resurfaced in other displays for their persistence, but perhaps there was always a better alternative whether it was ultra-low-power LCDs or more recently e-ink style devices.
For more bleeding-edge 1950s radar displays, we’ve previously brought you Volscan, a radar with an early form of GUI, which no doubt was one of those which consigned dark-trace CRTs to history.
Aside from idle curiosity, very few of us need to see inside chips and components to diagnose a circuit. But reverse engineering is another story; being able to see what lies beneath the inscrutable epoxy blobs that protect the silicon within is a vital capability, one that might justify the expense involved in procuring an X-ray imager. But what’s to be done when such an exotic and expensive — not to mention potentially deadly — machine breaks down? Obviously, you fix it yourself!
To be fair, [Shahriar]’s Faxitron MX-20 digital X-ray microscope was only a little wonky. It still generally worked, but just took a while to snap into the kind of sharp focus that he needs to really delve into the guts of a chip. This one problem was more than enough to justify tearing into the machine, but not without first reviewing the essentials of X-ray production — a subject that we’ve given a detailed look, too — to better understand the potential hazards of a DIY repair.
With that out of the way and with the machine completely powered down, [Shahriar] got down to the repair. The engineering of the instrument is pretty impressive, as it should be for something dealing with high voltage, heavy thermal loads, and ionizing radiation. The power supply board was an obvious place to start, since electrostatically focusing an X-ray beam depends on controlling the high voltage on the cathode cup. After confirming the high-voltage module was still working, [Shahriar] homed in on a potential culprit — a DIP reed relay.
Replacing that did the trick, enough so that he was able to image the bad component with the X-ray imager. The images are amazing; you can clearly see the dual magnetic reed switches, and the focus is so sharp you can make out the wire of the coil. There are a couple of other X-ray treats, so make sure you check them out in the video below.
Over the past decades we have been able to observe a change in the Earth’s climate, caused by an increasing amount of energy being retained in the atmosphere. This in turn has affected weather systems around the globe, causing more extreme weather. As a result, the prospect of weather control is more relevant than ever for the nations which are most directly impacted by severe rain and winds. Although the concept of weather modification is not new, it used to be primarily focused on rather limited aspects, such as cloud seeding to increase precipitation.
Recent proposals such as Japan’s weather modification moonshot program seek to find ways to prevent or lessen the impact of torrential rains, typhoons and similar extreme weather events which accompany climate change. This proposal is part of Japan’s multi-topic Moonshot R&D program which seeks to advance the state of the art in a wide range of fields in a very significant way by 2050. As far as weather modification is concerned, this naturally raises many questions. Clearly we are capable of affecting the climate through emissions of e.g. greenhouse gases and large-scale construction, but are there ways in which humans can affect the climate and weather in a more refined manner that benefits society, or is this something which will remain beyond our grasp for the foreseeable future?
