Ion Thrusters: Not Just For TIE Fighters Anymore

March 3, 2022 by Lewin Day 42 Comments

Spacecraft rocket engines come in a variety of forms and use a variety of fuels, but most rely on chemical reactions to blast propellants out of a nozzle, with the reaction force driving the spacecraft in the opposite direction. These rockets offer high thrust, but they are relatively fuel inefficient and thus, if you want a large change in velocity, you need to carry a lot of heavy fuel. Getting that fuel into orbit is costly, too!

Ion thrusters, in their various forms, offer an alternative solution – miniscule thrust, but high fuel efficiency. This tiny push won’t get you off the ground on Earth. However, when applied over a great deal of time in the vacuum of space, it can lead to a huge change in velocity, or delta V.

This manner of operation means that an ion thruster and a small mass of fuel can theoretically create a much larger delta-V than chemical rockets, perfect for long-range space missions to Mars and other applications, too. Let’s take a look at how ion thrusters work, and some of their interesting applications in the world of spacecraft!

Continue reading “Ion Thrusters: Not Just For TIE Fighters Anymore” →

Remembering The MIT Radiation Laboratory

February 7, 2022 by Chris Lott 32 Comments

Back in the late 80s, our company managed to procure the complete 28 volume MIT Radiation Laboratory (Rad Lab) series, published in 1947, for the company library. To me, these books were interesting because I like history and old technology, but I didn’t understand why everyone was so excited about the acquisition. Only a cursory glimpse at the volumes would reveal that the “circuits” these books described used vacuum tubes and their “computers” were made from mechanical linkages. This was the 1980s, and we worked with modern radar and communications systems using semiconductors, integrated circuits, and digital computers. How could these old musty books possibly be of any practical use? To my surprise, it turned out that indeed they could, and eventually I came to appreciate the excitement. I even used several of them myself over the years.

Radiation Lab? Nuclear Radar?

In the years leading up to WW2, the idea of a civilian organization of scientists that would operate independently of the military and government bureaucracies was being championed by Dr. Vannevar Bush. The military and scientists had not worked well together during the first World War, and it looked like science and technology would be playing a much bigger role in the future.

It seemed certain that America would enter the conflict eventually, and Dr Bush and others believed that a new organizational framework was called for. To that end, the National Defense Research Committee (NDRC), which later became the Office of Scientific Research and Development (OSRD) was pitched to President Roosevelt and he approved it in June of 1940.

Almost immediately, a gift fell in the lap of the new organization — the Tizard Mission which arrived in the states from the UK in Sep 1940. They brought a literal treasure chest of technical innovations from the British, who hoped that US industry’s cooperation could help them survive what looked like certain and imminent invasion. One of those treasures was the cavity magnetron, which our own Dan Maloney wrote about a few years ago.

Within a few weeks, under the guidance of young Welshman “Taffy” Bowen, they had reviewed the design and gathered up the necessary equipment to fire it up. A 10 kV anode power supply and a 1,500 gauss electromagnet were procured, and the scientists gathered at the Bell Radio Laboratories in Whippany New Jersey on Sunday, Oct. 6, 1940. They powered up the cavity magnetron and were blown away by the results — over 10 kW of RF at 3 GHz (10 cm) from something the size of a bar of soap. Continue reading “Remembering The MIT Radiation Laboratory” →

3D Printed Radiation Shields Get Put To The Test

February 4, 2022 by Tom Nardi 19 Comments

Don’t get too excited, a 3D printed radiation shield won’t keep you from getting irradiated during WWIII. But until the Doomsday Clock starts clanging its midnight bell, you can use one to improve the accuracy of your homebrew weather monitoring station by keeping the sun from heating up your temperature sensor. But how much does it help, and what material should you load up in your extruder to make one? Those questions, and more, are the topic of a fascinating whitepaper included in the upcoming volume of HardwareX.

Design and Implementation of 3-D Printed Radiation Shields for Environmental Sensors not only tests how effective these low-cost shields are when compared to an uncovered sensor, but addresses specific concerns in regards to leaving 3D printed parts out in the elements. Readers who’ve squirted out a few rolls worth of the stuff will know that common polylactic acid (PLA) filament, while easy to work with and affordable, isn’t known for its resilience. In fact, one of the advertised properties of the renewable plastic is that it’s biodegradable (theoretically, at least), so leaving it outside for any length of time sounds like it’s bound to go poorly.

PLA’s mechanical strength dropped rapidly.

To make a long story short, it does. While the team demonstrated that the PLA printed radiation shield absolutely helped preserve the accuracy of the temperature and humidity sensors mounted inside of it, the structure itself began to deform rapidly from UV exposure. Further tests determined that the mechanical strength of the PLA showed a notable reduction in as little as 30 days, and a sharp decline after 90 days.

Luckily, there was more than one plastic horse in the race. In addition to the PLA printed shield, the team also tested a version printed in acrylonitrile styrene acrylate (ASA) which fared far better. There was no visible deformation of the shield, and after 90 days, the reduction in mechanical strength was negligible. It even performed a bit better when it came to shielding the temperature sensor, which the team believes may be due to the material’s optical transmission properties.

So there you have it: a 3D printed radiation shield will absolutely improve the accuracy of your weather sensors, but if you want it to last outside, PLA just isn’t going to cut it. On the other hand, you could also save yourself a whole lot of time by just using a stack of plant saucers. Whatever works.

Thanks to [tahnok] for the tip.

As apples travel down the conveyor belt, they are scanned using InGaAs and CMOS cameras. The InGaAs camera will show defects beginning to form under the skin that a human eye cannot see; the CMOS camera will show visible defects. (Credit: Hamamatsu)

Shining A Different Light On Reality With Short-Wave Infrared Radiation

February 3, 2022 by Maya Posch 23 Comments

As great as cameras that operate in the visual light spectrum are, they omit a lot of the information that can be gleaned from other wavelengths. There is also the minor issue that visibility is often impacted, such as when it’s raining, or foggy. When this happens, applications such as self-driving cars which rely on this, have a major issue. Through the use of sensors that are sensitive to other wavelengths, we can however avoid many of these issues.

Short-wave infrared radiation (SWIR) is roughly the part of the electromagnetic spectrum between 1.4 μm – 3 μm, or 100 THz – 214 THz. This places it between visible light and microwaves, and above long-wave IR at 20 THz – 37 THz. LWIR is what thermal cameras use, with LWIR also emitted by warm objects, such as the human body.

SWIR is largely unaffected by water in the atmosphere, while also passing through materials that are opaque to visible light. This allowing SWIR to be used for the analysis and inspection of everything from PCBs and fruit to works of art to capture details that are otherwise invisible or very hard to see.

Unfortunately, much like thermal camera sensors, SWIR sensors are rather expensive. Or they were, until quite recently, with the emergence of quantum-dot-based sensors that significantly decrease the costs of these sensors.

Continue reading “Shining A Different Light On Reality With Short-Wave Infrared Radiation” →

Underwater Tanks Turn Energy Storage Upside-Down

February 2, 2022 by Lewin Day 129 Comments

Pumped hydro storage is one of the oldest grid storage technologies, and one of the most widely deployed, too. The concept is simple – use excess energy to pump a lot of water up high, then run it back through a turbine when you want to get the energy back later.

With the rise in renewable energy deployments around the world, there is much interest in finding ways to store energy from these often-intermittent sources. Traditional pumped hydro can help, but there is only so much suitable land to work with.

However, there could be a solution, and it lurks deep under the waves. Yes, we’re talking about underwater pumped hydro storage!

Continue reading “Underwater Tanks Turn Energy Storage Upside-Down” →

Floating Solar Farms Are Taking The World’s Reservoirs By Storm

January 24, 2022 by Lewin Day 60 Comments

Photovoltaic solar panels are wonderful things, capable of capturing mere light and turning it into useful electricity. They’re often installed on residential and commercial rooftops for offsetting energy use at the source.

However, for grid-scale generation, they’re usually deployed in huge farms on tracts of land in areas that receive plenty of direct sunlight. These requirements can often put solar farms in conflict with farm-farms — the sunlight that is good for solar panels is also good for growing plants, specifically those we grow for food.

One of the more interesting ideas, however, is to create solar arrays that float on water. Unlike some of the wackier ideas out there, this one comes with some genuinely interesting engineering benefits, too!

Continue reading “Floating Solar Farms Are Taking The World’s Reservoirs By Storm” →

Printing Your Own Exoskeleton

January 20, 2022 by Matthew Carlson 23 Comments

While not quite in a cave, the idea of making your own exoskeleton with limited tools does have a Tony Stark esque vibe. [Andrew Piccinno] is a mechanical engineer pursuing the dream of 3D printing a full-body exoskeleton called 3X0. It’s a project he’s been ruminating on since college, but the work really began in earnest about five months ago. Unfortunately, there are too many pictures to include here, but check out his Instagram or makeprojects for more photos.

To make sure parts fit, [Andrew] started with creating a mesh of his body. After running fifty pictures of himself holding relatively still through some photogrammetry software, he had a decent mesh. While measurements weren’t millimeter-accurate, the relative sizes of everything were reasonably accurate. While the design is modeled with his measurements in mind, all the different pieces are parametric, which in theory would allow someone to tweak the designs to fit their own body.

So far, all the parts have been entirely 3D printed, except for steel balls bearings, gas pistons, and tension bands. The non-3D printed parts are picked to be easy to obtain as the gas piston is just 100 N furniture pistons. The design process includes quite a bit of math, motion study, and simulation to make sure the part that he’s printing will not only fit but move correctly. Many parts, such as the shoulder, are built around a large custom bearing that allows the piece to move correctly with the user’s joints.

While still in the middle of development, [Andrew] has made some serious progress, and we’re looking forward to seeing it completed. The current design is primarily passive with just a few springs and pistons, but he is already looking forward to making it active to the degree that it can augment a user’s motions rather than just taking the load off. It’s clear that [Andrew] believes that exoskeletons are a look into a potential future, and we couldn’t agree more. In a similar vein, perhaps the techniques used in this powered exoskeleton arm on a budget could be used to power the 3X0?