The field of space vehicle design is obsessed with efficiency by necessity. The cost to do anything in space is astronomical, and also heavily tied to launch weight. Thus, any technology or technique that can bring those figures down is prime for exploitation.
In recent years, mercury thrusters promised to be one such technology. The only catch was the potentially-ruinous environmental cost. Today, we’ll look at the benefits of mercury thrusters, and how they came to be outlawed in short order.
Depending on who you ask, the Norden bombsight was either the highest of high tech during World War II, or an overhyped failure that provided jobs and money for government contractors. Either way, it was super top secret in its day. It was also expensive. They cost about $25,000 each and the whole program came in at well over a billion dollars. The security was over the top. When not flying, the bombsight was removed from the plane and locked in a vault. There was a pyro device that would self-destruct the unit if it were in danger of being captured. So why did one of the most famous missions of World War II fly with the Norden replaced by 20 cents worth of machined metal? Good question.
You often hear the expression “less is more” and, in this case, it is an accurate idea. I frequently say, though, that “just enough is more.” In this case, though, less was actually just enough. There were three reasons that one famous mission in the Pacific theater didn’t fly the Norden. It all had to do with morale, technology, and secrecy.
We see tons of projects with the infamous “Blue Pill” STM32 boards. They are cheap and plentiful and have a lot of great features, or at least they were before the chip shortage. I recently picked up a “Black Pill”, which is very similar but has an even more powerful processor. For a few bucks, you get an ARM CPU that can run at 100 MHz (but with USB, probably 96 MHz). There’s 512 kB of flash and 128 kB of RAM. There’s a USB type C port, and even a button and an LED onboard. The thing fits on a breadboard and you can program it with a cheap STLink dongle which costs about $10.
The Black Pill module on a breadboard.
Of course, you then have to consider the software. The STM32Cube stuff is a lot to set up and learn but it does let you do just about anything you can imagine. Then there is the STM32Duino plug-in that lets you use it as a beefy Arduino. That works and is easy enough to set up. However, there’s also Mbed. The only problem is that Mbed doesn’t work right out of the box. Turns out, though, it isn’t that hard to set up. I’ll show you how easy it is to get things going and, next time, I’ll show you a practical example of a USB peripheral that uses the mBed RTOS features.
First Steps
Obviously, you are going to need a Black Pill. There are at least two choices but for as cheap as they are there is little reason not to get the STM32F411 version that has more memory. The DIP form factor will fit in whatever breadboard you happen to have and a USB C cable will power the board so unless you are driving a lot of external circuitry, you probably don’t need an external supply.
Identifying new species is key to the work of zoologists around the world. It’s an exciting part of research into the natural world, and being the first to discover a new species often grants a scientists naming rights that can create a legacy of one’s work that lasts long into the future.
Traditionally, the work of taxonomy involved capturing and preserving an example of the new species. This is such that it could be classified properly and studied in detail by scientists working now and in the future. However, times are changing, and scientists are beginning to identify new species on the basis of videos and photos instead.
In planetary exploration circles, Mars has quite a bad reputation. The Red Planet has a habit of eating spacecraft sent there to explore it, to the degree that nearly half of the missions we’ve thrown at it have failed in one way or another. The “Mars Curse” manifests itself most spectacularly when landers fail to negotiate the terminal descent and new billion-dollar craters appear on the Martian regolith, while some missions meet their doom en route to the planet, and an unlucky few have even blown up on the launchpad.
But the latest example of the Mars Curse, the recent cancellation of the second half of the ExoMars mission, represents a new and depressing failure mode: war — specifically the Russian invasion of Ukraine. The international outrage over the aggression resulted in economic sanctions and diplomatic isolation of Russia, which retaliated by ending its partnership with the European Space Agency (ESA), depriving the mission of its launch vehicle and dooming the mission that would have landed the rover Rosalind Franklin on Oxia Planum near the Martian Equator in 2023.
While there’s still a chance that administrators and diplomats will work things out, chances are slim that it will be in time for the narrow launch window that the mission was shooting for in September of 2022. That means the Rosalind Franklin, along with all the other flight hardware that was nearly ready to launch, will have to be put in storage at least until the next launch window opens in 2024. That begs the question: how does one put a complex spacecraft into storage? And could such mothballing have unintended consequences for the mission when it eventually does fly?
Fifty years ago, Hewlett-Packard introduced the first handheld scientific calculator, the HP-35. It was quite the engineering feat, since equivalent machines of the day were bulky desktop affairs, if not rack-mounted. [Rob Weinstein] has long been a fan of HP calculators, and used an HP-41C for many years until it wore out. Since then he gradually developed a curiosity about these old calculators and what made them tick. The more he read, the more engrossed he became. [Rob] eventually decided to embark on a three year long reverse-engineer journey that culminated a recreation of the original design on a protoboard that operates exactly like the original from 1972 (although not quite pocket-sized). In this presentation he walks us through the history of the calculator design and his efforts in understanding and eventually replicating it using modern FPGAs.
The HP patent ( US Patent 4,001,569 ) contains an extremely detailed explanation of the calculator in nearly every aspect. There are many novel concepts in the design, and [Rob] delves into two of them in his presentation. Early LED devices were a drain on batteries, and HP engineers came up with a clever solution. In a complex orchestra of multiplexed switches, they steered current through inductors and LED segments, storing energy temporarily and eliminating the need for inefficient dropping resistors. But even more complicated is the serial processor architecture of the calculator. The first microprocessors were not available when HP started this design, so the entire processor was done at the gate level. Everything operates on 56-bit registers which are constantly circulating around in circular shift registers. [Rob] has really done his homework here, carefully studying each section of the design in great depth, drawing upon old documents and books when available, and making his own material when not. For example, in the course of figuring everything out, [Rob] prepared 338 pages of timing charts in addition to those in the patent. Continue reading “Remoticon 2021 // Rob Weinstein Builds An HP-35 From The Patent Up”→
With the news here in Europe full of the effect of the war in Ukraine on gas supplies and consequently, prices, there it was on the radio news: a unit of measurement so uniquely British that nobody uses it in the real world and nobody even has a clue what it really means. We’re speaking of the Therm, one of those words from our grandparents’ era of coal gas powered Belling cookers and Geyser water heaters hanging over the bath, which has somehow hung on in the popular imagination as a mysterious unit of domestic gas referred to only in the mass market news media. What on earth is a therm, and why are we still hearing it on the news in the UK?
You can’t Buy A Therm
Asking the internet what a therm is reveals the answer, it’s 100,000 BTU. What’s a BTU? A British Thermal Unit, another anachronistic measurement five decades after the UK went metric, it’s the amount of energy required to raise a pound of water by a degree Fahrenheit. Which in turn is about 1,054 joules, in today’s measurements. So a therm is thus a unit of energy, can we take a look at our gas meters and see how many of them we’ve used this winter? Not so fast, because gas isn’t sold by the therm. Older gas meters had cubic feet on them, and we’re guessing that now they’re calibrated in cubic meters. We can’t even buy a therm of gas, so why on earth are the British media still using it? Continue reading “Just What On Earth Is A Therm?”→
