NASA’s Voyager Space Probe’s Reserve Power, And The Intricacies Of RTG-Based Power Systems

Launched in 1977, the Voyager 1 and 2 space probes have been operating non-stop for over 45 years, making their way from Earth to our solar system’s outer planets and beyond. Courtesy of the radioisotope thermoelectric generators (RTGs) which provided 470 W at launch, they are able to function in the darkness of Deep Space as well as they did within the confines of our Sun-lit solar system. Yet as nothing in the Universe is really infinite, so too do these RTGs wear out over time, both from natural decay of their radioactive source and from the degradation of the thermocouples.

Despite this gradual drop in power, NASA recently announced that Voyager 2 has a hitherto seemingly unknown source of reserve power that will postpone the shutdown of more science instruments for a few more years. The change essentially bypasses a voltage regulator circuit and associated backup power system, freeing up the power consumed by this for the scientific instruments which would otherwise have begun to shut down years sooner.

While this is good news in itself, it’s also noteworthy because the Voyager’s 45+ year old Multi-Hundred Watt (MHW) RTGs are the predecessor to the RTGs that are still powering the New Horizons probe after 17 years, and the Mars Science Laboratory (Curiosity) for over 10 years, showing the value of RTGs in long-term exploration missions.

Although the basic principle behind an RTG is quite simple, their design has changed significantly since the US put a SNAP-3 RTG on the Transit 4B satellite in 1961.

Continue reading “NASA’s Voyager Space Probe’s Reserve Power, And The Intricacies Of RTG-Based Power Systems”

Alternative Uses For Nuclear Waste

Nuclear power is great if you want to generate a lot of electricity without releasing lots of CO2 and other harmful pollutants. However, the major bugbear of the technology has always been the problem of waste. Many of the byproducts from the operation of nuclear plants are radioactive, and remain so for thousands of years. Storing this waste in a safe and economical fashion continues to be a problem.

Alternative methods to deal with this waste stream continue to be an active area of research. So what are some of the ways this waste can be diverted or reused?

Fast Breeders Want To Close The Fuel Cycle

The Superphénix reactor in France is one of a handful of operational fast-neutron reactor designs.

One of the primary forms of waste from a typical nuclear light water reactor (LWR) is the spent fuel from the fission reaction. These consist of roughly 3% waste isotopes, 1% plutonium isotopes, and 96% uranium isotopes. This waste is high in transuranic elements, which have half-lives measured in many thousands of years. These pose the biggest problems for storage, as they must be securely kept in a safe location for lengths of time far exceeding the life of any one human society.

The proposed solution to this problem is to instead use fast-neutron reactors, which “breed” non-fissile uranium-238 into plutonium-239 and plutonium-240, which can then be used as fresh fuel. Advanced designs also have the ability to process out other actinides, also using them as fuel in the fission process. These reactors have the benefit of being able to use almost all the energy content in uranium fuel, reducing fuel use by 60 to 100 times compared to conventional methods.

Continue reading “Alternative Uses For Nuclear Waste”

Hackaday Links Column Banner

Hackaday Links: October 27, 2019

A year ago, we wrote about the discovery of treasure trove of original documentation from the development of the MOS 6502 by Jennifer Holdt-Winograd, daughter of the late Terry Holdt, the original program manager on the project. Now, Ms. Winograd has created a website to celebrate the 6502 and the team that built it. There’s an excellent introductory video with a few faces you might recognize, nostalgia galore with period photographs that show the improbable styles of the time, and of course the complete collection of lab notes, memos, and even resumes of the team members. If there were a microchip hall of fame – and there is – the 6502 would be a first-round pick, and it’s great to see the history from this time so lovingly preserved.

Speaking of the 6502, did you ever wonder what the pin labeled SO was for? Sure, the data sheets all say pin 38 of the original 40-pin DIP was the “Set Overflow” pin, an active low that set the overflow bit in the Processor Status Register. But Rod Orgill, one of the original design engineers on the 6502, told a different story: that “SO” was the initials of his beloved dog Sam Orgill. The story may be apocryphal, but it’s a Good Doggo story, so we don’t care.

You may recall a story we ran not too long ago about the shortage of plutonium-238 to power the radioisotope thermoelectric generators (RTGs) for deep-space missions. The Cold War-era stockpiles of Pu-238 were running out, but Oak Ridge National Laboratory scientists and engineers came up with a way to improve production. Now there’s a video showing off the new automated process from the Periodic Videos series, hosted by the improbably coiffed Sir Martyn Poliakoff. It’s fascinating stuff, especially seeing workers separated from the plutonium by hot-cells with windows that are 4-1/2 feet (1.4 meters) thick.

Dave Murray, better known as YouTube’s “The 8-Bit Guy”, can neither confirm nor deny the degree to which he participated in the golden age of phone phreaking. But this video of his phreaking presentation at the Portland Retro Gaming Expo reveals a lot of suspiciously detailed knowledge about the topic. The talk starts at 4:15 or so and is a nice summary of blue boxes, DTMF hacks, war dialing, and all the ways we curious kids may or may not have kept our idle hands busy before the Interwebz came along.

Do you enjoy a puzzle? We sure do, and one was just laid before us by a tipster who prefers to stay anonymous, but for whom we can vouch as a solid member of the hacker community. So no malfeasance will befall you by checking out the first clue, a somewhat creepy found footage-esque video with freaky sound effects, whirling clocks, and a masked figure reading off strings of numbers in a synthesized voice. Apparently, these clues will let you into a companion website. We worked on it for a bit and have a few ideas about how to crack this code, but we don’t want to give anything away. Or more likely, mislead anyone.

And finally, if there’s a better way to celebrate the Spooky Season than to model predictions on how humanity would fare against a vampire uprising, we can’t think of one. Dominik Czernia developed the Vampire Apocalypse Calculator to help you decide when and if to panic in the face of an uprising of the undead metabolically ambiguous. It supports several models of vampiric transmission, taken from the canons of popular genres from literature, film, and television. The Stoker-King model makes it highly likely that vampires would replace humans in short order, while the Harris-Meyer-Kostova model of sexy, young vampires is humanity’s best bet except for having to live alongside sparkly, lovesick vampires. Sadly, the calculator is silent on the Whedon model, but you can set up your own parameters to model a world with Buffy-type slayers at your leisure. Or even model the universe of The Walking Dead to see if it’s plausible that humans are still alive 3599 days into the zombie outbreak.

Hackaday Links Column Banner

Hackaday Links: October 20, 2019

It’s Nobel season again, with announcements of the prizes in literature, economics, medicine, physics, and chemistry going to worthies the world over. The wording of the Nobel citations are usually a vast oversimplification of decades of research and end up being a scientific word salad. But this year’s chemistry Nobel citation couldn’t be simpler: “For the development of lithium-ion batteries”. John Goodenough, Stanley Whittingham, and Akira Yoshino share the prize for separate work stretching back to the oil embargo of the early 1970s, when Goodenough invented the first lithium cathode. Wittingham made the major discovery in 1980 that adding cobalt improved the lithium cathode immensely, and Yoshino turned both discoveries into the world’s first practical lithium-ion battery in 1985. Normally, Nobel-worthy achievements are somewhat esoteric and cover a broad area of discovery that few ordinary people can relate to, but this is one that most of us literally carry around every day.

What’s going on with Lulzbot? Nothing good, if the reports of mass layoffs and employee lawsuits are to be believed. Aleph Objects, the Colorado company that manufactures the Lulzbot 3D printer, announced that they would be closing down the business and selling off the remaining inventory of products by the end of October. There was a reported mass layoff on October 11, with 90 of its 113 employees getting a pink slip. One of the employees filed a class-action suit in federal court, alleging that Aleph failed to give 60 days notice of terminations, which a company with more than 100 employees is required to do under federal law. As for the reason for the closure, nobody in the company’s leadership is commenting aside from the usual “streamlining operations” talk. Could it be that the flood of cheap 3D printers from China has commoditized the market, making it too hard for any manufacturer to stand out on features? If so, we may see other printer makers go under too.

For all the reported hardships of life aboard the International Space Station – the problems with zero-gravity personal hygiene, the lack of privacy, and an aroma that ranges from machine-shop to sweaty gym sock – the reward must be those few moments when an astronaut gets to go into the cupola at night and watch the Earth slide by. They all snap pictures, of course, but surprisingly few of them are cataloged or cross-referenced to the position of the ISS. So there’s a huge backlog of beautiful but unknown cities around the planet that. Lost at Night aims to change that by enlisting the pattern-matching abilities of volunteers to compare problem images with known images of the night lights of cities around the world. If nothing else, it’s a good way to get a glimpse at what the astronauts get to see.

Which Pi is the best Pi when it comes to machine learning? That depends on a lot of things, and Evan at Edje Electronics has done some good work comparing the Pi 3 and Pi 4 in a machine vision application. The SSD-MobileNet model was compiled to run on TensorFlow, TF Lite, or the Coral USB accelerator, using both a Pi 3 and a Pi 4. Evan drove around with each rig as a dashcam, capturing typical street scenes and measuring the frame rate from each setup. It’s perhaps no surprise that the Pi 4 and Coral setup won the day, but the degree to which it won was unexpected. It blew everything else away with 34.4 fps; the other five setups ranged from 1.37 to 12.9 fps. Interesting results, and good to keep in mind for your next machine vision project.

Have you accounted for shrinkage? No, not that shrinkage – shrinkage in your 3D-printed parts. James Clough ran into shrinkage issues with a part that needed to match up to a PCB he made. It didn’t, and he shared a thorough analysis of the problem and its solution. While we haven’t run into this problem yet, we can see how it happened – pretty much everything, including PLA, shrinks as it cools. He simply scaled up the model slightly before printing, which is a good tip to keep in mind.

And finally, if you’ve ever tried to break a bundle of spaghetti in half before dropping it in boiling water, you likely know the heartbreak of multiple breakage – many of the strands will fracture into three or more pieces, with the shorter bits shooting away like so much kitchen shrapnel. Because the world apparently has no big problems left to solve, a group of scientists has now figured out how to break spaghetti into only two pieces. Oh sure, they mask it in paper with the lofty title “Controlling fracture cascades through twisting and quenching”, but what it boils down to is applying an axial twist to the spaghetti before bending. That reduces the amount of bending needed to break the pasta, which reduces the shock that propagates along the strand and causes multiple breaks. They even built a machine to do just that, but since it only breaks a strand at a time, clearly there’s room for improvement. So get hacking!

The Deep Space Energy Crisis Could Soon Be Over

On the face of it, powering most spacecraft would appear to be a straightforward engineering problem. After all, with no clouds to obscure the sun, adorning a satellite with enough solar panels to supply its electrical needs seems like a no-brainer. Finding a way to support photovoltaic (PV) arrays of the proper size and making sure they’re properly oriented to maximize the amount of power harvested can be tricky, but having essentially unlimited energy streaming out from the sun greatly simplifies the overall problem.

Unfortunately, this really only holds for spacecraft operating relatively close to the sun. The tyranny of the inverse square law can’t be escaped, and out much beyond the orbit of Mars, the size that a PV array needs to be to capture useful amounts of the sun’s energy starts to make them prohibitive. That’s where radioisotope thermoelectric generators (RTGs) begin to make sense.

RTGs use the heat of decaying radioisotopes to generate electricity with thermocouples, and have powered spacecraft on missions to deep space for decades. Plutonium-238 has long been the fuel of choice for RTGs, but in the early 1990s, the Cold War-era stockpile of fuel was being depleted faster than it could be replenished. The lack of Pu-238 severely limited the number of deep space and planetary missions that NASA was able to support. Thankfully, recent developments at the Oak Ridge National Laboratory (ORNL) appear to have broken the bottleneck that had limited Pu-238 production. If it pays off, the deep space energy crisis may finally be over, and science far in the dark recesses of the solar system and beyond may be back on the table.

Continue reading “The Deep Space Energy Crisis Could Soon Be Over”