CNC Tellurion Lets You See the Earth and Moon Dance

Kids – they’re such a treasure. One minute you’re having a nice chat, the next minutes they’re testing your knowledge of the natural world with a question like, “Why can we see the Moon during the day?” And before you know it, you’re building a CNC Earth-Moon orbital model.

We’ve got to applaud [sniderj]’s commitment to answering his grandson’s innocent question. What could perhaps have been demonstrated adequately with a couple of balls and a flashlight instead became an intricate tellurion that can be easily driven to show the relative position of the Earth and Moon at any date; kudos for anticipating the inevitable, “Where was the moon when I was born, Grampa?” question. The mechanism is based on the guts of a defunct 3D-printer, with the X-, Y-, and Z-axis steppers now controlling the Earth’s rotation and tilt and the Moon’s orbit respectively, with the former extruder drive controlling the tilt of the Moon’s orbital plane. A complex planetary gear train with herringbone gears, as well as a crossed-shaft helical gear set, were 3D-printed from PLA. The Earth model is a simple globe and the Moon is a ping-pong ball; [sniderj] is thinking about replacing the Moon with a 3D-printed bump-map model, a move which we strongly endorse. The video below shows the tellurion going through a couple of hundred years of the saros at warp speed.

There’s just something about machines that show the music of the spheres, whether they be ancient or more modern. And this one would be a great entry into our 3D-Printed Gears, Pulleys, and Cams contest too.

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The “Impossible” Tech Behind SpaceX’s New Engine

Followers of the Church of Elon will no doubt already be aware of SpaceX’s latest technical triumph: the test firing of the first full-scale Raptor engine. Of course, it was hardly a secret. As he often does, Elon has been “leaking” behind the scenes information, pictures, and even video of the event on his Twitter account. Combined with the relative transparency of SpaceX to begin with, this gives us an exceptionally clear look at how literal rocket science is performed at the Hawthorne, California based company.

This openness has been a key part of SpaceX’s popularity on the Internet (that, and the big rockets), but its been especially illuminating in regards to the Raptor. The technology behind this next generation engine, known as “full-flow staged combustion” has for decades been considered all but impossible by the traditional aerospace players. Despite extensive research into the technology by the Soviet Union and the United States, no engine utilizing this complex combustion system has even been flown. Yet, just six years after Elon announced SpaceX was designing the Raptor, they’ve completed their first flight-ready engine.

The full-flow staged combustion engine is often considered the “Holy Grail” of rocketry, as it promises to extract the most possible energy from its liquid propellants. In a field where every ounce is important, being able to squeeze even a few percent more thrust out of the vehicle is worth fighting for. Especially if, like SpaceX, you’re planning on putting these new full-flow engines into the world’s largest operational booster rocket and spacecraft.

But what makes full-flow staged combustion more efficient, and why has it been so difficult to build an engine that utilizes it? To understand that, we’ll need to first take a closer look at more traditional rocket engines, and the design paradigms which have defined them since the very beginning.

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Make Your Lego Fly

We probably all used to make our Lego fly by throwing it across the room, but Flite Test have come up with a slightly more elegant solution: they converted a Lego quadcopter to fly. They did it by adding a  miniature flight controller, battery and motors/rotors to replace the Lego ones in the Lego City Arctic Air Transport kit. This combination flies surprisingly well, thanks to a thoughtful design that balances the heavier components inside the case.

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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.

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Oops… Britain Launched A Satellite, But Who Remembers It?

Did you know Britain launched its first satellite after the program had already been given the axe? Me neither, until some stories of my dad’s involvement in aerospace efforts came out and I dug a little deeper into the story.

I grew up on a small farm with a workshop next to the house, that housed my dad’s blacksmith business. In front of the workshop was a yard with a greenhouse beyond it, along one edge of which there lay a long gas cylinder about a foot (300mm) in diameter. To us kids it looked like a torpedo, and I remember my dad describing the scene when a similar cylinder fell off the side of a truck and fractured its valve, setting off at speed under the force of ejected liquid across a former WW2 airfield as its pressurised contents escaped.

Everybody’s parents have a past from before their children arrived, and after leaving the RAF my dad had spent a considerable part of the 1950s as a technician, a very small cog in the huge state-financed machine working on the UK’s rocket programme for nuclear and space launches. There were other tales, of long overnight drives to the test range in the north of England, and of narrowly averted industrial accidents that seem horrific from our health-and-safety obsessed viewpoint. Sometimes they came out of the blue, such as the one about a lake of  highly dangerous liquid oxidiser-fuel mix ejected from an engine that failed to ignite and which was quietly left to evaporate, which he told me about after dealing with a cylinder spewing liquid propane when somebody reversed a tractor into a grain dryer.

Bringing Home A Piece Of History

The remains of the Black Arrow first and second stages, taken from the Skyrora promotional video.
The remains of the Black Arrow first and second stages, taken from the Skyrora promotional video.

My dad’s tales from his youth came to mind recently with the news that a privately-owned Scottish space launch company is bringing back to the UK the remains of the rocket that made the first British satellite launch from where they had lain in Australia since crashing to earth in 1971. What makes this news special is that not only was it the first successful such launch, it was also the only one. Because here in good old Blighty we hold the dubious honour of being the only country in the world to have developed a space launch capability of our own before promptly abandoning it. Behind that launch lies a fascinating succession of forgotten projects that deserve a run-through of their own, they provide a window into both the technological and geopolitical history of that period of the Cold War.

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Operation Backfire: Witness to the Rocket Age

As the prospects for Germany during the Second World War began to look increasingly grim, the Nazi war machine largely pinned their hopes on a number of high-tech “superweapons” they had in development. Ranging from upgraded versions of their already devastatingly effective U-Boats to tanks large enough to rival small ships, the projects ran the gamut from practical to fanciful. After the fall of Berlin there was a mad scramble by the Allied forces to get into what was left of Germany’s secretive development facilities, with each country hoping to recover as much of this revolutionary technology for themselves as possible.

V-2 launch during Operation Backfire

One of the most coveted prizes was the Aggregat 4 (A4) rocket. Better known to the Allies as the V-2, it was the world’s first liquid fueled guided ballistic missile and the first man-made object to reach space. Most of this technology, and a large number of the engineers who designed it, ended up in the hands of the United States as part of Operation Paperclip. This influx of practical rocketry experience helped kick start the US space program, and its influence could be seen all the way up to the Apollo program. The Soviet Union also captured V-2 hardware and production facilities, which subsequently influenced the design of their early rocket designs as well. In many ways, the V-2 rocket was the spark that started the Space Race between the two countries.

With the United States and Soviet Union taking the majority of V-2 hardware and personnel, little was left for the British. Accordingly their program, known as Operation Backfire, ended up being much smaller in scope. Rather than trying to bring V-2 hardware back to Britain, they decided to learn as much as they could about it in Germany from the men who used it in combat. This study of the rocket and the soldiers who operated it remains the most detailed account of how the weapon functioned, and provides a fascinating look at the incredible effort Germany was willing to expend for just one of their “superweapons”.

In addition to a five volume written report on the V-2 rocket, the British Army Kinematograph Service produced “The German A.4 Rocket”, a 40 minute film which shows how a V-2 was assembled, transported, and ultimately launched. Though they are operating under the direction of the British government, the German soldiers appear in the film wearing their own uniforms, which gives the documentary a surreal feeling. It could easily be mistaken for actual wartime footage, but these rockets weren’t aimed at London. They were being fired to serve as a historical record of the birth of modern rocketry.

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The Thrill of Building Space Hardware to Exceptionally High Standards

It’s fair to say that the majority of Hackaday readers have not built any hardware that’s slipped the surly bonds of Earth and ventured out into space proper. Sure we might see the occasional high altitude balloon go up under the control of some particularly enterprising hackers, but that’s still a far cry from a window seat on the International Space Station. Granted the rapid commercialization of space has certainly added to that exclusive group of space engineers over the last decade or so, but something tells us it’s still going to be quite some time before we’re running space-themed hacks with the regularity of Arduino projects.

Multi-use Variable-G Platform

That being the case, you might assume the protocols and methods used to develop a scientific payload for the ISS must seem like Latin to us lowly hackers. Surely any hardware that could potentially endanger an orbiting outpost worth 100+ billion dollars, to say nothing of the human lives aboard it, would utilize technologies we can hardly dream of. It’s probably an alphabet soup of unfamiliar acronyms up there. After all, this is rocket science, right?

There’s certainly an element of truth in there someplace, as hardware that gets installed on the Space Station is obviously held to exceptionally high standards. But Brad Luyster is here to tell you that not everything up there is so far removed from our Earthly engineering. In fact, while watching his 2018 Hackaday Superconference talk “Communication, Architecture, and Building Complex Systems for SPAAACE”, you might be surprised just how familiar it all sounds. Detailing some of the engineering that went into developing the Multi-use Variable-G Platform (MVP), the only centrifuge that’s able to expose samples to gravitational forces between 0 and 1 g, his talk goes over the design considerations that go into a piece of hardware for which failure isn’t an option; and how these lessons can help us with our somewhat less critically important projects down here.

Check out Brad’s newly published talk video below, and then join me after the break for a look at the challenges of designing hardware that will live in space.

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