In two weeks the Hackaday Community is gathering in Belgrade for Europe’s greatest hardware con, The Hackaday Belgrade Conference — an event not to be missed — but of course the city itself is a spectacular place to visit and has the perfect feel for those who like to build electronics. Why not join us for your own geek world tour to Serbia? Here’s a few of the things you’ll want to see while in Belgrade.
Belgrade is a tech center and a hidden jewel of Europe. Need proof? Fly into Belgrade, and you’ll land at Nikola Tesla Airport. Pick up a car at the airport and you’ll pass a great glass torus housing Serbia’s Museum of Aviation. Here, you’ll find aircraft from both sides of the cold war, Sabres and MiGs, Hurricanes and Messerschmitts, a quite rare Sud Caravelle, and the canopy of the only stealth bomber ever to be shot down. It’s an aviation geek’s paradise, and you haven’t even left the airport.
What else is in store for you when you visit Belgrade? For the Hackaday crowd, the most interesting bit will probably be the Nikola Tesla Museum. You might know of Nikola Tesla from a webcomic, but he’s actually the greatest inventor of all time, even more so than Elon Musk. Tesla invented radio, even though Marconi got the credit. Tesla invented radar and discovered x-rays. The only person they could find to portray a figure like Tesla in The Prestige was David Bowie. Nikola Tesla is the most iconic inventor to ever live (change my mind), and his museum is in Belgrade.
Self-driving cars have been in the news a lot in the past two weeks. Uber’s self-driving taxi hit and killed a pedestrian on March 18, and just a few days later a Tesla running in “autopilot” mode slammed into a road barrier at full speed, killing the driver. In both cases, there was a human driver who was supposed to be watching over the shoulder of the machine, but in the Uber case the driver appears to have been distracted and in the Tesla case, the driver had hands off the steering wheel for six seconds prior to the crash. How safe are self-driving cars?
Trick question! Neither of these cars were “self-driving” in at least one sense: both had a person behind the wheel who was ultimately responsible for piloting the vehicle. The Uber and Tesla driving systems aren’t even comparable. The Uber taxi does routing and planning, knows the speed limit, and should be able to see red traffic lights and stop at them (more on this below!). The Tesla “Autopilot” system is really just the combination of adaptive cruise control and lane-holding subsystems, which isn’t even enough to get it classified as autonomous in the state of California. Indeed, it’s a failure of the people behind the wheels, and the failure to properly train those people, that make the pilot-and-self-driving-car combination more dangerous than a human driver alone would be.
A self-driving Uber Volvo XC90, San Francisco.
You could still imagine wanting to dig into the numbers for self-driving cars’ safety records, even though they’re heterogeneous and have people playing the mechanical turk. If you did, you’d be sorely disappointed. None of the manufacturers publish any of their data publicly when they don’t have to. Indeed, our glimpses into data on autonomous vehicles from these companies come from two sources: internal documents that get leaked to the press and carefully selected statistics from the firms’ PR departments. The state of California, which requires the most rigorous documentation of autonomous vehicles anywhere, is another source, but because Tesla’s car isn’t autonomous, and because Uber refused to admit that its car is autonomous to the California DMV, we have no extra insight into these two vehicle platforms.
Nonetheless, Tesla’s Autopilot has three fatalities now, and all have one thing in common — all three drivers trusted the lane-holding feature well enough to not take control of the wheel in the last few seconds of their lives. With Uber, there’s very little autonomous vehicle performance history, but there are leaked documents and a pattern that makes Uber look like a risk-taking scofflaw with sub-par technology that has a vested interest to make it look better than it is. That these vehicles are being let loose on public roads, without extra oversight and with other traffic participants as safety guinea pigs, is giving the self-driving car industry and ideal a black eye.
If Tesla’s and Uber’s car technologies are very dissimilar, the companies have something in common. They are both “disruptive” companies with mavericks at the helm that see their fates hinging on getting to a widespread deployment of self-driving technology. But what differentiates Uber and Tesla from Google and GM most is, ironically, their use of essentially untrained test pilots in their vehicles: Tesla’s in the form of consumers, and Uber’s in the form of taxi drivers with very little specific autonomous-vehicle training. What caused the Tesla and Uber accidents may have a lot more to do with human factors than self-driving technology per se.
You can see we’ve got a lot of ground to cover. Read on!
What kind of power service is in the United States? You probably answered 120-volt service. If you thought a little harder, you might remember that you have some 240-volt outlets and that some industrial service is three phase. There used to be DC service, but that was a long time ago. That’s about it, right? Turns out, no. There are a very few parts of the United States that have two-phase power. In addition, DC didn’t die as quickly as you might think. Why? It all boils down to history and technological inertia.
You probably have quite a few 120-volt power jacks in sight. It is pretty hard to find a residence or commercial building these days that doesn’t have these outlets. If you have a heavy duty electric appliance, you may have a 240-volt plug, too. For home service, the power company supplies 240 V from a center tapped transformer. Your 120V outlets go from one side to the center, while your 240V outlets go to both sides. This is split phase service.
Industrial customers, on the other hand, are likely to get three-phase service. With three-phase, there are three wires, each carrying the line voltage but out of phase with each other. This allows smaller conductors to carry more power and simplifies motor designs. So why are there still a few pockets of two-phase?
There’s a Starman, waiting in the sky. He’d like to come and meet us, but he’ll have to wait several million years until the Yarkovsky effect brings him around to Earth again.
In case you’ve been living under a rock for the past few weeks, SpaceX recently launched a car into space. This caused much consternation and hand-wringing, but we got some really cool pictures of side boosters landing simultaneously. The test launch for the Falcon Heavy successfully lobbed a Tesla Roadster into deep space with an orbit extending out into the asteroid belt. During the launch coverage, SpaceX said the car would orbit for Billions of years. This might not be true; a recent analysis of the random walk of cars revealed a significant probability of hitting Earth or Venus over the next Million years.
The analysis of the Tesla Roadster relies on the ephemerides provided by JPL’s Horizons database (2018-017A), and predicts the orbit over several hundred years. In the short term — a thousand years or so — there is little chance of a collision with anything. In 2091, however, the Tesla will find itself approaching Earth, and after that, the predicted orbits change drastically. As an aside, we should totally bring the Tesla back in 2091.
Even though the Tesla Roadster, its payload adapter, and the booster are inert objects floating in space right now, that doesn’t mean there aren’t forces acting on it. For small objects orbiting near the sun, the Yarkovsky effect is a huge influence on the orbit when measured on a timescale of millennia. In short, the Yarkovsky effect is a consequence of a spinning object being heated by the sun. As an object (a Tesla, or an asteroid) rotates, the side facing the sun heats up. As this side faces away from the sun, this heat is radiated out, imparting a tiny, tiny force. This force, over a period of millions of years, can send the Tesla into resonances with other planets, eventually sending it crashing into Earth, Venus, or the Sun.
The authors of this paper find there is a 6% chance the Tesla will collide with Earth and a 2.5% chance it will collide with Venus in the next one Million years. In three Million years, the probability of a collision with Earth is 11%. These are, according to the authors, extremely preliminary calculations and more observations are needed. If the Tesla were to hit the Earth, it’s doubtful whatever species populates the planet would notice; the mass of the Tesla is only 1250 Kg, and Earth flies through meteoroids weighing that much very frequently.
Love it or loathe it, launching a sports car into space is a hell of a spectacle, and did a great job at focusing the spotlight on the Falcon Heavy spacecraft. This led [Rogelio] to wonder – would it be possible to snap a photo of Starman from Earth?
[Rogelio] isn’t new to the astrophotography game, possessing a capable twin-telescope rig with star tracking capabilities and chilled CCDs for reducing noise in low-light conditions. Identifying the location of the Tesla Roadster was made easier thanks to NASA JPL tracking the object and providing ephemeris data.
Imaging the Roadster took some commitment – from [Rogelio]’s chosen shooting location, it would only be visible between 3AM and 5:30AM. Initial attempts were unsuccessful, but after staying up all night, giving up wasn’t an option. A return visit days later was similarly hopeless, and scuppered by cloud cover.
It was only after significant analysis that the problem became clear – when calculating the ephemeris of the object on NASA’s website, [Rogelio] had used the standard coordinates instead of the actual imaging location. This created enough error and meant they were looking at the wrong spot. Thanks to the wide field of view of the telescopes, however, after further analysis – Starman was captured, not just in still, but in video!
We’ve been having a lively discussion behind the scenes here at Hackaday, about SpaceX’s forthcoming launch of their first Falcon Heavy rocket. It will be carrying [Elon Musk]’s red Tesla Roadster, and should it be a successful launch, it will place the car in an elliptical orbit round the Sun that will take it to the Martian orbit at its furthest point.
On one hand, it seems possible that [Musk]’s sports car will one day be cited by historians as the exemplar of the excesses of the tech industry in the early 21st century. After all, to spend the millions of dollars required to launch the largest reusable space launch platform ever created, and then use it to hurl an electric vehicle into orbit round the Sun seems to be such a gratuitous waste of resources, an act of such complete folly as to be criminal.
Surely even given that there is a reasonable chance of a first launch ending in fiery destruction it must be worth their while canvassing the universities and research institutions of the world with the offer of a free launch, after all there must be a significant amount of science that would benefit from some cost-free launch capacity! It seems a betrayal of the famous “Why explore space” letter from the associate science director of NASA to a nun who questioned the expenditure while so many in the developing world were starving.
Testing
But on the other hand, first launches of rockets are a hazardous endeavour, as the metaphorical blue touchpaper is lit on the world’s largest firework for the first time. Satellites are expensive devices, and it would be a foolhardy owner who entrusted their craft to a launch vehicle with a good chance of a premature splashdown.
Launch of first Arianne 5. Not where you want your pricey satellite.
First launches traditionally carry a ballast rather than a payload, for example NASA have used tanks of water for this purpose in the past. SpaceX has a history of novelty payloads for their test launches; their first Dragon capsule took a wheel of cheese into space and returned it to Earth. We picture Musk looking around a big warehouse and saying, “well, we got a lot of cars!”
There is a fascinating question to be posed by the launch of the car, just what did they have to do to it to ensure that it could be qualified for launch? Satellite manufacture is an extremely exacting branch of engineering, aside from the aspect of ensuring that a payload will work it must both survive the launch intact and not jeopardise it in any way. It’s safe to say that the Roadster will not have to function while in orbit as the roads of California will be far away, but cars are not designed with either the stresses of launch or the transition to zero gravity and the vacuum of space in mind. Will a glass windscreen originally specified for a Lotus Elise on the roads of Norfolk shatter during the process and shower the inside of the craft with glass particles, for example? There must have been an extensive space qualification programme for it to pass, from vibration testing through removal of any hazards such as pressurised gases or corrosive chemicals, if only the folks at SpaceX would share some its details that would make for a fascinating story in itself.
Space Junk
So the Tesla Roadster is a huge publicity stunt on behalf of SpaceX, but it serves a purpose that would otherwise have to have been taken by an unexciting piece of ballast. It will end up as space junk, but in an orbit unlikely to bring it into contact with any other craft. If its space-suited dummy passenger won’t be providing valuable data on the suit’s performance we’d be extremely surprised, and when it is finally retrieved in a few centuries time it will make a fascinating exhibit for the Smithsonian.
Given a huge launch platform and the chance to fill it with a novelty item destined for orbit,the Hackaday team stepped into overdrive with suggestions as to what might be launched were they in charge. They varied from Douglas Adams references such as a heart of gold or a whale and a bowl of petunias should the rocket abort and the payload crash to earth, to a black monolith and a few ossified ape remains to confuse space historians. We briefly evaluated the theory that the Boring Company is in fact a hiding-in-plain-sight construction organisation for a forthcoming Evil Lair beneath the surface of Mars, before concluding that maybe after all the car is a pretty cool thing to use as ballast for a first launch.
It may be reaching towards seven decades since the first space programmes successfully sent rockets beyond the atmosphere with the aim of exploration, but while the general public has become accustomed to them as routine events they remain anything but to the engineers involved. The Falcon Heavy may not have been developed by a government, but it represents every bit as astounding an achievement as any of its predecessors. Flinging an electric vehicle into orbit round the Sun is a colossal act of showmanship and probably a waste of a good car, but it’s also more than that. In hundreds of years time the IoT devices, apps, 3D printers, quadcopters or whatever else we toil over will be long forgotten. But there will be a car orbiting the Sun that remains a memorial to the SpaceX engineers who made its launch possible, assuming it doesn’t blow up before it gets there. What at first seemed frivolous becomes very cool indeed.
We’ve seen a fair amount of Tesla coil builds, but ones using vacuum tubes are few and far between. Maybe it’s the lack of availability of high power tubes, or a lack of experience working with them among the younger crop of hackers. [Radu Motisan] built a vacuum tube Tesla coil several years back, and only just managed to tip us off recently. Considering it was his first rodeo with vacuum tubes, he seems to have done pretty well — not only did he get good results, he also managed to learn a lot in the process.
His design is based around a GI-30 medium power dual tetrode. The circuit is a classical Armstrong oscillator with very few parts and ought to be easy to build if you can lay your hands on the tricky parts. The high voltage capacitors may need some scrounging. And of course, one needs to hand-wind the three coils that make up the output transformer.
Getting the turns ratios of the coils right is quite critical in obtaining proper power transfer to the output. This required a fair amount of trial error before [Radu] could get it right.
The use of a 20W fluorescent tubelight ballast to limit the inrush current is a pretty nice idea to prevent nuisance tripping of the breakers. If you’d like to try making one of your own, head over to his blog post where you will find pictures documenting his build in detail. If you do decide to make one, be extremely careful — this circuit has lethal high voltages in addition to the obvious ones, since it operates directly from 220 V utility supply.
His design is based around a 
