Predicting Starman’s Return To Earth

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.

Photographing Starman From a Million Miles Away

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!

[Rogelio]’s work is a great example of practical astronomy, and if you’re keen to get involved, why not consider building your own star tracking rig? Video after the break.

[Thanks to arnonymous for the tip! If that’s a nickname and not just a request to be anonymous but misspelled.]

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Are There Better Things To Hurl Into Orbit Than A Sports Car?

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.


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.

Tesla Coil uses Vintage Tube

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.

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Tesla Model S Battery Pack Teardown

We’ve heard a lot about the Tesla Model S over the last few years, it’s a vehicle with a habit of being newsworthy. And as a fast luxury electric saloon car with a range of over 300 miles per charge depending on the model, its publicity is deserved, and that’s before we’ve even mentioned autonomous driving  driver-assist. Even the best of the competing mass-produced electric cars of the moment look inferior beside it.

Tesla famously build their battery packs from standard 18650 lithium-ion cells, but it’s safe to say that the pack in the Model S has little in common with your laptop battery. Fortunately for those of a curious nature, [Jehu Garcia] has posted a video showing the folks at EV West tearing down a Model S pack from a scrap car, so we can follow them through its construction.

The most obvious thing about this pack is its sheer size, this is a large item that takes up most of the space under the car. We’re shown a previous generation Tesla pack for comparison, that is much smaller. Eye-watering performance and range come at a price, and we’re seeing it here in front of us.

The standard of construction appears to be very high indeed, which makes sense as this is not merely a performance part but a safety critical one. Owners of mobile phones beset by fires will testify to this, and the Tesla’s capacity for conflagration or electrical hazard is proportionately larger. The chassis and outer cover are held together by a huge array of bolts and Torx screws, and as they comment, each one is marked as having been tightened to a particular torque setting.

Under the cover is a second cover that is glued down, this needs to be carefully pried off to reveal the modules and their cells. The coolant is drained, and the modules disconnected. This last task is particularly hazardous, as the pack delivers hundreds of volts DC at a very low impedance. Then each of the sixteen packs can be carefully removed. The packs each contain 444 cells, the pack voltage is 24 V, and the energy stored is 5.3 kWh.

The video is below the break. We can’t help noticing some of the rather tasty automotive objects of desire in their lot.

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Tesla Vs. Edison

The phrase “Tesla vs. Edison” conjures up images of battling titans, mad scientists, from a bygone age. We can easily picture the two of them facing off, backed by glowing corona with lightning bolts emitting from their hands. The reality is a little different though. Their main point of contention was Tesla’s passion for AC vs. Edison’s drive to create DC power systems to power his lights. Their personalities also differed in many ways, the most relevant one here being their vastly different approaches to research. Here, then, is the story of their rivalry.

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Autopilots Don’t Kill Drivers, Humans Do

The US National Highway Traffic Safety Administration (NHTSA) report on the May 2016 fatal accident in Florida involving a Tesla Model S in Autopilot mode just came out (PDF). The verdict? “the Automatic Emergency Braking (AEB) system did not provide any warning or automated braking for the collision event, and the driver took no braking, steering, or other actions to avoid the collision.” The accident was a result of the driver’s misuse of the technology.

quote-not-a-true-targetThis places no blame on Tesla because the system was simply not designed to handle obstacles travelling at 90 degrees to the car. Because the truck that the Tesla plowed into was sideways to the car, “the target image (side of a tractor trailer) … would not be a “true” target in the EyeQ3 vision system dataset.” Other situations that are outside of the scope of the current state of technology include cut-ins, cut-outs, and crossing path collisions. In short, the Tesla helps prevent rear-end collisions with the car in front of it, but has limited side vision. The driver should have known this.

The NHTSA report concludes that “Advanced Driver Assistance Systems … require the continual and full attention of the driver to monitor the traffic environment and be prepared to take action to avoid crashes.” The report also mentions the recent (post-Florida) additions to Tesla’s Autopilot that help make sure that the driver is in the loop.

The takeaway is that humans are still responsible for their own safety, and that “Autopilot” is more like anti-lock brakes than it is like Skynet. Our favorite footnote, in carefully couched legalese: “NHTSA recognizes that other jurisdictions have raised concerns about Tesla’s use of the name “Autopilot”. This issue is outside the scope of this investigation.” (The banner image is from this German YouTube video where a Tesla rep in the back seat tells the reporter that he can take his hands off the wheel. There may be mixed signals here.)

cropped_shot_2017-01-23-181745There are other details that make the report worth reading if, like us, you would like to see some more data about how self-driving cars actually perform on the road. On one hand, Tesla’s Autosteer function seems to have reduced the rate at which their cars got into crashes. On the other, increasing use of the driving assistance functions comes with an increase driver inattention for durations of three seconds or longer.

People simply think that the Autopilot should do more than it actually does. Per the report, this problem of “driver misuse in the context of semi-autonomous vehicles is an emerging issue.” Whether technology will improve fast enough to protect us from ourselves is an open question.

[via Popular Science].