Hackaday links: July 31, 2022

Don’t look up! As of this writing, chances are a Chinese Long March 5B booster has already completed its uncontrolled return to Earth, hopefully safely. The re-entry prediction has been continuously tweaked over the past week, until the consensus closes on July 30, 2022 at 5:08 p.m. UTC, plus or minus an hour either way. This two hour window creates A LOT of uncertainty as to where the 25 ton space junk will end up. Given The Aerospace Corporation’s latest prediction, likely surface tracks cover much of the open ocean, with only parts of Mexico and South America potentially in sight, as well as parts of Indonesia. Most of the material from the huge propellant is expected to burn up in the atmosphere, but with the size of the thing, even 20% reaching the ground could be catastrophic, as it almost was in 2020.

[Update: US Space Command confirms that the booster splashed down in the Indian Ocean region at 16:45 UTC. No word yet on how much debris survived, or if any populated areas were impacted.]

Good news to all, thanks to 3D printing, we now know the maximum height of a dive in water that an average human being can perform without injury. And it’s surprisingly small – 8 meters for head first, 12 meters if you break water with your hands first and 15 meters feet first. Keep in mind this is for the average person; the record for surviving a feet-first dive is nearly 60 meters, but that was by a trained diver. Cornell researchers found these numbers by printing models of human divers in various poses, fitting them with accelerometers, and comparing the readings they got with known numbers for deceleration injuries. There was no mention of the maximum survival abdominal flop, but based on first-hand anecdotal experience, we’d say it’s not much more than a yard.

Humans have made a lot of space travel over the past sixty years or so, but nearly all of it has taken place either in low Earth orbit or by flying over our neighbors in the solar system. Sure, we’ve landed many probes, but mostly on the Moon, Mars, and a few lucky asteroids. And Venus, which is sometimes easy to forget. We were reminded of this by this cool video of the Soviet Venera 14 landing in 1982, one of the few attempts to land on our so-called sister planet. The video shows the few photographs Venera 14 managed to take before it was destroyed by the heat and pressure on Venus, but the real treat is the sound recording the probe managed to make. Venera 14 has captured the sounds of its own operations on the Venusian surface, including what sounds like a pneumatic drill being used to sample regolith. It also captured, as the narrator put it, “the soft breath of the Venusian wind” – as soft as ultra-dense carbon dioxide hot enough to melt lead can get, anyway.

So when you buy a Tesla, what do you actually get? This seems like a silly question, at first glance. You’re buying a car, aren’t you? Maybe not, if one Tesla Model S90 owner’s bad experience is any indication. The details are hard to follow if you’re unfamiliar with Tesla’s pricing models, but essentially each battery has a maximum capacity that’s limited in software based on how much range you’re paying for. The Tesla owner in question bought his S90 model used and was getting the 90kWh range he was expecting. But when he went to upgrade his car from 3G telemetry, Tesla locked its battery at 60kWh and demanded $4,500 to unlock it.

Fortunately, the owner was able to take the matter to Twitter, where the Court of Public Opinion quickly ruled against Tesla, which reversed the change at no cost and apologized for the misunderstanding. Good for them, but it raises a lot of questions about ownership – it seems more like you’re granting a limited right to use a vehicle than buying it outright, and that seems to apply even once the vehicle is moved to the secondary market.

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