Hackaday links: July 31, 2022

do not search! As of the time of this writing, there is a good chance that the Chinese booster Long March 5B has already completed its uncontrolled return to Earth, hopefully safely. The return prediction has been constantly revised over the past week or so, until consensus closed on July 30, 2022 at 17:08 UTC, whether that be or not. This two-hour window creates a lot of uncertainty about where the 25-ton piece of space debris will end up. Given a recent prediction by the aerospace company, potential surface tracks cover much of the open ocean, with potentially only parts of Mexico and South America in the crossfire, along with parts of Indonesia. Most of the material in the massive booster is expected to burn up in the atmosphere, but with the thing’s size, 20% of it hitting Earth could be nearly as catastrophic, as it 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 for everyone – thanks to 3D printing, we now know the maximum diving height in water that an average human can perform without injury. And they are surprisingly small – 8 meters for the head first, 12 meters if you break the water with your hands first, and 15 meters first. Keep in mind that this is for the average person; The record for surviving a dive with a foot dive is about 60 metres, but that was done by a trained diver. Cornell University researchers came up with these numbers by printing models of human divers in different poses, fitting them to accelerometers, and comparing the readings they obtained with known numbers of deceleration injuries. There was no mention of the maximum survivable belly flopping, but based on first-hand anecdotal experience, we can say it’s not much more than a metre.

Humans have done a lot of spaceflight in the past 60 years or so, but almost all of it has been either in low Earth orbit or over our neighbors in the Sol system. Sure, we’ve landed a lot of probes, but mostly on the Moon, Mars, and a few lucky asteroids. And the flower that is easy to forget sometimes. We were reminded of this fact by this wonderful video of the 1982 Soviet landing of Venera 14, one of the few attempts to land on the so-called sister planet. The video shows the few images Venera 14 was able to capture before heat and pressure ravaged Venus, but the real cure is the audio recording that the probe was able to make. Venera 14 picked up the sounds of its own processes on the surface of Venus, including what sounds like an antenna drill used to sample the regolith. It also picked up, as the narrator put it, “the gentle blow of Venus’ winds”—in any case, it could be as gentle as super-dense carbon dioxide hot enough to melt lead.

So when you buy a Tesla, what do you actually get? It seems like a silly question, on the face of it. You are buying a car, right? Probably not, if the Tesla Model S90 owner’s bad experience is any indication. It’s hard to follow the details if you’re not familiar with Tesla pricing models, but basically, each battery pack has a limited maximum capacity in software depending on how much you’re paying for it. The concerned Tesla owner purchased his used S90, and was getting the 90 kWh range he was expecting. But when he went to upgrade his car from third-generation telemetry, Tesla shut down his battery to 60 kWh 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 decided against Tesla, who returned the change without charge and apologized for the misunderstanding. Good for them, but it raises a lot of questions about ownership – you seem to be licensing a limited right to use the car rather than buying it outright, and this seems to apply even once the car has moved to the secondary market.

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