Hackaday Links: July 31, 2022

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Don’t look up! As of the time of this writing, there’s a decent chance that a Chinese Long March 5B booster has already completed its uncontrolled return to Earth, hopefully safely. The reentry prediction was continually tweaked over the last week or so, until the consensus closed in on 30 Jul 2022 at 17:08 UTC, give or take an hour either way. That two-hour window makes for a LOT of uncertainty about where the 25-ton piece of space debris will end up. Given the last prediction by The Aerospace Corporation, the likely surface paths cover a lot of open ocean, with only parts of Mexico and South America potentially in the crosshairs, along with parts of Indonesia. It’s expected that most of the material in the massive booster will burn up in the atmosphere, but with the size of the thing, even 20% making it to the ground could be catastrophic, as it nearly 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, everyone — thanks to 3D printing, we now know the maximum height of a dive into water that the average human can perform without injury. And it’s surprisingly small — 8 meters for head first, 12 meters if you break the water with your hands first, and 15 meters feet first. Bear in mind this is for the average person; the record for surviving a foot-first dive is almost 60 meters, but that was by a trained diver. Researchers from Cornell came up with these numbers by printing models of human divers in various poses, fitting them with accelerometers, and comparing the readings they got with known figures for deceleration injuries. There was no mention of the maximum survivable belly flop, but based on first-hand anecdotal experience, we’d say it’s not much more than a meter.

Humans have done a lot of spacefaring in the last sixty years or so, but almost all of it has been either in low Earth orbit or as flybys of our neighbors in the Sol system. Sure we’ve landed plenty of probes, but mostly on the Moon, Mars, and a few lucky asteroids. And Venus, which is sometimes easy to forget. We were reminded of that fact by this cool video of the 1982 Soviet landing of Venera 14, one of only a few attempts to land on our so-called sister planet. The video shows the few photographs Venera 14 managed to take before being destroyed by the heat and pressure on Venus, but the real treat is the sound recording the probe managed to make. Venera 14 captured the sounds of its own operations on the Venusian surface, including what sounds like a pneumatic drill being used to sample the regolith. It also captured, as the narrator put it, “the gentle blow of the Venusian wind” — as gentle as ultra-dense carbon dioxide hot enough to melt lead can be, anyway.

So when you buy a Tesla, what are you actually getting? It seems like a silly question, on the face of it. You’re buying a car, right? Maybe not, if the bad experience of a Tesla Model S90 owner is any indication. The particulars are hard to follow if you’re not familiar with Tesla’s pricing models, but essentially, each battery pack has a maximum capacity that’s limited in software depending on how much range you pay for. The Tesla owner in question bought his Model S90 used, and was getting the 90-kWh range he was expecting. But when he went in to upgrade his car from 3G telemetry, Tesla locked his battery to 60-kWh and demanded $4,500 to unlock it.

Luckily, the owner was able to take the matter to Twitter, where the Court of Public Opinion quickly decided against Tesla, who reverted the change without charge and apologized for the misunderstanding. Good for them, but it raises a lot of questions about ownership — it seems more like you’re licensing a limited right to use a vehicle rather than buying it outright, and that seems to apply even once the vehicle moves to the secondary market.

12 thoughts on “Hackaday Links: July 31, 2022

  1. I just saw that on my phone news posting today. I’m wondering now that I have seen the post about the falling object over TX. the other day, if that was from the booster or a meteor? I watched it on the video someone captured on the dash cam of their Tesla, no audio and it burned bright for a long time then went dark. Couldn’t tell which direction the path was in the video. Haven’t seen anything else about it or the Chinese booster re entering Earth Atmosphere.

  2. A long time ago, in a land far away, the “Long March” Chinese rocket was selected to launch some satellites to the designated orbit.
    The best plans of men fell apart as soon as the crews arrived, and were bused to the launch area.
    Engineers assumed there would be plenty of housing and wonderful Chinese Cuisine for chow time.
    Alas, this was not to be..
    Provisions were not available and after a short while, peasant workers were sent out in the fields to scavenge grains or rice to feed the troops.
    A rush load of supplies were ordered, and when the customs inspectors placed in in quarantine, all good thoughts were off.
    Adding insult to injury, the Long Mach exploded destroying all cargo.
    I think the Long March is a bit better these days, but still, buyer beware.
    And no, I can’t really say any more details.

  3. Did we miss hearing lightning strikes under wat.. the extreme pressure of the atmosphere? It would be like explosions under water. Or did it just not compute in soviet tech.

    1. First owner got battery replaced under warranty, but the service center didn’t have any 60kWh packs, so they gave him 90kWh. They were supposed to lock the capacity to 60kWh, but for some reason didn’t (and replaced decals from S60D to S90D?). Now third owner wanted new onboard computer, they “corrected” their earlier mistake.

      1. No. And hell, no.

        That is about the most idiotic thing I’ve ever heard of.

        Software limiting the usable capacity by thirty percent. What a waste of materials and resources.

        That kind of crap needs to be stopped. The sooner, the better.

  4. “printing models of human divers in various poses, fitting them with accelerometers, and comparing the readings they got with known figures for deceleration injuries”

    Sounds like junk science to me. For one thing, bodies are not uniformly made of rigid material.

  5. Regarding Tesla battery capacity limiting, what’s old is new again. Many years ago IBM computers would ship with a full capacity memory, but jumpers controlled how much memory was available. Up your contract, an IBM tech would come out and reset the jumpers accordingly. Likewise printers had variable lines-per-minute capacities; the actual speed of the printer depended upon your contracted price for it. I’ve been told you could actually hear the printer pausing if it was set to print at a lower speed.

    1. They (IBM) were famous for shenanigans like that. I recall an article in a decades old Linux magazine recalling a “Research Job” with IBM, and the programmer discovered a hidden folder that copied everything done on the computer, uploaded it to the IBM server. Calling out the supervisor, the programmer was fired and walked off the site.
      Not being there, I suspect it was the beginning of “Tracking” the users. Your mileage will vary.

  6. Yeahhhh that diving one is junk. Maybe if “untrained” literally means rank novice who has never even gone off a spring board at the neighborhood pool. The 3D printed guy diving with his hands out has his hands in the praying position (usually when diving it’s more Superman style if that makes sense) and they aren’t even touching. There is a jet of water coming between them too. And there is nothing special about using 3D printing, tho could have been done with any dummy in existence since forever.

  7. Those diving numbers are completely bogus. Anyone that’s grown up around a lake or river will tell you point blank that a 45 foot jump “feet first” is a fraction of the height where you’re realistically facing a risk of injury. I grew up boating on Rough River Lake in KY which meant daily cliff diving. I’ve jumped off a 70 foot cliff the impact with the water wasn’t the least bit bad. Pull your arms in and point your toes. Anything 50ft+ does hurt like heck if you leave your arms out. I landed square on my back off a 50 ft cliff and it felt like hitting concrete but the extent of the physical injury was simply getting the breathe knocked out of me. My dad grew up jumping off the top of rail road bridge on Green River which is close to 75 ft and once landed on his back as well. Same experience. Feels like you just hit a brick wall but only knocks the breathe out of you.
    As far as how high is truly safe – my uncle jumped off the top of the auto bridge on Green River which is 125ft. No injuries. Something interesting is that he didn’t use the feet first “needle” style on his jumps. He used a cannonball technique and swore that was the best method as it kept you from slowly falling backward and hitting at an angle on your back.
    I’m always amazed how dangerous people think it is to jump from moderate heights into deep water. Like a suicide jumper on a bridge. Just let the person jump, it’s not going to kill them.
    I don’t understand why researchers publish findings as fact which can be easily falsified if they just asked around. People regularly jump from heights two to three times these figures recreationally with no issues.

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