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Why don't passanger airplanes come with parachutes for people?
  • https://en.wikipedia.org/wiki/Nick_Piantanida

    This guy was in a remote controlled, parachute equipped gondola at 17km altitude wearing a pressurized suite. His suit broke and even though the emergency descent of the gondola was immediately activated to descend safely, he later died from embolism (bubbles forming in the blood because of rapidly decreasing pressure). Passenger jets cruise at about 11km so i gather it would be similar.

  • It's like the Pyramids guys; How tf did they do it?
  • In terms of modern shells being more complex in general: yes and no. modern shells pretty much always use some kind of electronic fusing, sometimes multiple kinds of electronic fuses. back then they had bombs, mines and grenades with literal clockwork inside and electronics was still very rare. also fuses and primary charges were not easy to produce reliably.

  • World’s 1st nuclear fusion-powered electric propulsion drive unveiled - Interesting Engineering
  • There has been some fusor research going on for decades. The issue that killed that direction of fusion research was ultimately that the electrons do not behave as the initial simple models suggested and in the real world the power loss from the fast electrons is just too big for any reasonably sized device to allow for self sustaining fusion.

  • Why is it dangerous to chain power dividers?
  • Other commenters have pointed out the problems with overloading of connectors and reduced efficiency because of the added resistance but there is another really important reason not to chain power strips: circuit breakers work best against short circuits when the resistance between the breaker and the short is fairly low (for instance less than 0.5Ω) so that the current will quickly go over the rated current of the breaker. If the resistance is a lot higher because you have too many extensions between the breaker and the fault, the time the breaker needs to react will go up. Counterintuitively this usually means more energy will be turned to heat by the fault.

    In extreme cases this can mean the difference between a broken power strip that you can just throw out and a burned down house.

  • Descaling liquid
  • If you want to be super exact about it it would be roughly 4 times the mass of limescale + mass of already dissolved CaCO3 in your tap water (you can look that up if you know the hardness index of your water).

    But really just don't be stingy with citric acid and it will be fine is what i am saying.

    Here is the math:

    Spoiler

    2 frac {210.14 g/mol } {100.0869 g/mol} approx 4.2

    <math xmlns="http://www.w3.org/1998/Math/MathML" display="block"> <semantics> <mrow> <mn>2</mn> <mrow> <mfrac> <mrow> <mn>210.14</mn> <mrow> <mi>g</mi> <mo stretchy="false">/</mo> <mi mathvariant="italic">mol</mi> </mrow> </mrow> <mrow> <mn>100.0869</mn> <mrow> <mi>g</mi> <mo stretchy="false">/</mo> <mi mathvariant="italic">mol</mi> </mrow> </mrow> </mfrac> <mo stretchy="false">≈</mo> <mn>4.2</mn> </mrow> </mrow> <annotation encoding="StarMath 5.0">2 frac {210.14 g/mol } {100.0869 g/mol} approx 4.2</annotation> </semantics> </math>

  • Descaling liquid
  • Note that citric acid works a bit more nuanced than many other descalers: it acts as a chelating agent at high concentrations (2x the Ca2+ concentration) and is more effective at removing scale because of this effect, but at lower concentrations the effect might actually be reversed because it can form solid calcium citrate, which has a very low solubility in water.

    If you are using citric acid based descaler you should make sure that you are always using enough of it to avoid the formation of calcium citrate.

  • The lethal doses of 55 substances
  • I think they are referring to Uranium with natural isotopic abundance. Which is complete bullshit when you put a picture of a nuclear power plant behind it – which in most cases can not function with the natural isotopic abundance (heavy water reactors being the exception, not the rule).

  • What Would Happen if Every American Got a Heat Pump
  • first you would need to know what COP you could reasonably get, which among other things depends on the average outside temperature during heating season if you want to use an air sourced heat pump.

    The COP can be in a largish spectrum depending on these factors but typical values are 3.5 for average homes in temperate climate. Higher if you live in a warmer climate and lower if you live closer to the arctic. If you want to really do the math it might be good to get help from a professional specialising in heat pumps.

    Edit: this is for heating use only. A heat pump can also be used for cooling but then the climate effect is inverted.

  • Fedora boot error after changing btrfs root subvolume name
  • It's just the basic posix shell syntax. It just looks weird because they are using lots of library functions and in-place substitutions. also apparently the function, to translate a system path to something grub will understand, is an ELF binary 0_o

  • InitialsDiceBearhttps://github.com/dicebear/dicebearhttps://creativecommons.org/publicdomain/zero/1.0/„Initials” (https://github.com/dicebear/dicebear) by „DiceBear”, licensed under „CC0 1.0” (https://creativecommons.org/publicdomain/zero/1.0/)US
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