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Joined 3 years ago
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Cake day: June 10th, 2023

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  • Also for unmanned aircraft, using helium instead of hydrogen is just crazy

    Is it? Hydrogen is about half the mass of helium, but the trick is what you’re displacing to generate lift.

    1 cubic meter of air is around 1.2 kilograms, depending on a variety of factors.

    1 cubic meter of helium is around 0.18 kilograms, displacing the atmosphere to generate about 1.02 kilograms of lift.

    1 cubic meter of hydrogen is around 0.08 kilograms, displacing the atmosphere to generate about 1.12 kilograms of lift, a shade under a 10% increase over helium.

    That can be significant, depending on other engineering constraints; but is it “crazy” different?

    (Numbers will vary with temperature and pressure, back of envelope calculations, etc. etc.)


  • This… strikes me more as self-aggrandizing than informative.

    Yes, many technical folks are put off by certain marketing tricks. Good marketers just use different techniques when targeting people in this market, when they bother to at all.

    We’re not immune to manipulation; and thinking that we are makes us more susceptible to it.


  • Just went through this with both kids… The word “need” always implies a goal. “I need x (to do y)”. Without context, the goal is generally either survival, or more often, comfort: “I need a drink.” “I need a break.”

    When you’re speaking in the context of doing something, as superglue was, that becomes the implied goal. “I need those recommendations to automatically populate (in order for my wife to be comfortable using this)” is a perfectly valid use of the word “need”.