• dual_sport_dork 🐧🗡️@lemmy.world
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    6 days ago

    I know it’s not funny, but helicopter ejection seats work by (typically explosively!) jettisoning the rotors prior to the launch of the seat.

    At Mach 19, however, you would have probably roughly a 1 in 12 not to take one of the rotors right to the dome on the way out. Do you feel lucky, pilot?

  • kersploosh@sh.itjust.works
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    6 days ago

    There’s an additional health benefit. If your spine is turned to jello then you never have to worry about herniated discs in your old age!

  • eatCasserole@lemmy.world
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    6 days ago

    Helicopters are actually really neat. If they suffer a loss of power, they can spin up the rotor while falling, and then reverse the blade pitch and turn all that momentum into lift and make a soft landing. Or something like that. Smarter Every Day can explain better: https://youtu.be/BTqu9iMiPIU

    • Bytemeister@lemmy.world
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      4 days ago

      Sort of correct. They can feather the blades to induce auto-rotation. Long explanation short, the rate the blades rotate is based on the total airflow though the rotor disk from any angle, so much like a glider, you can trade forward speed for vertical speed/rotor speed.

    • Rivalarrival
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      6 days ago

      Check out “gyrocopters”. They look kinda like helicopters, but their rotors are not connected to the engine. Instead, they use a propeller to drive the aircraft forward, and airflow drives the rotor disk.

      They operate on the same basic principle as autorotation, but for normal flight rather than arresting an emergency descent.

      • eatCasserole@lemmy.world
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        5 days ago

        The longest helicopter autorotation in history was performed by Jean Boulet in 1972 when he reached a record altitude of 12,440 m (40,814 ft) in an Aérospatiale SA 315B Lama. Because of a −63 °C (−81.4 °F) temperature at that altitude, as soon as he reduced power, the engine flamed out and could not be restarted. By using autorotation he was able to land the aircraft safely.

        What a mad lad, setting two records at once.

  • then_three_more@lemmy.world
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    6 days ago

    So I assumed the rotas were about 3 meters from the cocpit and asked Gemini.

    To calculate the g-force experienced during this acceleration, we need to go through a few steps:

    1. Convert Mach 19 to meters per second (m/s):
    • The speed of sound in air varies with temperature. At a standard temperature of 20°C (68°F), the speed of sound is approximately 343 m/s.
    • Mach 19 is 19 times the speed of sound.
    • Therefore, Mach 19 ≈ 19 * 343 m/s = 6517 m/s.
    1. Calculate the acceleration in m/s²: We can use the following kinematic equation:
    • v_f² = v_i² + 2 * a * Δx
      • Where:
        • v_f is the final velocity (6517 m/s)
        • v_i is the initial velocity (0 m/s, assuming starting from rest)
        • a is the acceleration (what we want to find)
        • Δx is the distance (3 meters)
    • Plugging in the values:
      • (6517 m/s)² = (0 m/s)² + 2 * a * (3 m)
      • 42,471,289 m²/s² = 6 * a m
      • a = 42,471,289 m²/s² / 6 m
      • a ≈ 7,078,548.17 m/s²
    1. Convert the acceleration to g’s:
    • One g is the acceleration due to gravity at the Earth’s surface, which is approximately 9.81 m/s².
    • To find the acceleration in g’s, divide the calculated acceleration by the value of one g:
      • g-force = a / 9.81 m/s²
      • g-force = 7,078,548.17 m/s² / 9.81 m/s²
      • g-force ≈ 721,564.5 g Therefore, you would experience an acceleration of approximately 721,564.5 g while accelerating to Mach 19 over a distance of 3 meters. Important Note: This is an extremely high level of acceleration, far beyond what any known biological organism or material could withstand. Such forces would be instantly fatal and would likely cause catastrophic structural failure.

    I’m sure someone who’s better at maths than me can tell me where the llm has gone wrong. But it sounds impressive.

    • Nasan@sopuli.xyz
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      5 days ago

      Powered by nitrous oxide like in the true crime documentary 2 Fast 2 Furious