We all know the pictures of the astronauts on the ISS floating around. We also suspect that a lack of gravity is bad for the body as the muscles go weak and such.

Why don’t spaceships just rotate to cause the effect of artificial gravity through centrifugal forces?

  • deegeese@sopuli.xyz
    54·
    19 hours ago

    You said force of rotation but the chart is talking about RPM.

    Still only 1G.

    • Windex007@lemmy.world
      4·
      15 hours ago

      Everyone is doing a terrible job of explaining, but they’re right.

      Gravity, 1G, is described on terms of an acceleration. 9.81m/s2.

      What is an acceleration? Is is the rate of change of a velocity. If a velocity changes slowly, it means the acceleration is low. If the velocity changes quickly, the acceleration is high.

      Now, imagining a record player. Or cd player. Or your spinning wheel of choice:

      You know that points farther away from the center are moving faster in absolute terms compared to points closer to the center.

      Because the points farther from the center have a larger velocity, that means after some rotation, the total change of velocity for the outer points must be larger than the change of velocity for inner points. So, points farther away must have greater acceleration.

      So, the apparent acceleration changes according to how far things are from the center point. This is why it really isn’t the case that it would be 1G everywhere. 1G is a specific acceleration, if if we’ve established that acceleration isn’t constant across the radius, then it can be 1 G only at one spot, not all.

    • Luminous5481 "Lawless Heathen" [they/them]@anarchist.nexusEnglish
      61·
      17 hours ago

      You said force of rotation but the chart is talking about RPM.

      yes, you have forgotten to take into account the Coriolis force and the effect it would have on your astronauts.

      https://ntrs.nasa.gov/api/citations/20070001008/downloads/20070001008.pdf

      At body motions or centrifuge rotation rates that are small in magnitude, the effects of the Coriolis force are negligible, as on Earth. However, in a centrifuge rotating at several rpm, there can be disconcerting effects. Simple movements become complex and eye-head movements can be altered: turning the head can make stationary objects appear to rotate and continue to move once the head has stopped. This is because Coriolis forces also create cross-coupled angular accelerations in the semicircular canals of the inner ear (see Figure 4-01) when the head is turned out of the plane of rotation. Consequently, motion sickness can result even at low rotation rates (<3 rpm), although people can eventually adapt to higher rates after incremented, prolonged exposure (see Chapter 3, Section 3.1).

      in other words, the higher the RPM needed to generate 1g, the worse the effect of the Coriolis force on the astronauts.