• Question: What side affects do astronauts get from the G force when they go up in rockets?

    Asked by smileysoph to Adam, Catherine, Karen, Leila, Nazim on 21 Mar 2012.
    • Photo: Leila Battison

      Leila Battison answered on 21 Mar 2012:

      G force effectively increases the gravity acting on your body, so it increases your weight (not your mass).

      It’ll make breathing difficult, because the forces pull down on your rib cage.
      Your blood might get pulled away from your brain, and that is bad, because your brain needs the oxygen in your bloood to function.
      You might lose your peripheral vision, get tunnel vision, and may even black out.
      And the blood vessels in your skin might burst, giving you a rash called ‘geezles’.

      But astronauts are trained in excercises that can lessen these effects, and get lots of practice gos in a big spinning centrifuge!

    • Photo: Adam Stevens

      Adam Stevens answered on 21 Mar 2012:

      Leila has explained pretty well the problems.

      There are lots of things that rocket designers do to make the whole thing bearable though.

      For a start, astronauts normally sit facing or with their backs towards the force, so it’s doesn’t have the same effects of just increasing gravity. The body can cope a lot better if the extra G force is that way.

      So, the extra gs squeeze your chest making it quite hard to breathe, and it presses blood into places it shouldn’t be.

      It also squeezes your eyeballs and reduces the blood, which means they don’t work as well. You lose the vision around the edges first, then everything starts to go grey as the rods and cones stop working.

      Normally though, astronauts don’t describe the experience as that bad. With special suits that help by squeeze blood back to the right places and the way the rockets are designed, the G forces they feel are no worse than a fighter pilot pulling a really tight turn. They don’t last that long either.

      The worst is the sustained extra G at liftoff, but that generally isn’t too high. On reentry they feel a lot of extra force but over less time. In fact, the vibration is normally worse!

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