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If a humanoid robot or other similar weight and sized robots used ionic thrusters on their feet/base of their body to fly and hover along the ground, how far would they need to hover from the ground or near things to make sure the thrusters don't cause any damage to surfaces or things?

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    $\begingroup$ The world most powerful ion engine can produce a whopping 290mN of force... my apologies you'd better stick to jumping that's over 9000000mN! $\endgroup$
    – user6760
    Jun 13, 2020 at 17:26
  • $\begingroup$ I was sure what method they should use to hover, rotary blades or jets might be the most effective but they don't seem advanced enough for an advanced civilization. $\endgroup$
    – user69935
    Jun 13, 2020 at 17:56
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    $\begingroup$ There are ion engines which throw ions behind them at great speed, and ion engines which use charged particles to entrain air and make wind. What are your robots using? $\endgroup$
    – Willk
    Jun 13, 2020 at 18:55
  • $\begingroup$ @willk from your previous suggestion some of my small drones will use that method as well as an earlier flapping method, for these human sized robots one idea is iron man style feet and hands another is hovering life forms or robots, I don't know which engine is best for the task of lifting a mass of 50kg-200kgfor flight and hovering with precision movements? $\endgroup$
    – user69935
    Jun 13, 2020 at 19:35
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    $\begingroup$ Throwing heavy ions at immense speeds will be very tough on the surroundings. That is particle radiation. You would be able to tell where Iron Man had landed because all the vegetation there would die of radiation poisoning. That method works fine in space where you are limited in what you can take with and there is nothing around to kill. But in the atmosphere probably safer to throw large volumes of charged gas around at slower speeds. $\endgroup$
    – Willk
    Jun 13, 2020 at 20:37

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"Ionic thrusters" ...

If you talk about ion drives, in the real world these are low-thrust, high-$I_{sp}$ designs. Good to move a space probe, but unable to hover in any serious gravity field.

Real ion drives have been tested in chambers like these, which gives you an upper limit on the safety distance -- less than the length of the chamber.

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    $\begingroup$ They also function only in vacuum (which is why they need to be tested in chambers like those). There's also "lifters" which work by partially ionizing and propelling air, but those are bulky, fragile, and hopelessly inefficient...I'm not sure if one's been built yet that can lift its power supply. In the real world, you'd only use ion thrusters to "hover" on small asteroids, and it'd be more like stationkeeping next to the asteroid. $\endgroup$ Jun 13, 2020 at 16:59

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