Comment by mLuby | Hacker News Reader

Comment by mLuby | Hacker News Reader

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I hope air-breathing ionic propulsion takes off because even if it turns out to not be great for satellites it'd be wonderful for (small) aircraft. Aircraft are very loud thanks to their engine and propellers/jets. Recent experiments showed its possible to fly with no moving parts using ionic flow: https://www.youtube.com/watch?v=IorDYGI1uqc (9min) I for one would love to fly (on) such a quiet plane, like a glider. Compare muscle car rev to electric car silence.

It also reminds me of the Bussard ramjet, which I thought is considered ineffective due to creating more drag than thrust. Maybe the environment makes a difference?

I wonder if it'd be more effective to use antipodal ground transmitters to beam power up to the satellite, rather than the satellite using solar panels? Less concern about sCaRy high-power microwaves when aiming them from rather than at Earth, though it could still interfere with aircraft and unintended satellites in the cone of effect.

The noise from engines isn't from their combustion or their moving parts. It's from the massive air flow they cause. Ionic engines aren't going to be much quieter for aircraft, assuming they're even possible to move that much air.

Also air breathing ionic propulsion kind of depends on the external presence of ions, which requires space conditions, not normal atmospheric conditions.

Eh, kinda. While most noise from a jet engine at the ground comes from the shear forces from the fast moving compressed exhaust stream interacting with slow moving surrounding air, the engine itself isn’t quiet.

Even in situations where you don’t get that exhaust stream, (such as helicopter turbines spinning up with the clutch out), they’re very loud. Hearing protection required loud.

And very little of a rotary planes noise is coming from airflow or from the prop directly, most of it is coming from the engine itself. At best at least half.

Presumably an ionic drive couldn’t create the pressure differential levels of a jet engine, or probably even a prop, so they’d have relative large, relatively slow moving masses of air to work. So noise should be a lot lower from that, and also from lack of a internal combustion or turbine engine screaming it’s hardest.

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