This is entirely correct: ask anyone from an aeronautics background: tip speed is king when you consider noise, and that's it. Huge effort goes into reducing the noise produced by the high blade tip speeds of turbo-prop engines.
If you want a quieter fan: slow the blade tip speed, simple as that. (although I think this new fan design does have advantages, particularly the increased air-flow near the fan axis).
It ionizes hydrogen with microwaves an then accelerates them with magnetic fields. While it doen't provide thrust like a chemical rocket, it certainly has many, many times more thrust than a ion engine.
What? why ionize hydrogen? It's so light. Ion thrusters use the heaviest inert gas viable: Xenon, in order to get any reasonable thrust as all.
A specific impulse is the number of seconds 1 kg. of fuel could produce 1 kg. of thrust.
thrust is measured in Newtons.
This VASIMR thing sounds like a microwave MPD, with a nuclear power source. The question is: why lug a massive nuke power supply when you have the Sun? In terms of Amperes per kg, IMHO solar panels are much cheaper than a nuke reactor.
Slashdot Mirror
This is entirely correct: ask anyone from an aeronautics background: tip speed is king when you consider noise, and that's it. Huge effort goes into reducing the noise produced by the high blade tip speeds of turbo-prop engines.
If you want a quieter fan: slow the blade tip speed, simple as that. (although I think this new fan design does have advantages, particularly the increased air-flow near the fan axis).
What? why ionize hydrogen? It's so light. Ion thrusters use the heaviest inert gas viable: Xenon, in order to get any reasonable thrust as all.
A specific impulse is the number of seconds 1 kg. of fuel could produce 1 kg. of thrust.
thrust is measured in Newtons.
This VASIMR thing sounds like a microwave MPD, with a nuclear power source. The question is: why lug a massive nuke power supply when you have the Sun? In terms of Amperes per kg, IMHO solar panels are much cheaper than a nuke reactor.