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General Science / Re: Aerospace: Magnetic Levitating Rim Driven Ducted Fan - Possible or Not?
« on: 22/12/2023 08:48:58 »
Problem with the Halbach array is that the strong field direction alternates, so the net field at any distance greater than the period of alternation is zero, and you can't use it to generate repulsion between moving objects. No big deal if you just want to stick a souvenir on a refrigerator, but you need a unidirectional convergent radial field to suspend Supervolant's rotating fan.
Also worth considering the aerodynamic efficiency of the system. The edges of the fan generate most of the thrust because they sweep a large area per rotation, so you want to keep the airflow around the edges as unobstructed as possible: close ducting induces drag on the fan tips. This means that your maglev can't use the "very near field" approximation of Reply #7 but will require a much larger field.
The center of the fan, on the other hand, produces very little thrust, so you might as well ignore it and put a ball bearing in the middle. Then you can drive the fan with any motor you like.
Short of going nuclear (and the Godiva nuclear airplane project wasn't much of a success) the highest practicable energy density is the oxidation of hydrogen, whether by combustion or in a fuel cell, and I don't see any battery system being able to compete. In the meantime, combining hydrogen with carbon does give us a very convenient range of fuels for every form of aviation.
Also worth considering the aerodynamic efficiency of the system. The edges of the fan generate most of the thrust because they sweep a large area per rotation, so you want to keep the airflow around the edges as unobstructed as possible: close ducting induces drag on the fan tips. This means that your maglev can't use the "very near field" approximation of Reply #7 but will require a much larger field.
The center of the fan, on the other hand, produces very little thrust, so you might as well ignore it and put a ball bearing in the middle. Then you can drive the fan with any motor you like.
Short of going nuclear (and the Godiva nuclear airplane project wasn't much of a success) the highest practicable energy density is the oxidation of hydrogen, whether by combustion or in a fuel cell, and I don't see any battery system being able to compete. In the meantime, combining hydrogen with carbon does give us a very convenient range of fuels for every form of aviation.
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