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#276 Yesterday 08:00:50
- tahanson43206
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- Registered: 2018-04-27
- Posts: 21,457
Re: kbd512 Postings
For SpaceNut re lubrication of bearings ....
A possible solution to the very real problem you have identified is to allow for the rotating habitat batons to turn with only magnets keeping the walls of the rotating components away from each other. This could be done during flight when there are no forces acting to move the fuselage. When it becomes necessary to apply force for navigation, the rotating components could be brought back together so they can accept acceleration loads.
I've never heard of such a system, and there may be practical reasons why it would not work.
I'm pretty sure magnetic bearings do exist, but the machines involved might be small.
(th)
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#277 Yesterday 12:30:07
- kbd512
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- Registered: 2015-01-02
- Posts: 8,187
Re: kbd512 Postings
tahanson43206,
Using rings of permanent magnets in a Halbach array could lock all rotating and "stationary" parts of the vehicle in place without physical contact. Permanent magnets are typically heavier than electromagnets for the field strength they provide, but they do not require any input electrical power. For the strength of the field required for this application, stronger fields are likely irrelevant. Beyond that, we really don't want the magnets to be "turned off" in this application. The vehicle will function best if the magnets are "on" at all times, and the various parts "float" perhaps a centimeter away from each other.
The label "air" would be replaced with "vacuum" in space:
A planar permanent magnet array:
Axial flux electric motor:.jpg)
Halbach arrays can also be incorporated into a "curved" inner and outer lip type of geometry, so that the magnetically suspended habitation modules cannot readily "fly apart", even if the magnets themselves fail.
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#278 Yesterday 13:20:38
- kbd512
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- Registered: 2015-01-02
- Posts: 8,187
Re: kbd512 Postings
tahanson43206,
A much cheaper option would be using full ceramic bearings with minimal Silicone-based lubricant. At 6rpm, the duty cycle is 3,153,600 cycles per year.
A drastically cheaper option would be using standard Babbitt metal bearings with lubricants. Much hay is made over this, but the battery operated tools used by the astronauts to repair the Hubble Space Telescope, such as the bit driver they used to unscrew and re-torque bolts, did in fact use bearing lubricants. The photovoltaic arrays on the ISS do in fact use sealed metal bearings with a vacuum-compatible grease.
That means there are 3 ways to solve this centering and bearing problem:
1. Contactless permanent magnets or electromagnets.
2. Dry or minimally lubricated ceramic bearings.
3. Lubricated metal bearings.
Option 1 is scientifically interesting because it will theoretically never fail from direct contact friction.
Option 2 can work, but is also expensive at the scale required and will still require periodic replacement.
Option 3 will work for many years before replacement and is exhaustively well proven on Earth and in orbit aboard ISS.
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