Talk:Magnetic sail

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Contents 1 superconducting ? 2 is "magnetic sail in magnetic field" illustration correct ? 3 Deleted illustration 4 Merge From Mini-magnetospheric Plasma Propulsion

[edit] superconducting ?

A magnetic sail or magsail ... a large loop of superconducting wire

Does it have to be superconducting ?

Given the low field strenghts needed, I guess not, but then it constantly drains energy from its onboard electric power source, dissipating it in loop by Ohm's law, shortening the total time of acceleration (and thus limiting maximal velocity) of spacecraft. Besides, wire would have to be thicker and therefore heavier.

[edit] is "magnetic sail in magnetic field" illustration correct ?

A magnetic sail in magnetic field (represented by magenta arrows). The sail generates its own magnetic field, represented a small bar magnet. The ambient magnetic field pulls on the magnetic sail like any other magnet. The force on the sail is to the left.

I'm almost certain this is incorrect. A constant (over the volume enclosing loop) magnetic field exerts no net linear force on a current loop. However, it *does* exert a torque on that current loop. The torque tends to "line up" the loop with the field. Once it is "lined up", there is no net torque on the loop (only a force on each small segment of the loop pulling it out from the center of the loop). By "lined up", I mean that the loop's "dipole vector" (at right angles to the plane of the loop) is anti-parallel to the magnetic field vector. The magnetic field produced by the loop tends to cancel out the ambient magnetic field.

On the other hand, if the magnetic field is diverging (stronger in some place than others), there *can* be a net linear force on a current loop. I don't think any magnetic sails designs make use of this property.

(EditHint: move this to a physics page ?)

-- DavidCary 07:24, 11 Jul 2004 (UTC)

I could create a less mspaint-ish illustration, once I know what it should actually depict (I'm not too good at physics, damn me). So, if you have any exact ideas, please tell me. Until then, I'll do the other illustration. Frank Miller 22:45, 2 December 2006 (UTC)

[edit] Deleted illustration

I deleted the illustration Magnetic sail in a magnetic field. It was not terribly informative, and (as discussed above) did not accurately illustrate where the force comes from. The force on a magnet in a magnetic field comes from the gradient of the field, not from the field itself. In the illustration as shown, there would be a restoring torque on the sail if it is rotated, but no net force. The actual physics are much more difficult to show in a simple illustration. Geoffrey.landis 17:13, 28 February 2007 (UTC)

[edit] Merge From Mini-magnetospheric Plasma Propulsion

I merged Mini-magnetospheric Plasma Propulsion into this page. There was a fair bit of shared material, and the concept of M2P2 can only really be understood once you understand the magnetic sail. --Dashpool (talk) 16:26, 1 June 2008 (UTC)

See Talk:Mini-magnetospheric plasma propulsion. --Dashpool (talk) 06:58, 3 June 2008 (UTC)

Steering magnetic sails: [[1]] --Dashpool (talk) 08:10, 3 June 2008 (UTC)