How to transport a ball of liquid, molten metal nearest to the Sun possible? It must be close to the Sun for the metal to stay molten.

However, to stay safely cool enough, the spacecraft must always remain in the shadow of the molten metal ball. Liquid iron would radiate intensively, this radiation (1500C) would be far lesser than the Sun's (6000K) a secondary heat shield for the radiant heat off the ball of metal would be needed.

How would a spacecraft stay in the shadow of the ball, unattached, and yet exert force on it in order to guide and adjust its trajectory repulsively?

This answer in this link helps with determining the metal: https://chemistry.stackexchange.com/questions/112627/what-emits-the-least-light-when-hot

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    $\begingroup$ @uhoh few meters but if a bubble was inside it to lessen the weight, air or something would it still remain a stable sphere with the pocket in the center when nears the sun? $\endgroup$ – Muze the good Troll. Apr 13 '19 at 0:42
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    $\begingroup$ the question is, why would you want your material to be in a liquid state and unattached? It'd be much easier to have the material as a solid, in panels on the outside of the hull if you want to use it as shielding. $\endgroup$ – Hobbes Apr 13 '19 at 7:54
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    $\begingroup$ A hot molten metal like iron would not deliver a good cool shadow. It would radiate intensively in the infrared and visible spectrum. If it's temperature is in steady state, it will radiate away all that energy received from the sun. The spacecraft would need a heatshield against the radiation of the liquid metal. $\endgroup$ – Uwe Apr 13 '19 at 10:21
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    $\begingroup$ @OrganicMarble I imagine a layer of liquid tungsten, behind that another layer of solid tungsten, behind that the ordinary mirror-based heat protection and active cooling. Such a construction could visit the upper atmosphere of the Sun. $\endgroup$ – peterh - Reinstate Monica Apr 13 '19 at 16:23
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    $\begingroup$ @Muze I think a liquid metal shield, whose form is controlled diamagnetically, could work. $\endgroup$ – peterh - Reinstate Monica Apr 13 '19 at 19:36

For your goal, molten metal is not suitable, or at least, has no benefits.

Metals are generally good conductors of heat. So all that heat from the Sun will be distributed quickly throughout the metal blob, until all sides are at equilibrium temperature. That will be a bit lower than the temperature from direct insolation (the sphere will radiate heat in all directions, so some of the heat will be redirected away from the satellite).

You'd achieve the same with a solid metal shield with a large radiator: a shield facing the sun, the radiator and spacecraft behind the shield. The radiator is perpendicular to the shield.

This would be much easier to control than a liquid blob.

You don't need molten metal. Inside jet engines, parts like turbine blades are routinely operated at temperatures above their melting point. This is achieved by cooling the blades internally. You can use the same strategy on a heat shield: run lots of cooling ducts through the heat shield, and use a large radiator as a heat sink.

  • $\begingroup$ Possibly, but I'd use a liquid-cooled solid shield instead. $\endgroup$ – Hobbes Apr 13 '19 at 19:11

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