Energy costs of giving Mars and Venus moons: moving gas giant moons vs. capturing a rogue planet?

As many here likely know, one of the factors that make both Mars and Venus uninhabitable to humans are their lack of a magnetosphere to keep solar winds out.

In the setting I am working on, I wanted Mars and Venus to be terraformed. Among the steps taken in the terraforming process; they would each have a moon put into orbit in order to introduce tidal forces to the planets.

I've thought of three possible solutions to giving either a moon:

• Scientists discover a window in which they can launch a gas giant moon out of orbit on a path that, with possible adjustments made along the way, would result in it being caught in a new orbit without disrupting any other planetary bodies. Earth sends out crews to set up automated systems that will act once the window arrives. It could possibly create two colonization ready worlds in one go depending which moons are commandeered.
• A small rogue planet is spotted on a path through/near our solar system and unmanned vessels are sent to adjust its course to capture it into a stable orbit around Venus or Mars. (Only one of them would be terraformed in this scenario, which is fine.)
• Dwarf planets and larger asteroids are gathered to create an artificial moon which is then placed into orbit around its new home. Assembly can either take place either in orbit, before being moved or on the way to its new destination. As it turns out, there is insufficient material in the asteroid belt to accommodate this method. Which would bring us to ripping moons out of orbit, but multiple smaller ones rather than a single big one.

Assuming that thrusters on the scale to safely move planets are created (even if they're seen as somewhat ludicrous in-world) and that the proposed moons from all three methods are the same proportion in mass to each of the planets they will be sent into orbit of, which of these methods would be the most energy efficient?

I know all three are going to have crazy expensive energy/time demands, but I want to know which one is the least crazy of the three.

Writer's note: The ludicrous scale and increased taxes to fund this massive project are meant to be part of the backstory and one of the factors that drives the outer colonies to declare independence from Earth's interstellar government.

As a side question, would it be possible to use the insertion of said moon into Venus's orbit to also increase its astonishingly slow rotation speed? To kill two birds with one stone. (Just as something to save the time/fuel/money.)

posted almost 7 years ago

Arvex‭

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