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What if Energy was (Nearly) Free?
anvilmark asks: "Sci-Fi and sci-fi games often incorporate the romantic idea of 'free trader' ships with ports of call on a myriad planets across the galaxy. Recently I was toying with the physics of propelling such ships and their cargos out of a gravity well and realized the astronomical amounts of power it would take to do it (not to mention interstellar travel). This led naturally to contemplating how cheap energy would have to be in order to make this activity profitable. To make a long story short (too late!), I began wondering what would happen if the introduction of fusion power takes energy costs from pennies per kilowatt hour to pennies per megawatt hour (or GWH)? How do you envision the world changing if energy costs became a trivial part of economic equations?"
Your memory about G-force is incorrect. The mass would have to be of the entire earth (or so) because nearly all of that mass would be fuel. That would be what's required to accelerate a modern rocket to near light speeds. Of course, then it would have to decelerate.
Economics strikes again: if it really would cost trillions and trillions, you've got the real problem that we don't have trillions and trillions to spend. The whole GDP of the US is in the neighborhood of $6 trillion, and the world overall certainly doesn't exceed $20 trillion. So what you're proposing is tantamount to suggesting we put everyone on Earth into working on power sats, dropping everything else from food production to programming video games.
I doan' theeeeenk so, Cisco.
Solar power is certainly a fine idea, but out here at the Earth's orbit, it's still only 1 kW/m^2, and the best conversion efficiencies are still less that 20 percent -- in other words, we'd really get about 5 m^2 per kilowatt. It'd take a big satellite to replace one of those 10 GW reactors.
"Essentially for free" is flawed too, but I'll leave the reason for that as an exercise.