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Comment by HenryKissinger | Hacker News Reader

Some pollution is an inevitable consequence of economic development.

It would be great if we could move our most polluting activities (factories, refineries) to the Moon or Mars.

That’d be inconceivably far in the future. It’d need to be more economical to transport goods through space…

Two-way cargo transport through vacuum has zero net energy cost, just like a counterweighted elevator on Earth, only more so -- no vacuum here. With reasonable intelligence and infrastructure we should approach that limit.

Design sketch from 1978, with numbers: https://frc.ri.cmu.edu/~hpm/project.archive/1976.skyhook/pap...

There isn’t energy cost between bodies, but there are huge energy costs getting into orbit, leaving orbit, and getting into the destination body’s orbit

Factories, refineries, and raw materials don't need to be on planets. There are disadvantages to siting on planets besides the added transport costs.

> getting into the destination body's orbit

I said round-trip energy costs. The delta-v for arriving cargo to enter orbit equals the delta-v for departing cargo. Over a full cycle of sending equal payloads both ways, the net change of energy and momentum is zero. I linked to an analysis of one way to harness this. When the skyhook in the linked example boosts a payload from Venus-Earth Hohmann to Earth-Mars Hohmann, the skyhook's orbit gets perturbed; but it gets the opposite perturbation on the boost on the opposite traffic.

(This is not the only non-rocket approach to free-space transport with potentially low marginal cost.)

Heavy industry in space is a ludicrous idea for the next few centuries. We will need to significantly rework industrial processes to avoid the heat buildup currently offset by the planet. No one will be operating a foundry in space anytime soon.

Niche applications like low-temperature ZBLAN manufacturing might make more sense.

I disagree about centuries because the rate of progress so far belonged to a regime of launch costs of thousands of dollars per kg or worse. (Though "centuries" is at least more realistic than "inconceivably far". People were conceiving it in the 1970s and earlier.)

Maybe we'll use mass drivers to cool platforms in a couple hundred years. Maybe we'll reuse the slugs to excavate other bodies.

> move our most polluting activities (factories, refineries) to the Moon or Mars

The delta-v required to move objects between planets is measured in thousands of m/s (e.g. just getting to low earth orbit requires about 10000 m/s), and the fuel required goes up exponentially with delta-v.

As Elon Musk put it: "If you had crack-cocaine on Mars, in prepackaged pallets, it still wouldn't make sense to transport it back here."

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