A Realistic Vision of Moon-Lifting

Mass-Lifting from The Moon

The Mass Distribution Problem

Many people are surprised to find out that our moon is larger than all objects in the asteroid belt put together by a large margin. Evolution of our solar system by gravitational interactions and collisions underwent something like Ostwald ripening:

Lifting — Essentially Complete Deconstruction of an Astronomical Object

A launch gun on the moon is “mass-lifting”, but make the object itself the first word in that phrase, “moon-lifting”, “asteroid-lifting”, or “star-lifting” and you express a very different concept. While mass-lifting would bring a marginal fraction of the mass out of the gravity well, moon-lifting would completely destroy the object’s gravity well, dispersing the material en-mass into chunks which are all much smaller than the original object.

Why Would We Ever Do This?

To repeat the scenario mentioned about O’Neil habitats, someone would likely process the materials to make the steel hulls of massive space habitats.

Mining Trace Minerals

A growing number of asteroid bulls believe that we will conduct mining operations on asteroids. The point is not to transport the entire mass, but to set up refining operations on the asteroid and only deliver a small quantity of precious metals extracted from it. Digging into a body with significant gravity presents a sort of complication that’s not necessary for small objects. As such, moon lifting could eventually become something tantamount to strip mining in space where enormous quantities of matter are scoured by methods that have extreme economies of scale by traversing newly exposed surfaces from a moon or asteroid.

Spin-Up Disassociation

High gulfs of Delta V introduce massive inefficiencies, and the concept of moon-lifting benefits from the fact that only relatively low Delta V values are involved. Because of that, completely ordinary materials can be employed in the operations to disassociate the mass of the object. The most obvious first step to this is to simply spin the moon until parts of it begin to break apart. The angular momentum isn’t actually that hard to provide, since it comes from the produce of (mass) x (radius) x (velocity). In our scenario, a large radius is the trump card.

Very Janky Illustration of Spin-Up for Moon-Lifting

Followup Calculation Work

There’s much too much to say about this topic to put in an introduction article. My arguments here inherently hinge on the crude numbers on the subject. As I’ve argued again and again, good futurism involves comparing quantities that we can know about competing future scenarios. Again, moon-lifting is like strip mining, so we’re balancing the benefit of getting those materials against the energy needed to lift the material. That energy is approximately equal to the total binding energy of the object.

Binding Energy from Wikipedia, Note the R⁵ Factor — Size Dominates the Discussion

Perspective on Gross Energy Needed

I like the units of TW-years, Terrawatt year units. Earth right now consumes around 15 TW, maybe 16, my memory could be a few years outdated. So right away, we can start talking about a role of thumb about which moons are viable to moon-lift without assuming a starkly different scale of industrial society in space than what we have on Earth.

Competitive Comparison to Asteroid Herding

Destruction of a moon is a competitive process with going out into deeper space, capturing an asteroid, and bringing it back near to the rest of your facilities. Both of these processes can have hard numbers put on them, and even better, time tables. Asteroids are in heliocentric orbits, so there’s a certain time measured in years that it would take to move one into the needed orbit. Since moons are clustered more toward planets, they are likely (not guaranteed) to already be in the general region where it’s needed, with only the gravity well (from binding energy) standing in the way.

Competitive Comparison to Space Steel Manufacturing

This one is more difficult to explain, and it involves a more fringe concept, described in my alternate blog on the subject.

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Alan

Alan

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Obligatory analytical writing, online participation account for Medium. Engineering, software, books, space, constant daydreaming.