“The Moon is a Harsh Mistress” is not an instruction manual

Part of my series on countering common misconceptions in space journalism.

Well, dear reader(s), we’re getting close to the bitter end here. I’m on shaky ground. This blog is about misconceptions that are neither common nor found in space journalism. But someone once said something that annoyed me and so now we have a blog about it.

To begin with the usual disclaimer, I’m not a book critic. Nor have I ever been to the Moon. I have, however, written reviews or technical commentaries on this blog of several books, including “The High Frontier” and “The Martian”.

The Moon Is a Harsh Mistress: Robert A. Heinlein: Amazon.com: Books

“The Moon is a Harsh Mistress” by Robert Heinlein is a fun book and it’s not particularly hard sci-fi, so I will resist the urge to be a joyless bore and abstain from enumerating technical problems with the plot. It’s a novel. It has technical inaccuracies. If you’re into that sort of thing, my review of “The Martian” is a good place to start.

No, it turns out that Heinlein’s book is a fine piece of writing on its own terms. What ruined it for me is its use by a small hard core of fans to argue about vision for space exploration, as though it was some kind of holy text or scientific primary source. Indeed, since its publication in 1966 it has spawned countless imitators, almost all of which (if I may go so far as to say) completely miss the point. If you disagree, well, I could be wrong. It has happened before.


TMiaHM is a coming-of-age story set on a subterranean Moon city. To create narrative conflict, this city is expected to squander its limited water supplies growing grain (!) to ship to Earth with an electromagnetic mass driver. Manipulated by a sentient AI (the main character!), the supporting human characters foment a violent revolution which culminates in their kinetic bombardment of strategic targets on Earth, as though the Moon was some sort of strategic high ground.

While some readers celebrate a thread of libertarianism that runs through the novel, it is worth pointing out that few derivative works by other authors captured the quotidian weirdness that Heinlein managed to bake into the Moon’s social culture. In particular, the unbalanced gender disparity leads to the adoption of an alternative family unit where marriages occur in concatenated “lines” rather than persistent diads. This draws on Heinlein’s interest in the free love movement, which he wrote as early as the 1930s.

Much of the book is consumed with theorizing about violent revolution, and draws heavily on the American revolution, while its publication anticipated the global socialist instability of 1968 by a few years.

The ambiguity of its moral message is a testament to the complexity of the text, but to me the “boys own adventure” and risk-free libertarianism reading misses the point. Of course, if there is anything more petty than taking a novel literally, it would be criticizing that action, so I will desist. Soon.

Let’s be specific. In what ways does this novel (and others in the genre) fail as an instruction manual?

We know that a Moon city is not a good place to grow plants, that water is relatively abundant on the surface near the poles, and that underground construction is pointlessly difficult. So any future Moon city will have to be structured around some other premise, which is to say its foundational architecture on both a social and technical level will be completely different.

We know that AIs are pretty good at tweaking our amygdala, but strictly speaking we don’t need to build one on the Moon, and I would hope its existence is strictly orthogonal to the question of political control.

Lunar cities, and all other space habitats, are tremendously vulnerable to physical destruction. This means that, for all practical purposes, Earthling power centers hold absolute escalation dominance. No combination of sneaky AIs, secret mass drivers, or sabotage would be enough to attain political independence through force. If space habitats want some degree of political autonomy, they will have to obtain it through non-violent means. Contemporary science fiction author Kim Stanley Robinson makes this argument powerfully in this recent podcast, when discussing how he structured the revolutions in his Mars trilogy.

Lastly, the “Brass cannon” story is like “Starship Troopers” – a falsifiably satirical critique of popular conceptions of political control. For some reason, libertarians swarm Heinlein novels and space advocacy conferences like aphids in spring. I will resist the temptation to take easy shots, but point out merely that every real-world attempt at implementation of libertarianism as the dominant political culture has failed, quickly and predictably. This is because libertarianism, like many other schools of thought that fill out our diverse political scene, functions best as an alternative actually practiced by very few people. It turns out a similar thing occurs in salmon mating behavior.

I always try to end these blogs on a constructive, positive note. When we set out to build cities on the Moon and Mars, we do so because we are inspired by compelling visions, often delivered within powerful narratives told by gifted story tellers. But narrative is something constructed from reality, not the other way around. In getting down to the nuts and bolts, we must abandon our preconceptions and instead reason by first principles.

14 thoughts on ““The Moon is a Harsh Mistress” is not an instruction manual

  1. Sometimes a good story can be a great and entertaining one but when groups try using for an example of their views it is pointless and out of context in a way.


  2. There’s a big difference between fictional libertarians and real people of any kind. Fictional libertarians have superhuman productivity and (ironically) social organization. A lunar city populated by such paragons has an overwhelming advantage in a confrontation with a bunch of Earth worms who are hopelessly deficient both in moral fiber and in the True Doctrine that is it’s source. Such an Earth can’t feed itself. No escalation is possible for the worms, because they don’t have any righteous principles worth starving themselves over.

    Liked by 2 people

  3. Not related to either tunnels or TMiaHM, but today I want an air-breathing first stage for the Mars-bound model of Starship.

    Starship’s current mission is Starlink, mainly. There will be no Martian city without funding, after all. For Starlink, there’s no benefit to launching near the equator, if I understand the conclusions from the orbital mechanics correctly. So there’s very little benefit in having the first stage be essentially a carrier aircraft. You can easily have your launch site be at about the right latitude for the orbital mechanics, and it’s a pretty good latitude for reliable weather, too.

    For Mars, you would like to launch from the equator. But tropical latitudes are far from most of your infrastructure, and they have a rainy season. If your rocket is cruising on an over-sized jetliner at the moment of ignition, you can put it in exactly the right spot for your launch window, no matter what the weather is like at ground level.


      1. I’m not finding it by searching for “air launch” or “stratolaunch”. I did find your post on gerrymandering, so at least it wasn’t wasted time.

        In the present tense, yes, I think you’re right that there is no benefit to air launch. But if we were launching millions of tons of propellant to send hundreds of thousands of tons of payload to Mars, after squeezing all the lower-hanging fruit pretty hard, I’m guessing that it would be worth launching from fairly near the equator. Think of it as a launch volume so high that it supports its own dedicated airline from the home country to the launch site.


      2. I couldn’t find the post either. There are three possible benefits, two of which are insignificant: Weather, Spin, and Air Density.

        Weather: For a rocket you have to land and reuse, weather probably blocks landing even if you avoid it on launch.

        Spin: As you note, 80 m/s isn’t much.

        Air Density: You get to put bigger bells on your engines, and also fight through less air (and maybe not throttle down at Max Q?). I’ve read that launching from airplanes can basically double your cargo to orbit, though I imagine that decreases with increasing rocket size.

        Months ago I did back-of-envelope for F9, looking at building a vertical-jet-engine VTOL launch platform. IIRC it would have been worth it for non-reusable F9, but not for reusable.


  4. That’s less than I was implicitly thinking. I’m used to taking for granted that we have to machine away every unnecessary milligram and optimize every last m/s of delta v, so I don’t have to think about just how small any particular savings is.

    Developing the carrier aircraft, the support frame, and the retrieval system for the frame — all of that is fixed cost, and I assume that the scale of launch needed for a city on Mars is going to overwhelm almost any fixed cost. At least, if we go big enough for the resulting city to be viable.

    That leaves the question of the variable costs. A rocket that’s launched from a carrier aircraft has to have the interior structure tolerate being horizontal while fully loaded with fuel and payload. Are we adding enough milligrams to more than offset the advantage of not having to worry about the weather at the moment of ignition because we’re already above the tropopause? Are the ongoing costs of operating a triple wide runway (or whatever it would come out to) greater than the savings from those few m/s off the delta v? I don’t fool myself into thinking I know. I just like the idea of having a launch system be such a mature technology that we’re optimizing stuff where the fixed cost is prohibitive now. And I get to imagine a gigantic frame parachuting down to a drone ship.

    There are a lot of posts on here about big rockets. I’m still not sure which you’re referring to. But I’m still finding good stuff I had missed, so I’m happy. I’ll probably put up a comment on the stupid organizations one, with my pet idea about police.


    1. So BFR version 2 will have a launch mass beyond 10,000T. That’s 100x more than really big jets today. I’m not sure what Stratolauncy can do but it’s huge and also nowhere near that.

      Liked by 1 person

  5. Bummer. That’s a larger multiple than I was imagining, based on how planes look and how the Starship prototype looked in the video where Musk gave a speech next to it. I suppose I didn’t adequately adjust for full tanks versus mostly-empty aluminum tube. Making wings strong enough at the length needed for that weight would probably take too much mass per unit length.

    But hey, it’s just an idle thought, not a serious suggestion. The people making Stratolaunch have to deal with the realities of an under-sized rocket, but as a casual speculator I can just shove it a few years farther into the future, make it out of unobtanium, and fire the rocket for additional acceleration at takeoff. Go faster, and you can get your lift from a shorter wing.


  6. How much difference is there between launching at the best possible moment, and launching any random time in the launch window?


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