Searching for asteroids and other small dark solar system bodies with a network of ground-based stellar occultation cameras

Searching for asteroids and other small dark solar system bodies with a network of ground-based stellar occultation cameras

Casey Handmer October 2018

Apologia

This is a blog written for a general audience. To the readers who (unlike me) actually know what they're talking about with respect to asteroids and astronomy, my deepest apologies. I hope that this is at least amusing, and I would be thrilled to learn of my mistakes. I do not have time or expertise to fully cite every idea or concept, but I have attempted to use phrases that, if googled, would point the reader in the right direction. Onwards!

Summary

A network of hardware-agnostic all sky cameras positioned all over the world can achieve a dense covering of the entire sky, with respect to stellar occultations of near-visible stars down to magnitude 7, out to the orbit of Jupiter at 5.2 AU. Such a system, decentrally implemented and operated, could rapidly survey the entire population of inner solar system asteroids larger than tens of meters, in just a few years. Gathered data will also reveal information about asteroid size and shape, irrespective of the body's albedo. Extensions of the fundamental concept using hardware readily available in 2018 could track solar system bodies of similar size well out into the Kuiper Belt, albeit at substantially increased cost.

What do we want?

Asteroids, millions small rocky bodies that exist primarily between the orbits of Mars and Jupiter, are still relatively unexplored and undiscovered. Of the estimated two million or so larger than 1km, only about 100,000 are known, skewing strongly towards the larger and closer specimens. 

Why do we want it?

In addition to their intrinsic scientific value and interest, asteroids routinely impact the Earth, with consequences ranging from a bright fireball (particle size <1cm) to major damage to a city (<10m, such as Chelyabinsk in 2013) to total destruction (<100m, such as Tunguska in 1908) and even planetary scale extinction events (Dinosaurs!!!).

This diagram shows what fraction of near Earth asteroids are currently known. Each image represents 100 objects, and any of them would be a really really bad day if they hit Earth.

https://www.nasa.gov/mission_pages/WISE/multimedia/gallery/neowise/pia14734.html 

Why is it hard?

While 916 of an estimated 981 near-Earth asteroids larger than 1km are known, vast numbers of smaller asteroids remain undiscovered. Smaller asteroids are hard to discover with telescopes using light reflected from the sun, and not just because they're tiny. They're also often surfaced with material as dark as charcoal, making them extremely difficult to see with reflected light. 

How will we do it?

Stellar occultations have been used to study asteroids for more than 50 years. A stellar occultation occurs when an asteroid or planet passes between the observer and a distant star, momentarily blocking its light. Because asteroids are quite small relative to the Earth, a stellar occultation makes a "track" across the Earth's surface, such as the one shown below.

http://www.asteroidoccultation.com/2018_10/1003_6_56712_Map.gif

asteroidoccultation.com lists predicted occultations of known asteroids passing the Earth so that a network of astronomers can point their telescopes at the correct star and, these days, take a video of the star momentarily winking out. When all the videos are combined with their GPS locations and times, the exact shape of the shadow, and hence the asteroid, can be derived. 

With a powerful enough telescope, hundreds of thousands of stars are visible. The Earth itself is about 12000km wide, and subtends a virtual beam into space in the direction of every star. If a body passes through any of these beams, a sufficiently sensitive photometer will detect the changing brightness of the corresponding star. As the Earth moves through its orbit, this pompom of beams will scrape out a volume within the solar system. If there are enough beams, essentially the entire volume of the inner solar system will be covered in the course of one year.

This diagram shows the Earth's orbit projected on a sphere of radius 3AU. Each star traces out an ovoid, depending on its declination. Combining the ovoids of thousands of stars covers the entire sky with a forest of beams, through which the odds of an asteroid passing without being seen goes to zero. In this diagram, each line is much wider (by roughly 10 times) than the actual beam subtended by the Earth, and the colors are a happy accident. 

In order to estimate the density of coverage, I randomly generated points in the sky then measured how close they were to the nearest beam, for stars brighter than a certain level. If they passed within an Earth radius, then they would generate a stellar occultation. I considered that good enough for detection.

These histograms show the numbers of samples that approach an Earth beam. While the brightest stars do not effectively cover the night sky, my rudimentary calculations show that 82% of the entire sky is covered in one year by just the brightest 5000 stars out to a distance of 3AU, which is roughly the middle of the asteroid belt. Including magnitude 7, which are just dimmer than visible, most points would be detected multiple times per year. It is captivating to think that if humans were able to keep records and time extremely accurately, they could have used this method in ancient times with only their eyes!

This graph summarizes the above histogram, showing that tracking of 5000 stars (M6) is adequate to cover 82% of sky in a year, while tracking of 15000 stars (M7) covers 70% of the sky in only 13 weeks.

Why is this better than the previous approach?

The traditional survey method has significant advantages. A single telescope, operating in an automated fashion, can survey the entire (night) sky in a night or two. Comparing multiple subsequent days enables rapid discovery of moving objects, and completely automated pipelines such as NEO-WISE (https://neowise.ipac.caltech.edu/) have resulted in the discovery of many thousands of asteroids. 

In contrast, an automated stellar occultation asteroid discovery system requires a coordinated network of thousands or millions of all sky video cameras, sophisticated statistics and software, patience, and must contend with the existing, non-ideal distribution of stars.

Stellar occultation has one principle advantage. Because stars are so bright and so far away, they are effectively point sources. Asteroids much too small and dark to be seen using traditional telescopes can still block light from distant stars, enabling their detection. In this way, stellar occultation thumbs its nose at the inverse square law, though without violating any laws of physics. 

When I began thinking about this problem last week, it occurred to me that this was, in some sense, the astronomy analogue of the STED/STORM family of super-resolution microscopy techniques, in that it exploits the statistically regular point spread function of a point source. Super-resolution microscopes are also real headaches to implement, but worthwhile for particular use cases. In this case, because there are millions of undiscovered and otherwise undiscoverable asteroids, it might be worth the trouble to attempt detection using stellar occultation.

What are its limitations?

As previously hinted, like any other experiment there are numerous technical challenges to overcome. This is a non-exhaustive list!

- Diffraction. For sufficiently distant stars and small asteroids, the occultation produces a diffraction pattern on the surface of the Earth rather than a discrete, hard-edged shadow. Given better than binary photometry, occultation diffraction patterns can be measured using the proposed network. 

- Seeing/scintillation. The Earth's atmosphere tends to wobble and in doing so produces 'twinkle' that naturally varies the brightness and apparent location of stars in the sky. This introduces a noise source that drowns out the occultation signal from particularly small asteroids. Collocating sensors within 10m, necessary to detect asteroids of similar scale, would suffer correlated scintillation noise. Combining data from a more broadly separated set of sensors could still detect the smallest asteroids, provided there were enough of them.

- Light pollution/sky glow. In many parts of the world, light pollution affects the visibility of the dimmer stars, particularly over the timescales (milliseconds to seconds) necessary for stellar occultations. Additionally, the sky is too bright to see almost all stars during the day, so the network would only be useful for searches during the night. In practice, apparent magnitude 7 and brighter stars still densely cover a 3AU sphere even without a space-based detector system, which can point much closer to the sun.

- Other sky objects. Planes, birds, clouds, meteors, insects, and satellites can all occult stars or introduce noise. Fortunately, occulations occur on a planetary scale, so more local noise sources can be readily filtered out. Indeed, a widely distributed network of all sky cameras would also be useful for tracking meteors and discovering the remnants of long-period comets, which also pose an existential threat to humanity.

- Sensor density. The mean free path of any given occultation track between sensors on the Earth determines how effective the proposed network is at detecting every occultation, and particularly the occultations by small objects that have narrow tracks. My analysis assumes that millions of sensors based on mobile phone hardware are positioned over the entire dark-sky land area of the Earth. Note that the network would still have substantial scientific value at smaller scale, but comprehensive exploitation of the opportunity requires an extensive network on Earth.

- Stellar radius. All the stars in the sky that are visible to the naked eye are either very bright, very close, or both. For particularly wide stars in the night sky, a small, close asteroid won't completely eclipse it. Instead of going completely dark for a fraction of a second, the star will only dim slightly. Star catalogs include star angular diameter, so excluding problematic stars for smaller objects is trivial. 

- Statistical inference. The proposed network will require a multifaceted data pipeline to first discover and measure an occultation, reconstruct an occultation track, generate candidate object sizes and orbits, and then produce predictions of future occultations that can be used to refine orbits. Yes, a dense covering of the sky guarantees repeated occultation observations of every body over a period of years, allowing orbital elements to be calculated. Nonetheless, processing all the data efficiently is a worthy problem.

- Pixel edges. As an example of hardware specific issues that complicate mere photometry, an all sky camera will not track individual stars. This means that stars will move through the visual field, crossing pixel boundaries and, in some cases, even sharing pixels with other stars. The detector software will need to include a star tracker so it knows what it's looking at and doesn't confuse sensor noise and pixel boundaries with an actual occultation. Detector orientation is otherwise hard to measure.

- Hardware heterogeneity. As much as I would love to spend someone else's money on a million ARGUS-IS gigapixel cameras (https://en.wikipedia.org/wiki/ARGUS-IS) and slap on a 3m fish eye lens, the proposed system will have to contend with hardware heterogeneity. This means that none of the cameras will be perfect, they will all be different, and the software they run will have to have sophisticated hardware models to compensate for these differences. One compelling option is to use retired smart phones with fish eye lens attachments and solar panels for power, and send reduced data back to base with the cellular network. 

- Deep sky limitations. Finally, the inverse square law does come back to bite when considering outer solar system uses of such a network. Stellar occultations for Kuiper belt object discovery and atmosphere measurement is an area of active research (e.g. https://www.lpi.usra.edu/books/ssbn2008/7022.pdf), but even the system I'm envisioning wouldn't be capable of producing a *dense* dragnet of the sky that far from the sun. There are two main reasons for this. The first is that the projection of Earth's orbit (parallax) gets smaller and smaller, reducing the length of the locus by a factor 1/r. The second is that the projection of the Earth's disk also covers less of the sky, shrinking the area of coverage by 1/r^2. This still scales better than direct discovery, which scales as 1/r^4! But surveying the sky at 60AU would require 20^3 = 8000 times as many stars as at 3AU, necessitating using all the stars up to magnitude 16, which is comparable to the brightness of the nearer Kuiper belt objects themselves! All things being equal, an aperture 100 times greater would be required to gather photometric data of stars this faint, while the sheer number of objects would complicate automated tracking. Furthermore, stars at this magnitude are predominantly located in the galactic plane and are not comprehensively surveyed. I'm not saying it's impossible, but it's a different sort of problem.

A vision for practical implementation

As of today, my best vision for deploying this instrument is the development of an app that runs on smartphones. Each phone would use its camera, an aftermarket fixed focus fisheye lens, GPS, Bluetooth, and a cellular connection, and power source such as a solar panel or very long USB cable.

Each phone's software incorporates a star tracker that monitors the brightness of each star while it sits within a pixel, checking for a dimming that is statistically at variance from background sensor noise. 

A candidate detection is tagged with location and the specific star, then compared within a local decentralized cluster of 2-15 phones within a ~100m area. Given a concurrence, the event is uploaded using a cellular or satellite network in compact text form, containing the following information: GPS location, start and end time, degree of extinction, an event reference number, phone configuration, orientation, and ID numbers, (most likely) star, and event's declination and right ascension. Local weather data (e.g. percent of the sky visible) is also included. 

The cellular connection is also used to receive information about predicted tracks. If the event is thought to involve a diffraction pattern, ring system, or atmosphere, then more detailed photometric data can be taken and uploaded for analysis.

On a remote server, incoming events are binned by sky location. Any event that does not have corroborating occultations of the same star are thrown out. Multiple events are reconstructed into tracks, depending on where they were observed, and a further statistical test ensures that a majority of the local clusters along the track all detected the event. For diffraction patterns, all relevant data can be processed together to pull the signal from the noise.

With sensors capable of tracking magnitude 7 and brighter stars, essentially all of the estimated two million asteroids larger than 1km (and billions of smaller ones) will be detected every year. Earth over(under)takes the slower moving main belt asteroids frequently enough that nearly every asteroid will be detected multiple times over a few year period. The final task of the central server is to process occultation event detections to deconflict coincidences. That is, if two million asteroids are detected twice, there are four thousand billion possible double detections. The vast majority of these can be excluded on physical grounds, but of the remaining, say one billion candidate orbits, each will generate at least one predicted occultation per year. This may seem like a lot, but each camera is tracking about 7000 stars at once, for 31 million seconds a year - a total of 210 billion star-seconds! With a decent sized dataset, most of the remaining candidate orbits can be excluded and asteroids definitively discovered. Finally, combining information from multiple occultations, the asteroids' shapes can be deduced.

Final Thoughts

Earth has a surface area of 510.1 million km^2. As of 2018, the are of the single largest telescope is 84m^2. The total area of all the optical telescopes is less than 0.002km^2. The total area of all human pupils is about 0.7km^2. All the rest of the star light that falls on the Earth is wasted! While radio astronomers have long used telescopes across the world for very large baseline observation, the use of such a huge canvas for visible observation is limited by the severe physical difficulty of recording a visible light signal at about a million billion Hertz. With stellar occultation, this limitation can be removed. Using the entire Earth and millions of artificial eyes to stare at the night sky is the only practical way to discover and catalog every asteroid that orbits between Earth and Jupiter, including every main belt asteroid, down to a size of tens of meters. 

How to rig an election, or yet another think piece on gerrymandering

How to rig an election, or yet another think piece on gerrymandering

Casey Handmer, 4 January 2018 (revised and published October 2018)

This technical note lays out a recipe for gerrymandering any given set of congressional districts.

Context:

https://www.wired.com/story/pennsylvania-partisan-gerrymandering-experts/

Why is gerrymandering bad?

Gerrymandering is bad for two related reasons:

• It subverts the will of the people, by skewing the x-intercept of the swing/representation graph, as shown below.

• It radicalizes representatives, whose representation tends over time towards more homogeneous, less diverse congressional districts.

These two reasons drive partisan polarization for many, though not all, issues, and contribute to inefficiencies in the governing process.

There is a perception that a gerrymandered district is obvious, but a formal definition is surprisingly non obvious. Some ridiculous shape might help with the "know it when you see it" definition, but formally convex districts can also be gerrymandered. For the purposes of this discussion, I will consider a set of districts gerrymandered if their boundaries are statistically robustly shifting the x intercept of the swing/representation graph.

This graph shows a roughly even split of gerrymandering that ensures house safety even with a 5% swing. https://urbanmilwaukee.com/wp-content/uploads/2016/12/image00-3.png

There are many proposals for algorithms or mechanisms that can select less gerrymandered districts. My favorite proposal (today) is the "I cut, you choose" procedure, where each major party takes turns to draw one district of the appropriate size within the remaining area. This can tend to minimize the negative partisan effect of existing gerrymandering, but I will show that it doesn't actually solve the problem. It merely shifts it somewhere else.

Finally, there are a few other structural weaknesses of the US voting system, including the electoral college and non-preferential voting, but let's focus on one thing at once.

A note on divisive political issues

Elections in the US, where voting is non-compulsory, often swing on whether or not so-called "single issue voters" bother to show up. As a result, there is a disproportionate focus in partisan media and political commentary on a reasonably small set of these polarizing issues. Let's call them highly motivating divisive issues, or HMDIs.

There are many divisive issues out there, but only some are sufficiently motivating to be "big hills to die on." A good test case for whether an issue is an HMDI is whether it's the sort of thing that ruins Thanksgiving. It'll split a room and people just won't shut up about it, happily burning their family in the process.

The peculiar thing about HMDIs is that so many of them are fundamentally niche issues for the vast majority of US voters. I'm not saying they're not important or bellwether issues, but they just don't have a huge impact on the personal lives of most voters. For example:

• Background checks for gun owners, almost all of whom would pass.

• Abortion, despite the fact that most people will never have one.

• Immigration, despite the fact that only a tiny number of people immigrate to the US.

• Gay marriage, despite the fact that no-one's proposing to force anyone to marry a gay person.

• Drug decriminalization, despite drug use being a personal choice.

My hypothesis is that the modern Democrat and Republican parties accidentally found themselves on either side of these issues which not only split the electorate roughly evenly, and along ideologically simple lines, but also conveyed a slight, unintentional x-intercept bias. Then the redistricting machine did its usual amplification procedure and here we are. In fact, we've even seen historical examples of both parties being on the other side of former HMDIs such as slavery, social security, or federalism.

Let's get technical

We know that our current congressional districts are drawn to classify voters with known preferences into different groups to "pack and crack," or try to dilute the influence of opponents while amplifying the influence of allies. Therefore, it's fair to say that the current US electoral district boundaries are, in some sense, a representation of the natural distribution of an inhomogeneous electorate and its preferences. Remember that humans self-sort and self-segregate in statistically significant ways, but that any given divisive issue doesn't predict another particularly well. I would estimate that the total space of >500 issues can be covered reasonably well by the first 15 principal components in terms of geographic voter allocation.

I hypothesize that, were another HMDI to become politically important in the next decade, and its preference prevalence to differ from the background of existing liberal/conservative splits, even a bit, that congressional districts would be redrawn to maintain their maximally gerrymandered state.

Therefore, it's fair to say that it's possible to construct a perturbative map from an existing electorate to a future one, where the set of voters and their most important issues changes, but there is a smoothly continuous variation of district boundaries that maintains a maximum of partisan advantage.

The big idea

This perturbative map rests on a hidden assumption that it's possible to analyse the stated and latent preferences of any demographic and to (re)draw a maximally gerrymandered district accordingly.

Given a weighted ranked set of HMDIs, then, it is possible to score any given (set of) potential congressional boundaries for partisan advantage, and select one accordingly. Given that it's difficult to be precise about which HMDIs matter and how much, this is not a particularly sound method for preventing gerrymandering, though it is a good (and proven) approach for maximizing gerrymandering.

The inverse map is more interesting. For any given set of congressional boundaries, the inverse map can generate a weighted ranked set of HMDIs. If, for example, congressional boundaries were redrawn at random after every election, political consultants would perform the inverse map to determine which issues were most likely to swing the election in any given district, then try to push a local agenda that raised the profile of these issues. It is important to note that while some of the issues are likely to be important to voters on both sides of the issue, other issues are likely to convey partisan advantage for only one party. For a historical precedent, see the staggering rise of anti-Muslim animus since 2001, becoming a supreme court issue (the Muslim ban) in only 15 years.

There is a further implication. Given a map gerrymandered to favor (say) Republicans, there will be a set of issues which divide that region to give, with the exact same boundaries, a gerrymandered advantage to Democrats. In reality, these issues are likely to be mostly relatively unimportant. But that doesn't mean it's not worth looking.

In other words, for any given map, electorate preoccupation with some issue will render partisan advantage. "This map is gerrymandered on abortion."

Conversely, for any given issue, there is a unique map which maximizes partisan advantage for this issue. "We gerrymandered this map on abortion."

Why is this interesting?

Do you find endless debates about abortion boring, but want to see some federal political attention given to, say, climate change, space exploration, or world peace?

Why is our political process obsessed with such insipid HMDIs? Who is driving this train?

I think it's fair to say that beyond a certain point, HMDIs function as memes that self-select given the existing set of congressional districting rules. This is a natural instability in the system and probably can't be avoided.

This is interesting because when maps are redrawn they can alter the relative importance of second-billing issues. We've already seen this - I don't think Newt Gingrich intended his strategy for political conservatism to see a resurgence of Nazism.

But a more involved quantitative understanding of this process, particularly if its precise workings can be concealed, leaves open the potential for major political meddling.

Let's redraw some districts around people who care about climate change and peaceful uses of rockets.

"The Program," or, a strategy for universal prosperity in the twenty first century

Energy! What is it, how do you get it? 

Energy has an esoteric physics definition, but for the purposes of this blog, energy is the ability to do useful work. Work energy per unit time is power, while force multiplied by distance is work.

Throughout human history, if a human wanted something done, they had to use muscle power. Muscles, powered by food grown using sunlight, water, and ambient carbon dioxide, was the limiting factor in the deployment of work for useful things. There were a handful of exceptions in the form of water or windmills, of course. 

That all changed in the 18th century when engineers in Britain devised the first practical steam engines. For the first time, mechanical power could be harnessed to operate pumps, mills, and vehicles, that wasn't derived from mammalian metabolism. 

This first industrial revolution was followed by the widespread development of factories and assembly lines in the 19th century. 

At around this time the gasoline internal combustion engine was developed, such that by the 1930s rubber wheels on bitumen were overtaking trains as a preferred land surface transportation mechanism.

The Second World War saw the rapid maturation of aviation and oil extraction technology, and from 1948 until 1973, world per capita energy consumption grew at 7% per year. Physicist Gerard O'Neill predicted that by the year 2000, humanity would need space solar power to continue its incredible growth. 

What does this story mean? Gasoline is a fuel, or a mechanism for the storage and convenient dispatch of mechanical energy. In this, it is hard to beat, as it is pourable, readily available, and incredibly energy dense. While highly flammable, it can be made safe to use. 

7% annual energy growth encapsulates billions of humans being lifted from the poverty of preindustrial subsistence agriculture. With gasoline powered machines, an individual human can be so much more productive, enabling great increases in quality of life. 

Of course, this trend has not continued to the present. Instead, we had a series of oil shocks and a plateauing of wealth in developed countries. Indeed, recent trends seem to point toward a zero-sum struggle for control of limited resources, rather than confidence in limitless growth, at least to the point of post-scarcity. Indeed, energy has only gotten more expensive. 

The figure below shows 5-year smoothed data for US per capita energy consumption and the price of crude oil. The period from 1939 until 1973 was marked by robust growth and steady, slightly declining oil prices. The period from 1973 until present has endured great uncertainty and change in the price of oil (up to 20% per year for several years!), and a commensurate loss of steady growth in the exploitation of energy. 

I believe that worldwide economic stagnation in the 1980s and 1990s was headed off only by the coincidental development of consumer-accessible computers.

Computers are a very unusual case, as they have gotten twice as good every 18 months for many decades, at least until recently. To provide an example of how unusual this is, the Curiosity Mars rover uses a particular kind of space-grade chip, which is necessarily of rather poor performance compared to the state of the art. The Mars Helicopter doesn't have enough power to run this chip, so the engineers had to select an option that was smaller and less power hungry. In any other field, this would imply even poorer performance, but because this is a computer, the smaller chip is 60 times as powerful, which is a great boon to the software developers! 

Moore's Law has tapered off in recent years due to fundamental physics, but I think that we're a long way from fully exploiting the potential of current computer hardware. 

While our civilisation has failed to obtain an infinite supply of ever cheaper energy, the growth of wildly cheap computing capacity has allowed us to subvert that constraint to some extent. Although computers don't perform mechanical work in any macro sense, their prodigious abilities with logic and calculation have extended the cognitive capacity of humanity in the same way that engines have extended our muscles. 

Of course, this has further exacerbated a chronic oversupply of human labor present since the end of WWII, since all human needs could now be met in developed countries with a ten hour work week. Today, we are seeing the computerized automation of middle management, such that employees of organizations like Uber are actually dispatched by an algorithm. And when one considers the affordability of real estate it's clear that in this period of macroscale industrial stagnation much value has been stealthily inflated away.

After this necessarily imprecise historical and economic review, it's time for me to pull out my crystal ball and talk about The Program.

I was discussing an application of cheap solar energy with my cousin J when my reference to The Program elicited a blank stare. This blog is my attempt to structure on paper my thoughts about energy policy over the next 30 years.

When we think of 2050, we think of supersonic passenger jets, flying cars, good food, free education, housing, healthcare, and other trappings of a wealthy, prosperous society. Yet even in 2018, nothing can happen without oil. Oil is a dirty, messy business that destroys the environment, corrupts governments, ruins our health, and poisons the atmosphere. But for all that, we can't live without it because, as explained earlier, it can give any human on Earth the superhero capacity to dispatch, as a rough average, 100 times more work than their muscles could achieve on their own. 

Given that oil is not only poisonous, it's also finite, a replacement will have to be found and deployed, and in our lifetime. 

While it's possible to chemically synthesize fuels at huge expense, I'm going to focus this blog on the technology that will prevail, namely electricity. 

Electricity and magnetism are magic. Like gasoline, electricity is a form of energy that can flow down conductive wires and, with motors, perform mechanical work. Its technological maturation has progressed alongside fuels and is so successful that everyone can get it from outlets in their walls.

Whereas a 19th century factory may have transmitted energy from a central steam engine using belts or shafts, these days nearly everything is run using electric motors. My robot vacuum has 12 motors in it! 

But while electricity has been the go to for appliances for decades, and not just because no-one wants to run a dishwasher with a motorcycle engine, gasoline has been the traditional energy source in mobile applications. 

This reminds me of the old joke about electric helicopters, which is that they needed a very long extension cord! In all seriousness, boats, cars, planes, and rockets needed fuels they could carry with them, so electricity was not an option. Recall why gasoline is such a compelling fuel! Cheap, pourable, energy dense, safe enough. 

When my father built the house in which I grew up in 1986, he used power tools powered by the mains, and drove a petrol powered car. When I attempt to construct things, I use battery powered tools and drive an electric, battery-powered car. No-one has a gas-powered mobile phone. World battery production is growing as batteries power ever-larger vehicles. The Tesla Gigafactory will reach 35GWh production later this year, two years ahead of schedule. There are serious proposals to build battery ships to transport electricity from solar farms in North Africa to Northern Europe!

In 1973, battery technology was not very advanced. In 2018, there are battery-powered planes that have crossed the English Channel. In short, the geological and geopolitical shortage of oil that halted the mechanical progress of humans is finally ready to be circumvented. 

Lithium batteries, like all products, require the mining of certain materials which have environmental effects. Needless to say, for equivalent work, lithium batteries are much less harmful than oil! They're also highly recyclable.

To get technical for a moment, the energy density of gasoline is about 46MJ/kg. The energy density of the best batteries is about 1MJ/kg, which improves by about 5% per year. The saving grace is that electric motors can be 95% efficient, while a car engine would be lucky to reach 15% efficiency, with the rest being wasted as heat. That means that on a per kg basis, batteries+motors are only 7 times less mass efficient than gasoline+engines. Further, electric motors have much higher power density, so can be lighter. Finally, vehicles such as cars spend most of their mass budget on things other than fuel and power train, so extra batteries can be added with only marginal increases in weight. This is notably not the case with long haul jets (50% fuel mass fraction) or rockets (95% fuel mass fraction) which both consume an inordinate amount of fuel.

To consider my personal carbon footprint, I use low wattage LED bulbs, but every time I fly to Australia my share of the plane's fuel is about 500kg, or 180 gallons. Each way. Driving a Hummer wouldn't make much difference!

A frequent though inaccurate criticism of electric cars is that the electricity they use, generated by coal, just moves the pollution elsewhere. This is imprecise, as electric cars are about 5 times as efficient at using energy due to regenerative braking and better motor efficiency, while electricity power plants are about twice as efficient as car engines, primarily because they operate at steady state and have better heat disposal mechanisms available.

Incidentally, while batteries are not yet good enough to operate long haul flights, there are now hundreds of companies developing short range electric commuter planes. Further, the power density and mechanical simplicity of electric motors allows for vertical take and landing, like a helicopter. Finally, I think that electric power has unique advantages which point the way to cost effective consumer supersonic flight, which is definitely part of my awesome vision for the future.

Nevertheless, The Program does not stop once it has succeeded in supplanting gasoline as the fuel of choice for all vehicles except orbital rockets. Indeed, as far as global warming goes, humanity could burn all the oil and all the gas and do relatively little harm compared to reserves of coal. Coal, a black, carbon rich fossil of trees, stores concentrated ancient sunlight and is extremely popular as a source of electricity.

While wind power has matured in recent years, the most applicable renewable natural resource is solar power. The sun is about 110 times wider than the Earth and will burn for another five billion years. During the day, every square meter of the Earth's surface receives about a kilowatt of power. It just rains down from space for free. It powers trees, so anywhere there's green, there's solar power.

But recall that preindustrial societies are solar powered! Horses and cows eat solar powered grass and humans eat wheat, corn, cows, and so on. No-one is deriving nutritional value from coal. How can solar power produce enough energy for our civilization?

The answer rests in efficiency. A modern commercial solar panel is about 20% efficient. Combined with a 80% efficient power transmission system, a 90% efficient battery charger and a 75% efficient cordless drill, about 10% of that kW of solar power, or 100W, makes it to the work piece.

Contrast this with agriculture, which also requires arable land, fertilizer, pesticide, and irrigation. Plants spend most of their energy transpiring water to keep cool in the sun, and are less than 0.1% efficient at converting solar energy into digestible starch. Cows or yeasts are about the same. Then the human metabolism is about 5% efficient at converting consumed energy to mechanical work.

So while a solar powered electric system is 10% efficient, an agricultural system is 0.000005% efficient. This is the main reason that farms are really big. To create value, they have to capture a lot of sunlight, which is rather dispersed. This is also the reason why biofuels can never scale to completely replace gasoline. Their end-to-end efficiency is thousands of times lower than solar and batteries, and there isn't enough arable land to produce enough ethanol. Not even close.

To dwell on power transmission for a moment, let's consider trees. Trees are self-powered, but they're not generally considered to be capable of locomotion. Animals that move need to eat a lot of plants to concentrate the stored solar energy. This is why very few animals bother with photosynthesis. Likewise, some electrical applications require so little energy that they can be powered directly by solar panels. But most human machines are too energy intensive to be powered in this way.

For instance, at highway speeds my car consumes about 15kW. If this were provided by a solar panel, in addition to being unable to drive at night, the car would need to be 50m long to fit in a standard lane. In the US this may be permitted on certain roads at certain times with escort vehicles; the SpaceX Falcon 9 rocket first stage is of a similar size.

Clearly, solar panels on houses or in dedicated farms are needed to concentrate the sun's power. A transmission grid continues to dispatch the supply to the end user.

How many solar panels are needed? Lots and lots! For a rough estimate, recall that solar is about 2000 times as efficient as non-meat food production, but that per capita energy consumption is only 1% food in industrial societies. Therefore, about 5% of the area devoted to agriculture is necessary to meet foreseeable electricity needs. About 11% of Earth's land surface is used for crops, so we're talking about 0.5%.

As an example, using only desert military bases in California and Nevada, which receive a lot of sun, would produce enough power to supply the entirety of North America. In practice, a mix of rooftop solar and utility farms in sunny areas is the most robust approach.

It's instructive to consider areal land uses for other forms of energy production. In Australia's picturesque Hunter Valley, there are several enormous open cut coal mines. I computed that a solar farm operating for 20 years will produce energy equivalent in value to a coal seam 3m thick. That is, even if the coal is at the surface, and it's not, if it's less than 3m thick it's better to use as a foundation for solar panels than to dig it up and burn it. Further, there aren't that many coal seams that thick anymore! A similar argument about nuclear power, given a 20km exclusion zone, shows that more energy rains down from the sky in that area than can be produced by fission.

Coal - leave it in the ground.

Like wind, solar is not a continually available resource. It varies daily and seasonally. For this reason, a smarter grid with responsive demand, intersticial storage, and a rational pricing strategy is a worthy goal. In practice, this means that in the future power will be very cheap at noon and during summer, so all sorts of new applications are possible. My favorite examples, though far from exhaustive, are aluminium production and mass desalination for agriculture, both of which require power below the price of 1c/kWh.

Indeed, in 2017 solar power supply bids reached 2.7c/kWh in Mexico, indicative of a long awaited reversal of the decades-long trend of gradually increasing energy costs. Extrapolating is risky business, but at present rates solar power will reduce in price by a factor of 10 every 17 years. Continuing that trend, in 2050 power will be cheap enough to artificially refill rivers parched by global warming with pumps and desalination, for example.

This trend need not stop in 2050. It is my belief that by the time I die, historians will see the period between 1973 and 2013 as an anomaly, a blip, a detour into computing on an otherwise unbroken industrial trend towards ever greater deployment of useful energy for peaceful humanitarian purposes.

What is The Program? The Program is a vision for the mass deployment of solar power, smart grid technology, grid storage, and electric vehicles. It is now economically viable to talk about public funding of generational infrastructure on the supply side, while a clear roadmap will drive private innovation in vehicle design. 

Unpopular opinions in space

One of the fun things about speculative technology is encountering people with different views, and then trying to understand why and how, essentially, the same set of axioms leads to a different conclusion. In some ways, the community can be divided up into camps, representing the acolytes of various well-known thinkers in the area. As an example, concerning where humans should live in space, some people suggest the Moon, others Mars, others asteroids, Venus, or giant stations in deep space. For a second example, opinions differ about where the money may come from. I previously dealt with the funding question in another blog: http://caseyexaustralia.blogspot.com/2017/09/how-to-fund-space-settlement-where-does.html 

In this post, I'm going to air three unconventional if not unpopular opinions, then spend a few thousand words explaining my views on them. I will endeavor to use accessible math and be quite clear about which axioms can be altered. My intention is to continue the conversation and to have, in one place, a concise summary of a point of view which can be referred back to as necessary.

Rule 1: There is no problem in space that can't be most effectively solved by building a bigger rocket on Earth.

Rule 2: There is no commodity resource in space that could be sold profitably on Earth.

Rule 3: Self-replicating robots and matter compilers do not exist.

The implications of these rules are not as dire as they may seem. In particular, my recent book on Mars industrialization (https://www.amazon.com/How-Industrialize-Mars-Strategy-Self-Sufficiency-ebook/dp/B07GN3BJX3/) shares these axioms and retains an optimistic tone.

Why are these rules true? Read on!

Rule 1: There is no problem in space that can't be most effectively solved by building a bigger rocket on Earth.

In short, big rockets are expensive, but managing interfaces in a vacuum is much, much more expensive. Case in point: The ISS.

Unfortunately there are very few large rocket development programs to use as baselines, but there are a few. The Saturn V, which could launch 110T to LEO, cost about $1.2b to develop in 2016 dollars. The Soviet Energia was considerably cheaper. The SLS has already consumed tens of billions, but it is well understood in the industry that it is not exactly a lean program. SpaceX is developing the BFR using only internal funds, and will probably spend a similar amount to the Saturn V, though with a lower per-flight cost and much higher overall performance. 

In contrast, the ISS, which tested the idea of assembling a space station from modular parts launched using a partially-reusable shuttle, has cost $150b, and has taken the better part of 30 years to build, including on-Earth fabrication. And for that cost, a disproportionately high fraction of the overall station mass is consumed by the interfaces: heavy airlocks, narrow connecting passages, and architectural constraints. Further, the station will need to be retired in the next decade or so, as the "sausage link" interfaces are subject to bending fatigue that is gradually weakening them.

In a recent Quora question, I pointed out that a single expendable launch of the BFS would deliver much more volume to LEO than the entire space station (https://www.quora.com/How-many-BFR-launches-would-it-take-to-loft-the-entire-ISS-into-its-current-orbit/answer/Casey-Handmer). That is to say, a Skylab-style station based on BFR could be launched in one go, at a cost equivalent to the marginal cost of a single spaceship at retirement, which is close to nothing. 

Why is this true? The reason is that all large pressurized volumes require assembly from various sub-components. For Boeing jets, this is done in Renton, near Seattle. Even there, in a climate controlled factory, it is a serious headache. It requires a small army of engineers and technicians. But it is still cheaper to do it there, in the factory, than in flight or on the side of a small runway somewhere in the middle of Wyoming. 

In short, as much construction and integration as possible should occur on Earth, where labor costs are about a million times lower than in space. Payloads should be launched in the largest possible units, in plug-and-play configuration. And that is why, even though building an enormous rocket is extremely expensive, it is the cheapest way to do business in space.

Are there limits to this? Yes, of course. The largest rockets ever flown delivered about 100T to orbit. It is not clear to me that rockets could efficiently deliver more than about 1000T to orbit in a single shot, with chemical rockets. This is due to fundamental limitations on the strength of materials in pressurized combustion chambers, fuel and material density, and Earth's gravitational field. But 1000T to LEO is a very, very large chunk of stuff compared to the current model for doing business.

Note: While I personally think that there are all sorts of good reasons to pursue reusable rockets, and that larger rockets in the correct configuration are easier to make reusable due to improved margins, this rule doesn't imply that reusable rockets are necessary. In particular, the space station would have been much cheaper and faster to build if it were launched on a Shuttle-derived expendable heavy lift stack. 

Rule 2: There is no commodity resource in space that could be sold profitably on Earth.

One possible exception: The elixir of life, if it could only be obtained on the Moon. 

The usual examples range from water or Helium-3 mined on the Moon, to platinum-rich asteroids, to space-based solar power.

This rule comes down to a discussion of intrinsic value. Clearly, to be worthwhile, a space-based resource has to command an exceptionally high value-per-mass. There are a handful of commodities on Earth with values as high as $100,000/g, such as listed here: https://brightside.me/wonder-curiosities/the-16-most-expensive-materials-in-the-world-188955/ 

It is important to note that none of these are intrinsically valuable. The illegal drugs are expensive because there's a high cost to being caught making them. The diamonds are expensive because their market is manipulated. And rare metals are expensive because they're very hard to chemically extract from rocks, but also because they're basically never used in industry. That is to say, there is no demand for them. 

In particular, of all rare, valuable commodities there isn't a single one with a high level of baseline usage. This means that if the supply suddenly increased, because of an additional discovery, the price would collapse. Even if there was an asteroid of pure platinum orbiting the Moon, and there most certainly is not, increasing the global supply beyond baseline of about 40T/year would simply reduce the market price. 

As for water on the Moon, water isn't even intrinsically valuable or rare on Earth. In fact, as I showed in a previous blog (http://caseyexaustralia.blogspot.com/2017/04/does-lunar-resource-exploitation-make.html), it is probably cheaper to import water from Earth to the Moon than to extract it there. And even if it were cheaper to obtain water on the Moon, there is zero case to export water from the Moon to anywhere else. 

Finally, let's consider Helium-3. Helium-3 is a nice example, because it is relatively much more abundant on the Moon, and it is currently very expensive on Earth due to rarity. It is even used in some industrial and scientific processes as a refrigerant. But in order to make a business mining it on the Moon, adequate demand to both keep costs and revenues high must exist. For this, we are told, Helium-3 is a natural fuel for nuclear fusion. There may come a time when lunar Helium-3 fuels fusion-powered interstellar voyages, but I am unable to not put that in the science fiction bucket. 

So what would a space resource have to look like, quantitatively, to make a business selling it on Earth? My interest here is to be inclusive, so I will underestimate fixed costs as much as possible on the first pass. Let's say that although currently it costs about $3000/kg to launch something to LEO on a reusable F9 flight, SpaceX's BFR reduces that further to $100/kg. Let's suppose that further the cost of delivering cargo to the Moon using hardware based on the BFR is $1000/kg and the cost of returning cargo from the Moon $10,000/kg, which assumes at least local oxygen propellant production. By comparison, the cost of shipping a container half way around the world is about $0.10/kg. 

The question, then, is what commodity is relatively much more available on the Moon than the Earth to make up for the fact that shipping it is 100,000 times as expensive. I am not aware of any physical matter, short of the elixir of life, that would make this worthwhile. Yes, a tiny number of high net worth individuals may want to travel there for tourism, but that doesn't approach a billion dollar industry.

But what about space-based solar power, popularized by Gerard O'Neill in The High Frontier? While shipping matter to and from space is enormously expensive, it is much cheaper to beam microwaves as they have no intrinsic mass. 

Gerard O'Neill's book was written in the early 1970s, when it seemed as though the world was headed for a Malthusian crisis of population and energy consumption. This is not the case anymore. Indeed, the fundamental challenge with space solar power is that although the solar resource in space is about 3 times as good as the best places on Earth, the transmission losses from space are comparable in magnitude. Economically, it is much cheaper to deploy solar photovoltaic panels on Earth than in space, where at best the delivery costs are 1000 times higher, the maintenance costs a million times higher, and the environment much more difficult to deal with. 

As Elon Musk has concisely pointed out, the fundamental problem with space solar power is that it's obtaining a commodity, power, somewhere where it's expensive and selling it somewhere where it's cheap. This is not a good business. Indeed, it would make more sense to beam power from Earth to space stations, if they needed it. And, more generally, the same goes for supply chains for any other product.

That's not to say that microwaves have intrinsically low value. The trick is to use them for something other than carrying power, namely, information. And indeed, the majority of the space industry, and almost all of the non-military space industry, is dominated by microwave communications. The dispatching of information, through space, from specialized satellites made in factories on Earth. And SpaceX has a play in this market too, with their StarLink internet constellation. The right kinds of information, at the right place and time, are very valuable indeed.

Note: This rule doesn't necessarily apply to Earth-based manufacturing with a step performed in zero-G LEO. There are a number of companies pursuing niche products that exploit zero-G processes to make stuff, and at a potential level of revenue adequate to cover the cost of launch and recovery. These products however, do not necessarily lead to a generic space industrial capacity, or generalize in any particular way. There is no good reason, for instance, to extract material precursors from a passing asteroid instead of launching them from Earth.

Rule 3: Self-replicating robots and matter compilers do not exist.

In answer to the previous two rules, some proponents of space settlement argue that it's not necessary to launch giant payloads from Earth. All that needs to occur is the launch of a small, robotic egg to a convenient asteroid. Once there, it will process the raw materials to produce whatever it needs, build thrusters, antennas, copies of itself, habitats, food, televisions, whatever. This asteroid will then be a glorified robot and can be steered back to the Earth in preprocessed, highly valuable form to be used as a mine or space station or interstellar spaceship or whatever.

This idea sounds great, and variations of it have been kicking around since at least the time of the ancient Greeks. The fundamental problem is that such a compact universal factory, or egg, simply does not exist.

That's not to say it could not exist. Indeed, E. coli is a very capable self-replication machine, given the appropriate environment. However, no known life form prospers in vacuum, and that's not for a lack of searching on the part of astrobiologists. So any matter-compiling asteroid-munching probe would have be mechanical in nature, not biological. And there are no robotic self-replicating factories in existence, not even close. 

Indeed, the reason that there are so few countries capable of heavy industry, and all of them are very large, wealthy countries, is that industry is big. Why must industry be so big? The self-replicating machine that is modern industry requires about a million different kinds of specialists. Specialists train for years to be sufficiently efficient at their given tasks, without which the final product, such as an iPhone or fighter jet, may well take infinite time to complete.

There are numerous theoretical approaches to matter compilers, or rapid, atomic-level 3D printers, but I am not aware of any that pose a credible threat to the current industrial status quo. It would be cool, but as far as I'm concerned, we're more likely to have a vibrant lunar Helium-3 mining industry in 50 years than access to universal matter compilers. 

What does this mean? There is no way to do advanced industry in space without thousands to millions of humans. There are no miracle shortcuts. We just have to find a way to support thousands to millions of humans in space, probably on a planet with a diverse array of natural resources.

How to Industrialize Mars

How to Industrialize Mars

Casey Handmer

Remarks from talk given at the Mars Society Convention, August 23 2018, now in blog form.

I always prefer to start talks with a recognizable image. In this case, this is a Mars Global Surveyor image of Gale Crater, looking south. The crater is about 150km wide, and the Curiosity Rover is currently driving around near the right hand edge of the central mound.

Although I’ve probably seen this photo a thousand times, I only just noticed the Pancake Delta feature, just right of center at the top of the image.

I’ll start with just a bit about me. I have many interests, though I’m formally trained in physics. I earned my PhD at Caltech in 2015, studying gravity in an effort to understand warp drive. Since it turned out to be impossible, I switched to working on the Hyperloop, where I was the levitation engineer, and more recently I’ve moved to JPL, where I work on GPS instruments. These pictures show me exploring the remnants of Siberian industry, a Tesla coil I helped build for Burning Man, and pointing at the Great Unconformity, a billion year gap in the geological record visible at the bottom of the Grand Canyon.

This is also the place for the great disclaimer, beginning with the obvious stuff. It is a great honor to be here speaking to you all, but I must stress here I represent my own views and research, not that of my employer!

Second, I don’t have a crystal ball. I don’t know for sure how to build a city on Mars. But this applies to most of us. We are all mostly not doing Mars settlement full time. Instead, we come together at events like these to share our ideas and enthusiasm and then spread it like the conference flu.

Finally, this talk/blog is derived from a book on the subject available gratis at: www.caseyhandmer.com/home/mars/, also available on Amazon at https://www.amazon.com/How-Industrialize-Mars-Strategy-Self-Sufficiency-ebook/dp/B07GN3BJX3/ for the princely sum of 99c. This work is a hobby of mine, it’s not my main gig, and my principal goal is to develop and workshop these ideas and disseminate them as widely as I can.

The goal here is to think systematically about visions of the future. It’s to inspire a more vibrant, rigorous level of discourse. It’s to help us find ways to find the right questions, questions that help us find useful answers.

Let’s begin by defining autarky. It means economic independence or self-sufficiency.

Google trends shows that this word became very important in the 1930s when impending total war in Europe demanded industrialization for survival. Even though the word had been around since the early 17th century, it was the second world war, or the war of machines, that drove home the importance of industrial self-sufficiency.

The Martian, with Matt Damon, is one of my all time favorite films. When we think of self-sufficiency on Mars, we think of growing potatoes. But what would have happened to Watney without a ride home? The book is quite explicit about this. Even if he had plenty of supplies? Even with a thousand qualified friends and greenhouses more like the incredible farms in Holland, which have the highest productivity on a per-area basis on Earth? Death is inevitable.

In the book of The Martian, Andy Weir writes that Watney depends on life support machines, including an oxygen generator, water reclaimer, and pressure vessel, to survive. These machines were made on Earth and beyond a handful of very basic repairs, cannot be built or maintained in space, and will not last forever.

Unlike the popular but flawed traditional colonial picture, humans cannot survive on Mars with 40 acres and a donkey. Like European geopolitics in the 1930s, survival in such an inherently hostile environment is simply not possible by analogy with the US history of rugged agricultural pioneers on the frontier. In fact food isn’t even the first thing to be produced locally, being rather hard to grow without lots of related infrastructure.

It’s worth stating that while self-sufficiency for a Mars city is a worthy goal, in all but the most catastrophic scenarios, Mars and Earth would continue to trade essential parts. In the early days of the Mars city, actuaries will be able to calculate the consequences of supply interruption, just as they do for remote outposts and bases on Earth. Although manifests will be designed to minimize the disruption caused by a low level of supply interruption, total isolation will inevitably result in death after a few months or years. As the city develops greater industrial capacity, this grace period will gradually extend until the point where isolated survival is possible indefinitely, even though it would be far from optimal! The capacity for indefinite isolated survival is autarky.

What is the alternative to agricultural analogies? How can we think systematically about industry in space?

I would hope that my readers become very familiar with Cody Reeder! He has one of the most incredible YouTube channels: Cody’sLab. On this channel, he demonstrates the basis of a lot of primary production, including mining, farming, prospecting, and chemical purification. But even a thousand Codys would not survive very long on Mars.

Unlike Mark Watney, Cody has chemical and technical expertise adequate to build the necessary equipment from scratch. But while a thousand Codys could probably make *anything,* they could not make *everything* faster than the rate at which it breaks down in normal use. Indeed, if you watch the videos about his ranch, just keeping all the tractors and trucks running, in Utah with breathable air and access to McMaster-Carr, is sometimes pretty tough.

It is simply not enough to grow some food. Living on Mars is more like living indefinitely in a submarine. It will require automated manufacturing and, among other things, lots of metal. So let’s think big! Really big!

This is Australia’s main steel works, BlueScope Steel, which employs 16,000 people and produces about three million tonnes a year. It takes 30 minutes to walk across, but probably wouldn’t be big enough for a self-sustaining city on Mars.

This is the Tesla Gigafactory, which is pioneering the next generation of industrial automation. The Gigafactory makes cars and batteries, but Mars will eventually need at least basic chip fabs, an advanced composites supply chain, and active industrial research.

Again, the aim here isn’t to be completely descriptive. My goal is that this helps you develop a new thought, an incisive question, or a new strategy.

This is a good point to deal with a common diversionary tactic. Wouldn’t it be nice if self-replicating machines existed? 3D printers are very exciting precisely because they offer a technological shortcut for certain kinds of manufacturing. But they are not self-replicating machines, not by a long shot. They require very carefully curated input material and can produce only a limited range of parts.

Are self-replicating machines possible? Yes! Given the right resources, biological organisms can reproduce themselves, including my favourite here, Mr Platypus, and everyone else’s favorite, e coli.

But the platypus makes eggs containing baby platypuses, and e coli produces e coli. Convincing e coli to print a CPU or the platypus to lay an air filter would be something else!

So when we think of a self-replicating machine to solve all the industrial problems, we’re really describing a self-replicating factory or process that actually can produce anything. Which is nothing less than our modern globalized industrial society, in total. At least until someone builds a matter compiler, a regular staple of science fiction and asteroid mining concepts.

So we return to the original question, how to compactify the entire industrial stack and ship it to Mars?

What sort of scale are we talking here anyway? Is this a big problem? Oh yes!

China, 1410m	Mexico, 129m	Turkey, 81m
India, 1339m	Japan, 128m	Thailand, 69m
USA, 325m	Ethiopia, 105m	UK, 66m
Indonesia, 264m	Philippines, 105m	France, 65m
Brazil, 209m	Egypt, 98m	Italy, 59m
Pakistan, 197m	Vietnam, 96m	Tanzania, 57m
Nigeria, 191m	Germany, 82m	South Africa, 57m
Bangladesh, 165m	DR Congo, 81m	Myanmar, 53m
Russia*, 144m	Iran, 81m	South Korea, 51m

x

Here’s a list of the 27 most populous countries. The bolded ones contain essentially a complete industrial stack, by which I mean the ability to produce, within its own borders, all or nearly all technology necessary to produce the most advanced machines, including container ships, fighter jets, rockets, computers, mobile phones, and nuclear weapons. Russia doesn’t anymore, but it did until quite recently. South Korea does, sandwiched between Japan and China. Germany does, as a hub of sorts for the rest of Europe.

These data strongly suggest that a scale in the hundreds of millions is necessary to have enough labor specialization to support a complete industrial stack, and that’s on a planet on which we have evolved to survive essentially naked. Launching one hundred million people to Mars would be a major headache.

Let’s look at some counterexamples. Economically isolated countries like Albania, Cuba, North Korea, and Iran have every reason to attempt industrial autarky, and in many cases have tried really really hard. Yet even Cuba, with 11 million people, a very benign climate, and ample natural resources, has not succeeded. Australia, with 22 million, is not even close.

I like to think that with further advances, it might be possible to achieve autarky on Mars with *only* a million people, after 50-100 years of transport and building. But this would not be easy.

For comparison, imagine taking Iceland in 2018, a country with 350,000 people. Without imports, Iceland would regress to 18th century standards of living within a few years.

The OOCL Hong Kong, the world’s largest containership, can carry about 22,000 containers, which is roughly equivalent to 2000 flights of SpaceX’s BFR. I estimate is at least several decade’s worth of flights. So, given only unlimited money and one containership of gear, one has to reproduce the industrial versatility if not the might of Japan in Iceland by 2050, without substantial population growth. It’s almost unimaginable. But not quite!

Let’s talk about how to increase per capita human productivity in Iceland, or on Mars, by a factor of a hundred or so. The trick is the mechanization of labor, which is related to why whales have big mouths.

Consider a pre-industrial agricultural society, such as the fields pictured above. All available energy in the form of work is derived from solar power, from photosynthesis, and all available physical labor is from human muscle. Therefore, the total output of the system is limited, fundamentally, by how much energy all the humans can consume and digest.

Yet the gap in GDP between industrialized and pre-industrialized societies is a factor of 30-60. By freeing themselves from the requirement of work of sweat off the brow, a single human can control a gigantic, usually gasoline-powered, machine, or even remotely program one, to perform labor on its behalf.

We’ve already seen that while on Earth, a sufficiently motivated, knowledgeable individual can survive in many places with no resources, an industrial Mars will require the production efficiency of a hundred million humans. The fundamental problem for industrial human societies on Mars is a terrible shortage of labor, so the solution is to automate, mechanize, and outsource non-local tasks. By how much?

Consider the manual-mechanized continuum graph. For any level of technology, there is an optimal blend of human and machine labor. Compare, for example, the manual construction of the pyramids and the rapid modern construction of a house by a skilled contractor.

As technology improves, the optimal point moves to the right, but it is *never* most efficient to completely automate something, even the construction of a moon or Mars base. Complete automation is a subset of the self-replicating machine problem. A complimentary mixture of humans and machines is the way to go.

Take for example these two drilling systems. One is eight orders of magnitude more expensive, but doesn’t need a human to “line it up”. And sometimes it breaks down for a year at a time. Perhaps NASA paid too much for the rover, and it’s only 7 orders of magnitude more expensive than a human-controlled tool?

from future import industry

How can we achieve a Japanese level of industrial versatility and power with Iceland-style population? We must grow the fraction of labor that’s automated as the base scales. For instance, if the base doubles in size every launch window, the productivity of the supporting industries must also double, without doubling their labor requirement. Instead, individual labor productivity must also double at close to the same rate.

What does increasing individual productivity by three orders of magnitude look like? For inspiration, let’s consider the development of programming languages. The answer is the sequential interposition of layers of automated abstraction between the human and the physical stuff. This approach is only cost effective in situations of profound labor shortage, such as keeping up with exploding capability and complexity of modern computers.

Computer languages have evolved some hierarchy like machine code, Assembly, C, C++, Python. Each step encapsulates another layer of abstraction between the human writer and the fundamental logical operations, allowing much more powerful things to be done with a given labor pool. But let’s not stretch the analogy too much.

The final question I want to cover is order of industrial roll out. What resources get made first? As a case study, consider this incredible open source robot arm, the BCN3D-Moveo (https://github.com/BCN3D/BCN3D-Moveo). Mars will need a lot of robot arms, so this isn’t a bad place to start.

Here’s (the interesting half of) the BOM, or bill of materials. This is a shopping list from which the arm can be made. Broadly speaking, components fall into five groups: Structure, fasteners, bearings, motor, and power.

• Structure, which are the bones, base, and carry the weight of the arm.
• Fasteners, such as bolts, rivets, screws, nuts, clips, and so on.
• Bearings, which enable two adjacent hard parts to swivel past each other with low friction and wear.
• Motors, which provide the forces. Motors are deceptively cheap due to mass manufacture, but often require weird magnets and low sulfur high conductivity copper and other things that are hard to come by on any randomly selected part of Mars.
• Power, which includes cables that move electricity around but also printed circuit boards, control logic, microcontroller chips, and other components which are relatively cheap on Earth, light, and very difficult to make from scratch.

I tabulated the cost as a proxy for manufacturing difficulty and the mass as a proxy for transportation difficulty from Earth. While a workshop on Mars could make any of these parts, mass local manufacture will proceed in order of mass divided by difficulty of manufacture, which is the order tabulated above.

This is what you’ve been waiting for, the roadmap for industrialization. There’s a lot going on in this figure, so let’s unpack it!

On the left, I’ve ranked successive orders of magnitude of industrial “closure”, or local production capacity. Starting with oxygen, then water and fuel, plastics and some food, then masonry, structural metals, then alloys, electronics, advanced chemistry and computer processors.

On the bottom, we have population. Today, we are in the bottom left, with only robots. With local production of oxygen and fuel, humans can explore and even operate outposts like the Antarctic stations. But at some point vast quantities of cargo and humans will have to be shipped to traverse this dangerous area of potential collapse. This area is dangerous because the population is too large to be evacuated and too small to be self-sufficient. The city traverses the graph toward the top right, such as the trajectory marked in red. Ultimately, the city has a large population and a diverse, self-sufficient industrial base.

The major primary industries deal with mining of any desired element. Because each mine will have to operate in the hostile Mars environment, emplacement of primary industry incurs a much steeper labor penalty than increasing complexification of secondary manufacturing, which can be conducted entirely inside large, pressurized, climate controlled habs.

For this reason, from the exploration phase until the cusp, marked with a purple dot, each order of magnitude of mass self-sufficiency requires more than that of people. Beyond this point, marking the completion of a local basic material supply chain, relatively small additions of population have an outsized effect on industrial closure. I estimated the critical stage on this graph is from about 1000 people to 100,000.

The fundamental limit here is Earth-Mars cargo capacity, as illustrated by the grey lines. Cargo capacity is determined by how fast we can build gigantic rockets here on Earth. Today, SpaceX can build about 20 cores a year, but Boeing can build 560 737s a year, a machine of comparable complexity. So I think this is a tractable problem, within the capabilities of our current civilization.

In summary, autarky is possible, but requires a really bold vision for scale, lots of giant rockets, lots of people, lots of ongoing, though non-infinite, investment of money and effort on Earth.

What questions do you have?