Principles of Mars urban planning (first pass)

Autarky Complete and indefinite self sufficiency, or breakout capability to reach such with trivial effort.

Regular readers will know that I occasionally discuss aspects of Mars settlement. This blog is inspired by some slides presented by SpaceX at IAC2017, which showed a SimCity base growing on Mars. Since Mars cities won't look like this, what will they look like?

The first city on Mars is oriented toward rapidly developing autarky, to minimize exposure to the period of time when the base is dependent on shipments from Earth. This differs a lot from a mostly static Antarctic station outpost, and thus determines a lot about how the city must be planned. No one knows for sure how many people are needed for autarky, but is likely at least a million and will thus require decades of blistering growth. The primary role of fixed infrastructure on Mars then, besides keeping death out, is enabling growth.

In Estimating Mars Settlement Rates, I attempt to estimate growth rates using ship construction and utilization estimates, combined with a population/self sufficiency relation. The Earth Mars launch window occurs every 2.2 years, and initial population growth targets are a factor of 4 per window, later dropping to a factor of 2 depending on ship production, capacity, and reuse.

No city in history has needed or managed to sustain growth this fast. On Mars, the primary task is building more city for impending arrivals, and the primary constraint is labor availability. To maximize production efficiency, construction will need to use mechanization, automation, and wherever possible, a shirtsleeves environment.

All this is fairly obvious. Can we now draw a map? Not really. I don't know what a self sustaining Mars city looks like and I probably will not live long enough to find out. Indeed, attempting to learn from experience that doesn't yet exist is a pointless endeavor. But I will wave my hands a bit about the first decade of growth.

In addition to enabling its own maximal growth, the Mars city will perform every other kind of function from life support, transport, recycling, and entertainment to privacy, education, mining, manufacturing, communication, and emergency management. Some of these functions will be distributed, others more centralized. To maximize the utility of limited living space, for instance, compact apartment geometries can be imported from Earth, while landing and launch operations, and other especially hazardous activities, will have to be separated from more vulnerable or less defensible areas. Practically speaking, all functions span a continuum from local to centralized. Somewhere in the middle of this continuum is a point of mandatory separation, and it is here around which individual pressure vessels, habs, vaults, arcades, tunnels, small domes, and vehicles will be divided from each other.

All of the more local functions (health, education, libraries, sport, food, recreation, spirituality, music, common space, food distribution, non-transformative recycling, life support, temperature control, atmospheric processing, grid stabilization, communications, data storage, residential, non-hazardous industrial live-work spaces, etc) are ideally collocated. Since these all take place in a climate controlled pressure vessel, each pod is self-contained and resilient enough to withstand substantial extrinsic challenges, while nominally meshing and sharing capacity with adjacent systems. Vacuum ops are required only for initial construction and exterior maintenance. Everything else is done in shirtsleeves at minimal marginal labor cost.

Opinions vary on ideal structure design and material, and methods will no doubt continue to evolve drastically during deployment. My personal preference is for hangar-like structures. A cylindrical roof spreads pressure, requires no internal support, can be shielded with dirt, and unlike spherical domes, has simple curvature and decouples ideal volume from geotechnical concerns in the foundation. With few or no windows, the interior could be somewhere between a modern submarine or a Vegas casino - both structures quite comfortable despite uninhabitable exterior environments. I envision structures ranging in size from Quonset huts to Hangar One at Moffett field and larger.

Arched structures of various scales (lrtb). Quonset huts, Project Iceworm, South Pole logistics archways, some building in Hawthorne, Hangar One, Atlantic City Convention Hall.

They may be connected by sealable bulkhead doors, while the roof can support solar panels or farms, especially the equatorward face of east-west oriented pods. They also have good volume to material/labor ratios. Building materials can range from curved prefab panels to locally produced concrete or brick. Brick vaults may be assembled robotically without formwork using a variety of techniques. Brick and concrete structures are compressional so need preloading before pressurization with several meters of dirt. Numerous other materials and methods are possible, including inflatables.

A growing Mars base, then, could be a densely packed crosscutting network of arched pods, with outskirts being built out at ever more ambitious scale. Manufacturing, chemical work and other non residential activities can be confined to dedicated pods, which can be repurposed (loft conversion!) over time as demand shifts.

Primary demand for water, (nuclear or solar) power, fuel synthesis and storage is associated with launch, so it makes sense to collocate much of this capacity outside the city. Pads with retractable hoses and robot arms can handle ship surface operations at each pad. If the city outgrows the spaceport, construction of new pads and pipes is much less labor intensive than demolishing and/or rebuilding pressurized pods. Spaceports will ideally be located 5-10km north and/or south of the city to keep east-west approach/departure paths clear. On Mars this is well over the horizon!

While it may be possible to house a million people under a square km of high rise roofs, and contain industrial processes under 10sqkm, farming on Mars, while not an immediate priority, will eventually require the bulk of covered land, perhaps 100sqkm. It makes sense to operate at the same pressure as the base, rovers, and suits (perhaps 340mbar) but with enriched CO2 for plant growth, and every other trick worked out by decades of dedicated research that hasn't happened yet! The primary difference between farming and habitation structures is that farms need transparent roofs, though ideally still with a layer of water, ice, or glass to mitigate radiation. I like the idea of transparent inflatables sealed to the ground at the periphery and anchored with cables at regular intervals to spread the pressure load into the ground. There's no reason why residential pods couldn't be interspersed between greenhouses. These structures, similar in concept to an air mattress, would look a bit like this.

One final consideration is scaling and congestion. Pod bulkhead doors are natural choke points. While clever neighbourhood designs will keep the base walkable for most activities (food, hygiene, schooling, training, recreation), movement of large equipment or lots of people may require progressively larger thoroughfares. This is a great problem to have, since that many people on Mars implies many other problems have already been solved! I think use of tunnel boring machines for subgrade roads and repurposing of legacy structures will prevent problematic congestion.

This is my first pass at Mars urban planning. I have no doubt overlooked many details and obvious issues. I'm interested in developing sensible system design axioms from which any given city plan can be more-or-less trivially derived. I don't know of much other work done with such an aggressive focus on growth, and I'm curious to get a better understanding.

Visit to Ohio and Australia

Last week, C and I had back-to-back weddings and excitement. 

Photos: https://photos.app.goo.gl/1gD4PDoqNNXiaNa02

It started late Friday evening. We found our way to a conspicuously ultra-baseline economy flight, settled in behind an actual dog, and took the red eye direct to Columbus, Ohio. There, we met C's mother's new cat and celebrated the delightful marriage of E and G, whose subsequent honeymoon was, we hear, rather exciting!

I ate a belated birthday cake and then we flew back west once more, passing over spectacular canyon scenery, various faults, a Hyperloop prototype, and the Ivanpah solar thermal plant on the California-Nevada border. Back in LA the sky was a bruised colour from numerous fires, and we found our way to a lounge in the international terminal. 

Later that evening, we boarded a flight to Sydney. I read a few books, watched the latest Pirates of the Caribbean film, and tried to understand system properties of urban planning in space. On the ground, we were unexpectedly collected at the airport by my parents B&A, and whisked off to our rental apartment. We had planned relatively little for the first few days so that essential tasks like finding suits could be taken care of. I squeezed myself into a sharp blue number, while finding time for a few hikes, avocado toasts, and admiring the luxury cat home my parents transformed their flat into.

All too soon it was time to dress up and help my brother M into a matrimonial state. The wedding went off without a hitch. Or rather, only one hitch! We had readings from Song of Solomon and sang Jerusalem, and I didn't burst into flames. Then out to the harbour foreshore for photos, then the golf club for a fabulous dinner reception. Once again I was required to engage in some gentle brotherly ribbing as I gave a mercifully short speech welcoming my new favourite sister (sorry A) into the family.

C and my wedding in August was conducted on a remote island, so it was fortuitous that M was able to assemble the entire family in one place for C and my convenience so soon after. I enjoyed catching up with all the rellies, recharging my accent, and doing some sneaky research into my family's more mysterious origins on the continent. This will be the subject of a future blog post!

Well, we breathed a huge sigh of relief, borrowed dad's car, and set off on a road trip to see a bit more of Australia than we had on prior trips. Australian roads are good but the speed limits are horribly low and the drive thus extremely boring. We did see a good variety of wildlife though. 

First stop was the NSW central coast, where we gatecrashed my grandmother's choir rehearsal, investigated the giant pelicans, went for a hike, and attempted to avoid being dive bombed by seagulls while rowing around the bay. C and I cooked a huge dinner for my grandparents which was well received. One of the parts were potato latkes, which seem to me to be a lot of work to get out something which is basically a baked potato. 

After a couple of days we set out once more, traveling via Norah Head Lighthouse, where we got the best Australian accent lesson ever, to Buttai, a remote corner of the Hunter Valley where my great grandfather used to "go off the leash" with his brothers in semi retirement, reliving their incredibly poverty stricken childhood. Sooner or later the entire area will be strip mined, so good to check it out while I have the chance. 

We continued up the road, turning off on the Bylong Valley Way, a picturesque route through the Wollemi National Park, and also soon to be strip mined. At the town, we enjoyed a quick snack in the general store and explored a nearby graveyard. Almost all the graves dated from around Australia's regional grazing boom (1870-1930) but there were two fresh graves from 2015 in which a 97 year old couple had been (post mortem) interred.

Nearly there. We arrived in the late afternoon at my aunt G's farm outside Rylstone, finding noone but a lot of dogs and a half-cooked dinner. Perfect for exploration, so we found the new house site, the folly (a whimsical shed to contain us) and, eventually, living humans. 

There was much excitement in town because it was the start of the semi-annual international chainsaw large scale wood sculpture symposium. Later, we met a local who was involved in making a horror film documentary, so all things considered it was an ideal time to spend a few days sleeping in an isolated shed with no electricity, running water, phone service, or much but trees and kangaroos around. 

We enjoyed meeting the sculptors and seeing the incredible art being installed everywhere. We found a lot of large spiders, not all of them still alive. The biggest by far was Mr Tiny, a 4" wide huntsman spider who kept a few eyes on us while we took a shower. Later he refused to stand still so we took him outside. 

Overnight it began to rain, so the next day we suited up and went for a quiet walk down the main ridge of the property. This part of the world has some incredible "beehive" sedimentary rock formations. I have long had a secret ambition to hollow one of them out and build a cozy house inside. Once, I stayed in hollow rocks in central Turkey. It might be easier to build the house and then clad it in rock-like material. Getting useful windows that are invisible from outside would also require some finesse. 

All too soon it was time to head back to the city. We drove south and east via the Three Sisters near Katoomba, then spent a few hours at my old school talking to students about careers in STEM fields. That evening we gathered a few friends and gatecrashed my sister's house for an amazing dinner of purple risotto and music. The following day we relaxed with family, hung out with my old neighbours whose house is full of Antarctic art, and then flew back to the US. About an hour after taking off I looked out the window and saw Lord Howe Island cruising by! It's also a pretty cool place to visit, some time.

Recently it has seemed as though I make it to Australia about once a year. It's odd to see evidence of how much time has passed, but I'm sure the experience is similar for Australian residents who rarely see me! I have a few more years before my grey hairs become overwhelmingly obvious, I think.

SpaceX update at IAC 2017

Late last Thursday evening I enjoyed watching Elon Musk deliver his second update on SpaceX's plans for Mars, or Making Humans Multiplanetary. If you haven't seen it, watching this video will make the rest of this blog much less confusing. I've written a bit about Mars over the years, and I'm always excited to hear what SpaceX has been up to.

A year ago, I wrote a blog about the plan as then presented, and I'm thrilled to see its evolution and write a bit about my new thoughts. I'm going to split this blog into three parts. The first will deal with the major development - money. The second will discuss the mission profile. The last will deal with Mars urban planning.

Money

In 2016, it wasn't immediately obvious how to pay to develop the Mars rocket let alone run the program. A couple of months ago, I wrote a blog on this topic. And I'm thrilled that not only did I not guess what SpaceX was planning (though I was closish), what they have proposed is a better idea than anything I wrote about there.

SpaceX plans to retire the Falcon and build only BFRs for every mission it can think of. It will redirect all its engineering know how to building the new system, and thus finally find a method to freeze design of the Falcon 9 at Block 5 without further meddling! Why is Falcon a dead end? It is not fully reusable.

SpaceX can build and sell the Falcon 9 for about $65m for a single expendable launch. While their recovery of the first stage can help their business both by decreasing their fixed costs by a factor of perhaps three and increasing the number of boosters available, they can do a lot more. Even if they could refly the first stage hundreds of times with marginal cost per launch, the fixed cost of the expendable second stage, which must be near $10m, means that they can't revolutionize launch completely.

Here comes the realization. At $65m a launch they're already crushing the competition. With the landing of the booster SpaceX lacks credible competition for at least a decade. They could lower their launch cost to maybe $20m a launch and nourish the microsatellite market, but the overall demand for launches is likely to remain fairly static in terms of mass to orbit. This is because thousands of cube sats don't weigh much compared to the really big communications and military satellites.

Enter the BFR. The BFR might cost $500m to build. But if SpaceX charges $65m a launch - the same as it is doing today - and the BFR is entirely reusable, then it can recoup that cost within the first year of launches and then some. The BFR only has to fly about 10 times to close the business case, and there's no reason it couldn't eventually fly hundreds of times. Given that the cost of fuel is somewhere around a million dollars per launch, SpaceX has a huge advantage, because customers have no ability to force the price down against other competition who already charges between four and ten times as much as SpaceX.

The BFR is hugely over specced for any launch currently manifested. With a nominal capacity of 150T to LEO and perhaps 40T to GTO, there isn't a satellite it can't launch. Hell, it could probably launch any existing satellite into the sun. Well, not quite - it turns out that's really difficult. Does it matter that there's no real demand for 150T to LEO launches? Does it matter that the BFR will thus fly 5% full for most launches? Not if those launches are profitable. The airline industry's costs are about 13% for fuel, so a single BFR launch may cost as much as $5m, but SpaceX won't have many of the airlines fixed costs, like hiring pilots. So while the BFR's capacity could enable huge space telescopes or probes to Saturn or gigantic space stations, it can also fly mostly empty, or perhaps carry SpaceX's own cargo (such as fuel or internet satellites) with its excess capacity.

Here's another way to think about it. Given the current cost of launch is 100x the fuel cost, a fully reusable rocket could be 100x too big and still make economic sense. Why 150T, then? SpaceX wants these rockets to be big, for moving stuff to Mars. But really large rockets are harder to build and transport. Elon tweeted that the BFR was sized to fit through a door in an assembly facility. The door size constraint also set the size of the Saturn V.

Since last year's presentation, the performance of the Raptor engine has deteriorated slightly, which probably reflects its development path. It's worth pointing out that while a heavier BFR with a less exquisite Raptor might not be very useful for flying back from Mars, it is still capable of flying there, and more than capable of launching stuff into orbit around the Earth. Big dumb rockets suffer a design constraint which is that small changes in structural efficiency have big (and bad) effects on overall system performance. A good illustration of this is the evolution of the Falcon 9 rocket. When it first flew, it could only just loft 9.5T into orbit. Today, it is rated at 22.8T, even though the underlying plan remains the same. What changed? The engines got a bit better, and the rocket got a bit lighter. Imagine if the Mars ship, designed to lift 228T to Mars, turned out for the first few years to only lift 95T? The mission would be over. Elon briefly addressed this in the talk, when explaining a benefit of on-orbit refilling of fuel and oxidizer. Even if the booster turns out to suck, the spaceship can still be fully fueled in orbit, retiring that developmental risk.

What about the possible use case for high speed transport on Earth? Very roughly, the numbers check out here too. Oxygen and methane cost about $200/tonne, and each rocket needs about 4000T of fuel. So taking the airline numbers again, each flight could cost $5m. If each rocket can carry 150T of payload, that's about 1500 passengers, so the per head cost might come to $3000, which is comparable to current long haul costs. Interestingly, over shorter distances, the spaceship alone (without the booster) could make a flight. So this seems to address current usage patterns and cost structures, though is much more marginal than the launch business. Finally, although Elon would no doubt love a launch pad near every city, they are noisy places and town planners generally did not provision for the 4-6 mile exclusion zone they require. My eyebrows remain raised!

So what are we to make of the other efforts to bring about industrial capture of disruptable industries? Even though SpaceX's plan is to capture the launch market with a fully reusable rocket ("shuttle done right") it has a few other plays in internet satellites (Starlink) and tunnel boring (The Boring Company). I think these efforts are developing technology which is important for the Mars project and may eventually become huge sources of revenue themselves.

Mission Profile

Elon Musk provided a few updates on the mission profile. As an example, the spaceship has enough ΔV to fly to the Moon and back without lunar refueling if refilled in an elliptical Earth orbit. This would take about three times as many tanker flights, first to fill up a tanker completely in LEO, then fly that to an elliptical orbit several times to refill the spaceship. A Mars ship launched like this could also take much more cargo to Mars, though its Mars entry would be proportionately more difficult.

I have heard some discussion about distribution of the engines and their uses. It is important to remember that the rocket is ten times heavier when fueled up, and the bigger engine bells work much better in space. Therefore, while one Raptor engine is adequate to land a nearly empty spaceship, all 31 on the first stage are needed to lift the whole stack off the Earth. Similarly, a fully fueled ship lifting off from Mars needs four high efficiency vacuum engines, while two sea level engines are adequate for landing.

I was fascinated to see the section on the Mars entry profile, as I wrote a somewhat less sophisticated model to study this problem some time ago. Landing on Mars is very difficult for all kinds of reasons, but attentive watchers may have noticed that the spaceship enters the atmosphere upside down. Why is that? It turns out that entering the Mars atmosphere at 8500m/s, as SpaceX plans to do, is easily fast enough to skip off and escape the planet entirely. The spaceship is a lifting body and uses its lift not to fight gravity, but to help gravity pull the vehicle closer to the ground as it tries to skip off the atmosphere. In my model I computed that the spaceship would have to fly below about 40km to be able to beat centrifugal force. In this way, the entering vehicle curves around the planet. When its speed drops below Mars orbital velocity (~3700m/s) then it gradually rolls to a nose up attitude, where its lift continues to dissipate speed until, falling straight down it lights the engine and performs a flawless landing on the surface. The 2017 spaceship has really pointy legs, so I hope they pick a really hard flat surface to land on.

The LEO refilling concept has also been simplified. Rather than two spaceships flying close along side like mating whales, they now back up to each other. A small thruster creates enough force for fuel to drain from the tanker to the ship. Alternatively, if the parking orbit is low enough, residual atmospheric drag could provide some ullage force.

Although this was not explained, I presume that the landing pads build on Mars have hatches beneath which coiled hoses can be lifted to the spaceship for autonomous refueling. For this and related reasons, I think the spaceship might need a robot arm. Similarly, while a crane on the ship can lower cargo to the surface, an established Mars base would have to have mobile gantries that can be rolled alongside like siege machinery to facilitate rapid unloading and loading of cargo.  

Mars urban planning

Finally, Elon had a couple of slides on how the Mars base would grow. I like the images. I like all space-related concept art. www.humanmars.net has some of the best!

But these images are very Sim City. Will a Mars base actually look like that? What will a Mars base look like? Why? I talked a bit about Hab design principles in my Mars book. But Mars urban design is not an established field, and I think Elon was trolling us with this design. Indeed, I think SpaceX's main goal at present is to systematically derisk a human Mars mission to entice NASA and Congress to bite. Designing Mars bases is a few steps ahead. Moreover, SpaceX would like other titans of industry to join in and collaborate on these issues.

In particular, all those glass domes are just 200m from the landing pad! How far from the landing pads does the city have to be? What are its primary functions? What are its design principles? All these questions are good topics for a future blog. But clearly balancing primary needs for transport, power, water, fuel, and above all growth, are non-trivial!

Conclusion

I can't wait to see what comes out over the next year. This, the settling of another planet, remains the single most challenging, exciting, and worthy problem for all of humanity. I firmly believe that if my generation doesn't achieve this, the eventual extinction of humanity is all but certain. For more in this vein, check out these epic Wait But Why posts.

Estimating Mars settlement rates

Question:

How to get to an industrially self-sustaining Mars settlement in the minimum time?

Previously I've approached the broader problem in a book (http://www.caseyhandmer.com/home/mars) and several blogs, focused on a transport roadmap (http://caseyexaustralia.blogspot.com/2017/05/a-roadmap-to-industrially-self.html) and potential sources of money

(http://caseyexaustralia.blogspot.com/2017/09/how-to-fund-space-settlement-where-does.html). In this blog I'll attempt to integrate previous knowledge and make projections about time frames and costs.

Edit: Now all the data is available (csv) so you can slice and dice it.

In the previous post, I used the following graph to explain the relationship between population and self-sufficiency under a variety of scenarios, including constant and linearly increasing cargo capacity. It turned out that the final result did not much depend on how many rockets were available when, but the timescale certainly does. In this blog, I will build on the SpaceX exploration architecture. The most fundamental bottleneck is the rate of rocket construction and launch, so we will explore how construction rate affects the population and self-sufficiency timeline.

This graph shows a schematic relationship between population (horizontal axis) and mass self-sufficiency (vertical axis) under a cargo-constrained Mars settlement scenario. The settlement begins at the bottom left and scales towards the top right, where at some population likely exceeding a million people they are sufficiently industrially diverse that they no longer depend on crucial technology to be shipped from Earth.

Before I dig into actual numbers, I'm going to state my assumptions. For better or for worse, a lot of space-exploration themed writing, technical or otherwise, does not hew to the best possible standards for rigor. Here, I'm not going to delve into religious disputes about asteroid mining, lunar fuel stops or any other peripheral concept that's not related to the core bottlenecks.

There are two primary phases of the settlement timeline. The first, corresponding to the region of the red line below the purple cusp in the diagram above, marks the phase where scaling population within the limits of cargo shipments is a growing challenge. Loosely speaking, this challenge peaks with the successful instantiation of ore mining and refining for every industrially relevant metal and chemical - requiring interaction with the raw, unfriendly Mars environment. This phase is also the phase most directly applicable to current technology and projections.

Assuming the first phase proceeds more or less as planned and everyone doesn't die, the second phase marks the rush from the cusp to full industrial independence. By this point in the program, at least decades after initial landings, technology at every point of the exercise will have evolved to the point where predictions are difficult to make in 2017. Specifically, I expect that the forcing function of extreme Mars labor scarcity will result in drastic improvements in rockets, automation, manufacturing, and so on. It is possible, even likely, that this flowering of technology will reduce the minimum viable technology population more rapidly than ever-expanding immigration increases it.

That is, at the point of the cusp perhaps 20 years after initial landings, best estimates may still place the minimum viable population at 10 million, at least 30 years away even if the population doubles each launch window. At that cusp, net immigration could be in the tens of thousands per window but will have to increase to 100x that, something I think it rather unlikely.

Instead, rapid improvements in extraction and manufacturing technologies will reduce the minimum viable population to less than a million and perhaps less than the tens of thousands. As this trend continues, it will be possible to launch entire self-sufficient cities in one go, and perhaps a few decades later Mars will have thousands of self-sufficient towns, even though the total population may never reach the 10 million originally required.

It is important to emphasize that self-sufficiency is represented in reality as more capability than practice, since trade will always help increase overall economic efficiency.

I will sketch a picture of phase two, but first I will provide some numbers. Afterall, if the first self-sustaining settlement doesn't get built, there'll be no way for the ones that come after.

Phase One

As I explain in my book, the hard part is getting rockets from Mars to Earth, and to a lesser extent, from Earth to Mars. Here, I'll explain the constraints on total shipping capacity, then build a model that creates a plausible shipping capacity roadmap.

A spaceship has a number of important properties.

Cargo capacity to the Martian surface. Based on the IAC2016 talk and subsequent tweets, initial SpaceX Mars ships will have a cargo capacity of around 300T to the Martian surface. Second generation ships may increase this to around 1000T, but further increases are limited by a variety of physical constraints including the thinness of Mars' atmosphere.

Whether it can be reused and rate of reuse. The Mars ship is composed of a space ship, a tanker, and a booster. Initial boosters and tankers will be flown 6-30 times to refill the spaceship. The first spaceship will fly to Mars, spend nearly 2 years on the surface making propellant, then fly back to Earth. While the first few spaceships will be put near the Smithsonian, later spaceships will be able to fly to Mars every launch window after the emplacement of a fuel/ox plant and storage by the launch zone. Much later, improvements in engines could permit two flights to Mars per launch window. Over this time, the total number of Mars flights a spaceship can perform before retirement will also gradually increase.

Rate of construction. These spaceships are super complicated and difficult to make. Initial spaceships could easily take multiple years to build. Over time, the construction time will decrease and a single line can make more of them per launch window, increasing the total number of spaceships. Additional parallel lines can be built, perhaps by other space agencies using related technology, which also increases the total number of spaceships.

So how many spaceships are there per year?

To answer this question I built a Mathematica model that takes as inputs a function for the construction rate of various types, and outputs all sorts of information about total flights and total mass. This model can be downloaded from my github at https://github.com/CHandmer/mars-cargo-model. But here are the key results.

This table contains a summary of all the different types and versions of spacecraft used in the model.

This is a reconstruction of build rate (per window) from the global manifest data. We see here that as Version 1 reaches rate Version 2 is in the early production phase, on a roughly 8 year design cycle. After 2042, Version 2 production dominates investment and an additional line is added.

This graph shows how spaceship production and reuse increase the payload to Mars year over year. From 2042, Version 2 lifts the total throughput by nearly an order of magnitude.

This graph shows the cumulative cargo transported to Mars, reaching the crucial million tonne mark in about 2052. Given that mass transport begins in 2027, this process takes only 25 years to achieve.

I had a couple of surprises when seeing the results of this model.

First, total payload capacity increases very quickly. The period of time for which an initial settlement is constrained by quasi-constant cargo capacity is basically non-existent. This actually makes sense heuristically, in that it's easier to build lots of spaceships on Earth than it is to build a complete industry in space. It has a positive consequence too, which is that if the general relation between population and mass independence is maintained, the overall population can be scaled up even more quickly than before.

The second surprise was that there is genuine utility to building a Version 2 spaceship with 3x the capacity - as it compresses the timescale to reach a million tonnes of cargo by 15 years.

So how quickly does the population scale?

This is another difficult question to answer, but assuming a population-industry trajectory like the red curve given in the first graph above, the total mass each sequential settler has to bring with them can be predicted and a population-mass relation extracted.

This graph shows the total mass payload per person, assuming that the first 10 people, landing in 2027, consume the 900T of payload then available, and that the residual payload is 500kg, enough for a person and the food they have to eat on the journey.

This graph shows how the cumulative mass shipped scales with population. The population reaches a million people as the cumulative mass hits 620,000 tonnes.

This graph shows how population grows as a function of time. Here, the population exceeds a million in the 2050 launch window, 23 years after first landing.

This graph shows the window over window fractional population increase. The population grows very rapidly in the first decade to around 10,000 people. This reflects the easy gains of rapidly increasing shipping capacity and gas/water processing for plastics and propellant. 10,000 people is enough to begin mining and processing of metal ores to complete the set of available Martian feedstocks for the development of advanced industry.

Window over window gains drop below 2 from 2045 as all available space in Mars ships is consumed with passengers. If further explosive growth is needed, more ships and more flights are needed to transport people.

What does it cost?

In the previous section we eliminated mass to discover the population-time relations. Here, we reslice the data to discover the mass per passenger on a launch window basis.

This graph shows that by 2033, cargo mass per passenger has fallen to about a tonne, putting a ticket within reach of a middle class family. Someone arriving in this launch window could be the 10,000th person on Mars, and will mark the transition from program-selected specialists to self-selected professionals.

In 2035, a Version 1 spaceship can carry about 300 passengers, each with a tonne of cargo. By 2044, a Version 2 spaceship can carry about 2000 passengers, each with 500kg of cargo.

Let's adopt some ballpark numbers. A version 1.5 spaceship+tanker+booster may be constructed for a price comparable to a modern composite passenger jet, say $500m. Each refit costs $100m (of which a tiny fraction is propellant), for a total lifetime cost over 16 reuse cycles of $2b, or $125m per flight. If this is split evenly in time and between 300 passengers in 2035, the per ticket cost is around $420,000. A version 2.5 spaceship+tanker+booster will cost $500m to build, $50m to refit, and fly 30 times. Split evenly, the per-ticket cost in 2044 is $33,000, for a $65m/flight total cost.

Unfortunately it is difficult to be more precise than this, due to multiple cascading uncertainties. By the onset of "general admission" tickets in 2035, many billions will have already been spent on development and construction of spaceships which may not recover their construction costs in regular service for decades.

That said, I can attempt to estimate development and construction costs. Design rate and cost for both spaceships is $500m and 20/window, which works out to around $4.5b/year. This starts at the beginning of the program, even if the production rate doesn't reach design rate until 8 years later. Thus construction costs alone reach $4.5b/year in 2022 and $9b/year in 2032.

Reuse costs are initially low due to low numbers of reused spaceships, but eventually dominate overall program costs. By this point, however, ticket revenue will effectively offset this cost, and eventually fund the construction of new ships and entire program.

The primary financial outlay, then, occurs between 2018 and 2040, and may total $132b at an average of $6b/year.

This graph shows how the number of ships built and launched varies over time. If refit costs are 20% building costs, then building costs dominate until about 2040, by which time general admission revenue can begin to cover much of the program's operating costs.

Model Limitations
This model is generated from rocket building history alone. It doesn't take into account any other aspect of the universe, including human mortality, accident rates, or the possibility of mission failure. While guessing numbers and adding them to the model is technically easy, I judge that it would greatly increase uncertainty (fudge factor) while not adding much insight. Model complexity is only useful up to a point.

Phase Two

Earlier, I defined phase one as the era of cargo constraint, and phase two as the era of accelerating returns. As we've seen above phase two has a different kind of restraint, namely an immigration capacity restraint. By 2045, the critical path for growth is how many people can fit on a Version 2 spaceship, although under nominal predictions a million people are reached only 5 years later, by 2050.

Here, I will wrap up by listing technology concepts that could lift this constraint and permit further high rates of growth into the future.

• Higher construction rate of Version 2. Constraints on construction and launch rate are so low that many thousands of ships could be launched every window. Construction rates could climb into the hundreds per year in a single factory. Ticket revenue could fund this, if a positive margin on launch business was maintained.
• Faster ships that can launch multiple times in longer launch windows. This requires better engines and better mass ratios, but eventually there could be cargo and people arriving year round.
• Entry of other companies and agencies into the bargain. Could achieve 10x, possibly 100x on rate.

On the flip side, I think it's likely that the minimum viable population requirement will shrink to the point that even small outposts will have the ability to reach full autarky.

Project Timeline

Mars 2020 - Aquifer search probes land, Version 0 ships performing atmospheric tests on Earth.

Mars 2026 - First 10 crew arrive, 3 ships on surface. They scale propellant plant, assemble a lot of base for new arrivals.

Mars 2030 - Middle of explosive growth phase, base population grows to near 1000. Pilots for all primary industries established.

Mars 2035 - First private and 10,000th settler arrives. Mars spaceport hosts dozens of Version 1 ships and the Version 2 prototype, looming over the rest.

Mars 2043 - Ticket prices fall below $100k and the population exceeds 100k. All secondary industries at least in pilot phase. "Mission accomplished"

Mars 2050 - Population on Mars exceeds a million. Dozens of outposts formed.

Mars 2060 - A web of towns and cities all over Mars, with the first base and by far the largest forming a sort of hub.

How To Fund Space Settlement - Where Does The Money Come From?

Regular readers will know of my enthusiasm for the settlement of humans in space. Last year, I wrote a book (caseyhandmer.com/home/mars) about unsolved technical problems connected to Mars. Here I'm going to take a slightly different tack and talk about the financial question. In a previous post (http://caseyexaustralia.blogspot.com/2017/05/a-roadmap-to-industrially-self.html) I talked about launch cadence and shipping for industrialization of Mars on a rapid timescale. This discussion is oriented towards that problem, but I hope will be general enough to be useful for any other potential destination, including the Moon, asteroids, deep space, low Earth orbit, or beyond.

Aspects of this discussion often take on a religious tone. Here, my only goal is to explicate various options and perhaps list the strengths and weaknesses of each proposal - certainly no single approach is adequate to the task. It is clear that this is a problem that can consume extremely large sums of money!

How much exactly? It is difficult to know for sure. Using the industrialization text as a start, I propose that a population of 10,000 people can be reached on Mars in 20 years with a steadily growing launch cadence, requiring the construction of a new giant rocket every year, with re-use gradually becoming more widespread. The construction of this vehicle, plus tech for the ground, could run into the billions of dollars per year. Therefore I will baseline assumptions that a Mars settlement program will require billions, but perhaps not many tens of billions, per year for the indefinite future. This sounds like a lot of money. This isn't the place to justify expenditure of huge quantities of treasure on a project that will benefit practically no-one alive today, and maybe no-one ever. I will state merely that it is of the order of NASA's current budget, or slightly less than the cost of air conditioning in military bases in Afghanistan. It is also comparable to national expenditure on cosmetics, or a medium scale infrastructure project such as maintaining the interstate system.

In the following I have split various proposals into a few subheadings, but there is substantial crossover.

Finance

Broadly speaking, finance-backed concepts draw on the only limitless resource on Earth - human greed - and try to provide a mechanism for a big payday down the road. Generally speaking, any Mars-related investment could probably get better returns in less time on any other project on Earth. In particular, most very wealthy people don't have 50 years to wait for their money to grow! This is the primary obstacle to finance-based funding methods. Nevertheless, the quantities of money being spent, and the outrageous scarcity of certain key resources along the way, make for many business opportunities with shorter timescales for ROI. No-one doubts that settlement of space won't make a lot of people very wealthy, but the overall source of wealth is another question entirely!

- Value capture. As space transport tech improves (as it must), the value of assets in space increases disproportionately. It is possible to hedge this increase in value by, say, buying options on likely sources of key resources on Mars and holding the paper until someone needs to buy it. The primary weakness of this approach is that ownership of resources in space may be very hard to enforce, and existing legal frameworks are still very underdeveloped. Certain strategic materials or manufacturing know how on Earth has already proven to be a good bet.

- Arbitrage. Similar to value capture. Find a way of pricing some asset that has a lot of uncertainty in its future valuation, or is significantly undervalued in the market, and place a bet. Financial instruments surrounding insurance were key components of both the Dutch East India company and the 2008 financial crash. There's plenty of money available if one can figure out how to direct it.

- Triangle trade. This will be useful down the track, where Mars will be the obvious staging post for asteroid mining in the main belt, if there's ever a need for that. The Mars settlement has to get to a certain size before this is possible.

- Media rights. It may be possible to control the flow of information to and from Mars well enough that selling the media rights provides enough capital to keep the program going. This was the idea behind Mars One, and I doubt it would produce enough revenue, at least after all the middle men on Earth have taken their cut.

- Blockchain. Never say never. A Mars currency ICO? Or space-resource backed currencies more generally? I can imagine blockchain-based technologies becoming part of a collaborative design and manufacturing effort, but I doubt there are enough users and buyers of crypto currency to provide the steady stream of money needed.

Philanthropic

There is a long history of philanthropic space exploration. Indeed, since the invention of the telescope by Galileo, nearly all major telescopes have been funded by wealthy donors of one sort or another. Why? There's an industry devoted to discovering ways to get the rich to part with their money, but many of the 19th century industrialists who funded the famous instruments of Southern California wanted to contribute a positive legacy.

- There are people who are so rich they have nothing to spend their money on but more money. Or a space program! At the most basic level, if each California billionaire bought the naming rights to one big rocket for a billion dollars, the problem would be largely solved. Who doesn't want to name a gigantic rocket in honor of Steve Jobs?

- Crowd funding. Relatively small contributions by some large number of people can raise stupendous sums of money, as the IRS has shown.

- At a more general level, space tourism could be a source of revenue, much as a handful of enthusiasts can get flown to the south pole or space station for absurd sums of money. The only other way to go is to be a professional, and that's more time consuming! I think the number of people who can afford to go to Mars and want to go will be quite small for quite a while though.

- There are companies with enormous and partially idle engineering resources. Caterpillar, AECOM, and numerous others have the technical might to solve corners of the problem without breaking a sweat. But why would they? It could help them compete for talent, provide prestige, training, brand development, or could form part of an incentives package with policy support.

Open Source/Volunteer/Collaborative Venture

This approach is very underdeveloped. Part of funding the space program is about finding ways to make it cheaper. There are tens of thousands of qualified engineers out there who could contribute their time after hours, if only there was a mechanism, platform, or more precisely, a protocol to form the method of exchange. While few in number, there are some prominent success stories borne of this approach, including the Linux kernel and open source software more generally. Applying OSS/Agile/SWE techniques to hardware engineering is an area of active experimentation. But finding a way to tie together any program that must involve more engineers than can fit in a meeting with something better than the status quo - reams of paper - is a goldmine in itself. If a hardware-oriented project management mechanism became the defacto standard, like git etc. has in software, then this provides an additional incentive for large companies to contribute resources to the problem.

Policy/Government

Policy or law is the biggest stick with which to hit this problem by far. It's also the hardest to motivate, though perhaps a first move from a private company could see multiple governments reactively entering the space.

- Revision of the outer space treaty can enable a land grab or resource race. There are precedents for the governing body to issue resource or access licenses preferentially based on contributions to the central task. Either way, there needs to be well developed mechanisms for ownership, disposition of risk, dispute resolution, and evolution of the standards as new problems manifest.

- Jobs program. Just spend a whole lot of money in key districts and states. Not the best way to minimize costs, but probably the best way to mobilize public money.

- Social movement. Oriented towards planetary defense or fear of losing ground to a rival nation.

- Restructuring of defense budget. This is the biggest slice of the pie by far, and most of the same companies would be making the money. Would require a broad consensus, so hard to do in a proactive way.

- Bailout/rescue of failing private mission. Perhaps private space development needs additional investment to rescue the sector or safeguard strategically important technology. There is a precedent for this in the resurgence of the Russian space program in the 1990s due to strategic foreign investment.

Industrial capture

Many of the above approaches place a lot of control or uncertainty beyond the realm where it can be definitively controlled. A more direct method is to directly create wealth and then use it for whatever you want, as long as that is space settlement. At its core, all wealth is created the same way. Create demand, then control supply. The more of each, the better. Creation of whole new classes of things to own, or whole new markets, are surefire ways to create the opportunity for fabulous wealth.

- Technology. Invent a magic widget everyone wants. Or find a way of generating something (eg energy) more cheaply. Defend the IP. Bank the difference.

- Capture an industry. Is there a big industry out there with lots of revenue, lots of profit, and low competitiveness? Time to disrupt. SpaceX seems to be making a play towards satellite internet (a whole blog post in itself) and large infrastructure projects. The Boring Company seems poised to exploit a lot of latent demand for reduced travel time in congested cities.

- Space mining/resource exploitation. If it was possible to mine certain strategic resources in space and find a market for them, then an industry devoted to that could be financed or bootstrap. The main obstacle to this concept is the sheer cost of doing anything in space. It may even be cheaper to supply the moon with anything it needs from Earth, rather than to obtain it locally. Mars will need local resources, but it's hard to imagine something valuable enough to be worth shipping all the way back to Earth, except passengers and functional spaceships.

Exotic/Enabling tech

One way to reduce the required sums of money dramatically is with advanced or even exotic technology. I'll rank these roughly by level of plausibility.

- Re-usability and in situ resource utilization. This alone can reduce current costs by a factor of 100 or more.

- Space power. There is probably no way to make money selling space-based solar power to the ground, but space nuclear reactors for use on Mars or gigantic mirrors for terraforming are an interesting concept.

- In space manufacturing. One driver of space costs is launch costs. Launch a factory once and make everything in space (from asteroids, say) and that problem can go away. It's not clear to me what the critical size of this industry is, but I'd estimate somewhere north of a million tonnes produced per year before launching from Earth becomes bottlenecked somehow. Note that self-replicating robots lower costs on Earth too!

- Advanced propulsion. Anywhere from nuclear thermal rockets to warp drive. There's no reason why such concepts can't be developed in parallel with existing methods, but I don't think it's a good reason to wait.

- Life extension. Perhaps during my lifetime we'll solve aging and humans, freed from their four score and ten will think about problems on a longer time scale. I think life extension is probably key to very long space voyages, and may unlock ways to avoid possible space-related illnesses. But I'm not holding my breath.

Conclusion

What do you think? Which of these sources will prove to be the most enabling?