Lifting Civilization
Martian colonization will happen on a scale that is hard to comprehend.
Every now and then you hear something about going to mars. Maybe it's a JPL probe, an Elon Musk tweet, or a CNBC article. If you're anything like me, you have a flash of excitement followed by a sober reminder that any large scale missions are likely far off. If you're like the general populace, your emotions may range from apathy to amusement.
Even people involved in the space community, for whom mars missions are top of mind, often think of our first interplanetary efforts as being similar to the Apollo missions. Go there, leave a flag and footprints, and come home. Maybe the more ambitious follow on missions can set up a temporarily habitable Mars base with room for a small crew, similar to the South Pole Station.
In this post we'll dive in to what Mars colonization really means. What will it actually take to set up a permanent, self sustaining civilization on the Red Planet? In doing so, we'll see that even conservative estimates place the effort far, far beyond the largest industrial efforts ever undertaken by mankind. If these efforts do play out (which I am optimistic of!), they will reshape our global economy, our industrial base, and our understanding of what megaprojects really look like.
Self Sustaining is the key word
Much fanfare will be made of the first person to set foot on Mars. Much less attention will be paid to the moment that really matters: the moment Mars civilization stops requiring resupplies from Earth.
It's doubtful that moment will even be noticed, since it requires deep analysis of the Martian industrial base and economy. It's likely that certian esoteric materials or components that could be made indigenously won't be for cost or convenience reasons. So the true moment of theoretical self-sustainability will likely be missed.
Why is self-sustainability important? For the full answer, I'd recommend reading Tim Urban's amazing blog post series. In short, adding planetary redundancy to a civilization drastically increases it's survivability. This may be a requirment for human civilization to pass the Great Filter. It may be the single most important thing humanity can / will ever do.
Mass Requirements
To build a truely self-sustaining civilization, you need to recreate the entire industrial base. Meaning every single thing that needs to be produced for modern civilization, including every feedstock, needs to be produced locally.
This requires a lot of mass, and a lot of people.
No compprehensive studies have been done yet to pinpoint an exact number of people or mass, but a good estimate is 1 million people. Meaning you need to transport 1 million people and all the mass to support them, as well as all mass required to bootstrap civilization, from Earth to Mars.
To do this, we would need to build a conveyor belt of mass from Earth to orbit to Mars and run it for decades. Enter Starship.
The Starship Program
Starship was primarily designed with this purpose in mind. The name of the game is throughput. We need rapid full reusability on every part of the system, capable of sustaining ludicrous launch cadences. Let's do the math on how much we would need to launch to get 1 million people to mars by 2050.
First let's estimate that we'll need to send 1,000 full starships to Mars every launch window, and approximate the launch windows to be once every 2 years.
1,000 starships to mars every 2 years = 1,000 ships to LEO + 6,000 fuel tankers to LEO = 7,000 launches LEO launch window: 2 years = 365 * 2 = 730 days 7,000 / 730 = 9.58 ~= 10 launches per day 10 / 4 launch towers (2 FL and 2 TX) = 2.5 launches per day per tower
So right off the bat, this is not only far more than a traditional launch provider can handle (lol), it's far more than Falcon 9 era SpaceX can handle.
If we want to do multiple launches per day, we can't use droneships, period. The time it takes to transport the boosters back to the launch site quickly becomes the bottleneck.
Even if the boosters return to the launch site, they need to be refurbished, re-mounted on the launch pad and refueled within ~8 hours, with a new payload stacked and ready to launch again. The Falcon architecture simply was not built for this level of reusability.
But it gets worse. Since rockets use cryogenic fuel, we need to worry about boiloff while they're in space. The longer they sit with fuel in orbit, the more fuel boils off. Let's assume we can limit the boiloff such that it can sit in orbit for 3 months before boiloff levels become unsustainable. So we need to launch all of our Mars transit fuel in the last 3 months before the transfer window in one big "burst" phase. Let's recalculate our launch cadence for this burst.
Burst launch window: 3 months = 90 days 6,000 fuel launches / 90 days = 66.6 launches per day 66.6 / 4 launch towers = 16.6 launches per day per tower
Woah. Ok, this is getting nuts.
So every 86 minutes, we need to launch from each tower. Now we are starting to see why some of the seemingly strange Starship design decisions were made.
Let's start with perhaps the strangest: no landing legs. SpaceX is designing Superheavy to be "caught" by the same tower it launched from. This is essentially the most efficient way to "land" the booster, since the tower can simply lower the booster back into place to launch again. No refolding legs when you don't have them, no transferring from the landing pad when you don't have a landing pad.
In theory, we only need 4 superheavy boosters (one for each tower), but in practice I assume we'll have some redundancy. Say a 3-fold redundancy. So we'll need 4 * 3 = 12 boosters. Not unthinkable.
But the ships are a different story. Of course we need the 1,000 original ships that will make the journey. We'll also need a large amount of tankers. Let's assume each tanker can service 2 ships. That's 500 tankers needed to fuel the full fleet. With 1.5 fold redundancy, we're looking at 750 tankers. So in total we need 1,750 ships.
The tankers can be re-used for each transfer window, but it's highly unlikely we'll get any of the Mars-bound ships back, so we'll need to make 1,750 ships for the first transit, and 1,000 ships for each subsequent window.
Now we're seeing why SpaceX chose to use stainless steel over advanced composites used by other launch providers. These things need to be rolled off the assembly line at a rate of 1,000 / 730 = 1.3 ships per day.
The amount of fuel required is also mind boggling. If each launch uses 3,400 (booster) + 1,200 (ship) = 4,600t of methalox, and each ship requires 1,200t before the Mars transfer, each transfer window requires 4,600 * 7,000 + 1,200 * 1,000 = 33,400,000t of methalox.
Sourcing and refining that level of RP-1 is extremely difficult. Sourcing that level of methane is possible (potentially through Terraformers!). Plus, return flights need to source fuel on Mars, which has abundant atmospheric CO2 and H2O, the feedstocks for the Sabatier process.
These are the base estimates. The true numbers will be more aggressive to provide some buffer for error and account for the fact that the Hohmann Transfer Window occurs every 17 months, not 2 years.
Feeding the machine
Now we're starting to see the full extent of this program. Entire industries will be formed and oriented around providing the capacity to produce ships, fuel, and most importantly payloads. National economies will be made by supplying this effort. During the burst window, you can set up a BBQ at Starbase or KSC and watch the largest rocket ever made launch every 43 minutes.
Of course all eyes will be on the launch sites and parking orbits, but that will represent less than 1% of the true scale. When you account for the administration, planning, supply chains, manufacturing, construction, recruiting, and sheer engineering, you likely end up with a level of economic activity similar to that of world superpowers.
This level of industrial activity needs to happen with complete alignment of national governments. Everything from launch licencing, trade agreements, regulatory predictability, and public opinion need to be in sync or this giga-scale civilization mover stumbles.
This might explain certian powerful people becoming more politically involved in recent years, but I'll leave that speculation up to the reader.