Forget about making interstellar trade possible, even with Einstein's laws of space and time, where it seems that you get to places faster than the speed of light. Just don't try to go back, because 100's of years , if not 1000's of years have passed. There are no physical goods that would make sense to send between stars, except for reproducing killer robots that can grow humans (well, only killing if they ask our permission.)
There have actually been some papers on the effects of interstellar trade (by Pual Krugman, Nobel prize winner!) The main conclusion is that interest rates on the linked star systems should be correlated. Looking at correlation of interest rates between earth based countries, the correlation is probably pretty low. Let's consider the secondary effects of trade, planets that trade with the planets that you trade with: the effects have to be very, very small. So you can make any calculations only assuming that you take into consideration the directly nearby stars.
Assuming that all trade between planets is mostly in services, information, and weightless goods, how much of current worldwide trade does that consist of? The total weightless trade amount was $5 trillion dollars per year or about $700 per person per year (all in 2014); which seems like a lot since a significant portion of the world's population gets by on less than $400 per year. Since the total economy is about $80 to $100 Trillion (depending on how you count it) this means weightless trade is about 5% of the economy of the world. Trade in goods(non-weightless goods) is about three to four times bigger. or about 20% of the average economy is now done via trade. The average GDP per capita world wide is about $10,000 per person per year. So trade per capita is about $2,000 per year.
Let's look at an analogy to Mars for trade: Hawaii, the most isolated place in the world. Hawaii imports between $6.7 and 3.8 billion per year; or about $4.2 to 2.5 thousand per person per year. And the imports are mostly energy.
Since the per capita income in Hawaii is about $46 thousand dollars, Hawaiians import about 6-10% of their income. That's almost twice as much as the average per capita trade of the world average. Mars is going to have to be at least twice that (if not more) so expect the per capita trade to be around 12 to 20% when we have 1.5 million people on Mars. Earlier, it will be even higher.
So we have a few questions to answer: How long does it take to get that many people on Mars? How much capital does it take? How much trade will they need? How expensive is it going to be to transport that trade? How are you going to get energy to Mars? (all solar? nuclear? Not wind or water.) And maybe, finally, why the hell would anyone want to go to Mars in the first place? You do know there's no air there? Terra-forming Mars will definitely take a long time (how long?) and be very expensive. You won't be able to walk outside without a space suit on for at least a hundred years... Are you nuts?
To be specific: Yes, the human race is nuts; but in a good way.
Interplanetary trade must happen.
The question is what form will it take?
So let's figure out what it takes to make interplanetary trade possible. That would mean Earth to Mars. Let's assume that Mars will be settled, and probably terra-formed in the near future. How much capital must we invest in Mars to survive? How many people are required? How long does it take?
How much does it cost to get to Mars?Elon Musk has promised trips to Mars for $500,000 in the year 2025. This includes a ton of cargo (another good question - what do you take?) He's going to send up the first few flights of 1 - 2 hundred people per flight, like a cruise ship. He's assuming that he can send stuff to Mars for $250 per pound. Does that make sense?
How much does it take to ship stuff around the earth (which is way cheaper than shipping it to space, by the way.) And there's an easy way to estimate this, just look at the energy required. The costs will be relatively proportional.
Recently it costs a max of $50 to ship one ton in bulk anywhere over water ( It costs about $400 to ship a container to the United States from China, about $800 to ship from India, and $1,300 to ship from Sierra Leone. A container can hold just under 40 tons (just like a truck can carry.)) And it costs about $2 per mile to transport 40 tons of stuff over the ground. To go 2000 miles (anywhere on the earth) it will cost $100 to move a ton on the ground. So you can get one ton of stuff to anywhere on the earth for about $150. <Or you could fly it anywhere: Between 1955 and 2004, air freight prices fell from $3.87 per ton-kilometer to less than $0.30, in 2000 U.S. dollars. don't believe this.> In addition to these costs, getting stuff to the launch site, you have to send the stuff to Mars.
How much energy does it take to move a ton over the earth? Trucks get 8 mpg and fuel costs about $3 per gallon, so it costs $3/8 per mile or $0.325 per mile per 40 tons or $0.08 per ton per mile. To get the delta-v needed to get to Mars you need to use 2.7 times the fuel weight over the cargo weight. How much does 3 tons of fuel cost? That's about 20 barrels of oil, at current prices that's about $800 per ton of cargo. If you took that ratio of energy to costs (a factor of 25) then it will cots about $20,000 a ton to get stuff to Mars. And Elon is saying he can get the costs done to $500,000 per ton. He's got a 25 x expendable costs. He definitely needs to reuse that rocket, though, just like you reuse a truck or a ship, because rocket ships are quite expensive.
How big will the Mars transportation industry be?
Currently to cruise around the world on a cruise ship is close to $35,000 and takes about 90 days. You can do the same thing in a jet for $90,000 and it takes 30 days. It looks like this business has about 5 participants and they run about 30 flights each with 50 people on each, so total revenue for this industry is about $4 billion ($4,000,000,000.) The cruise part of the market is probably about 10 times that size or a $40 billion industry.
Elon is talking about trips to Mars; he's saying the size of the trip to Mars industry is about $150,000,000 per trip. This means if he grows the industry to match the existing luxury jet industry then he could have 24 Mars flights and get 3,000 people per year on Mars. If he was to grow that exponentially, well, now we're talking. Let's say that trips to Mars were as popular as the cruise industry: That would be 240 Mars flights and 30.000 people per year to Mars. How long do you think that would take? The travel industry grows at about 5.4% per year, for a long time. That means it doubles in size every 13.3 years. It would take ~5 doublings to go from 3,000 to 30,000, or about 65 years. Wow. Too long. Let's say that the Mars tourist industry grows by 24% a year (then it doubles every 3 years, so it only takes 20 years. That's more like it. Now how long does it take to get Mars to the size of Hawaii, which has 1.5 million people? Just over 5 more doublings. Or another 20 years. Not too bad. We could get 10 million people up there in about 50 years.
They will need factories to build buildings, since you can't live outside. They will need factories to build solar panels, since that will be cheaper than importing them (or oil) from Earth? Maybe. What can you sell? Only intellectual property. Mars is never going to send anything back to earth except people. It's going to send intellectual property to earth and expect earth to send it physical things in return. Until there are enough people on the planet to sustain themselves. How long does that take? And how many people does it require? Let's say that we need to be as big as France or Germany to be a self-sustaining modern country, or have a population of 50 million. Or another 5 to 10 years. So it will take 55 to 60 years to get a sustainable Mars colony. And that doesn't get started for another 10 years. So we could have Mars settled in 2085 to 2095. Or around the turn of the next century.
Are we doing better than last time?
What's our nearest historical analogy? The European settlement of the new world? Mars is much harder to live in than the new world: no oxygen, no edible foods, no life; on the positive side: no animals or previous inhabitants. So what things do I need to live? Atmosphere. Water. Food. Electricity (Power). Transportation. Entertainment. Life. Silicon chips. Displays. Printers. Medical Care. Housing. Furniture. Pets. We're getting pretty far down the Mazlow hierarchy here. But how many people actually came from Europe to the Americas each year?
According to wikipedia, about 47 million people have emigrated from Europe to the Americas, which now have about a billion people (after 500 years.) The Europeans first came to America with Columbus, but none of them stayed until 105 years later in 1607. LEt's set the start point of when the first thing got into space (should actually be from when the first person gets to Mars... but close enough.) That would be 1957 or 60 years ago. So if having Mars settled is 70 years in the futre, it will take us about 130 years to settle Mars from our first voyage into space. That seems to be a little bit faster the speed that the New World was settled, since that took about 300 years.
After about 200 years there were 1.2 million people who immigrated and about a total of 4 million in population, which implies that everyone who came over had about 4.1 kids net, per couple per generation.
Since the cross-Atlantic settling took about about 45 days. This implies that over the 400 years 10,000 people per year immigrated, or about 300 people per day, which means about one ship per day. And since the round trip time is 90 days, we need about 90 ships going back and forth. Oh wait, there's all the people that went over and came back. During that time about a quarter of the people returned. So, it doesn't make that much difference. Maybe 125 ships. There were probably more ships that were just cargo ships.
Let's compare that rate of flow to our current expeditions into space. So far, the longest anyone has stayed in space is one year. We've essentially had someone in space full time since 1957 (just after my birth day) in various space stations or rockets. But they've all come back. We won't really know how fast we can settle another planet until we go to Mars. It would be interesting to look at the first 50 years of travel to the new world and compare it with our travel into space. So far, it's hard to tell if we're ahead or behind. But since the first permanent settlement in the new world took over 100 years, we still have 50 years left.
I think we will kick butt on the settlement time, in a much harsher environment. We're just oodles of times more intelligent today then we were 500 years ago. How much more smarter? You can only look at the world's average GDP (Gross Domestic Product.) The ration of current GDP to GDP 500 years ago is about 60 to 1. And we are growing much, much, much faster since the industrial revolution. The first steam engine was invented in 1700. Our growth in GDP didn't take off for 100 years after that. The Victorian era or the 1800's. The growth changed from 0.1 % to 3 %. Once we learned how to produce energy our economy's GDP (a measure of what a collection of people can produce) doubled every generation. And it doesn't look to slow down any time soon.
How many people do we have to seed Mars with?
To make an estimate of how many people we would need to make Mars an independent colony you can look at the smallest viable independent countries. Switzerland or New York (8 million.) Greece (10 million.) Poland or California (38 million.) France or England (65 million.) Germany (80 million.) EU, North America, South America are around 400,000,000 people. These would definitely be survivable number of people. How about a single country or state? California or France are probably big enough to be an independent unit. So 30 to 60 Million people. The economy would be about $1.5 Trillion. As in the US today, if it was able to import 5 - 10 % of it's economy; at $1000 per kilo transportation costs (not to mention the 6 month delay) Mars can import 150.000 kilos of stuff. Or about 30 launches/year for trade (not people.) So almost one launch per week. Not too bad. 10% of the average that we sen to the new world during the first 400 years. Wait. Not sure what the cargo shipping was. That was a bunch bigger than the people shipping. Maybe the same size?
Can we get to Mars that fast?
How do you get to Mars? Well it starts with one launch per year. Then two launches per year. Then 4 launches per year. Then keep growing that exponentially. What does it look like? If we double that every year we can fly 10 million people to Mars in 15 years. That should be a reasonably self sustaining economy. Let's say you can only double the size every 3 years, then it takes 45 years. With that size of an economy you can have several fabrication plants for chips. You can have a car factory or two. You can build computers, phones, displays and all the internet type things. You also need buildings and atmosphere and water and food, oh my!
And eventually you want these things outside in the open. That takes a lot of effort. And hundreds of years of time. Not an easy job. But look at the Dutch. They've reclaimed dirt from the sea for hundreds of years. It can be done. Humans can take on great engineering projects, and make them happen. The interstate system. The phone system. The cable system. Settling Mars. Terra-forming Mars. Wonder how long that would take? Could you do it in 50 years? That would be way faster than the Europeans settled the new world. But let's just assume it's as fast as the new world settlement, 500 years? From 0 to 750 million. Doubled in population every 25 years, or about 3% growth per year. Not too shabby. Just a slowly increasing exponential growth that overwhelms all the imaginable numbers.
Are we ahead of or behind schedule?
I'm thinking we're ahead of schedule. But it's so early it's hard to tell. It's hard to imaging that we can't settle Mars in 500 years. Especially considering that I think it's likely we'll see the first people land on Mars in the next 10 to 15 years.
Thanks for reading.