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Thoughts on Space Commerce
What happens in an environment with spacecraft that are constant acceleration, but slower than light speed

by Roger Bourke White Jr., copyright May 2006


It takes a long time to travel from one star system to another. Even at the speed of light, it takes four years to travel from our solar system to the Alpha Centauri, the next nearest solar system.

For most science fiction writers, this is too long, so they fabricate some sort of faster-than-light (FTL) technology so their story line can advance. (Warp, sub-space, and hyperspace drives are some perennial favorite names.)

The problem with this is: There is no FTL technology in our real-world foreseeable future and no theoretical breakthrough in sight that would permit it.

In our real world, the fastest starships that can be devised with known sciences and technologies will be constant acceleration ships. These can rapidly approach the speed of light, but never surpass it.

What will space travel and space commerce be like with slower-than-light (STL) constant acceleration propulsion?

Constant acceleration propulsion is quite different from what we are using for spaceship propulsion today. At present, we are using boost-and-coast propulsion systems for our spacecraft. A rocket engine fires for a short time to get the spacecraft up to speed, then the spacecraft spends a long, long time just coasting along, and finally, there is another short burst of rocket fire to brake the spacecraft at its destination. This is the simple version of boost-and-coast technology. We don’t fire the rockets longer because rocket fuel is heavy and bulky –- look at how big the fuel tanks are on the Space Shuttle or any other missile of today.

Let us presume that mankind can take the next big step -- and it is a big one -- and develop propulsion systems that can fire all through the journey, not just at the beginning and end. Spaceships which have this kind of propulsion are constant acceleration spaceships. Let’s presume mankind will be able to develop constant acceleration starcraft, and that those starcraft become the primary method for moving and communicating between stars. Let us further presume that these interstellar starships will maintain a constant 1G acceleration, so that people on board will experience a healthy and comfortable Earth-like gravity for the duration of the trip.

When we have this kind of environment, when the fastest communication system is the same as the fastest transportation system, and both take years to make a journey, the situation is similar to that on our Earth during the 18th and 19th centuries when sailing ships were the fastest way to move between Europe, Asia, and America.

I will be modeling what we will experience in the future off of what we humans experienced in that era. (The development of transcontinental and transoceanic telegraph lines in the 1850's ended the era.)

More on the Axioms of Space Commerce

I have said a lot about the axioms of space commerce in the previous chapter. Here is a bit more amplification.

More on the axiom space commerce must be profitable or extensive space travel won't happen.

Think for a moment about the question of who discovered America? Compare the effects of Leif Ericson, a Viking, discovering America in 1003 with those of Christopher Columbus, an Italian working for Spain, discovering America in 1492.

When Ericson returned with news of its discovery, his community said, “That's nice," and did little to exploit the news. The result was a minor curiosity of history. Columbus's discovery was followed by millions of people, and millions of investment dollars, heading for the New World and then back to Europe. This massive follow-up is why we remember Columbus's discovery so vividly.

Likewise, Neil Armstrong is steadily becoming a curiosity of history as manned space commerce within the solar system does not develop. Space commerce will happen when ways are found to make billions and trillions of dollars from traveling through space. We won't have space commerce until the many people who engage in it become rich beyond our wildest dreams. This is what happened to the Portuguese, Spanish, and Dutch who opened up the New World and Far East trade routes in the 1500’s and what happened to the Silla (pronounced “Shilla”) Dynasty Koreans who opened up the China-Japan trade routes in the 600’s.

Now assuming space commerce happens, which is assuming that:
a) many people are making trillions doing it, and
b) that planetary people have figured how to get their share of the trillions,
let’s talk about what space commerce will look like.

First, a Constant Acceleration Physics Primer: Ship Time Versus Planetary Time

The space travel we are doing these days (the beginning of the 21st century) is based on boost-and-coast rocket technology -- the propelling rocket engine fires powerfully, but only briefly, and when it is done, the spacecraft spends the rest of its journey coasting to the destination. This technology has gotten exploring probes to the planets of the solar system, but its performance is too low to get people comfortably around the solar system, much less from one star to another. Journeys using boost-and-coast technology take years to get around the solar system, and using it for interstellar journeys would mean journeys that would take thousands-to-millions of years. It would take hundreds of years to get a ship from the Solar System to the Alpha Centauri system, the nearest star, 4 light-years (LY) away. This level of performance is just too low to allow space commerce to develop.

For space commerce to happen, we will have to jump up to a new level of performance. The new performance level will come from developing constant acceleration spaceships -- ships in which the engine is firing all the time. It is either constantly pushing the ship faster and faster towards its destination or constantly slowing the ship down so it will stop when it arrives at the destination. This is what constant acceleration means.

When a ship travels this way going from one star to another, it will spend much of its time near the speed of light. This means time is going to tick away at very different rates for those on planets and those on the ships. This difference is important because it makes space commerce a lot easier.

Journey Time: Planetary Perspective

When a ship leaves one star system and heads for another at 1G acceleration, it will take about six months to reach .9C (90 percent of the speed of light), and that is close to as fast as the starship will ever go when one is watching it from a planet. (The top speed is “not quite 1C”. The ship will approach it asymptotically – always getting closer, but never reaching it.) So from a planetary perspective, constant acceleration starship journeys look as if they have three legs: First, an accelerating-to-lightspeed leg that lasts about six months, then an at-lightspeed leg that lasts most of the journey, and finally a decelerating-from-lightspeed leg that also lasts about six months. The rule-of-thumb time to make a journey, any constant acceleration journey, is the light years (LY) to the destination plus a year for starting and stopping. A trip to Alpha Centauri (4 LY away) takes 5 years, and a trip to the center of the Milky Way (30,000 LY away) takes 30,001 years.

A second curiosity about constant acceleration journeys when viewed from the planetary perspective: The ship's acceleration makes almost no difference to the duration of the journey because all constant acceleration ships will get to near light speed comparatively quickly and then spend the rest of the journey traveling at near light speed. This means that a ship traveling at .5G will take just about the same time to make a journey as a ship traveling 5G.

Journey Time: Ship Perspective

For the ship, and the people on the ship, the journey duration looks dramatically different than it does from the planetary perspective. For the people on the ship, the journey duration looks like it is described by Newton’s physics, not Einstein’s physics: The ship accelerates towards the destination for half the journey and breaks for half the journey. All the time the ship is accelerating, it looks as if it's coming to the destination faster and faster, and all the time it is decelerating, it looks as if the approach is slowing down. In sum, the journey always takes a lot less time from the ship perspective than from the planetary perspective, and the duration of the journey is quite sensitive to the acceleration -- the more acceleration that is applied, the shorter the journey.

The difference between ship time and planetary time can be dramatic: A ship journeying from the Solar System to the Galaxy Center at 1G acceleration will take about 340 years to make the journey ship's time, and 30,000 years to make the journey planetary time.

Since stars and planets in the Milky Way galaxy do not move at near light speed relative to each other, clocks on all the planets tick at pretty much the same rate. Planetary time applies to both the departure planet and the destination planet. 

Destination 1G 2G 5G 10G Planet time
Alpha Centuri 4 2.8 1.8 1.3 5
Serius 7 5 3 2.2 13
Galactic Core 340 244 155 110 30,000

Mixing Genetics and Space Travel

We don't have FTL technology, but we do have genetic engineering. How can genetics affect space travel?

From the starship frame of reference, acceleration is important, so the higher the acceleration that can be sustained, the shorter the travel times become.

Humans are well-adapted to 1G acceleration and not well adapted to much more than that.

It should be possible to engineer a "dwarf" race of humans with robust limbs and circulation systems. This race could feel comfortable in a 2G environment, perhaps a bit more.

And more is possible: If a body is buoyed up by floating in water, then even more G's can be sustained. I propose "porpoise people". These are genetically modified people, or cetaceans, who spend their travel time swimming. I suspect these people should be able to sustain up to five G's, or so. The limiting factor may be overcoming the high pressure side effects of high-G and simply getting air into these beings' lungs.

Once an organism is floating completely immersed in water, higher G forces start acting like higher pressure. So organisms that are well adapted to living deep in our earthly seas may provide sources for even higher G-adapted beings. I propose "squid people" as the ultimate high-G organisms that can come from an Earthly origin. They could perhaps be comfortable at ten G's.

Beyond carbon-based life, we can turn to silicon-based life -- cyberbeings and robots of some nature. These may be good to about 20 G's.

The Mixed Bag of Space Ships

As space commerce becomes well established among many worlds, I envision a mix of all these kinds of ships and races. The 1G "space liners" will carry tourists, and colonists who aren't in a hurry. These will be crewed by a mix of planetary humans and dwarfs. Next up will be the pure dwarf-crewed liners that travel at 2G. Passengers and cargo won't do much while they are traveling on a 2G ship, but they will get to their destination more quickly. At faster than 2G, many kinds of cargo will suffer, but what can survive gets there faster. The silicon-based ships will arrive at distant locations almost as quickly as light itself, but the kinds of cargo that can survive 20G acceleration for many years will be limited.

How Big Will the Ships Be?

Since interstellar spaceships will travel for years-to-decades between destinations (ship time), and because of the difference in time passage for planets and spaceships, the crew will rarely meet up again with planetary friends and relatives, so the crew will become a community unto itself. The smallest successful social unit for mankind living on Earth is small tribes or villages, so it's likely that successful interstellar spaceships will carry crews at least the size of small villages (50-100 people) and, more likely, the size of small towns to small cities (100-10,000 people).

For the same reason, the wealth that the crew accumulates from successful ventures will be associated with the ship. There will be no home planet that the ship returns to where the crew will retire and add to the wealth of the community. This is because as the ship travels, its home planet will age dramatically, so it will become as strange a place to the crew as any other planet they travel to.

For these reasons, the ships and their crews will circulate among various planetary communities and trade with those communities they travel among, but the crew will not consider themselves a part of any of these communities.

What Will the Ships Carry for Cargo?

The ship's cargo is the hardest thing to speculate on. It must be hugely valuable (See the First Axiom), but what that will be is hard to guess -- just as it would have been hard to guess in 1300 that in 1600 moving silks and spices would make citizens of the Dutch Republic (now Holland) the richest people in the world, by far. It would likewise have been unpredictable that potatoes, tomatoes, and tobacco would become South America's most valuable exports.

Even with the best technology imaginable (but still possible), interstellar journeys will be long and expensive. Once again, the sailing ships of the 18th and 19th centuries provide a good model. The wind they used was a free fuel, but the ship required to harness that free fuel for a transoceanic journey was expensive to build, maintain, and crew.

The journeys of interstellar craft will take years-to-hundreds of years from ship perspective, and decades-to-tens of thousands of years from planetary perspective. This means that in conventional interstellar commerce, ordering something for delivery from another planet is impossible: A planetary merchant will not be able to look at his shelves and say, “Umm ... I need some more Zenubian Worm Wine. I'll fax an order to Planet Zenube today."

Instead, the spaceship crew will have to look at what is available to buy on a world and guess what will be sellable at some planet down the line. And like silks, china, and spices in the 18th and 19th centuries, the profit margins will have to be huge by contemporary Earth standards. For instance, the gross profit margin on spices in that era was about 3,000 percent.

It is unlikely that simple minerals, such as gold or diamonds, or simple knowledge, such as new math formulas, will be profitable cargoes for star ships. If something is of simple structure, it is likely to be easier to build a factory to make it at the destination planet. Likewise, if the something is composed of simple knowledge, such as the DNA sequence which makes a particular antibody, it will be cheaper to build a research lab at the destination to learn the knowledge. What will be profitable to carry across the depths of space will be complex goods -- goods that are hard to fabricate unless several conditions are met at the same place and time.

Surprisingly, this means that foodstuffs and fine manufactures are likely to be good cargoes -- the same stuff that the merchant sailing ships of the 18th and 19th centuries shipped. Attractive cargoes won't be commodity foodstuffs -- those prepared because they are cheap, easy and nutritious -- but delicacy foodstuffs. Ingredients for recipes that are devilishly difficult to prepare, even under the best of circumstances, will be prize cargoes. A fine French wine might be a suitable cargo, and perhaps something as specific as a Big Mac would be, but a generic hamburger or a generic hamburger recipe would not be.

Another quite complex and quite versatile item is a human being. It is likely that moving humans -- consensual or coerced (passengers or slaves) -- will be a profitable trade.

What Will an Arrival Be Like?

There will be big differences in the arrivals between sailing ships of old and starships of the future.

The first difference is that a starship will be headed toward a destination star system for decades-to-hundreds of years, and it will be braking the whole second half of the journey. This means that for years before arrival, the ship's engine will be spewing exhaust in the destination star's general direction. That exhaust will be visible to the destination planet -- looking like a new and distinctive kind of star. It will look distinctive because the exhaust is created by an object headed toward the planet at near light speed, which will blue shift all the radiation.  The ship will first appear to the destination planet as some sort of gamma ray or X-ray star, and then the wavelengths will lengthen rapidly and steadily as the ship slows – the light will get redder. (If this description of light waves changing wavelength seems confusing, look up “blue shift” and “Doppler Effect” for some help.)

This “star” will appear in the destination star system's sky long before the ship arrives, so there will be a long time to prepare for the arrival, both on the planet and on the ship.

Second, a spaceship making an arrival at a star system will be a risky event for both the ship and the planet -- either the spaceship or the planet could suffer catastrophe from the contact. Because the journeys take years-to-centuries, there is likely to be a huge technology difference between the ship and the planet, which means one will be at risk of being dominated by the other. If the ship is higher technology, the situation is similar to high-tech Europeans engaging in the spice, silk, and china trade in the 17th and 18th centuries. At first the Europeans had little impact, but as their technology grew in power and desirability, they came to dominate the Asian and African communities, even though their numbers were comparatively few. They came to dominate for two reasons: First, because they had valuable tools and techniques, and second, because they were invited to use those to intervene in local disputes. The domination of starships over planets won't be so pervasive because the starships have so few people and usually no desire to stay. But they can dominate, and they can drop off colonists, who will set up starship-friendly governments that are potentially long-lived. (The stories of Ancient Egyptians being aliens from space describe how such a relation might look to a primitive planetary inhabitant.)

If the space ships are of lower technology than the planet, the situation becomes similar to what happens when Stone Age culture people visit a modern city. If the Stone Age visitors unknowingly violate some of the city's rules, they end up in jail. An example would be Stone Age visitors getting thrown in jail for public drunkenness when after finishing their business in the city, they get a little too feisty in their celebrating, and they do it in the wrong places.

Busy Planet, Lonely Planet, Virgin Planet

If there is continual space traffic with a planet, the departing spaceships can give arriving spaceships details on the planet's condition. But if the traffic is sparse, what conditions will be on arrival is just a big guess. It will be a wild guess until the spaceship gets close enough to start monitoring star system radio traffic.

An arriving spaceship will encounter three different planetary scenarios:

A) The "busy planet", where there are outgoing ships that can talk to the incoming ships,

B) The "lonely planet", where the planet gets enough ships to know what space commerce is all about, but not enough that arriving and departing ships can talk to each other,

C) The "virgin planet", where ships come by so infrequently that space commerce is considered to be mythical.

The Busy Planet

In the busy planet scenario, business is the most predictable and most orderly. Regardless of the planet's tech level, the incoming ship will know where it stands with the planet because it can talk with outgoing ships to catch up on planetary current events. If the planet is mistreating ships, the outgoing ships can tell this to the incoming ships, and they will either avoid the planet or dominate it and punish the mistreaters. In sum, business is easy to do and predictable at busy planets, and starship voyagers will like that.

Note that the traffic must be frequent because ships moving at relativistic speeds with each other will have difficulty communicating. In addition to the clocks-ticking-at-different-speeds problem, the communicating radio waves are compressed into the X-ray haze at the front or lengthened into the microwave dark at the back and hard to pick out. The ships must be close to stopping or just starting out for easy communication to be possible.

The Lonely Planet

Business is riskier at the lonely planet. The incoming ship has no idea what the planetary tech level is, what the planet inhabitants want to buy and sell, or if the planet will attempt to capture and loot the ship. However, a lonely planet has heard about space commerce and knows it is beneficial, so it will communicate with the incoming spaceship, and it knows how to do so. In sum, commerce is risky, but at least both sides know what the game is all about.

The Virgin Planet

The virgin planet has not been visited in so long that it has forgotten space commerce. The planet's inhabitants have no idea what's in store. This means that their reactions are quite unpredictable and that they will take a long time to get organized for space commerce.

In sum, most starships won't like visiting a virgin planet because it will take them so long to conduct trade. This increases the likelihood that a ship that will stop is a rogue of some nature -- a pirate or a protester.

Getting Organized for the Visit

The planet knows the ship is coming, and both the ship and the planet know exactly when it will be arriving. Because ships are city-size and take years to travel from place to place, they will have manufacturing capability. In the busy planet and lonely planet scenarios, the ship and planet will do a lot of information sharing and negotiating while the ship is inbound. It is while the ship is inbound that 90-to-100% of the trading will be negotiated. The planet and ship will then use their manufacturing capabilities to prepare the goods they have negotiated to trade. What is left to do after the ship arrives is on- and off-load cargo and deal with surprises.

These cargos are worth trillions to the ship and planet. They are important, so there is both a lot of pressure to get commerce conducted successfully and a lot of temptation to defect (betray) and try to make even more money by breaking the agreement in some fashion.

On busy planets, defecting is not going to happen often because word of the defection will travel quickly to the incoming spaceships. Lonely planets have experienced the benefits of space commerce within the culture's memory, but because there is no one around to tattletale, defection will be more tempting. Virgin planets have no experience with space commerce, so defection is very likely until both sides have had the chance to take the measure of the other, and both have decided that cooperation will be the most profitable tactic.

Once a starship has arrived, the journey to the next star system will take decades to centuries, so there is little pressure for a starship to leave a star system quickly. If there is something to be gained by mixing starship manufacturing capability with planetary resources, the starship will be happy to remain in the star system for years or decades. Two cases for staying a long time that come to mind are:

a) The starship is participating in building a new starship, and

b) The starship is off-loading colonists who are going to build a starship-friendly world and then produce valuable cargo for the starship.

Who Will Communicate?

It is likely that both the planet and the spaceship will have official communicating organizations, and those handling official communications will declare that they have a monopoly on the ship-planet business. However, it is also likely that there will be attempts to "back channel" on both sides. Those attempts will originate from numerous motives, ranging from trying to do legitimate business with less red tape, to trying to organize smuggling, to trying to get help with political intrigues and community conflicts of various sorts. (“Community” in this usage can vary in size and meaning from family groupings, to cultural and economic groupings, to religions and nations, to a whole world or whole space ship – however people choose to identify themselves as “us” in an “us versus them” situation.)

How successful these back-channel communications processes will be depends on the social organizations of both the ship and the planet, so it will vary a lot from one planetary encounter to the next.

Who Owns the Cargo?

On a modern cargo jet, ship, or truck, the owner of the craft, the owner of the cargo, and the operator of the craft are usually three different entities -- a FedEx jet carrying Intel chips that have been bought by Dell Computer is flown by pilot Jones.

In interstellar commerce, the cargo and ship will be owned by the starship crew. This makes a big difference in deciding what cargo is valuable to carry. In modern Earthly commerce, the employees of stores and factories decide what cargo planes, ships, and trucks should carry. They do so by ordering goods and contacting shipping companies to carry those goods. In space commerce, the crew will decide what to carry, and they will decide by guessing what will sell well at subsequent destinations. The only ordering that can be done is the communication that goes on while the ship is inbound to the star system.

By modern Earth standards, this system will be hugely inefficient at getting the right goods to the right place. The modern concepts of Just-In-Time manufacturing systems and Supply Chain Management of inventories will have no meaning in space commerce. This is one more indicator of how really big the intrinsic profit margins for cargo must be before space commerce will develop.

Space War

What will conflict and conflict resolution be like in this environment?

First off, talking about a galactic empire makes no sense. Even having one star system conquer or own another star system makes no sense. With 1G constant acceleration starships, star systems are too far apart to have ownership mean anything. Plus, those who move between the star systems, the starships, are their own community. They have no inherent interest in promoting multi-star-system governments. The only way they will be interested in supporting a war between star systems is if a star system is wealthy enough to pay them to move an army.

But once the invading army gets moved, that army doesn't have to worry much about retribution from the mother planet, so it will run the newly conquered planet as the army leaders on the new planet see fit. To the starship community, this is just another form of colonization.

Most space conflict will be of the intra-solar system sort -- planet-versus-planet within a star system -- and there will be some spaceship-versus-planet conflict of the sort already discussed.

This holds true even if nasty, conquering aliens show up. Suppose a scouting Earth spaceship heads for the Galactic Core, and there encounters "Corg" -- a vicious conquering space race that will now come after humanity. The scout ship eludes the Corg and hotfoots it back to the Solar System to sound the alarm. How long does this simple process take?

It takes 30,000 years to get to the Galactic Core in planetary time, and about 340 years ship time. The return trip takes equally long, so it will have been 60,000 years on Earth since the scout ship left! It's not a question of how countries will have changed when the crew returns, it's a question of how species will have changed when they return! (Writing dates back to 5,000 years ago, and modern mankind has only been on Earth for about 30,000 years.)

In conclusion: We will not have meaningful interstellar wars.

There may be ship-versus-ship conflict. At each stop, a ship will gain trillions in wealth, and because it has no meaningful home planet, it will keep that wealth on board the ship in some fashion. This will make the ships attractive targets for robbery to others who have ships. Ships will worry about pirates.

Ships have a lot of people, too, so there is going to be a ship government, and there are going to be "haves" and "have-nots" on the ships. There will be ship protests and ship mutinies. Ship security will be concerned with external pirates and internal troublemakers.

Trillions and Trillions... of Dollars!

Keep in mind Axiom One: Space commerce is not going to happen until many people can get rich doing it. This means that space commerce will have enormous and surprising impacts on ship and planetary societies. As an example of enormous and surprising impact, think of how much Europe and America were changed by the discovery of the New World.

Keep in mind that gold and silver, the expected wealth producers from the New World, ended up being small potatoes compared to the surprise finds of tomatoes, potatoes, and other useful crops.

Those worlds who participate in space commerce will be wealthy, exciting, and surprising places, compared to Earth today and to those worlds which don't participate. The rich worlds that George Lucas showed us in his last three Star Wars episodes are the kind of wealth we can expect from space commerce. (But unlike in George Lucas's movies, spaceships will not come and go quickly.  Each one will come and go very slowly.)

Again, using a historical example, think of South America as a "spaceship" docking next to Europe in 1492. First to come from that docking was a whole bunch of gold and silver that enriched the risk-takers of Europe. After that came the clearly positive lifestyle changers that have become the French fries and tomato sauce of our day. Along with those clearly positive lifestyle changers came the equally popular, but more controversial, lifestyle changers that today are cigarettes and cocaine, and some clearly deleterious lifestyle changers such as syphilis. And if you're on the South American side of the docking, you get an alien invasion and colonization program that wipes out all existing political structures and religions in less than one hundred years. Whew! That's a gamble-and-lose-big surprise! (Note that the people survived and thrived even if the governments and religions didn't.)

This is the kind of high stakes game that will be played each time a starship docks at a star system. There will be a lot of people who get wealthy beyond imagination and a lot of people who don't want to play.

Note that because of the axioms, this change-the-world nature of space commerce is an integral part of what space commerce will be. If you’re going to have starships coming and going, the planetary world culture is going to be routinely turned upside down. This condition is not as strange as it seems at first. The “Four Tigers” of Asia – Hong Kong, Singapore, South Korea and Taiwan – went through this kind of dramatic change for decades from the end of World War Two through the opening decade of the 21st century.

In Conclusion

Space commerce will produce rich, exciting, and surprising communities, but those communities will not be tightly knit. Each star system will have its own community, and those communities will be tied together by a loosely-knit community of starship dwellers.

Time will pass on the starships very differently than it does on the planets. Travel times between stars, as witnessed by planetary inhabitants, will be the distance in light years plus a couple of years for starting and stopping. Travel times, as witnessed by starship inhabitants, will be much shorter and depend on ship acceleration, but still measured in years-to-decades.

The arrival of a starship will be long anticipated, and much communication will go on between a starship and its destination planet before it arrives. Much of the trading activity will be decided upon before the starship actually docks.

Starships will be city-size in population and do a lot of manufacturing while they are en route to star systems.

Because they are complex and can adapt well to many different circumstances, colonists will be a significant part of typical starship cargo.

Star system versus star system conflict will not be common because of the long travel times. Planet versus planet in the same star system, ship versus planet, and ship versus ship will be more common.

Landing at a lonely planet or a virgin planet will be a time of great uncertainty for a starship crew. They will not know what to expect from the planet's inhabitants, and they could get hurt by them. Landing at a busy planet is a much more predictable event because the crew can talk to departing spaceships before they land.

Starships will dramatically change the lifestyle of every world they come to. A visit will dramatically enrich both the star system and the starship, and the lives of the planets and the starships will not be the same.

To see a short story of mine built on these premises take a look at “The Colonists” in Tips for Tailoring Spacetime Fabric Vol.-1.

Update: This 26 Oct 13 Economist article, Starship Enterprises, talks about the economists who like to talk about space enterprise.

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