I have two binary planets, with technological level of about the present day. They've developed communication between the two planets, and scientists are trying to develop a method of getting people and materials there, and exchanging the materials for other things. With both planets communicating, in what kind of timeframe could I expect viable (for very large companies, like apple size,) interplanetary trade?

Note - The planets are 16,550 miles apart. Or 26,635 km.

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    $\begingroup$ 16550 miles is a very short distance in space, having two planets of any size that close together would likely cause all sorts of problems. For example, it's 238,900 miles between the earth and the moon. How big are these planets? $\endgroup$ Feb 19, 2016 at 18:00
  • $\begingroup$ @MichaelMcGriff There would definitely be problems, I'll probably ask a question about it. As for my arbitrary distance choosing go here. It gives the two planets and orbital period of 24 hours, or so I was told by the person who gave he accepted answer. $\endgroup$ Feb 19, 2016 at 19:05
  • $\begingroup$ are there specific goods than can only be produced on one of the planet (because of natural resources not being present on the other one), or are there technologies that one planet possesses that the other could not acquire easily, and would rather buy? $\endgroup$
    – njzk2
    Feb 20, 2016 at 3:30
  • $\begingroup$ if you consider planets of identical sizes, moving the distance up to the geostationary orbit would make them tidally locked, and it would be conceivable to build a bridge. $\endgroup$
    – njzk2
    Feb 20, 2016 at 3:33
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    $\begingroup$ The distance between the planets is completely irrelevant (within reasonable limits, of course if they were too far apart they would not orbit each other), because virtually all your fuel will be used to climb out of the gravity well of your planet. $\endgroup$
    – vsz
    Feb 20, 2016 at 9:16

8 Answers 8


0.088844797 seconds

The value of any material good * the cost of transport > its value on the other identical planet.

So Schematics, Information, media, Scientific data etc will be the primary goods to be traded and you can send those by Radio.

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    $\begingroup$ This is technically correct, but I was focusing more on physical goods. I did say on planet sends things there, then they send us things back. $\endgroup$ Feb 19, 2016 at 13:54
  • $\begingroup$ If the planets had different mineral compositions or biology then Gems and biologicals might be traded. $\endgroup$
    – King-Ink
    Feb 19, 2016 at 13:56
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    $\begingroup$ In fact this is the only viable answer. On this earth, if asteroids were solid diamond it would not be profitable to mine them even before considering the market glut effect. $\endgroup$
    – Joshua
    Feb 19, 2016 at 16:55
  • $\begingroup$ Consider the situation where on one of the planet one country has access to most of one type of resources. Other countries would have the choice to either buy from this country, or import them interplanetarily. There are many reasons why you would not want to buy from a given country. $\endgroup$
    – njzk2
    Feb 20, 2016 at 3:39
  • $\begingroup$ @njzk2 : consider the immense costs of the Apollo project, and that all they could transport back was a few kilograms. And the Moon has much smaller gravity and no atmosphere. If there was planet similar to the Earth in place of our moon, you could not send, with current technology, a mission with the capability of returning. You would require the other planet to build all the infrastructure to send your people back. $\endgroup$
    – vsz
    Feb 20, 2016 at 9:46

With our current technology level it's highly unlikely that any substantial transfer of materials would take place due to the exorbitant cost of lifting them into and out of the relevant gravity wells of the two planets. Very small high value objects might be worth transporting but in general the cost would not be worthwhile.

There would need to be some sort of massive breakthrough in launch efficiency (for example construction of a space elevator) to make this viable.

However what could well happen is the exchange of information and ideas. TV shows, entertainment, music, the internet would all be transmitted. Scientific ideas and patents might be recognised or traded between the two planets, etc.

These could and would happen now and bring value to both planets. Information transfer would be both easier and more valuable than any sort of physical trade for a very long time. It's impossible to predict how long as making travel cheap enough would need some sort of quantum leap in technology that is hard to predict.


If you have good communications then, ideas will flow between the two planets. Trade would likely consist of building manufacturing plants on the other planet to produce the items vs. actually shipping them. It would be much cheaper, to build something than to ship it through space and land it.

So the most likely things to ship would be biologicals. As in special foods or drugs that can't be reproduced in a lab without special plants, (that might or might not be able to grow on the other planet). This could also include animals, maybe for exotic rich pets or zoos.

Otherwise most other things could be transmitted as ideas that could be implemented.


Its conceivable that once communications are established huge combined efforts would be put forth by both planets. At first these could be focused on the construction of an hybrid system that uses a startram to launch a spaceplane. The goods first traded would be small payloads of rare and extremely precious materials, but once two planets cooperate you could expect leaps in technology in just a few decades that would make viable the transport of more common goods.

I think you would find a book like The Millennial Project an interesting read


As Soon As Possible

I would say that trade would proceed as quickly as rocket technology permits. However, we should be clear that the initial cargo would likely be the same as on Earth today for private space launches. There is really only one thing that is so valuable you would pay almost any price to launch it into space: yourself (where "yourself" == rich billionaire).

The first launches would likely be diplomatic missions between the superpowers on each planet. After that, luxury tourism would probably be the first private industry to finance inter-planetary launches. And naturally, once rich people can travel between the planets, they will insist on certain personal items being transferred to their off-world vacation home (pets, trophies, etc.).

Regular exchange of trade goods (non-people) would probably not occur until launch costs come down dramatically, or non-rocket solutions are developed (space elevator, tether, etc.). However, we are virtually guaranteed that powerful and rich people will want to travel off-world just as soon as it is feasible. The first off-world in-person delegation to arrive would literally be a world-wide event for both planets.

Also, consider that any superpowers with imperial ambitions would realize that having just one world to conquer is not enough. Such a nation would surely militarize space as soon as possible.


I am of the same idea as most people here: that with our current technology, it is possible but highly unfeasible to transport materials through space transport.

However, if you must transport materials and want to build a long term plan for it, here are some ideas you should consider:

1- Forget careful landing procedure. Too much hassle involving a lot of budget, headache, time consumption and fuel usage. Instead, wrap the stuff (it would probably be technological instruments) in layers upon layers of styrofoam and water-proof boxes and then shoot the rocket to point anywhere in the ocean area of the target planet.

2- Attach a lot of air-filled balloons in the rocket so that it would float upon falling in the ocean, instead of sinking.

3- Anywhere in a diameter of 100 km should be fine for the receiving party. There ought to be gps transmitters in the rocket that would transmit the location of the package for the receiving party.

4- Design the rockets so that they can be re-used after some repair and refueling. If that is not possible completely, at least make majority of its part reusable.

5- Since the distance between the planets is so less, the rockets can go unmanned, carrying only fuel, navigation system and the goods.

This way you would be able to make the transport hassle-free and would reduce a lot of costs involved with careful landing and whatnot.

  • $\begingroup$ Um, probably should involve at least a little bit of calculation. It might be considered a declaration of war when you drop a giant package onto a Capitol on the other planet. Also, I think we can do better than styrofoam. $\endgroup$ Feb 19, 2016 at 16:14
  • $\begingroup$ So you would risk destroying or losing your cargo to keep costs down? you would spend more in insurance money... $\endgroup$ Feb 19, 2016 at 17:13
  • $\begingroup$ @XandarTheZenon: Haha. Of course styrofoam was mentioned for the sake of shock proofing the package. If there are better options, why not! And no, I don't think there would be any war declaration when a protocol of sending and receiving has been agreed upon. And under NO CONDITIONS are you going to drop a rocket on dry land. Water bodies only! $\endgroup$ Feb 19, 2016 at 17:49
  • $\begingroup$ @ErikvanDoren: No. When you are going for mass transportation, you are first going to perform a series of exhaustive tests about the effects of shock on different materials and the materials which can be used for packing them, so as to make them shock proof. Only after rigorous testing are you going to start shipping objects that way. $\endgroup$ Feb 19, 2016 at 17:51
  • $\begingroup$ @YoustayIgo are you talking real world or hypothetical? Because when I send valuable stuff I prefer paying a courier and be assured the item arrives safe rather than risking it with cheaper mail options, the loss of the item would negate any saving, but that's just me i don't work in import-export $\endgroup$ Feb 19, 2016 at 17:59

Space Elevators & Tethers

The biggest issue would be getting materials on/off the planet. Currently it costs $20-25k per pound to put something into orbit. It's possible, but far from affordable...

I just happen to listen to a podcast from .Net Rocks talking about Space Elevators and Tethers released earlier this month.

We could have Space Elevators by 2035 and a Japanese Company is aiming to build one by 2050...

Even assuming it takes longer, I think it's easy to say that we could be easily moving stuff up and down space elevators by 2100.

Once we can do that, the cost of moving stuff up and out should drop from 20,000.00 to 200.00 per pound - and then lower as time goes on. It then becomes insanely affordable (compared to now) to move into orbit and back.

Your planets aren't that far apart (per comment, they are closer than us and the moon.), it's not that far of a stretch to take some of our puny space craft - add a few decades of research and improvements - and bam... easy to see trade blooming between the two planets: Just like it's easy to see a Moon colony being realistic and a Mars Colony not far behind once it costs 1/100th of what it costs now.

EDIT: Using a Lagrange Point

As per comments, I think it would be realistic - assuming we have progressed to the point to create carbon nano tubes to make a "Space Elevator" realistic - to assume that in 100 years or less you could create an elevator between the two worlds.

Between the two worlds should exist some sort of Lagrange Point - a balancing point of gravity. Place a station between the two worlds at that point. Then extend filaments towards each world. At some point, you have a platform at the end of each filament. One on each world - with a station in between. Assuming the rotations and equators don't match perfectly, you still have a suspended platform on each world. (If the equators/rotations match... then you just anchor them to the ground on each world... but I don't think the odds favor that scenario)

Now you don't even have to use rockets to get between the worlds... Elevator go up... Elevator go down... your standing on the other planet.

  • $\begingroup$ Don't worry, someone calculated it for me and they have to be that close to have an orbital period of 24 hours. $\endgroup$ Feb 19, 2016 at 18:54
  • $\begingroup$ @XandarTheZenon I imagine there are good reasons to be that close... space elevators, once built, would make getting to the moon easy... something closer would only be harder if the paths interrupted the "tethers" - or of the paths of the tethers (side going away from the planet) interrupt each other. Otherwise, elevator to each planet and short space flight between space stations. $\endgroup$
    – WernerCD
    Feb 19, 2016 at 19:08
  • $\begingroup$ Also, just thought of it: In the podcast, there is mention of running stuff along the tether (away from the planet)... get it up to speed, let it go and momentum alone would "sling-shot" it to the destination of choice. Not hard to imagine timed-daily slings from one planet to the next. $\endgroup$
    – WernerCD
    Feb 19, 2016 at 19:17
  • $\begingroup$ If the planets are mutually geosynchronous, a space elevator would actually be trivial to construct. Simply launch a tiny counterweight with a minimal tether, using a coil gun, anchor the counterweight on the other planet, then repeat until there are enough tether strands to weave into a rope of the desired strength. $\endgroup$ Feb 19, 2016 at 20:06
  • $\begingroup$ The Japanese Company link, goes to an article about Apple and the FBI, I'm guessing this is wrong...?? $\endgroup$
    – Ryan
    Feb 19, 2016 at 20:12

A few hours

Spacecrafts are very fast.

I suppose devices resembling the space shuttle would be suitable for this kind of endeavor. A launcher, with a reusable craft capable of precise reentry and landing.

The launcher itself can also be reusable, as SpaceX is demonstrating.

Plus, there would be vast commercial interests in doing this kind of things, so the progress in this specific domain would be much faster.

Why, though?

Whatever you can manufacture on one planet, you can probably manufacture on the other as well.

You need some form of competitive advantage, which can be availability of materials, labor cost, labor regulation, workforce qualification, politics, wars, industrial secrets, marketing...

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    $\begingroup$ The question was more, how long will it take to develop interplanetary trade, not how long will shipping goods take. $\endgroup$ Feb 20, 2016 at 3:54

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