# Are moon colonies scientifically easier than interstellar travel?

Is it easier to build colonies within the solar system than to send colonies to other stars?

Logically, wouldn't we have cities on Pluto sooner than we will have travelled to an exoplanet?

• Please be aware that you should wait at least 24 hours before selecting an answer. This is "should", not "must", but it's a good idea. What if a better answer comes along? What if someone points out that the answer you've selected has the minor drawback of being wrong? There's no hurry here, and fast selection will inhibit people from giving you different insights. – WhatRoughBeast Oct 30 '16 at 15:16
• thanks. why does anyone think such a simple and politically relevant question is a poor one. Colonising an oceanic exoplanet could mean sending only 2-3 ships there, whereas colonizing pluto would require massive mining and self replicating robot technologies. – aliential Oct 30 '16 at 18:19
• Nobody would want to colonise Pluto. – Karl Oct 30 '16 at 19:06
• Living on Pluto could be better than living in Tokyo. A lot of people live in climatized boats, and Pluto could accomodate boat based cities which have large aquaculture ponds and fusion reactors and it could be like living on the canary islands. if the entire surface of pluto was a boat city, perhaps it would be ok. Maybe pluto has a lot more H2O than mars and the moon do. – aliential Oct 30 '16 at 19:16
• As for " why does anyone think such a simple and politically relevant question is a poor one", please refer to description of downvote button: "This question does not show any research effort; it is unclear or not useful", emphasis mine. It looks like you didn't try to think about it; you didn't show any facts that would suggest there might be any doubt. – Mołot Oct 30 '16 at 20:51

The answer is simply yes. For example, Pluto is roughly four light hours distant from Earth, while the nearest known exoplanet is the Proxima Centauri system which is 37,168.68 times further away. So the distance travelled is so much further.

The energy cost of travelling to an exoplanet will be many thousands of times greater than the longest journey inside the solar system. This is at a minimum.

Assuming the most optimistic form of space travel, vehicles that accelerate at a continuous one gee. A spaceship will only take one week to travel to Pluto, while a trip to Proxima Centauri will take 5.243 years (approximately). proxima Centauri is also the nearest star to our solar system. Every other interstellar journey will take longer and the energy cost will be increasingly greater.

The planets, moons and asteroids of our solar system are simply vastly more accessible, travel time is so much shorter by comparison with journeys to even the closest stars, and the energy cost is much, much less too.

Communications within the solar system is much easier too. The longest time delays, say, for Pluto will be only four hours. With Proxima Centauri it will be never less than 4.243 years. This is only way. For two-way communications, the time delays are double.

Most definitely our species will establish settlements on the worlds of our solar system long before we do anything like that on any of the exoplanets.

• Thanks for the information! Someone secretly marked down my quesiton after. Wonder why. If you send a germ colony to an exoplanet, you could send just 1-2 germ ships and start again in the iron age to make engines and agriculture. If you had to colonize the moon and pluto, the germ ship would need self replicating and mining robots that can live in 70K temperatures, else it would require millions of tons of space freight to build stable room temperature bases. – aliential Oct 30 '16 at 18:29
• Nit picks: It's true that the longest time delay for (one-way) Earth-Pluto communications will be less than six hours.  (I question your "four" figure; my cursory research suggests that it is more than five.)  Of course, when Earth and Pluto are on opposite sides of the sun, there may be an additional delay caused by the need to route the communications through a relay (probably on another planet). But Neptune-Pluto communications could take over nine hours. – Peregrine Rook Oct 30 '16 at 19:13
• The distance of a space object is only one small part of the challenge to colonize it. The technology required to energize and mine Pluto may be of a higher difficulty than that required to send a ship full of zygotes and artificial wombs to another star. – aliential Oct 30 '16 at 20:09
• Peregrine, while you may be entirely right, I think that a4android's point is really that a couple hours isn't even comparable to the time needed for interstellar communication. – user19838 Oct 30 '16 at 20:34
• @comprehensible any "earth-like" planet will still be sufficiently different in some aspect that it's not survivable by an iron age colony; even more so because we can't really prepare the expedition appropriately beforehand just from very remote sensor readings. The "germ ship" has to deliver a payload equivalent to the payload required to colonizing Mars (which is just as earth-like as any remote colonization candidates), but deliver it much, much further with no chance of quick resupply if it turns out that for this planet you needed one extra feature to survive there. – Peteris Oct 31 '16 at 16:30

Not sure about cities on pluto, but in general interstellar expansion will be after our own stellar system expansion.

Reasons for that are energy and technology.

# Energy

Potentially you may send a human to almost any star in our galaxy, and it will take for him let say a month of subjective time.

So we can pack snacks in a fridge for him for a month, but it will cost a lot of energy to send him that way, at that speed.

Let say we send ISS(about 400t) and 600t supplies for it for 6 years+ and for interstellar mission objectives, at 2/3 of the speed of light to Alpha Centauri 4.37 light years away. Let say in some non-rocket launch fashion - we have to get somewhere 634195 GW$$\cdot$$year of energy and convert it with 100% efficiency into craft kinetic energy.

World energy consumption -- World total final consumption of 104,426 TWh (or 8,979 mega-tonne of oil equivalent) by fuels in 2012 (IEA, 2014)

104,426 TWh is equivalent to 11920 GW$$\cdot$$year.

Almost 2 orders of magnitude more than we consume (and produce this or another way) energy in the world, just for one small 1000t craft.

It is entirely possible for such a small craft to do what you have it designed to do - explore the system, start a new human civilization, blow that star, it is just matter of technology.

# Technology

Sure you do not have to spend 60 years of energy we currently produce, by sending that craft at lower speeds and extending travel time to those 60 years. By using recycling systems, energy generation units etc - all that technology may do for us. But effectively it is answering the question -- how can I live in earth orbit for 60 years, without supply from earth, or any other body in the solar system.

Solving that problem includes not only solving water, oxygen, food, waste recycling problems. It includes also hull integrity, radiation protection, electronic repair, meteorite protection, microbiology control etc. Basically, it means self-sufficient colony in space, even if it needs a supply once in 60 years. 60 years is a lot of time, considering that twice of that time back in the past, main transport was a horse, and considering that fact that this problem have to be solved for slow craft before its journey, as it will face it in star system were we do not know its local realities(we might guess, we might have solid guesses). And any solution for them will work in our system too.

It means exporting a lot of technologies and developing new - to work in space, to live in space.

So there is a wage - to use force or to use knowledge. But technology is a part of force solution too, you should have some technology to get that energy and deploy it in space. Are those big thermonuclear reactor, solar panels in space with 1000x1000km in size (40% efficiency) or something else - but those capabilities are the result of pretty heavy actions/work in space, if we look at it from our current perspective.
It is not a joke, this energy production, this power of energy source will be enough for 10-60 billion of people to live (food is included) better than most of the people live today on earth. And you need that all just for to send a small craft(in first fast case), and technology from second case (a slow case) which actually allow them to do so, to live in space in some kind of space habitats.

• space habitats is the reason why I'm not sure about Pluto colonies, just for fun yeah, not a problem.

# technology and energy

In fast case we may send 1000t craft per year at the expense, I would say, virtual lives of 60 billion of peoples. For same energy production, we may send a 100 times heavier craft with 60years of travel time.

But what will or can these 1000t and 100'000t crafts do, after they arrive in another star system. What are their capabilities? And is it really better then have 60 billion of peoples here in this solar system, or what could those technologies do in this star system(and you have to multiply what they can do in another system by, at least by 10000, here they can do at least 10000 times more than in another system).

If we have 10 billion of peoples, and energy for 100 billion, yes why not to send probes to make closeup photos. Or maybe build a bigger space telescope for this energy-money and get access to a wider spectrum of information, not the same as observation in a nearby system, but not less valuable for sure.

# conclusion

Everything you send interstellar, you send when energy generation and technology allows you to do that. Same technologies and capabilities mean already active live in this star system and great possibilities for this star system.

We will do that, we will send something interstellar, maybe even not so far in the future, but speaking of now at the moment about interstellar is the same how to discuss how many horses it needs to send a satellite to orbit. The answer will be - none, we do not need horses, we do need a proper technological solution even if it has horse arse in its past, it is not a horse.

What Is the Link Between a Horse's Arse and Space Shuttles

• Thanks MolbOrg! lots of interesting informations. The coulomb of deceleration is the same as the energy of acceleration. There is another solution. Maximum speed of slingshot using planets is about 0.027 percent of the speed of light, which means we can get to the nearest star in 20000 years. It would only then require a strong empty spacecraft with a 3d printer, and a lot of zygotes, and a computer that can renew itself for 20,000 years. Then the 3d printer and computer can print wombs, blood jars, lymph, and nursing/colonising robots for arrival at the star. – aliential Nov 1 '16 at 12:04
• @comprehensible solutions depend on what you like to achieve and which technologies you have, this as an example. There are lot of different proposals about how and what can be done. Example in this answer is only to illustrate some aspects of what we need, to have numbers to compare to what we have. It is not a lot of energy for space, it just us, we just have too little of it atm. – MolbOrg Nov 1 '16 at 14:35
• It can be done as you say. My attitude is - what will people here in the solar system to get from that launch, which problems it will solve. My opinions : As civilization, or as spices, we are very very pragmatic by nature. Sending zygotes will solve 0 problems here, and will create a lot of problems to solve - ethical and just a problems in future. When I say we will send - I mean, we easy will send at 0.99c a crafts with millions of people aboard, after we will have strong foot in this star system, in this or next century, just for fun and knowledge. – MolbOrg Nov 1 '16 at 14:35
• @comprehensible and for some reason I think Isaac Arthur youtube channel will be interesting for you. It is more about possibilities of future and is good example of space thinking, almost every video. – MolbOrg Nov 1 '16 at 15:34

As a4android suggests, simple logic suggests the answer is "yes". I'll expand a bit on the why.

Besides everything being much closer and in relatively fast communications distance to anything else, you are also much closer to a powerful source of energy: the Sun. Heading out to a distant planet or asteroid is much easier when you have access to large amounts of energy, and even with current technology, it is relatively simple to suggest ways to provide lots of energy to emerging settlements across the solar system.

Initially, we could send a colony to Mercury to build solar power satellites and use lasers or masers to beam the energy across the solar system, either to cooperative targets on spacecraft or to receivers on the colonies themselves. A photovoltaic panel "tuned" to the laser's frequency or a rectenna tuned to the maser's frequency can absorb the energy at very high levels of efficiency, and this will be relatively independent of the distance from the Sun itself. (Sunlight falls off in the inverse/square relationship, so regular PV arrays become virtually useless beyond the orbit of Mars).

Robert L Forward did calculations as far back as the mid 1970's for building lasers orbiting Mercury capable of putting out Terawatts of energy for propelling laser driven lightsails on interstellar voyages, the technology could be much more easily developed for planetary use without the expense and difficulty of tracking a spacecraft through interstellar space.

Going bigger, rather than building solar power satellites and lasers in solar orbit, the Sun's corona can be used as the lasing medium to drive lasers of incredible power. Warming Neptune's moon Triton so you can grow potatoes on the surface would be child's play with that level of power, and your Solar Empire could be extended to the Oort Cloud, roughly one light year in diameter.

Finally, given you have huge amounts of energy and building resources all in relatively close proximity, you could start converting the Solar System into a Matryoshka Brain (concentric Dyson swarms devoted to energy collection and computation, with outer layers using waste energy from the inner layers).

All this can be done much faster and more cheaply than an interstellar journey, which would take incredible amounts of energy to do quickly, or long periods of time (a hypothetical solar sail powered starship swinging around the sun might take 1000 years to get to Alpha Centauri).

Another more physically realistic approach would be to use the light from the Sun to accelerate.[29] The ship would first drop into an orbit making a close pass to the Sun, to maximize the solar energy input on the sail, then it would begin to accelerate away from the system using the light from the Sun. Acceleration will drop approximately as the inverse square of the distance from the Sun, and beyond some distance, the ship would no longer receive enough light to accelerate it significantly, but would maintain the final velocity attained. When nearing the target star, the ship could turn its sails toward it and begin to use the outward pressure of the destination star to decelerate. Rockets could augment the solar thrust.

Again, Yes, for many reasons.

The engineering of colonizing our own solar system is far simpler than going interstellar, and in the centuries of travel-time required to reach another solar system we could easily colonize our own. There's another, more subtle reason, though:

Colonizing your own system is almost a prerequisite

Think about just a few of the issues with launching from Earth

• High gravity limits the maximum size of any vehicle you launch, and costs huge amounts of fuel
• The dense atmosphere induces drag-losses and further complicates the engineering of your vehicle
• All of your resource extraction and industry has to be conducted in a delicate ecosystem that you really shouldn't disrupt

All of those make the massive manufacturing base needed for an interstellar or even intra-system fleet... Problematic to say the least. But what if I told you that there's a much better place to build our factories and launch complexes - A place we've already been, that already has flags and footprints, and is only a three-day journey away.

Yes, I'm talking about the Moon. It has a lot going for it.

• Lower gravity means that everything from mining machinery to skyscrapers to rockets can be built bigger, taller, and lighter.
• Lack of an atmosphere means there's no drag-losses to contend with, so rockets can be built yet lighter and more efficient.
• No biosphere means no EPA, meaning you can use more exotic, powerful, and efficient rocket engines, giving even further bonuses to the benefits listed above.
• The lunar regolith is rich in Iron, Silicon, Aluminum, and other bulk building materials. There's even considerable portions of Oxygen in the soil, so both the foundries and your own life-support system can be fed by simply shoveling dirt into them.
• The proximity to earth means that resupply and even rescue is comparably easy. If any disaster befalls your base, you only need to hold out for half a week before help arrives.

By now I've probably talked you into building a shipyard on the moon. Shipyards need workers, workers need medics, both need chefs... You get the idea. Building a lunar shipyard means building a lunar colony, and vice versa. The same applies to any large-scale asteroid mining operation, with just a few minor tweaks to the details.

• I'm pleased to see that answer. Last paragraph yea, I would say there are some options, specially I would build shipyard on moons orbit. But what you describe is also possible. – MolbOrg Nov 1 '16 at 5:44
• "Building a lunar shipyard means building a lunar colony..." Not necessarily, depending on what you mean by colony. You could just have an industrial base, like an oil rig (or like the massive installations on Pacific islands during WWII) that rotates workers in and out, and depends largely on supplies from Earth for survival. – jamesqf Nov 1 '16 at 18:38
• @jamesqf If reliance on imports is what makes or breaks a colony, then every nation on earth is just a very, very large island outpost. I get your point, though - It's a pretty big jump from having 1 year crew rotations to having a home-grown population. Look at it this way, though. They're probably going to grow their own food (Because feeding a mere 6 people on the ISS is already a logistical strain), be building most of their own spare-parts, have hospitals to treat the sick and injured, ect. They're only missing schools and children, and unless it's an all-male base, they'll have children. – UIDAlexD Nov 2 '16 at 13:41

Like others, my opinion is an unequivocal yes.

There are two major classes of reasons I see for it: time and money.

Travel is not easy. Typically speaking, the further you go, the harder it is. It's far easier for you to crash at a friend's house than it is to go to a foreign country and try to live there. Using current technology, this is rather monotonic. It's easier to get to Pluto than it is to get past it. Technology could change that. If you developed a fictional warp capability that could be used from Earth orbit, but which could not travel to anywhere closer than 1 light year, then you may come into cases where an interstellar trip consumes fewer resources than the interplanetary one.

The other reason is related to the time it takes to travel. The further you are from your parent, in terms of time, the more independent you must be. If something goes wrong on a Pluto colony that will destabilize the entire colony in 50 years, Earth can send aid to Pluto. If you're 50 light years away, and the same event happens, you can barely let Earth know the event occurred before you are dead.

The one counterexample I can see is if we find out that it is technically impossible to colonize other planets, for some yet-unknown reason, but we find an exoplanet that is sufficiently like Earth to permit life. We don't fully understand what is required to maintain Homo sapiens colonies in the long term yet. There may be some subtle factor that we simply do not yet understand. If one existed, then we may skip the planets entirely. This would not be unlike us skipping Mercury as a colony, because it's simply too hot to support life. We'll probably have interstellar colonies before we have living colonies on Mercury -- though don't count them out! Scientists are clever people!

I'm afraid I'll buck the trend and say no.

No one will care to make a city on pluto. The reason it was dropped from planethood it is not much more interesting than a number of things out where it is. This is likely to still be true when we have the choice of going places. And it's not like there is a shortage of places to go in the solar system.

While the the expected cost and technical hurdles of making and launching a self contained environment to another star are astronomical, getting a person to pluto and returning also has an expected cost too big to mean anything. And much less reason to try.

If you have the ability for a person to spend tens of years in space it would require to try for pluto without the mindboggling power of constant 1G acceleration it doesn't seem to be that much of a stretch to try for the hundreds of years to get to nearby stars.

• Interesting information. If any kind of safe synthetic organism, robot, AI, can be sent to another planet to multiply itself, humans will send it to the other planet as backup and to find resources. AI can design transistors for itself in most environments, preferably cold planets with some metals. Even if pluto is not a choice habitable planet, it can have some use as a way station, and can prehaps support aquaculture using it's vast light element reserves. – aliential Nov 1 '16 at 12:17
• It may be we release Van Nuemann machines out into the solar system, though Asimov's arguments against ring true to me. If we do that just means people won't be needed at all on uninteresting places. And if our robots are bothering with the ort cloud we probably have so much resources from the easier mining sites that sending missions out of the solar system is not that big a deal. – user25818 Nov 1 '16 at 12:42

I have to say no, depending on what exactly you define as a colony. If you just mean a base that gets regular support from Earth, like an oil rig or Antarctic research station, then that's fairly easy. But if you mean an actual colony, which I define as being capable of supporting human life indefinitely without support from Earth, then that's so difficult that we aren't really able to appreciate the scope of the problem.

Take for instance "cities on Pluto". Well, you can't have cities without (at the very minimum) an agricultural hinterland to support them. Agriculture in turn depends on a complex ecosystem, and we've no idea how to artifically maintain one of those. Perhaps if Mars could be terraformed, or large lunar craters could be roofed over, we could establish working ecosystems, but either of those is a massive task.