If humanity decided right now that they wanted to become a space empire and colonize the entire solar system would they be able to do it? One of the biggest problems with theoretically colonizing Mars is lack of funding and lack of fuel. Assuming that all of Earth, suddenly and universally, agreed to focus solely on colonizing the solar system (this includes Mars, all moons, all Lagrange points and ships to defend it all), would the Earth have enough fuel to accomplish this?

For clarification I am asking if all the fuel on Earth is enough to travel around an empire the size of the solar system.

  • 5
    $\begingroup$ First step is to build a massive space station, it is terribly inefficient to move things on/off planet. $\endgroup$ – Jared Smith Jul 6 '16 at 17:52
  • 6
    $\begingroup$ You have to define "fuel". Whatever fuel you pick, Earth is likely not the bottleneck; getting it into orbit and/or storing it on your vessel is. $\endgroup$ – chepner Jul 6 '16 at 19:03
  • 6
    $\begingroup$ "Ships to defend it" We would only need to maintain a token fleet with primitive projectile weapons. I doubt any colonies would be able to support their own infrastructure and armed resistance for centuries. Essentially factor defense out almost entirelyu imo. $\endgroup$ – JDSweetBeat Jul 6 '16 at 19:42
  • 15
    $\begingroup$ Defend from whom? Are there aliens in the picture? How advanced are they? If they're human rogues, how many? $\endgroup$ – Emilio M Bumachar Jul 6 '16 at 20:02
  • 5
    $\begingroup$ Given that large fusion reactor in the center of the system, fuel/energy is no issue at all - given enough time, we could do anything. That said, what is the timeframe for your question? Colonizing the Solar system in 1 million years is much less impressive. $\endgroup$ – Chieron Jul 7 '16 at 9:21

11 Answers 11


It's not the fuel or even energy. Just money.

There's no shortage of the components of rocket fuel. It takes energy to convert them into rocket fuel but we have that in plenty. If money were no object we could build solar or nuclear power facilities to generate as much rocket fuel as we want.

The primary thing stopping our expansion into the solar system is the cost of launch. When NASA was launching shuttles it cost $10,000 to launch a pound of cargo into orbit.

Once you're in orbit it's pretty smooth sailing (it takes months to get anywhere but a gentle thrust will do and that does not take an insane amount of fuel) there are all kinds of low reaction-mass propulsion systems

  • Ion drives
  • The new EM drive which nobody can explain but which seems to work
  • Solar sails sound dumb but work fine

So lets work on the Cost of launch. My favorite quote from one of the scrappy new rocketry pioneers was:

Rockets are built by hand by people with phds


  • Reusable rockets (Spacex has successfully landed first stage rockets 4 times)
  • Cheaper rocket assembly (this should happen naturally now that commercial spaceflight is taking off)
  • More seat of the pants design decisions (NASA's engineering is triple redundant which is great but we can accept more risk and move faster, cheaper and ultimately get better results) Armadillo aerospace is the poster boy. I believe Carmack once diagnosed a problem wrote a fix and pushed the patch to a rocket in mid-flight.

Alternate launch methods

  • High G launch with a space gun (bad for humans, fine for water dirt, steel rods)
  • Of course space elevators I suspect the first one will get blown to crap. I mean seriously imagine you're a terrorist that thing is going to look like the biggest target in the world.

Reduce the number and weight of things you need to launch: Raw materials food water/air

Sustainability: Ultimately you'll want to bootstrap mining and manufacture in space. (this is probably the point when you know you can colonize the solar system)

Sustaining life Food production in space Water harvesting in space Waypoints would really help (imagine how boring the martian had been if there had been a habitable terrarium and emergency shuttle in orbit before anyone went down to the surface)

  • $\begingroup$ Ha, commercial spaceflight taking off. $\endgroup$ – JesseTG Sep 8 '16 at 6:46
  • $\begingroup$ Couldn't resist the pun. $\endgroup$ – jorfus Sep 27 '16 at 22:22

As a common rocket fuel is Hydrogen and Oxygen, Earth definitely has enough fuel given the large quantities of water present.


Given any electrical source, Hydrogen and Oxygen can be separated and stored as cryogenic rocket fuels.


This would require a large amount of energy, but given the motivation it could be done.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Jul 8 '16 at 3:31
  • $\begingroup$ Josh, could you expand this answer a little? It sounds like you're saying we have ample ingredients to make fuel, but it'd help if you could connect the dots. If we have the ingredients but lack the ability to turn them into the needed fuel that doesn't help, after all. (I'm not saying we can't; I'm saying it would be better if your answer spelled it out.) Thanks. $\endgroup$ – Monica Cellio Jul 8 '16 at 3:33
  • $\begingroup$ @MonicaCellio It's quite easy to get hydrogen and oxygen out of water - just apply an electric current. This is taught in most introductory chemistry courses, but I agree that it being added to the answer would be helpful. $\endgroup$ – user14624 Jul 8 '16 at 3:41
  • $\begingroup$ High electrical energy demand industries are usually set up in areas with abundant energy supply. It is for this reason that aluminium refinement which is also electrolysis) happens in Iceland where there is abundant geothermal energy. There is enough energy in the planets core to keep generating electricity at high rates for centuries. If we needed it that could produce fast amounts of rocket fuel. Nuclear plants, hydro dams, wind farms (near the sea or rivers) could all also do this for decades per plant. Economics limits us, not fuel. Your petrol car will run out before your rocket. $\endgroup$ – TafT Jul 8 '16 at 10:35
  • 1
    $\begingroup$ Since electeolysis of water for rocket fuel does not need constant stable energy source, solar, wind etc energy sources would work very well (solar can also be used directly). So energy is not a problem. Also, generally best launch latitude is equator, which incidentally gets most solar power too, so if World was united for this, we'd have essentially unlimited fuel near launch sites. $\endgroup$ – hyde Jul 8 '16 at 11:29

The term "fuel" is actually very nonspecific. If I decide that NERVA derivative engines are the way to go, then the bottleneck is how much Uranium or Plutonium fuel I can access for the rocket motors, while using Kerosene and LOX has a different set of bottlenecks. Laser thermal launchers like Liek Myrabo's Lightcraft concept is different altogether, now the limiting factor is electrical energy to power the launch lasers.

Going to non rocket forms of launch like a space elevator or a Lofstrom Loop is a different technology and a different set of issues.

What is really needed is a definition of what the ultimate bottleneck is, and that is energy. The Earth receives something like 175 Petawatts of insolation during aa year, which is more than sufficient energy to create a space empire, or indeed anything at all that we want, and once we escape from Earth, the amount of energy we can collect is limited only by the annual energy output of the Sun.

So the first step of all is to ensure that we can efficiently access and manipulate the energy that we receive from the Sun, and then put it to good use. It is possible tat in the far future, we might even consider something like this: http://nextbigfuture.com/2016/02/physics-phd-reader-of-nextbigfuture.html

  • 4
    $\begingroup$ petawatt is a unit of power, not energy. either you receive 175 petawatts.hour over the course of a year, or you receive 175 petawatts at any given moment. (which in a year amounts to much much more watt.hours). $\endgroup$ – njzk2 Jul 6 '16 at 20:05
  • 1
    $\begingroup$ Sure, but how much of that is needed to keep the Earth in a good shape? Heating the air, ocean, ground. I'm just saying that it would be a bad idea to cut off that energy flow. We might regret that in the future when we realize that "Oops. Turns out that energy from the Sun was actually used for the whole ecosystem." $\endgroup$ – pipe Jul 6 '16 at 20:07
  • 2
    $\begingroup$ @pipe a large part of the energy that we harvest from the sun is quickly re-transformed into heat. (as long as it is used within the atmosphere). The rest is turned into heat as well, just more slowly $\endgroup$ – njzk2 Jul 7 '16 at 0:31
  • 1
    $\begingroup$ @njzk2 Yes, so it would be a bad idea to ship all of that energy off-planet in the form of high-energy fuel, because that would result in global cooling and we'd freeze to death. $\endgroup$ – user253751 Jul 7 '16 at 0:48
  • 1
    $\begingroup$ @pipe I think we'd rather have the opposite problem - capturing the incident solar energy and using it for work will be much more efficient at heating the planet, rather than cooling it. Don't forget that huge amounts of the incident sunlight is sent back to space due to the rather high albedo of Earth - quite efficient at avoiding heating, since the atmosphere is quite transparent to that. On the other hand, capture the light in a solar cell, use it to e.g. power cars, and you only emit infrared light - and the atmosphere is much less transparent to that. $\endgroup$ – Luaan Jul 7 '16 at 8:22

Nevermind fuel, how about all the advanced composite materials needed to build the spaceships?

Unless we find another source within our solar system, or accept that we will be getting around using solar sails, and taking years and years to get anywhere, no, humanity will not expand across the solar system.

  • $\begingroup$ I agree, also for Right Now I think fuel is a minimal worry. People are still trying to figure out how to colonize Mars successfully, let alone traveling into deep space to colonize something else. I'm sure with the world united it would speed up the process, but I think there are bigger hurdles than fuel as of Right Now. It could be another 50 years even with a united world for all we know to successfully colonize another planetary body for all we know. $\endgroup$ – Timmy Jul 6 '16 at 19:50
  • 2
    $\begingroup$ advanced composite - you mean aluminium lithium alloy? Since when carbon based materials and products of organic synthesis are rare and problem? We maybe produce them not very much efficient, and some not in greater quantities - but that's problem not of sources, but perfection of production. $\endgroup$ – MolbOrg Jul 6 '16 at 20:11
  • $\begingroup$ Advanced solar sails like the ones K Eric Drexler investigated as far back as 1975 could make high speed solar sailing very feasible. Indeed, some designs could reach Pluto in @ 3.5 years. The problem in that case is slowing down.... $\endgroup$ – Thucydides Jul 7 '16 at 4:38
  • 1
    $\begingroup$ @Timmy Why would you think a united world would make this easier, out of all things? The last time I checked, peaceful competition is the most innovative part of the world's economy, while the violent centralised "companies" are lagging far behind (e.g. state post, state transportation...). All we really need is public and private interest - something that gives us a good enough reason to go "out there", a good enough return on the investment. And right now, the only real interest in e.g. estabilishing a Mars colony is almost entirely academical (don't get me wrong, I love the idea). $\endgroup$ – Luaan Jul 7 '16 at 8:31
  • 1
    $\begingroup$ @Thucydides ... In space, you don't "reach" your destination, unless you can stop at it. :) $\endgroup$ – Seeds Jul 7 '16 at 16:54

More than enough.

If we were to start to colonize the Solar system, we've got an entire star's worth of energy to tap, and nearly a planet's worth of material in the Asteroid Belt to mine. The only things we really need earthbound resources for are getting a few loads of people and equipment out of our gravity well, and we are doing that fairly regularly today.

Additionally, there are energy resources we have here on earth we are only just beginning to figure out how to tap. There have been studies of using nuclear (fission) propulsion (whose main drawback appears to be popular fission-phobia). If/when we get Nuclear Fusion worked out, then we'd have access to an order of magnitude more energy output than that. And that's before you bother to get out of our gravity well and start mining our star and/or other local solar system sources for material.

There has even been some thought into trying to get more power than that via matter-antimatter drives, but we've currently got no driving need to spend the resources required to work out how to do it. If you're postulating that we suddenly would have that driving need, then more exotic solutions like that suddenly become a possibility.


Probably not.

But that's not as bad as it sounds: the main incentive to go build a space empire is precisely to access new resources. So the question becomes: do we collectively have enough resources on Earth (energy and materials) to access new resources to keep pushing the boundaries?

And this time the answer is probably yes.

Note: the answer could be different in twenty or thirty years. there's a minimum resources investment to get those extraterrestrial resources.

  • $\begingroup$ Based on what? There's no shortage of any of the constituent parts of rocket fuel. Launching cargo into space is super expensive but not because we're lacing the raw materials. $\endgroup$ – jorfus Jul 7 '16 at 22:24

You're asking the wrong question.

In order to get a payload out of Earth's gravity well, you need pretty hefty amounts of propulsion.

At the moment the only reliable way of achieving this is by rockets, which yes, require fairly vast amounts of a limited resource (fuel) to make the trip. This may not be sustainable.

Once you're out of the gravity well, you can generally get by with much smaller amounts of propulsion by substituting good math, physics, and some patience.

A better question might be "What technologies would need to be developed for Earth to become a solar empire?" to which the first answer would be "a better way of moving heavy stuff from surface to orbit, preferably one that doesn't require setting off barely controlled explosions." and work your way back from there.

  • $\begingroup$ We do have unlimited amounts of fuel - liquid hydrogen and liquid oxygen are used today to lift rockets. Of course, you need lots of energy to create and compress this fuel from air and/or water, but we (technically) have unlimited amounts of that from the sun. - but you're still right, we need better technologies to efficiently use this in greater quantities. $\endgroup$ – gbjbaanb Jul 7 '16 at 23:21
  • $\begingroup$ @gbjbaanb The amount of hydrogen and oxygen we have on Earth is finite, as well as the energy output from the Sun. Anytime that the phrase "unlimited energy" is used, that's a sure sign that something's fishy. $\endgroup$ – user14624 Jul 8 '16 at 3:45
  • $\begingroup$ @Mego unlimited as far as we're concerned. the sun spits out all that energy, and will continue to do so whether we harvest it or not. And when the sun stops doing so, we'll have other problems. As for oxygen and hydrogen. fundamental elements like that don't get "used up", we haven't developed nuclear fusion yet. $\endgroup$ – gbjbaanb Jul 8 '16 at 15:59
  • $\begingroup$ @gbjbaanb The sun outputs a finite amount of energy per unit of time. That's a far cry from "unlimited". And unless you're planning on capturing the water created from combusting the hydrogen and oxygen and separating it back via electrolysis (which would run an energy deficit, because you use more energy to electrolyse water than you get back from combusting the hydrogen and oxygen, not to mention the energy required to liquify the gases for use in a rocket engine), the hydrogen and oxygen are also finite. $\endgroup$ – user14624 Jul 8 '16 at 16:05

You need fuel only to move out of the atmosphere not to move in space, so yes probably the fuel is enough to colonize a new planet but not to move too many people from this planet, cause more people make rockets heavier which results in consuming more fuel.

But technically yes if you send ships with everything needed to survive and maybe 20-50 people per ship it would be enough to colonyze the entire solar system

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Jul 8 '16 at 3:51

In addition to the ocean, which is full of hydrogen and oxygen, we also have a giant fusion reactor already operating at the center of the solar system, and enormous reserves of hydrogen in multiple gas giants.

There is absolutely no shortage of fuel available.

We just have to decide to take advantage of it, and to continue to improve our engineering so that it is cost-effective to do so.


Just develop effective nano robots with self-replicating ability and put them on ships people've already sent all around Solar system. Then manage them to gather more resources and build colonies with climate suitable for people.

Mankind need just more knowledge, not energy.

Mankind is a quite stupid mind who doesn't know that Earth is round for a few thousand years. And after some similar discovering, people become so proud about their abilities, so most of them consider proven that God does not exist. Epic idiots.

People need knowledge, not brute force energy.


The biggest unknown aspect to colonizing the solar system is radiation and gravity.

What are the long term effects of 50% gravity? 33%? Can a human survive to reproductive age being born in an environment with higher background radiation than earth? We don't know. Only the men who went to the moon have ever been outside the magnetosphere so that is like 2 dozen examples for a week at a time. What are the health effects at 30 years?

For reference, If humans can live on surfaces with 30% or more of earth's gravity, that limits colonization to Venus, Mars and Mercury and none of the moons. If we can't live outside a magnetosphere, that eliminates the above planets and limits us to space stations in Earth orbit, near Ganymede and Callisto (the inner Jovian moons have very high radiation levels originating from Jupiter), within close orbit of Saturn, Uranus and Neptune.

  • $\begingroup$ we can live outside magnetosphere by creating it around ship(station), if it's needed, in same way we create magnetic field in other applications. If they bothered to build stations, they probably bothered to create magnetic field and layers of radiation protection. Also OP is asking about fuel consumption needed for travel in that solar empire, comparing for those fuel volumes which exists on earth. There is no rush in answering old questions, u have time to think about subject, and try to answer OP's question. Your current answer is more like premise to real answer. $\endgroup$ – MolbOrg Jul 26 '16 at 21:21
  • $\begingroup$ The OP asked, " If humanity decided right now that they wanted to become a space empire and colonize the entire solar system would they be able to do it?". The earth has a ~.5T magnetic field surrounding the entire planet. How do you propose creating that with modern technology? If you get to space there are four planets that are literally made of fuel. Fuel is not a problem. The unknown constraints of human physiology are. $\endgroup$ – kingledion Jul 27 '16 at 1:22
  • $\begingroup$ Earth's magnetic field Its magnitude at the Earth's surface ranges from 25 to 65 microteslas, There is scale of magnetic strength for different objects. Also from OP's - For clarification I am asking if all the fuel on Earth is enough to travel around an empire the size of the solar system. Overall quality of question is't so great, although it might have sense in some cases, even with planet masses used as reactive media, but look's like not OPs case. $\endgroup$ – MolbOrg Jul 27 '16 at 1:47
  • $\begingroup$ That should have been Gauss, not Teslas. Also, a refrigerator magnet may be stronger LOCALLY but obviously it is not protecting the earth from radiation. From here you can get an idea of how powerful such a magnet must be. It is not technically feasible. Also, it can be the correct answer to tell the OP that his is asking the wrong question. $\endgroup$ – kingledion Jul 27 '16 at 2:00
  • $\begingroup$ First value column is teslas, second is gauss - 1T == 10000Gauss. So 50mkT == 50e-6T == 0.000050T == 0.5Gaus. Ship usually is less then planet, way much less. But more important energy of magnetic field is proportional to volume of that field (which energy we calculate), so in cases we talk about ordinary 30km diameter ship, energy of magnetic field will be 1/400^3 (approximately, lazy to calculate atm and it depends). More important is that magnetosphere shield not radiation, but leakage of water and atmosphere of planet. Van Allen belt radiation isn't usual radiation for space, MS is a trap. $\endgroup$ – MolbOrg Jul 27 '16 at 3:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.