# Which heavenly bodies have stuff to make rocket fuel?

Which planets or large moons of our solar system are currently known to have the raw materials needed for us to produce rocket fuel?

Where else is already known to have what we need, readily available?

By "readily available", I mean that the material is lying out freely on large areas of the surface (like the lakes on Titan) or is available throughout the atmosphere at the surface (like on Mars) so that no searching or mining is needed.

By "rocket fuel", I mean the material used to launch a liquid-fueled rocket from the surface of that planet/moon.

By "planets or large moons", I mean roughly those bodies that are in hydrostatic equilibrium. (Since there are only 40 or so in the solar system, this can't be a very long list!)

To start off, literally everything can be used as rocket propellant. For a more practical approach though, water is a good resource for making hydrogen and oxygen.

In the Inner solar system we have water on Mars, bound as ice on the poles, and buried just under the surface in some places.

Ice on Mars

Recent findings by the Clementine Lunar Orbiter strongly suggest water in cold traps in the polar regions of the Moon. Ideas about mining the water of the cold traps is often combined with using the peaks of eternal light as the required energy source to crack the water.

As for the outer Solar system, most small objects partially consist of ice.

You also mention producing methane and oxygen from carbon dioxide, using imported hydrogen. This is good for planets with a carbon dioxide atmosphere, like Mars and Venus.

Even for bare rock bodies without an atmosphere, there are still options, like producing solid rocket fuel from aluminium. Other commonly occurring metals like iron or calcium may also be used.

If you are not so strict about "fuel", just propellant, there have been proposals for scooping the atmospheres of the gas giants. This may not be feasible due to the high delta-v required to climb out of their gravity wells.

Hydrogen, and maybe more important, water may be useful for a NTR, especially since you do not have to electrolyse the water before use.

Rocket fuels does in essence just require a chemical process producing a significant amount of energy and gasses, and NTR propellants are just anything liquid you can pump through your engine. (John Clarke even mentions mercury in his book Ignition due to its high density impulse).

A good site for learning about rocket propellants and ISRU is Winchell Chung's Atomic Rockets.

For an informal introduction to rocket fuel I recommend this video by Scott Manley:

When mass is hard to come by, like in empty space, other methods are used, for example using a sail to let the Sun push you. In interstellar space without any strong light source, methods for collecting the extremely low density interstellar clouds of hydrogen have been proposed.

• It's clearer and easier to just press enter twice to create a new paragraph rather than use <br>. Could you mention where that photo of the ice in a crater is from, for clarity? – kim holder wants Monica back Dec 15 '15 at 15:55
• Add interstellar space with scarce hydrogen for Bussard Ramjet. – SF. Dec 15 '15 at 15:55
• @kim holder Too used to HTML formatting. You can actually just hit enter? – Hohmannfan Dec 15 '15 at 16:03
• @SF Not sure if broadening it more will do any good. I is broad enough as it is! Also the question specifically says planets and moons. – Hohmannfan Dec 15 '15 at 16:14
• @Hohmanfan: Yes, but it also currently covers all semi-viable propellants that way. If one adds light propulsion (solar sail, mirror array), we have about all bases covered. – SF. Dec 15 '15 at 16:27

The "readily available" aspect of the question seems to need gas or liquid resources on the surface of the planet or moon, rather than solid materials that would need to be mined. In that case the list is quite small:

• Earth -- lots of water lying around that can be electrolyzed into hydrogen and oxygen. Occasional deposits of a variety of high energy compounds isolated by local lifeforms (who may object to you trying to use them without paying)
• Mars -- has atmospheric $$CO_2$$ which can be electrolyzed in the right solvents to produce carbon monoxide and oxygen. This isn't a great fuel, but it might suffice for Mars escape (see this question). Venus also has lots of $$CO_2$$ but too much gravity for carbon monoxide to get you into space sensibly.

If you allow yourself to mine and melt water ice, or drill a few km through a surface crust for liquid water, then the list gets a lot longer.

• Mars has ice, so you can make methane and oxygen or hydrogen and oxygen
• Ceres and EUropa have icy surfaces and subsurface oceans
• Ganymede, Callisto and Titan have icy surfaces and (probably deep) subsurface oceans. Titan also has surface hydrocarbons so you just need ice as an oxygen source
• Many comets and other moons are probably icy as well

There are also cases where you only have import some of your fuel. For Mars or Venus, if you import hydrogen (which is relatively low mass) you can react it with $$CO_2$$ to make methane and oxygen. For Titan you would only have to import oxygen.