Of or traveling between moons.

I'm (as far as I can tell) inventing the term interlunar to describe travel between moons in a single planetary system.

Travel between

  • Stars = Interstellar travel
  • Planets = Interplanetary travel
  • Moons = Interlunar travel (within the same planetary system)
  • Asteroids = Interasteroidal travel (within the same asteroidal group, e.g. Trojans)

Normally I think the word "Lunar" implies Earth's Moon (Luna) but I think we can control this through capitalization (capital Luna = Earth's moon, small luna = any moon).


  1. Ignore life support requirements for the moment.
  2. Assume a technological civilization develops on one of the moons of Saturn.


What is the minimum level of rocketry technology (perhaps type of rocket capable of performing the task?) required to support a civilization that spans the breadth of Saturnian moon system?

If you can, try to equate that to a year of human technological development (e.g. liquid fueled rockets developed by Robert Goddard circa 1926).

  • $\begingroup$ I can't help but think you also have to consider what level of tech is needed to extract rocket-fuel-materials in large volumes. Here on Earth we seem to have been able to find/discover/create fuel without much of an issue, but what if an explosive fuel was very very rare on your home moon? $\endgroup$
    – JPhi1618
    Oct 7 '15 at 22:22
  • $\begingroup$ I worry more about the ionic and electromagnetic environment around Saturn... "Relatively speaking, MeV ion and electron weathering is most important closer to Saturn, e.g. at Janus and Mimas, whereas keV ion weathering is most important farther out, at Dione and Rhea." from the abstract of people.virginia.edu/~rej/papers08/paranicas-icarus08.pdf $\endgroup$ Oct 8 '15 at 0:21
  • $\begingroup$ I think of the Saturnian system as "benign" but that's benign in relation to the Jovian system. That's one reason I asked to ignore environmental / life support considerations for the moment. My actual thought was a life form adapted for life under water. Meaning perhaps the ship's environment possesses enough water habitat to protect the crew. But I don't really want to tackle that aspect yet :) $\endgroup$
    – Jim2B
    Oct 8 '15 at 2:39
  • $\begingroup$ "Luna" is not the name of our moon. The name of our moon (according to the IAU, who is responsible for such things) is "The Moon". $\endgroup$
    – corsiKa
    Oct 8 '15 at 19:20
  • $\begingroup$ "Luna" is the Latin word for "Moon" $\endgroup$
    – Jim2B
    Oct 8 '15 at 21:30

Out of Saturn's 62 moons, only 13 are larger than 50km. Titan is by far the largest one and along with the next 6 largest moons accounts for over 99% of the combined mass of all moons. So let's focus on those 7 major moons. 5 of them are relatively close to Saturn, within 500 000 km, which is roughly comparable to how far the Moon is from Earth (384 000 km). Titan is a bit farther out - 1 220 000 km from Saturn, but only about half that from Rhea. I would expect that with Apollo type technology, you can put and sustain exploration stations on those moons and eventually inhabit them.

Since those moons are not very massive, you won't need super powerful rockets and should be fairly cheap to fly resupply missions between them. Moon's gravity is 1.622 m/s^2, compared with 9.8 m/s^2 for Earth. While Titan is almost twice as heavy as the Moon, it's still 4 times less than the Earth. The next largest moon Rhea is only 1/25 of the Moon's mass so there is virtually no gravity to overcome. A Saturn V rocket (which were used for Apollo) can deliver 48 600 kg payload to Moon orbit, so between those moons you'll be able to move enormous amounts of cargo very cheaply.

It's totally plausible for a civilization with 1970s type of tech to spread out through those moons similarly to how the pacific islanders spread through Polynesia. This scenario works even better if you take into account all the other smaller moons and use them to hop between the larger ones. You don't even have to have a rocket, you can drive a ground vehicle up a ramp and launch it in space. You can imagine "people" living in caravan like habitats that can just speeds up a hill and fly off into space on it's way to the next moon.

I ran a couple of quick calculations and came up with escape velocity for Rhea of 96 km/h (compared to 11.2 km/s for Earth), which is just about 60 mph.


Travelling between the moons is not going to be the hardest part, surviving on them is the problem. As ventsyv's excellent answer says even low power rockets and 1970's tech could handle travelling between moons in orbit around one planet.

However surviving on them is a far bigger challenge. We still don't know now how to make a stable enclosed ecosystem viable in the long term. You somehow need to shield people from radiation, deal with health issues from microgravity, grow food, run industry, etc.

To realistically do that you are going to need technology well ahead of the 70's in areas like robotics, automation, networking, agriculture, genetic engineering, etc.

With enough resources thrown at it we could do it now, and could probably have done it in the 90's. I'm not convinced it would be possible before then though.


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