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Living in space is pretty dangerous, and the wonderful people of the ISS float around the Earth at risk of radiation and micrometeoroids. I'm curious if they're any more safe than if they simply were on a base on the Moon. It seems to me the same dangers apply, but far more can be done with the microgravity and potential resources on the Moon.

If it is more dangerous, how much more and in what ways? And if the danger isn't that much different, why aren't NASA/ESA/Russia doing it?

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Here are a few reasons, probably not the only ones:

  • Radiation. The Moon isn't protected by Earth's magnetic field, so it gets more radiation. This isn't good in the long term. Also, radiation shielding is heavy. Aluminium just won't do it. The ISS gets protection from the magnetosphere but not from the atmosphere, so the astronauts still get 1 millisievert per day - 5x as much radiation as on jet aircraft and 365x as much as on the ground.
  • If something goes wrong, home is quite a long way away. The Apollo missions took a few days to reach the moon and a few days to come back. If something goes wrong on the ISS, the astronauts can get into a Soyuz capsule and be on the ground in a few hours (it's only ~300km away from Earth).
  • Added difficulty of having to land on the Moon. A few probes have crashed attempting to do so (e.g. Luna 15). It may be that the techique is perfected by now.
  • Two weeks of complete darkness, every month. The ISS orbits the Earth in just over 90 minutes, so it switches between day and night very quickly. This is not the case for any object on the surface of the Moon. As a result, solar power is probably unusable (this was a problem for the Jade Rabbit rover), you would have to use some form of nuclear power such as that used by the Curiosity MSL rover.
  • Toxic moon dust. It was found in the lungs of Apollo astronauts (because the way they would get into their lander after an EVA was to go in, close the door, pressurise, and take off their dust-covered suits). A possible solution would be a combination of docking port and spacesuit.
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    $\begingroup$ Oh, I forgot about the 2 weeks of darkness! So the ISS is protected by the Earth's magnetic field? I wasn't sure how protected because of some things I had read about potential solar storms which could be a problem for people on board. $\endgroup$
    – simontemplar
    Commented May 30, 2014 at 7:37
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    $\begingroup$ @simontemplar The ISS is protected by the magnetic field but not by the atmosphere (which also blocks things) - it orbits in the atmosphere's upper layers. The astronauts get as much radiation per day as people on Earth get per year - this results in lowered immunity, occasionally things like cataracts. Passengers on jet aircraft typically get 0.2 millisieverts of radiation per day (and they only spend 1 to 20 hours on the aircraft) which is still 5 times less than on the ISS. en.wikipedia.org/wiki/ISS#Radiation... xkcd.com/903 $\endgroup$
    – user3405
    Commented May 30, 2014 at 7:43
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    $\begingroup$ Another danger on the Moon is the [dust][1]. It was found in the lungs of the Apollo astronauts, but a [suitport][2] might solve that. Dust might've jammed the foldable solar panels of the Chinese rover [1]: universetoday.com/96208/the-moon-is-toxic [2]: en.wikipedia.org/wiki/Suitport $\endgroup$
    – LocalFluff
    Commented May 30, 2014 at 8:10
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    $\begingroup$ As user6297 pointed out, there's plenty of regolith available for radiation protection.It's possible people at a lunar base would endure less radiation. He also pointed out there are polar plateaus that enjoy nearly constant sunlight. $\endgroup$
    – HopDavid
    Commented May 30, 2014 at 14:12
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    $\begingroup$ Moon rock dust may be toxic, but it makes a great Portal conductor surface! $\endgroup$
    – Mason Wheeler
    Commented May 17, 2015 at 0:54
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If it is more dangerous, how much more and in what ways?

Proffesorfish and Eli Skolas have both given thoughtful answers comparing the hazards of I.S.S. vs Moonbase. If humans were preceded by robots to establish infra-structure, I believe a moonbase could be less hazardous. Radiation shielding from local resources could be added to Bigelow habs. At the poles there may be volatiles that could be harvested for life support as well as propellent.

Now for the second part of the question:

And if the danger isn't that much different, why aren't NASA/ESA/Russia doing it

We don't have a moon base because it's a lot harder.

The biggest difference between I.S.S. and a lunar base is delta V. It takes 9 km/s to reach the I.S.S. and 15 km/s to reach the lunar surface. At this time there's no infra-structure and thus no propellent available at the lunar surface. So another 3 km/s must be added for the return trip. An 18 km/s delta v budget is vastly different from a 9 km/s delta V budget.

A capsule from the I.S.S. re-enters at 8 km/s and one from the moon would re-enter earth's atmosphere at about 11 km/s. More robust structure and thermal protection would be needed.

Also a lunar soft landing is a lot harder than rendezvous with the I.S.S.

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    $\begingroup$ Considering we have already sent people to the moon and back before, the technology is there (and 40 years old). What you are basically saying is 'It's more expensive'. Still a valid reason though. $\endgroup$
    – Aeolun
    Commented Jun 1, 2014 at 3:46
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    $\begingroup$ The Apollo program was estimated at $109 billion and gave us 6 landings. That's 18 billion a landing. And those are just six sortie missions. Establishing a base would be much more ambitious. I believe establishing a moon base is something that could and should be done. But building a base with Apollo style rockets is cost prohibitive. $\endgroup$
    – HopDavid
    Commented Jun 1, 2014 at 5:50
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    $\begingroup$ Musk correctly notes spaceflight is expensive because of throw-away vehicles. Imagine what a plane ticket would cost if we trashed a 747 each trip. If Musk succeeds in easily reusable craft, that will change the game. $\endgroup$
    – HopDavid
    Commented Jun 1, 2014 at 18:49
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    $\begingroup$ I expect Musk to succeed with reusable boosters. But it looks like the upper stage will have a delta V budget of 8 km/s or more. With that sort of delta V budget you have a difficult mass fraction. More propellant and less dry mass leaves you with what I call a fragile cellophane and gossamer spacecraft. It's hard to imagine an upper stage that could survive re-entry. $\endgroup$
    – HopDavid
    Commented Jun 1, 2014 at 18:53
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    $\begingroup$ The Apollo program, besides just building and launching ships, also designed and developed many different technologies. That those costs were amortized over only six missions was unfortunate. However, the program built (but didn't fly) another three moonships; components for Apollo's 18, 19, and 20 were all built, but Pres. Nixon scrapped the flights. Although the flights would have cost money, building three more Command and Service Modules, Lunar Landers, Saturn Vs, Lunar Rovers, etc., cost, too. Some parts went to museums, others went to Skylab and the Apollo-Soyuz joint mission. $\endgroup$
    – Eli Skolas
    Commented Jun 1, 2014 at 22:35
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ISS and a Moon base are equally safe. As long as they don't suddenly explode or otherwise become death traps because of some technical malfunction in the human artefacts themselves, regardless of the space environment.

Among all the innovative suggestions about what could be dangerous, I want to remind of the fact that the only thing which has killed astronauts thus far, is technical malfunction! That goes for all the 18-19 who died in space (or rather, in Earth atmosphere during launch or reentry!) as well as for all the 5 astronauts (which I know of) killed on the ground during space specific training. Add to that a few of the about 500 who have been in space, are said to suffer lasting but minor health problems from microgravity.

Instead of a ton extra launch mass for increased radiation shielding, maybe a ton extra of redundancy for technical systems has a much greater life saving effect?

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    $\begingroup$ That's a good point, but conversely, note that these high survival rates aren't because we ignored all the threats either. It so happens that we protect from most of dangers either technologically or procedurally (and most commonly both). And yes, both technology and people, sadly, sometimes fail. I wouldn't want to comment on which of the two happen more frequently or why because I'm not qualified to do that, but I can imagine what e.g. Richard Feynman would have to say about it. But past success rate of doing X doesn't really guarantee future success rate of doing Y even if X ⊂ Y. $\endgroup$
    – TildalWave
    Commented Jan 23, 2015 at 17:25
  • $\begingroup$ @TildalWave 12 astronauts walked on the Moon. I understand that they beat the average American lifespan after that. Without any Moon related health problems from radiation, dust or whatever. 3 Apollo astronauts were nearly killed because of a technical malfunction in Apollo 13. The nuts and bolts made on Earth is obviously the totally dominating source of risk. And that risk is about as high on Earth as in space, as Apollo 1 shows. They were lost because of failure in their spacecraft prototype, not because of any space environment. $\endgroup$
    – LocalFluff
    Commented Jan 23, 2015 at 18:54
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    $\begingroup$ The prime evidence of the human factor in space is Armstrong manually guiding the Apollo 11 lander to a safe landing spot. (And before that some similar initiatives in LEO). The human factor is not a source of risk, but an asset for spaceflight. $\endgroup$
    – LocalFluff
    Commented Jan 23, 2015 at 18:59
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Since micro-meteor won't come from the lunar ground but can come from all around the space station it is at least 2 times safer.

But since there is gravity it attract a little more meteor, it is not easy to quantify those but if they are getting fast and have a lot energy (the scary one) they won't be impacted by gravitation.

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How safe a space settlement is depends on how well-established it is. The very first lunar base using inflatable structures would be vulnerable to radiation and small meteors as well as a critical malfunction, such as oxygen storage.

A well established base would probably be underground, at the pole, and have it’s own repair and refining capability. In time they would develop the ability to refine oxygen, water, aluminum, silicone and other local resources. The evolution from a temporary base to a self-sustaining colony could happen over time. The goal would be to be able to supply more needs locally and import less from the earth every year. That self-sufficiency can't happen in Earth orbit because there are no local resources. With self-sufficiency comes safety. Instead of fragile, lightweight, high-performance objects lifted from the earth, the structure of the colony and everything in it could be more massive and heavy duty, if it were made from lunar materials.

A well established lunar colony would need a completely reusable travel infrastructure. This would best be imagined in three legs, with completely reusable spacecraft. The first leg to low Earth orbit. The second leg would be and electric or nuclear rocket going from Earth orbit to lunar orbit. Finally would be a lunar lander going from the lunar surface to lunar orbit. This approach would not require a huge delta Vee for any of the rockets. That way they could be built robustly, to be practically reusable. So the Apollo model just doesn't apply.

A lunar settlement would be more vulnerable at first, but much safer in the long run.

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