Venus vs. Mars colonization

[Findthepin1]

16 hours ago, fredinno said:

Wouldn't an air-breathing engine need to convert Co2 to O2 before burning?

I meant, we need a CO2-breathing engine. One that doesn't need oxygen to work. 

[DBowman]

5 hours ago, AngelLestat said:

cooling by radiation is one of the less efficient ways to cool something.
In space is already difficult even when you can use very light surfaces and cool from both sides..
In mars on the other hand, you can only use 1 surface, you need to clean that from the dust which reduce your emissivity coefficient and it needs to be kinda strong to deal with wind storms (the pressure can be low, but the density depends on co2 and the dust in the air, the reynold number is low so the friction at higher wind speed rise.. then wind speed is what most matter in wind force, no the density).
This just mean that your radiators will be at least 3 times less effective than in space (which already are low efficient compared to other cooling methods)

I think buried radiators could be the way to go for Mars, conduct straight into the ground / permafrost.

[fredinno]

17 minutes ago, Findthepin1 said:

I meant, we need a CO2-breathing engine. One that doesn't need oxygen to work. 

CO2 is pretty stable, what with its double bond, I don't think that will work. Air-augmented is a better option- though those are lower ISP than air-breathing.

15 hours ago, AngelLestat said:

I never had faith in a mars colony, because I always thought it needed to be in low latitudes.

There you can no cool any nuclear reactor and it is also very dangerous due the low mass of mars atmosphere vs ours (204 times lower).
It does no have oceans so any polluting will make a mess in mars.  The cost of energy in those places can be as 3 or 4 times more expensive than earth.
For your habitat you need to dig into the ground to escape the radiation, but in many places the soil is not solid or safe.
You might have just water for consumption, but no enough for industrial process.

But if we change of paradigm and we start to think on the poles, then it has more sense.
Energy cost with nuclear can go down to half o less compared to the equator, it will need to be developed the thorium reactor and buried into the ice 50m at least, with extra tunnels and wells to be used as cold spot, in case you have a meltdown, the water and ice keep it isolated.
There is no much dust in the poles, that dust is danger and very annoying.
You can dig much more easier using heat, and the ice is a more safe structure material than dust and dirt.

There is no need of sunlight, you can grow plants like this, it is much more efficient:
http://www.gizmag.com/farmedhere-vertical-farm-west-louisville-foodport/41569/

That is just a cut, from above is radial and symmetric, two different artificial machine designs.
At the begining, the ice will have a temperature of -70 Celsius approx.
You need insulation panels attached to the ice walls to no melted and extra energy for heat.
Meanwhile the heat travels more far from the tunnels to the ice which each times the heat flow is reduce because it need to pass more ice layers. So after some years it reach the point where you just need to heat from 0 degree (ice instead -70).

I heard soil is a great place to put radiators and manage temperature. Venus is far harder in terms of heat management-especially since cooling is generally more difficult than heating.

[Rakaydos]

2 hours ago, fredinno said:

 

I heard soil is a great place to put radiators and manage temperature. Venus is far harder in terms of heat management-especially since cooling is generally more difficult than heating.

Which is the reason for the argument of 50 km vs 56 km. (1 bar pressure vs room temprature exterior)

[AngelLestat]

15 hours ago, DBowman said:

I think buried radiators could be the way to go for Mars, conduct straight into the ground / permafrost.

15 hours ago, fredinno said:

I heard soil is a great place to put radiators and manage temperature. 

Buried radiators would no work, in fact in that case the correct thing to use is "water pipes" in U inside these deep holes of hundred of meters (that is called geothermal).


Many houses use that with much lower thermal flux of course, in summer they extract the heat from the house and they exchange that with the ground, If in winter they dont reverse that process (extracting the heat from the soil to send it to the house), the next summer they will see their efficiency reduce, if they repeat that the third and four year, their efficiency will drop until the point where they can no inject more heat into the soil.

This happens because ground is a very good insulator.  Even if you have permafrost, would no help much, imagine that the different layer from the image, that is your permafrost).
The heat is transferred to the soil, this can storage a good amount due its thermal mass, but each time that the heat moves 1 meter away from the pipe (heat source), you are adding 1 meter of insulator, so each time less heat flux achieves to pass.

A nuclear reactor would reach that saturate step very fast.
Another concern of nuclear energy on mars, is that its atmosphere has 204 times less mass than earth atmosphere, and there is no oceans and its surface area is lower. So a nuclear accident there would be much more risky than here.
In low latitudes the only solution is Solar panels using hydrogen with fuel cell storage in case you need to face a global dust storm.
The cost of the energy would be 3 or 3.5 times higher than earth (on equal industrial capacity).

On the poles nuclear can be a good alternative..  the cost could be 1.5 times of the earth (just due extra precautions that you need to take and imported fuel).
Something like this (the location of the turbine is not good, I know): 


 

Quote

Venus is far harder in terms of heat management-especially since cooling is generally more difficult than heating.

But you dont need heat management to produce electricity, only you use my thermal idea with a steam airship, in which you have great heat management due wind and heat differences.

You just need a bit of air cooling (just the habitat section, no the whole envelope), at 53km height at 50 degrees of latitude, the temperature is 45c, all dubai building face that all days with air cooling.
If you go higher as Rakaydos said, you dont need cooling, but the pressure drops to 0.4 or 0.5 bar, and your envelope needs to be a 25% bigger.
Mars also needs to fight against temperature.

Edited February 24, 2016 by AngelLestat
word change: altitudes by latitudes

[kStrout]

Really the best option would be to just not colonize either and make space colonies. Forget landism in this Venus vs Mars argument, the real issue is planetism. Why live on a planet anyway? It's just an environment you can't control in a locked and natural(so inconvenient) location, all at the bottom of a gravity well trying to stop you from getting out if you ever want to. Orbital space colonies have none of these disadvantages, really we should be building these in the asteroid belt and non restricting ourselves to huge, inescapable chunks of rock.

[peadar1987]

A nuclear accident on Mars would actually not be as bad as one on earth, precisely because of the lack of atmosphere and ocean. Fallout particles are going to be a lot less mobile, and so the disaster area is going to be a lot more contained.

[DBowman]

4 minutes ago, peadar1987 said:

the disaster area is going to be a lot more contained.

and the whole planet is kind of a disaster area to start with

[AngelLestat]

12 hours ago, kStrout said:

Really the best option would be to just not colonize either and make space colonies. Forget landism in this Venus vs Mars argument, the real issue is planetism. Why live on a planet anyway? It's just an environment you can't control in a locked and natural(so inconvenient) location, all at the bottom of a gravity well trying to stop you from getting out if you ever want to. Orbital space colonies have none of these disadvantages, really we should be building these in the asteroid belt and non restricting ourselves to huge, inescapable chunks of rock.

We live in a gravity well and we are just fine..  "local economies".  

12 hours ago, peadar1987 said:

A nuclear accident on Mars would actually not be as bad as one on earth, precisely because of the lack of atmosphere and ocean. Fallout particles are going to be a lot less mobile, and so the disaster area is going to be a lot more contained.

less mobile? you still had winds on mars, dust storms cover the whole planet and those super radioactive particles would not take much time to spread over the world..  the only argument you can made is that mars already receives a lot of radiation, so maybe a little more does not do much harm...  It does if you want to explore the planet or if you want to preserve any trace of bacteria life that might be.
Besides, nobody owns mars..  so it will no be fair if 1 company or country ruins the planet (or help in this matter).
With venus is different, everybody will be agree that is already "ruined", and wind and solar energy are a much better solution for venus.

On the other hand oceans had so much mass, that a meltdown diluted in all that is not very alarming.. 

Edited February 24, 2016 by AngelLestat

[fredinno]

4 hours ago, AngelLestat said:

Buried radiators would no work, in fact in that case the correct thing to use is "water pipes" in U inside these deep holes of hundred of meters (that is called geothermal).


Many houses use that with much lower thermal flux of course, in summer they extract the heat from the house and they exchange that with the ground, If in winter they dont reverse that process (extracting the heat from the soil to send it to the house), the next summer they will see their efficiency reduce, if they repeat that the third and four year, their efficiency will drop until the point where they can no inject more heat into the soil.

This happens because ground is a very good insulator.  Even if you have permafrost, would no help much, imagine that the different layer from the image, that is your permafrost).
The heat is transferred to the soil, this can storage a good amount due its thermal mass, but each time that the heat moves 1 meter away from the pipe (heat source), you are adding 1 meter of insulator, so each time less heat flux achieves to pass.

A nuclear reactor would reach that saturate step very fast.
Another concern of nuclear energy on mars, is that its atmosphere has 204 times less mass than earth atmosphere, and there is no oceans and its surface area is lower. So a nuclear accident there would be much more risky than here.
In low altitudes the only solution is Solar panels using hydrogen with fuel cell storage in case you need to face a global dust storm.
The cost of the energy would be 3 or 3.5 times higher than earth (on equal industrial capacity).

On the poles nuclear can be a good alternative..  the cost could be 1.5 times of the earth (just due extra precautions that you need to take and imported fuel).
Something like this (the location of the turbine is not good, I know): 


 

But you dont need heat management to produce electricity, only you use my thermal idea with a steam airship, in which you have great heat management due wind and heat differences.

You just need a bit of air cooling (just the habitat section, no the whole envelope), at 53km height at 50 degrees of latitude, the temperature is 45c, all dubai building face that all days with air cooling.
If you go higher as Rakaydos said, you dont need cooling, but the pressure drops to 0.4 or 0.5 bar, and your envelope needs to be a 25% bigger.
Mars also needs to fight against temperature.

Yeah, that kind of geothermal heat-regulation is a kind of radiator- at least the closest thing to it on a terrestrial surface.

3 hours ago, AngelLestat said:

We live in a gravity well and we are just fine..  "local economies".  

less mobile? you still had winds on mars, dust storms cover the whole planet and those super radioactive particles would not take much time to spread over the world..  the only argument you can made is that mars already receives a lot of radiation, so maybe a little more does not do much harm...  It does if you want to explore the planet or if you want to preserve any trace of bacteria life that might be.
Besides, nobody owns mars..  so it will no be fair if 1 company or country ruins the planet (or help in this matter).
With venus is different, everybody will be agree that is already "ruined". 

On the other hand oceans had so much mass, that a meltdown diluted in all that is not very alarming.. 

Less force in the wind means that particles are more difficult to pick up. But yeah, the guy was kind of wrong.

[kStrout]

3 hours ago, AngelLestat said:

We live in a gravity well and we are just fine..  "local economies".  

That's because we only exist in this gravity well, when humanity spans the solar system we'll be connected by trade and tourism. If traveling across the solar system it's way easier to start in orbit and end in a different orbit; then to launch from the bottom of a gravity well with a giant rocket every single time.

Cavemen, first looking to expand could've had a similar argument. "We live in a cave; we do just fine here. Therefore we should expand by finding and colonizing more caves." But that's not what the next step was, the next step was to abandon caves and start civilization on the surface.

We've been living in a cave for thousands of years and only just learned how to get out, but instead of talking about how to set up a surface city you guys are arguing about which new cave we should colonize first.

[Bill Phil]

15 minutes ago, kStrout said:

That's because we only exist in this gravity well, when humanity spans the solar system we'll be connected by trade and tourism. If traveling across the solar system it's way easier to start in orbit and end in a different orbit; then to launch from the bottom of a gravity well with a giant rocket every single time.

Cavemen, first looking to expand could've had a similar argument. "We live in a cave; we do just fine here. Therefore we should expand by finding and colonizing more caves." But that's not what the next step was, the next step was to abandon caves and start civilization on the surface.

We've been living in a cave for thousands of years and only just learned how to get out, but instead of talking about how to set up a surface city you guys are arguing about which new cave we should colonize first.

Except caves are a bad example, since we didn't always live I them.

Even so, your argument stands.

[fredinno]

1 hour ago, kStrout said:

That's because we only exist in this gravity well, when humanity spans the solar system we'll be connected by trade and tourism. If traveling across the solar system it's way easier to start in orbit and end in a different orbit; then to launch from the bottom of a gravity well with a giant rocket every single time.

Cavemen, first looking to expand could've had a similar argument. "We live in a cave; we do just fine here. Therefore we should expand by finding and colonizing more caves." But that's not what the next step was, the next step was to abandon caves and start civilization on the surface.

We've been living in a cave for thousands of years and only just learned how to get out, but instead of talking about how to set up a surface city you guys are arguing about which new cave we should colonize first.

Well, the moon definitely can get stuff to Earth faster.

[AngelLestat]

8 hours ago, fredinno said:

Yeah, that kind of geothermal heat-regulation is a kind of radiator- at least the closest thing to it on a terrestrial surface.

Yes but properly speaking, we can't call something that transfers heat by contact "a radiator"

8 hours ago, kStrout said:

That's because we only exist in this gravity well, when humanity spans the solar system we'll be connected by trade and tourism. If traveling across the solar system it's way easier to start in orbit and end in a different orbit; then to launch from the bottom of a gravity well with a giant rocket every single time.

It seems that you misunderstood me.. you can read my previous post if you want some context.
My point was that you don't really need to trade with earth in order to achieve a thriving economy in other world.
World's provide much simple solutions for a colony, a place to live self sustained with a minimum trade.
A space station can work in small scale for tourism and some permanent residents, but there is no much more reason behind that, if you want to mine an asteroid, there is no need to move a whole space station to the asteroid location, just move the mining machines or move the asteroid.

8 hours ago, kStrout said:

Cavemen, first looking to expand could've had a similar argument. "We live in a cave; we do just fine here. Therefore we should expand by finding and colonizing more caves." But that's not what the next step was, the next step was to abandon caves and start civilization on the surface.

In fact, the first thing that cavemen did when they wanted to spread.. is search another cave and live there..  they cross over all the surface until find one.. because it was easier.

8 hours ago, kStrout said:

We've been living in a cave for thousands of years and only just learned how to get out, but instead of talking about how to set up a surface city you guys are arguing about which new cave we should colonize first.

What you can achieve living in orbit?  yes.. it cost you less deltav to reach other place..  but you are still in nowhere even if you change location...
I know, the argument is to mine asteroids from space with a whole industry that allow you to produce anything so you don't need to launch that from earth in case you want that thing up there. That has sense for the kind of people who wants to explore or be one of the few that will be needed to work there.
But what about the people who just want to live in one place?  Living in worlds is cheaper for those because is no cheap to make a safe self sustain space colony.
In any case a industrial space station will have much more sense in venus orbit, you have more sunlight and you can capture asteroids using the thick atmosphere.
 

[Bill Phil]

In Orbit it takes less energy to just spin to provide gravity. No reason for planets.

A better question is what can you achieve living on a planet. Nothing, really. It's hard to trade, and pretty much every economist agrees that trade is a key part to everyone getting rich. Why make it harder to trade for no reason?

Venus, Mars, or any planet can never be self sufficient unless you ship the things you need there. At least with our tech. But again, pure self sufficiency isn't a sustainable situation.

But orbital colonies will reach self sufficiency. They can move, and they can move to asteroids and mine them and stuff.

[kStrout]

59 minutes ago, AngelLestat said:

A space station can work in small scale for tourism and some permanent residents

I think you may be misunderstanding what I am saying I'm not talking about giant forms of the ISS, I'm talking about space colonies. Giant, artificial gravity generators with square kilometers of land. Land which is completely customizable to your preference.

1 hour ago, AngelLestat said:

But what about the people who just want to live in one place?  Living in worlds is cheaper for those because is no cheap to make a safe self sustain space colony.

Ok, so you do have a point here, space colonies are not cheap. But they're not that expensive either. Think about it, Industry is going to precede colonization when it comes to space, and industry is going to set up on asteroids because it's easier to export to Earth. By the time communities get up there there will be tons of building resources in orbit. Most of the mass of a space colony comes from shielding anyway, which can just be slag, the useless stuff mining operations have to get rid of. It's not going to be more expensive per m^2 to make habitable land in a space colony, It might even be cheaper.

46 minutes ago, Bill Phil said:

A better question is what can you achieve living on a planet. Nothing, really. It's hard to trade, and pretty much every economist agrees that trade is a key part to everyone getting rich. Why make it harder to trade for no reason?

Exactly, planets work [citation: earth]. But just because they work does not mean they are the best option, and it definitely doesn't mean they are the only option. Who conquered the world? The cave-hopping cavemen, or the first humans that started making surface settlements?

[fredinno]

6 hours ago, Bill Phil said:

In Orbit it takes less energy to just spin to provide gravity. No reason for planets.

A better question is what can you achieve living on a planet. Nothing, really. It's hard to trade, and pretty much every economist agrees that trade is a key part to everyone getting rich. Why make it harder to trade for no reason?

Venus, Mars, or any planet can never be self sufficient unless you ship the things you need there. At least with our tech. But again, pure self sufficiency isn't a sustainable situation.

But orbital colonies will reach self sufficiency. They can move, and they can move to asteroids and mine them and stuff.

Yeah, good luck moving an O'Neil Colony. The amount of Delta V needed is pretty immense.

It's also easier to expand on a planetary surface- the resources are right under you (not literally, but you get the point), and unless you are docked to an asteroid, you need to bring the building materials from elsewhere. Planetary surfaces also don't need to deal with as much radiation shielding, and in many cases, you don't need to design your colony for extra gravity. Anything smaller than 1/2 of the Moon can use a quasi- orbital colony, docked to the surface.

5 hours ago, kStrout said:

I think you may be misunderstanding what I am saying I'm not talking about giant forms of the ISS, I'm talking about space colonies. Giant, artificial gravity generators with square kilometers of land. Land which is completely customizable to your preference.

Ok, so you do have a point here, space colonies are not cheap. But they're not that expensive either. Think about it, Industry is going to precede colonization when it comes to space, and industry is going to set up on asteroids because it's easier to export to Earth. By the time communities get up there there will be tons of building resources in orbit. Most of the mass of a space colony comes from shielding anyway, which can just be slag, the useless stuff mining operations have to get rid of. It's not going to be more expensive per m^2 to make habitable land in a space colony, It might even be cheaper.

Exactly, planets work [citation: earth]. But just because they work does not mean they are the best option, and it definitely doesn't mean they are the only option. Who conquered the world? The cave-hopping cavemen, or the first humans that started making surface settlements?

Yeah, are you so sure? Ocean Colonies still haven't really taken off, you know, and those are comparable to free space colonies, being 100% artificial. I also don't see why the Moon would be a bad place to mine, you can get your resources back a lot faster (time=money) and the moon has lots of resources near the surface from constant impacts.

[kStrout]

4 hours ago, fredinno said:

Yeah, are you so sure? Ocean Colonies still haven't really taken off, you know, and those are comparable to free space colonies, being 100% artificial. I also don't see why the Moon would be a bad place to mine, you can get your resources back a lot faster (time=money) and the moon has lots of resources near the surface from constant impacts.

The moon is a great place, if you insist on colonizing a surface it is far better than Mars. But Because of it's low gravity and the fact that it still has a gravity well, It would not be a very good place for residential cities.

This leads into one of the biggest issues that will probably prevent this argument from ever being resolved before we actually try it. How do humans, mainly children, react to living their entire lives in a low-g environment like the moon or Mars? We haven't the slightest clue. It might turn out you can raise perfectly health children at 0.1g, or that birth defects lead to dysfunctional children raised at 0.6 gs. If we do just need a little gravity to develop, then a moon colony makes a lot of sense, but if we do need a significant fraction of a g to safely raise children, then that eliminates Mars and means the moon can only be a industrial body.

And as for the Ocean Colonies, there are three big differences: the first is that earth land is fertile and can be easily colonized, M-class planets are not common and there is only one in our solar system. The second reason is that it is easy to get from land to the sea on earth, not so much to go from surface to orbit. The final reason is that the solar system is full of asteroids just waiting to be mined and converted into habitats, the ocean? Not so much.

But yes, the best option from where we are today would be to set up a moon base in order to mine materials for colonies or other orbital infrastructure.

[fredinno]

3 hours ago, kStrout said:

The moon is a great place, if you insist on colonizing a surface it is far better than Mars. But Because of it's low gravity and the fact that it still has a gravity well, It would not be a very good place for residential cities.

This leads into one of the biggest issues that will probably prevent this argument from ever being resolved before we actually try it. How do humans, mainly children, react to living their entire lives in a low-g environment like the moon or Mars? We haven't the slightest clue. It might turn out you can raise perfectly health children at 0.1g, or that birth defects lead to dysfunctional children raised at 0.6 gs. If we do just need a little gravity to develop, then a moon colony makes a lot of sense, but if we do need a significant fraction of a g to safely raise children, then that eliminates Mars and means the moon can only be a industrial body.

And as for the Ocean Colonies, there are three big differences: the first is that earth land is fertile and can be easily colonized, M-class planets are not common and there is only one in our solar system. The second reason is that it is easy to get from land to the sea on earth, not so much to go from surface to orbit. The final reason is that the solar system is full of asteroids just waiting to be mined and converted into habitats, the ocean? Not so much.

But yes, the best option from where we are today would be to set up a moon base in order to mine materials for colonies or other orbital infrastructure.

Yeah, you do realise there's plenty resources in an ocean colony a few hundered meters deep? It's a lot easier to get that than from an asteroid.

[kStrout]

7 hours ago, fredinno said:

Yeah, you do realise there's plenty resources in an ocean colony a few hundered meters deep? It's a lot easier to get that than from an asteroid.

But those resources aren't any better than land-based ones, just harder to access. Unless that's not true in which case we build oil rigs, which are tiny floating cities of a sort.

[Bill Phil]

17 hours ago, fredinno said:

Yeah, good luck moving an O'Neil Colony. The amount of Delta V needed is pretty immense.

It's also easier to expand on a planetary surface- the resources are right under you (not literally, but you get the point), and unless you are docked to an asteroid, you need to bring the building materials from elsewhere. Planetary surfaces also don't need to deal with as much radiation shielding, and in many cases, you don't need to design your colony for extra gravity. Anything smaller than 1/2 of the Moon can use a quasi- orbital colony, docked to the surface.

Yeah, are you so sure? Ocean Colonies still haven't really taken off, you know, and those are comparable to free space colonies, being 100% artificial. I also don't see why the Moon would be a bad place to mine, you can get your resources back a lot faster (time=money) and the moon has lots of resources near the surface from constant impacts.

The delta V is the same, if we're doing Hohmann transfers. What is different is the required energy. But we're assuming the colony is in the Belt, since that's a pretty good location. There might not be a lot of asteroids in one place, but rendezvous takes very little energy, and if need be we can send out a craft to bring the roid, if small enough, to the colony.

Planetary surfaces do have to deal with that radiation shielding, they just get it from their atmospheres/distance from the sun. Mercury has a lot of radiation, and it's a planetary surface. Mars has quite a bit, too. 

The resources might be right underneath you, or maybe that's just useless resources. But even so, you can only dig so far down. You don't hace access to a bunch of the resources you might need. 

The only advantage of ge of planets is gravity, but then you have the disadvantage of gravity wells.

[Buster Charlie]

On 2/23/2016 at 5:55 PM, DBowman said:

and the whole planet is kind of a disaster area to start with

Haha, I love that though. An entire planet which humans cannot survive naturally due to lack of atmosphere,  lethal temperatures,  and don't forget high natural radiation....

 

And people are worried about a reactor failure.

 

It reminds me of hundreds of thousands of violent deaths and master destruction from a tsunami, being overshadowed by a comparatively benign nuclear reactor failure in japan. I bet all those people who died drowning wished they had to deal with a "disaster" involving radiation levels you'd experience flying from Japan to California. 

I suspect with all the hazards on Venus or mars, irradiation from a man made reactor is low on your list of worries.

[fredinno]

5 hours ago, Bill Phil said:

The delta V is the same, if we're doing Hohmann transfers. What is different is the required energy. But we're assuming the colony is in the Belt, since that's a pretty good location. There might not be a lot of asteroids in one place, but rendezvous takes very little energy, and if need be we can send out a craft to bring the roid, if small enough, to the colony.

Planetary surfaces do have to deal with that radiation shielding, they just get it from their atmospheres/distance from the sun. Mercury has a lot of radiation, and it's a planetary surface. Mars has quite a bit, too. 

The resources might be right underneath you, or maybe that's just useless resources. But even so, you can only dig so far down. You don't hace access to a bunch of the resources you might need. 

The only advantage of ge of planets is gravity, but then you have the disadvantage of gravity wells.

Yeah, the thing is planetary surfaces shield at least 1/2 the radiation from solar wind due to the surface blocking out 1/2 the horizon. Also, the belt is much farther than the moon, or even mars, and timescales will thus be longer. Time=money.

4 hours ago, Buster Charlie said:

Haha, I love that though. An entire planet which humans cannot survive naturally due to lack of atmosphere,  lethal temperatures,  and don't forget high natural radiation....

 

And people are worried about a reactor failure.

 

It reminds me of hundreds of thousands of violent deaths and master destruction from a tsunami, being overshadowed by a comparatively benign nuclear reactor failure in japan. I bet all those people who died drowning wished they had to deal with a "disaster" involving radiation levels you'd experience flying from Japan to California. 

I suspect with all the hazards on Venus or mars, irradiation from a man made reactor is low on your list of worries.

Well, if your reactor blows up, you're pretty much dead. I would still keep caution.

[insert_name]

44 minutes ago, fredinno said:

Yeah, the thing is planetary surfaces shield at least 1/2 the radiation from solar wind due to the surface blocking out 1/2 the horizon. Also, the belt is much farther than the moon, or even mars, and timescales will thus be longer. Time=money.

Well, if your reactor blows up, you're pretty much dead. I would still keep caution.

by keeping the reactor at a safe distance, you can avoid the explosion. contrary to popular belief nuclear reactors do not have enough fissile material to reach critical mass. As for the radioactive fallout, your hab should be rad-shielded anyways

[kStrout]

1 hour ago, fredinno said:

Yeah, the thing is planetary surfaces shield at least 1/2 the radiation from solar wind due to the surface blocking out 1/2 the horizon. Also, the belt is much farther than the moon, or even mars, and timescales will thus be longer. Time=money.

First off, solar wind is not the main radiation concern, it's cosmic rays that are the problem, on a place like Mars you would need to live at least 5-10 meters down to prevent cancer over long periods of time, which kinda ruins the fun of "I live on another planet."

Secondly, the asteroid belt is not the only place space colonies could be built, they could be built in LEO (actually really nice because of free radiation shielding), around the moon, or if you really want to go to Mars, Phobos and Deimos have enough materials  to make space colonies easily exceeding the livable area of earth.