Mars Colonization Discussion Thread

[DAL59]

If you want to do some complex radiation sims, go to NASA's OLTARIS.

https://oltaris.larc.nasa.gov/

[kerbiloid]

20 hours ago, PB666 said:

Lead would be a biproduct of asteroid mining just like any other metal.

How much lead do the asteroids contain? Especially Phobos. And how much asteroid iron should be melted to extract this by-product lead?
When you extract enough lead to build a cylinder, you already will have extracted enough iron to make a fleet of Death Stars.
The lead is a pure ballast, it doesn't have any construction purpose, it brings only mass. While the iron is a construction material itself, it is that what carries a mass.

According to wiki, current production/consumption: steel - 750 mln t/year, lead - 4..5 mln t/year.
And this is on the Earth, where the lead is kindly brought to us from beneath by millions years lasting geothermal processes, not is just scattered around in the crust.

20 hours ago, PB666 said:

Like I said gamma radiation is the least of your issues,

While you are floating in a tin can when the high-energy particles just pierce the walls, shooting the spacemen bodies.
When your hull will stop them all, the energy will be released as secondary beta- and gamma- particles. Beta is not a problem, mostly, until it gets caught and releases its energy as, say, X-rays.

Don't forget, you are talking about children and so, not about healthy expendable adults spending on ISS several months and getting cured all their life. Look at the former space crew members mortality.

20 hours ago, PB666 said:

you can grow healthy trees

Trees? How much biomass (including the soil humus) do you plan to deliver per human?
(Tip: a human needs about 1 hectare to be rich and happy. 1 hectare of soil contains amount of organics equivalent to 50..250 t of petrol in heat production (2..10% of the soil substance))
Here on the Earth there is about 10 times biomass more per every food chain level.
Why the terrestrial humans eat mostly grass and grass-eating one year-living animals, rather than just to be gardeners?

20 hours ago, PB666 said:

Secondarily the humans I would place in an interior centrifuge

Do you plan to use coaxial centrifuges one inside another? Every of them with mechanical bearings?

Will the air mass be common for them?
If no: will they use several pressurized hulls one inside another, not just one external one?
If yes: will the outer centrifuge rotate with 2g acceleration (as its radius will be ~2 times greater)?
In both cases: what about the air drag of the inner cylinder, and what about the reign of wind blowing between?

Where will the light come from to the inner, inhabited, cylinder?
 

20 hours ago, PB666 said:

Plants are much more tolerant of ionizing radiation that humans are

Cockroaches and turtles are even more tolerant, but will they herd them as cattle?

20 hours ago, PB666 said:

human males germline is much more susceptible to the effects of ionizing radiation relative to females, so protection of the germline largely involves protecting the males, making females more suitable farmers.

I can easily imagine a farmers' lead codpieces competition, but there are exact health standards.
Don't know about other countries, in USSR/Russia it's: 0.5 rem/year for civilians, 5 rem/year for atomic humans. Assumptions are inappropriate here.
Also we should presume that many of extraterrestrial activities will cause additional doses, so the daily doses should be even more negligible in the cylinder.
If they suffer from the lack of radiation, they at any moment can get a dose in X-ray cabinet.

20 hours ago, PB666 said:

"- Spacecraft can be constructed out of hydrogen-rich plastics, rather than aluminium. "

Hydrogen stops nucleons (i.e. primary space radiation). What happens then with its energy?
How many hydroaluminium hulls have already been tested?

20 hours ago, PB666 said:

Right now we are talking carbon-fiber which has moderate amounts of hydrogen.

Indeed. And your project presumes that the solar and galactic protons will hit the hydrogen atoms out of the construction itself.
How long will degrade the carbon hull under the proton rain to get weak?
An iron hull covered with an expendable lightweight layer (maybe made of of carbon, of course, though I would suggest silicate wastes left after the iron extraction, or even replaceable SiO₂ tiles*) will keep being strong much longer.

* Btw a stone tower floating in space would be looking great, imho.

20 hours ago, PB666 said:

The soil of such a craft would have both water

You should keep the water balance, dry and wet the soil when required. More water would be held in cysterns. Also, water is the easiest way to store your hydrogen and oxygen.
So, the water amount in the soil is negligible compared to your water cysterns.

Btw where the water will condensate? How will the bearings and cables protected from corrosion, and huts - from mildew?

20 hours ago, PB666 said:

in the form of composting organic matter (Cellulose).

Humus is not just cellulose. Mostly it's something like this.

Spoiler

If the organic matter in your soil consists of cellulose, this means that you haven't waited enough to let the straw and manure mixture become compost.
 

20 hours ago, PB666 said:

Don't assume that just because something is protective on Earth that it also protective in space.

Usually it is. Hydrogen cores don't get more massive, iron doesn't become less dense. Elementary particles don't know about gravity.

20 hours ago, PB666 said:

Most of the radiation exposure on Earth comes from Radon gas

In dungeons and first (ground?) storeys, when windows are closed for hours.  Mostly if the house is placed above a fault, granite rock or underground water.
Or in a granite house all the time.
There are enough emitting agents to keep 10..20 mkSv/h (and this is only gamma) even far from the radon sources, radon adds more drama..

20 hours ago, PB666 said:

As we can see the need for radiation protection is not so much the exterior level but interior, between the 'slowing down material' (Water, hydrocarbons, etc) and inhabitants.

I.e. placed between two layers of construction materials. Rather than just make the hull iron.
And if the intermediate (protective layer) is required, what happens all the time with the outer construction layer, as it constantly gets pierced with the protons flow enough intense to need that intermediate layer?

Edited November 11, 2017 by kerbiloid

[DAL59]

Trees might be a stretch, but hydroponics is very possible.  Plenty of ice in asteroids and on Mars.  

[Nibb31]

1 minute ago, DAL59 said:

Trees might be a stretch, but hydroponics is very possible.  Plenty of ice in asteroids and on Mars.  

Please stop with your "plenty of ice" statements. "Ice" is not an element. Most of the ice on Mars is CO2. Even if we do locate water ice, look at what a desalination plant looks like on Earth. Extracting drinking water from Mars will be orders of magnitude more complex, expensive, and power consuming than extracting it from sea water.

There is some water in the soil, but we don't know how much, how deep, or how hard it is to extract and purify. We also won't know until we actually send multiple missions, first to prospect, second to experiment ISRU, and third to produce massive amounts of H20 and Lox and CH4 on an industrial scale. With many years of iterations and launch windows, getting to that technology to TRL8 or 9 is not going to happen before at least a decade or two.

 

[DAL59]

Water ice does exist on Mars.  

[kerbiloid]

I would add that as far as I read in a 1970s book, when in 1960s they were trying to restore drinkable water from biological wastes, they found easier to get it from feces, rather than from urine, due to numerous solved compounds.
Martian ground does contain water, if call so a frozen urine of a poisoned crocodile.

Edited November 11, 2017 by kerbiloid

[Nibb31]

1 hour ago, DAL59 said:

Water ice does exist on Mars.  

Water glaciers might exist at high latitudes. Not much use for an equatorial base.

[Rakaydos]

Some serious effort into what would be needed for ISRU, not just for fuel but for plastics, fertilizer production, and more:

http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=42053.0;attach=1408769;sess=52089

[DAL59]

That is one advantage of venus balloon colonization- plenty of fertilizer and sunlight.  

[PB666]

4 hours ago, DAL59 said:

Water ice does exist on Mars.  

And there is no adequate power supply to extract it.

[PB666]

18 minutes ago, PB666 said:

And there is no adequate power supply to extract it.

 

5 hours ago, kerbiloid said:

How much lead do the asteroids contain? Especially Phobos. And how much asteroid iron should be melted to extract this by-product lead?
When you extract enough lead to build a cylinder, you already will have extracted enough iron to make a fleet of Death Stars.
The lead is a pure ballast, it doesn't have any construction purpose, it brings only mass. While the iron is a construction material itself, it is that what carries a mass.

According to wiki, current production/consumption: steel - 750 mln t/year, lead - 4..5 mln t/year.
And this is on the Earth, where the lead is kindly brought to us from beneath by millions years lasting geothermal processes, not is just scattered around in the crust.

While you are floating in a tin can when the high-energy particles just pierce the walls, shooting the spacemen bodies.
When your hull will stop them all, the energy will be released as secondary beta- and gamma- particles. Beta is not a problem, mostly, until it gets caught and releases its energy as, say, X-rays.

Don't forget, you are talking about children and so, not about healthy expendable adults spending on ISS several months and getting cured all their life. Look at the former space crew members mortality.

Trees? How much biomass (including the soil humus) do you plan to deliver per human?
(Tip: a human needs about 1 hectare to be rich and happy. 1 hectare of soil contains amount of organics equivalent to 50..250 t of petrol in heat production (2..10% of the soil substance))
Here on the Earth there is about 10 times biomass more per every food chain level.
Why the terrestrial humans eat mostly grass and grass-eating one year-living animals, rather than just to be gardeners?

Do you plan to use coaxial centrifuges one inside another? Every of them with mechanical bearings?

Will the air mass be common for them?
If no: will they use several pressurized hulls one inside another, not just one external one?
If yes: will the outer centrifuge rotate with 2g acceleration (as its radius will be ~2 times greater)?
In both cases: what about the air drag of the inner cylinder, and what about the reign of wind blowing between?

Where will the light come from to the inner, inhabited, cylinder?
 

Cockroaches and turtles are even more tolerant, but will they herd them as cattle?

I can easily imagine a farmers' lead codpieces competition, but there are exact health standards.
Don't know about other countries, in USSR/Russia it's: 0.5 rem/year for civilians, 5 rem/year for atomic humans. Assumptions are inappropriate here.
Also we should presume that many of extraterrestrial activities will cause additional doses, so the daily doses should be even more negligible in the cylinder.
If they suffer from the lack of radiation, they at any moment can get a dose in X-ray cabinet.

Hydrogen stops nucleons (i.e. primary space radiation). What happens then with its energy?
How many hydroaluminium hulls have already been tested?

Indeed. And your project presumes that the solar and galactic protons will hit the hydrogen atoms out of the construction itself.
How long will degrade the carbon hull under the proton rain to get weak?
An iron hull covered with an expendable lightweight layer (maybe made of of carbon, of course, though I would suggest silicate wastes left after the iron extraction, or even replaceable SiO₂ tiles*) will keep being strong much longer.

* Btw a stone tower floating in space would be looking great, imho.

You should keep the water balance, dry and wet the soil when required. More water would be held in cysterns. Also, water is the easiest way to store your hydrogen and oxygen.
So, the water amount in the soil is negligible compared to your water cysterns.

Btw where the water will condensate? How will the bearings and cables protected from corrosion, and huts - from mildew?

Humus is not just cellulose. Mostly it's something like this.

  Reveal hidden contents

If the organic matter in your soil consists of cellulose, this means that you haven't waited enough to let the straw and manure mixture become compost.
 

Usually it is. Hydrogen cores don't get more massive, iron doesn't become less dense. Elementary particles don't know about gravity.

In dungeons and first (ground?) storeys, when windows are closed for hours.  Mostly if the house is placed above a fault, granite rock or underground water.
Or in a granite house all the time.
There are enough emitting agents to keep 10..20 mkSv/h (and this is only gamma) even far from the radon sources, radon adds more drama..

I.e. placed between two layers of construction materials. Rather than just make the hull iron.
And if the intermediate (protective layer) is required, what happens all the time with the outer construction layer, as it constantly gets pierced with the protons flow enough intense to need that intermediate layer?

How much iron do you need, space craft are made primarily of aluminum, not iron. Weight is the enemy of space travel.

Beta is a skin hazard (risk of burns and skin cancers), Alpha can be skin or consumption hazard. The problem with your idea is that you think Iron is the best block agent, its not, the best blocking agent is liquid hydrogen. Your argument is akin taking a boomerang on an eel fishing trip. I repeat gamma is not the primary concern, cosmic rays are only radiation because of the velocity differential between the elements and the targets. If not for this they undergo electron capture and become hydrogen and helium. They are fundamentally different from gamma radiation and the method of remediating them is fundamentally different. The are fundentally different not because of the resting qualities but because of two KE, relative velocity and rotational velocity.  The critical point that unless you get them to cascade before they reach the living target, no amount of lead will protect you from the radioactivity they generate within your body.

Coaxial centrifuges are not neccesary in requiring bearing because of zero gravity one can use induction (https://en.wikipedia.org/wiki/Electromagnetic_induction) to maintain cylinders without solid bearings, In fact one can spin the inside structure by applying spin to the inside structure in the opposite direction, energy would be applied to resist the force of friction. When the structure needs to be move, just cancel (i.e. do nothing) and once they coast to a stop open the induction circuit and make the coarse change. ( You might want to drain bathtubs and sinks first). Induction circuitry has been used in the aquarium industry for a long time where the impeller needs to be in water and no-one wants to pass current through the water. They only requirment of a bearing less rotor is that you need a method of automatically balancing the rotor or risk the rotor glancing off the sides. This can be prevented by having rollers limiters along the sides at both ends of the cylinder. Of course entry and exit from the habitat cylinder would have to be from the top and bottom and people would have to climb to the habitation layer. The air mass in the cyclinder will be common and circulated between the two forcing air in from the top and exiting at the bottom.
 

[Hay]

1 hour ago, DAL59 said:

That is one advantage of venus balloon colonization- plenty of fertilizer and sunlight.  

And acid rain.

[PB666]

Water has a freezing from 6 millibars upward of 0'C
Chlathrates will freeze before CO2
CO2 has a freezing point at 6 mBar of -110'C
Methane has a freezing point of -182'C
Nitrogen,Oxygen, Helium and Hydrogen all freeze at tempetures below -200'C

The first ice that one is likely to find, and in particular seasonal ice on Mars is likely CO2 and CO2 chlathrates (because the H20 vapor pressure in martian atmosphere is close to zero)
As one moves north or as Winter progresses there is likely to be a layer of CO2 on top of the chlathrate layer.
The purest reservoirs of Martain ice a in the deepest layers of martian ice that fill permanently iced depression in the polar regions. These are probably mixed with martian dust.

 

[PB666]

Isn't it time we put this thread to rest?

[tater]

1 minute ago, PB666 said:

Isn't it time we put this thread to rest?

The idea was to keep this thread so that this subject doesn't keep derailing threads like the SpaceX thread, otherwise devoted to actual SpaceX news, launches, etc.

Edited November 11, 2017 by tater

[DAL59]

2 hours ago, PB666 said:

Isn't it time we put this thread to rest?

No! 

3 hours ago, Hay said:

And acid rain.

I meant within a blimp.

4 hours ago, PB666 said:

And there is no adequate power supply to extract it.

Solar power.  Or nuclear power.

[kerbiloid]

7 hours ago, PB666 said:

ow much iron do you need, space craft are made primarily of aluminum, not iron. Weight is the enemy of space travel.

There is a lot of aluminium on in Phobos, too. As in almost any piece of rock.
Spaceships do nothing here, the talk is about an orbital/surface base.
Iron (as well as aluminium) is one of the most common resources (rather than carbon and lead, btw).
You can get to any place in the Universe you wish to colonize and find there as many iron and alumosilicates as you wish. Just take them in any amount.
You don;t need to transport a marsillion tonnes heavy  base to anywhere, you can build it at that anywhere, delivering only industrial equipment.
If you can't - unlikely you can treat this colony as real colony, it's not self-sufficient. Then why those trees?

7 hours ago, PB666 said:

The problem with your idea is that you think Iron is the best block agent

Iron is one of the best block agents for everything except neutrons, and definitely the bestest of them in sense of availability. You can have it literally as much as dust.

7 hours ago, PB666 said:

the best blocking agent is liquid hydrogen.

That's why nuclear reactor shielding is made of reinforced concrete with lead balls and boron supplement, its control rods contain boron or cadmium, and a nuke charge is surrounded by a berillium reflector.
They don't use hydrogen at all.

The hydrogen advantage is based on its core least possible mass. It's just one proton. So, it takes, roughly, a half of the impulse and energy of a collided nucleon.
Btw,  you would also remember about deuterium. It has a nice cross-section value, that's why they use heavy water in nuclear plants.

If you use liquid hydrogen as a blocking agent, this would mean that in fact your protection is made of iron and aluminium of its insulated tank and cooling equipment.
Better just melt them into a metal plate, this would be more compact.
That's why a hydrogen-based neutron shielding is always used as hydrocarbons, dense and solid.

7 hours ago, PB666 said:

I repeat gamma is not the primary concern, cosmic rays are only radiation because of the velocity differential between the elements and the targets. If not for this they undergo electron capture and become hydrogen and helium. They are fundamentally different from gamma radiation and the method of remediating them is fundamentally different. The are fundentally different not because of the resting qualities but because of two KE, relative velocity and rotational velocity.  The critical point that unless you get them to cascade before they reach the living target, no amount of lead will protect you from the radioactivity they generate within your body.

The primary radiation is of course mostly protons and alpha.
But:
1. It's anyway has to release its energy in some kind of electromagnetism. Just to get stopped somewhere. This can be either a secondary electromagnetic radiation (even if through an induced cascade), or heat (which is released when too energetic atoms electromagnetically interact with each other), Anyway, you will get a whole spectre of photons from IR to gamma, the question is just in their distribution.
2. After a nukesplosion the land and object around GZ get somewhat activated, they get an induced radioactivity. It's usually much weaker than fallouts (unless a low-yield nuke has exploded in air), it usually disappears in about a day, but emits a whole bunch of radiations from nucleons to gamma, depending on isotopes appearing in the objects.

Say, this is how the Sun works:

¹²₆C + ¹₁H → ¹³₇N + γ + 1.95 MeV
¹³₇N → ¹³₆C + e⁺ + ν_e + 1.20 MeV
¹³₆C + ¹₁H → ¹⁴₇N + γ + 7.54 MeV

(Upd.: e⁺ btw annihilates with an electron, giving more gamma-photons.)

So, under the proton bombardment your carbon hull would emit several MeV gamma-photons per every collision, and the carbon will be turning into nitrogen.
Some time later the carbon hull will be full of atomic defects and bubbles, no matter how much hi-tech it was initially.
And as the carbon fiber hull mostly hopes for thin layer but strong structures, it would feel like a weathered blanket.

7 hours ago, PB666 said:

Coaxial centrifuges are not neccesary in requiring bearing because of zero gravity one can use induction (https://en.wikipedia.org/wiki/Electromagnetic_induction) to maintain cylinders without solid bearings,

This just means they use magnetic bearings.
They anyway have to be sealed, so they anyway will have friction. OK, let's suppose they don't.
Also magnetic bearings keeping two marsillion-tonnes heavy objects would use such strong magnetic fields that:
1. You will need a very massive hull to use it as a radiator for your thermonuclear reactor (because "need moar power!")
2. The colonists would better have healthy teeth. Because metal teeth will fly with jaws to the bearings.
(Don't forget that these bearings must withstand the lateral inertial accelerations, not just keep two objects apart.)
 

7 hours ago, PB666 said:

, In fact one can spin the inside structure by applying spin to the inside structure in the opposite direction, energy would be applied to resist the force of friction. When the structure needs to be move, just cancel (i.e. do nothing) and once they coast to a stop open the induction circuit and make the coarse change. ( You might want to drain bathtubs and sinks first). Induction circuitry has been used in the aquarium industry for a long time where the impeller needs to be in water and no-one wants to pass current through the water. They only requirment of a bearing less rotor is that you need a method of automatically balancing the rotor or risk the rotor glancing off the sides. This can be prevented by having rollers limiters along the sides at both ends of the cylinder. Of course entry and exit from the habitat cylinder would have to be from the top and bottom and people would have to climb to the habitation layer. The air mass in the cyclinder will be common and circulated between the two forcing air in from the top and exiting at the bottom.

1. What happens with objects and humans if the rotation suddenly stops? I.e. bearings fail, two cylinders touch each other.
2. What happens with artificial lakes and rivers in zero-G if the rotation stops?
(I would expect that every second survived colonist would move to an asylum for life, after floating inside a lava-lamp with tens-meters huge blobs above and beneath).
3. How to repair/replace the rollers of mechanical bearings?
4. What happens if no power in magnetic bearings?

So, any bearings of any kind mean several additional levels of redundancy and complexity: to quickly disable inactive layer of mechanical bearing or to keep hot several thermonuclear reactors to support a magnetic bearing.

Edited November 12, 2017 by kerbiloid

[Hay]

4 hours ago, DAL59 said:

No! 

I meant within a blimp.

Solar power.  Or nuclear power.

Good luck shielding that blimp, or producing basically anything there. A Venusian colony out of the picture, because it would be fully dependant on supplies from earth.

Edited November 12, 2017 by Hay

[Green Baron]

I stumbled upon this:

http://www.nejm.org/doi/full/10.1056/NEJMoa1705129

tl:dr: Degeneration of the brain leads to losses of cognitive abilities in long term space flights.

Just f information, i cannot judge the relevance.

[kerbiloid]

18 minutes ago, Green Baron said:

Degeneration of the brain leads to losses of cognitive abilities in long term space flights.

In terms of KSP: Stupidity grows.

[Green Baron]

You mean, we don't necessarily need space for this to happen ? :-)

[kerbiloid]

Why? Just I am impressed by KSP prediction abilities.

[PB666]

7 hours ago, kerbiloid said:

There is a lot of aluminium on in Phobos, too. As in almost any piece of rock.
Spaceships do nothing here, the talk is about an orbital/surface base.
Iron (as well as aluminium) is one of the most common resources (rather than carbon and lead, btw).
You can get to any place in the Universe you wish to colonize and find there as many iron and alumosilicates as you wish. Just take them in any amount.
You don;t need to transport a marsillion tonnes heavy  base to anywhere, you can build it at that anywhere, delivering only industrial equipment.
If you can't - unlikely you can treat this colony as real colony, it's not self-sufficient. Then why those trees?

Iron is one of the best block agents for everything except neutrons, and definitely the bestest of them in sense of availability. You can have it literally as much as dust.

That's why nuclear reactor shielding is made of reinforced concrete with lead balls and boron supplement, its control rods contain boron or cadmium, and a nuke charge is surrounded by a berillium reflector.
They don't use hydrogen at all.

The hydrogen advantage is based on its core least possible mass. It's just one proton. So, it takes, roughly, a half of the impulse and energy of a collided nucleon.
Btw,  you would also remember about deuterium. It has a nice cross-section value, that's why they use heavy water in nuclear plants.

If you use liquid hydrogen as a blocking agent, this would mean that in fact your protection is made of iron and aluminium of its insulated tank and cooling equipment.
Better just melt them into a metal plate, this would be more compact.
That's why a hydrogen-based neutron shielding is always used as hydrocarbons, dense and solid.

The primary radiation is of course mostly protons and alpha.
But:
1. It's anyway has to release its energy in some kind of electromagnetism. Just to get stopped somewhere. This can be either a secondary electromagnetic radiation (even if through an induced cascade), or heat (which is released when too energetic atoms electromagnetically interact with each other), Anyway, you will get a whole spectre of photons from IR to gamma, the question is just in their distribution.
2. After a nukesplosion the land and object around GZ get somewhat activated, they get an induced radioactivity. It's usually much weaker than fallouts (unless a low-yield nuke has exploded in air), it usually disappears in about a day, but emits a whole bunch of radiations from nucleons to gamma, depending on isotopes appearing in the objects.

Say, this is how the Sun works:

¹²₆C + ¹₁H → ¹³₇N + γ + 1.95 MeV
¹³₇N → ¹³₆C + e⁺ + ν_e + 1.20 MeV
¹³₆C + ¹₁H → ¹⁴₇N + γ + 7.54 MeV

(Upd.: e⁺ btw annihilates with an electron, giving more gamma-photons.)

So, under the proton bombardment your carbon hull would emit several MeV gamma-photons per every collision, and the carbon will be turning into nitrogen.
Some time later the carbon hull will be full of atomic defects and bubbles, no matter how much hi-tech it was initially.
And as the carbon fiber hull mostly hopes for thin layer but strong structures, it would feel like a weathered blanket.

This just means they use magnetic bearings.
They anyway have to be sealed, so they anyway will have friction. OK, let's suppose they don't.
Also magnetic bearings keeping two marsillion-tonnes heavy objects would use such strong magnetic fields that:
1. You will need a very massive hull to use it as a radiator for your thermonuclear reactor (because "need moar power!")
2. The colonists would better have healthy teeth. Because metal teeth will fly with jaws to the bearings.
(Don't forget that these bearings must withstand the lateral inertial accelerations, not just keep two objects apart.)
 

1. What happens with objects and humans if the rotation suddenly stops? I.e. bearings fail, two cylinders touch each other.
2. What happens with artificial lakes and rivers in zero-G if the rotation stops?
(I would expect that every second survived colonist would move to an asylum for life, after floating inside a lava-lamp with tens-meters huge blobs above and beneath).
3. How to repair/replace the rollers of mechanical bearings?
4. What happens if no power in magnetic bearings?

So, any bearings of any kind mean several additional levels of redundancy and complexity: to quickly disable inactive layer of mechanical bearing or to keep hot several thermonuclear reactors to support a magnetic bearing.

You are not familiar with gamma, I worked with gamma for 35 years, I was an RSO.
1. Gamma is all around you all the time. Most people are surprised to find there is more radiation already in a room than when they open a vial of isotope and start working with it. You actually have to be using millicurie amounts before you can see noticeable effects in ambient gamma rise.
2. Studies in N. Iran have demonstrated that people who have a 10 fold higher level of exposure to background gamma radiation are at no increased risk for birth defects or cancer. They instead increase the rate of DNA damage and repair and compensate. In fact at the sublethal dosage levels, it is not really clear what level of gamma is dangerous. Injestion of any isotope however carries increased risk
3. In an atmosphere gamma just doesn't travel that far, certainly not through a heterogeneous substrate. As I stated early tinting a 1 inch thick piece of plexiglass with a small amount of lead suffices to knock out almost all gamma radiation. Of course a mixture of metals is more effective but why do you need to, a heterogenous construct like the hull of such as ship will capture most of the gamma without any extraordinary effort, a good soil is compose of complex material.
4. In the area surrounding Chernobyl in Belarus there was a study done to find out why there was an increased level of radiation effects in some areas versus others after the fall-out was at ground level. The ground in these areas was radioactive, but that in-and-of-itself was not sufficient to increased risk of blood pathologies. Observers went to several farming communities, what they found was there was almost no risk in people ambiently exposed to radiation, but when people worked in the fields if they gathers stubble and burned it there was much higher risk. As it turns out the risk came not from exposure to the volatile salts liberated into the air by the piling and especially the burning process, and the risk turned out to be almost entirely an inhalation risk.
5. I used to work with so much radioactivity that if you sat a one side of a room (Geiger counter running) and me at the other with a , the radiation source I was working with while facing the other direction could ping that meter on the x/100 scale. It used to burn my finger where I held it for several days on occasion.

Gamma is not the danger that you think. READ

Second. Objects don't suddenly stop in space unless they collide with something mass. Rollers do not need bearing replacement they are only present to deflect imbalances, they otherwise are not moving because they are not touching (magnets are maintaining position, not the rollers). If the internal cylinder needs servicing just bring it to a stop

Third. By building reasonably size communities it is not neccesary to build thermonuclear power plants, particularly since the outside hull is moving at a reasonable speed on can have Solar Panels. Fission power plants can be shielded, but the bigger problem is that they have maintanence issues so scrub these until better plants. If you spin a ship at 1g on the outside edge then adding more solar is problematic because of the g-forces. At 0.1g you can increase the area point at the sun by 3 fold.

Forth. We have already discussed the fact that you do not understand cosmic radiation. Hydrogen is the best absorbent, you keep talking like its a gamma ray, its not. A cascade is just that, there are as many types of cosmic rays as there are clueless posts here by dreamy-eyed martian 'colonist'.(http://pdg.lbl.gov/2011/reviews/rpp2011-rev-cosmic-rays.pdf) Each energy level and type (proton, alpha, lithide, carbide, . . .  ) can spawn different types of radiation. Antimatter in cosmic rays are rare, just as in the rest of the universe. You cannot keep shielding everywhere within a structure in space, weight is your enemy, more so than the radiation. BY having a sufficient amount of secondary absorbent (space and low mass nuclei) there is increased probability of reducing the KE of the secondary rays. As stated early 3 cm of water suffices to remediate primary radiation, so at that point you have only secondary radiation and space is your best friend. "Understanding Space Radiation" (PDF). Lyndon B. Johnson Space Center. NASA. October 2002. Retrieved 2012-07-25. FS-2002-10-080-JSC

Galactic cosmic rays are the dominant
source of radiation that must be dealt with aboard the International
Space Station, as well as on future space missions within our solar
system. Because these particles are affected by the Sun’s magnetic
field, their average intensity is highest during the period of mini-
mum sunspots when the Sun’s magnetic field is weakest and less
able to deflect them. Also, because cosmic rays are difficult to
shield against and occur on each space mission, they are often
more hazardous than occasional solar particle events. They are,
however, easier to predict than solar particle events.  "Understanding Space Radiation" (PDF). Lyndon B. Johnson Space Center. NASA. October 2002. Retrieved 2012-07-25. "FS-2002-10-080-JSC"

 

The production of multiple secondary particles by cosmic rays under thick layers of lead has been studied with coincidence counters and with a cloud chamber. Part of the coincidences obtained under 15 cm of lead is attributed to groups of particles of atmospheric origin associated with extensive showers. The other part is due to a local effect produced in the lead by single penetrating particles. Among the particles emitted in these processes, some have the penetrating power of low energy mesons. 

Multiple Secondary Effects of the Penetrating Cosmic Radiation at Sea Level. Available from: https://www.researchgate.net/publication/243691638_Multiple_Secondary_Effects_of_the_Penetrating_Cosmic_Radiation_at_Sea_Level [accessed Nov 12 2017].Multiple Secondary Effects of the Penetrating Cosmic Radiation at Sea Level. Auger and Daudin, 1942

Finally I am not going to deal with your what ifs, since you don't seem to read the literature. The primary component of cosmic rays is Hydrogen (540 parts), Helium (:26 parts), Carbon (:2.2 parts).(2. AMS Collaboration, Phys. Lett. B490, 27 (2000); Phys. Lett. B494, 193 (2000).3. T. Sanuki et al., Astrophys. J. 545, 1135 (2000)). The primary secondary CR from carbon collisions is oxygen not nitrogen and positrons is rare (10E-4 per secondary electron/beta) and is only observed in the >10GeV range. Antiprotons, antideuterons, and antialpha particles are rare with proportions of secondary cosmic radiation below 1 in 10 million (K. Abe et al. , arXiv:1201.2967v1 (2012)).

 

 

[DAL59]

With sufficient power, you could make a artificial magnetosphere.  How much power would it need to decently protect a o'neil cylinder?

4 minutes ago, PB666 said:

Studies in N. Iran have demonstrated that people who have a 10 fold higher level of exposure to background gamma radiation are at no increased risk for birth defects or cancer.

Well, that supports Zubrin's claims.

[PB666]

13 hours ago, DAL59 said:

No! 

I meant within a blimp.

Solar power.  Or nuclear power.

Solar power is not adequate in the region of Mars where water is most abundant. Settlements above latitude 65' N or below 65'S  need another source of power.

There is no nulcear power source at presence suitable for the extraction of water from is most abundant sources on mars. The space reactors discussed so far are less than 10 kw.