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Antius wrote:I am a racist. I have racist opinions which I will share with people any chance I get.
I prefer logic and reasoned arguments to name calling JoshNH4H. The trail of blood left by Islam over the past millennia should speak for itself. No one with an ounce of care for the western world and its people should want anything to do with it. Allow those people to colonize another planet and you guarantee that that planet will be afflicted by the same war and murder that it's adherents have inflicted here on Earth.
I solved the equation embedded in this document...
http://www.asterism.org/tutorials/tut38 … iation.pdf
...to calculated the pressure at the centre of Phobos.
https://en.wikipedia.org/wiki/Phobos_(moon)
It works out to be 59.5KPa, which is 0.58 atmospheres. Therefore I would suggest that Phobos may be a useful potential shell world. A shaft could be dug to the gravitational centre of the moon and an internal cavity could be mined out, which could then be lined and pressurised. The excavated material could initially be used as reaction mass in mass driver impulse engines ferrying cargo between Earth and Mars. With a breathable internal atmosphere, mining of the moon will be substantially simplified.
As mining excavates larger proportions of the moon, pre-stressing cables could be laid across its surface to ensure it remains intact against internal pressure. These could also be made from excavated material.
A tower could be built to the L1 point some 3km above Stickney. Mass driver tugs could dock here to take on reaction mass and offload people and payload.
Ryan MacDonald is always a clear, concise and perceptive presenter. I found this video very helpful:
https://www.youtube.com/watch?v=6d6TA8xcdA8
Most surprising, he suggests that Space X think they can get the cost of launching the BFR down to $60 per kg. The launch cost from Mars should be even less, I would think.
Time to rethink the economics of Mars exports? If the cost of export is $50 per kg, all sorts of luxury goods like Mars wine become a possiblity.
He covers Lockheed's misconceived plans and also Mars One - the latter is a clear dud, probably not worth further consideration.
The gravity is substantially lower, so the vehicle launched from Mars would not require a lower stage and can avoid the operation cost associated with that. And the vehicle must return to Earth anyway is it is part of a reusable transport system.
But $60/kg is optimistic in either direction. These are low launch costs even to Earth orbit and assume that the launcher can follow an aircraft business model. Using the BFR as part of an interplanetary transport system, ties it up for over 2 years for each round trip.
Lets say it can shift 150t of cargo in either direction, costs $200m and carries out 10 round trips in it's lifetime. That is 1500t in each direction. For a vehicle with upfront cost of $200m, that is $66/kg. But that ignores a realistic discount rate and all other operating costs. If you want a realistic estimate, you must factor these in as well. At a guess, I would say you could double or triple this estimate to account for those costs. But you don't need to guess. You can work it out.
Why the hell would anyone be producing wine on Mars? It would be easier to grow it in the high arctic than it would on Mars. Shipping it back to Earth is just plain silly. On Earth, new world wines have put a dent in the European wine market because they can produce a product of the same quality at lower cost. Neither assumption is reasonably applicable to Mars. In fact it is difficult to conceive of any product that can be made there and exported to Earth at a comparative advantage.
Exporting to Earth orbit may be a different story. That is one comparative advantage that Mars does have. But it is weak, because we must ship the equipment to Mars first.
The Russians interfered in our electoral process, an investigation into whether Donald Trump and those around him had fore knowledge of those attempts. In what their relationships were with Russians, business relationships that might have made them vulnerable to Russian objectives. As Russia Probe Heats Up, Conservatives Call For Special Counsel Mueller To Quit, of course the GOP view the investigation as a witch hunt...Not...
Top House Intel member ‘can’t comment’ if Trump under investigation in Russia probe
Spacenut, how exactly did the Russians do that? From what I remember, Israel, Saudi Arabia and China all make significant campaign contributions to the Democratic party. Are you telling us that this is OK, but it is not OK for the Russians to do the same thing?
Whichever way the last election had gone, the US would be stuck with a president with dubious connections. Hillary Clinton is one of the most corrupt and thoroughly vile creatures on Earth. Trump managed to win the last election partly because the alternative was so evidently awful.
The biggest problem in my opinion would be growing enough food to feed a large population. This is the single most important reason that these places do not support large populations today. The holding capacity of the land is low. The conquest of the west was possible because huge swathes of prairie land were available to grow abundant crops. They both enabled the exercise and made it worthwhile. Siberia and Northern Canada are empty because they cannot replicate that advantage, or at least could not in the past.
Maybe food can be grown in polytunnels heated by nuclear waste heat. That could shift the equation somewhat. But then again, we tend to locate reactors close to existing demand centres. So it is difficult to see why any government or corporation would choose to locate one in the middle of nowhere. But this would appear to be a key enabling technology for arctic colonisation.
Department of Corrections!!?? Could these people possibly have chosen a more Orwellian name?
In my opinion, one of the most worthwhile outcomes of going to Mars is the ability to leave the stupidity that has poisoned the Earth behind. This pointless desert religion has never been anything but a bain to humanity. It spread by violent conquest from the 7th century onwards and wherever it goes, oppression and blind faith tend to supplant scientific enlightenment. These people have nothing to offer a new world and it would be a disaster if they got to Mars ahead of the rest of humanity.
Yuck. We should not allow this backward desert religion to poison another planet.
Ah yes, the "Racism doesn't exist and/or doesn't matter" argument.
If that's your claim, I'll leave this thread now as there's no point arguing with you.
Well, that's up to you of course. I am not saying that racial discrimination / prejudice does not exist. There will always be mistrust and prejudice between people of different ethnicities. But if it were the only reason that these people weren't doing well, it is difficult to explain why the Asians and Jews all do well in the US, many of them outperforming their white peers but the blacks are somehow unable to.
Wherever blacks go, they form poor and crime ridden communities. Racial discrimination by the evil white people is always the default answer they and their Marxist protagonists give, but it just doesn't stack up. These people never do well anywhere. At what point do we accept the fact that they are fundamentally different to us?
One reason that you would expect people of different races to have different life expectancies is that due to our long history of racist policymaking black americans have been disadvantaged in all sorts of ways. This has effects on the local availability of doctors, income (which unfortunately correlates to a significant degree with race and ethnicity), and insurance status.
The idea that we have failed because race and class (as well as your parents' incomes) are strong predictors of your own life expectancy, general health, and health insurance status is strongly supported by data and decidedly true.
No I don't think so. The Jews were historically discriminated against, hated and distrusted. They needed no help in becoming successful and wealthy people wherever they went. At the end of the day, we rise and fall on our abilities.
You might look to race and class inequality in the US as a driver of health disparities. Have a look at this map of life expectancy in Baltimore:
http://cnsmaryland.org/baltimore-health … korea.html
You all are probably not familiar with Baltimore and its neighborhoods, so I'll break it down: The white areas and the rich areas have high life expectancy. The black areas and the poor areas have low life expectancy. This is one of the fundamental problems with capitalist health insurance schemes.
Josh, Why would you expect people with significant differences in ethnicity, income and lifestyle to have the same life expectancy? It seems to me, that doesn't signify that the medical system is failing. People with more money can afford better food, private gym memberships and are also more likely to be intelligent, which correlates with taking better care of oneself, in terms of diet, exercise, etc.
The idea that we have somehow failed because some people have done better than others is false - we are all better off than people living 100 years ago. The fact that some people do better than others is a fact of life. We all have different abilities and also make different choices, that effect our material outcomes.
FYI Antius it has never been the case that Americans paid more for health insurance based on how well they take care of themselves and such discrimination is actually illegal now. Furthermore your observation doesn't really accord with reality (the plural of "anecdote" is not "data").
Well that undermines the whole point of health insurance doesn't it. You can't blame the system for being crap and inefficient if it is mandated that way by law. Nothing can be all things to all people.
So couple things on the previous posts...
Currently, the US healthcare model is primarily focused on reactive emergency level care. The underlying premise is that ethically, if you are in a critical state, we must care for you. Our entire system is currently predicated on that assumption. All else flows from that.
Our preventive care model is poorly designed and does not operate under the same ethical obligations. Hit by a car and bleeding out, we will help stabilize you. Hit by a car and can limp away, you better have insurance or cash if you want physical therapy.
So enter insurance, a form of legalized gambling where you are hedging against an eventuality. It used to be I pay $100 a month, regardless of if I used healthcare or not. If I did use healthcare, insurance footed the bill. If I didn't use it, insurance pocketed the money. So there was no incentive for me to NOT get healthcare. After all, the only winner here is the faceless insurance.
I didn't have to be frugal. I didn't have to shop around. I just showed up and the doctor cooked up a plan to keep me healthy. The doctor had no incentive to be frugal, or to order the generic drug or the cheaper, less complicated lab, or use the older medical device that was cheaper and 95% as effective as the newer model. Hell, outcomes didn't even matter- if I didn't get better, in a perverse way, the doctor made more money. Faceless insurance paid the bill. Times were good.
Then faceless insurance started saying, "hey, we have to approve your medical care first. We need to control costs...". And much complaining ensued. Who was insurance to decide who lived and died? Medical decisions were between patients and physicians after all.
So enter copays and deductibles. Contracted rates. In-network providers. This is a tool by faceless Insurance to get patients and providers to have skin in the game. Now, me, has to pay more than $100 a month. Now I have to think twice about that drug, that lab, that procedure. It's not a free lunch. It's not faceless insurance telling me not to get something done, it is my own self determination (based on personal financial constraints). Physicians agree to limited costs for the work they perform, which impacts how they guide care (doesn't determine it, but it does influence). Faceless insurance will approve expensive procedures based on agreed to medical conditions that must be proven by physicians (with onerous documentation and review, by design). Significantly expensive procedures or drugs are carved out in volumes of patient insurance contracts that allow insurance to shift near 100% cost to the physician or patient.
So why is it so broken? Greed. Profit motive is one of the problems with the market place. US healthcare has accepted that profit has a place in healthcare delivery. It doesn't need to be (there are proven US models that not non-profit). The other reason is that US population has a low tolerance for personal accountability/requirements when it comes to healthcare. Example: a yearly physical is not mandatory, but should be. It would help improve overall US health and begin the process of establishing preventive care as a way of life. Mandatory flu vaccines should be part of any health reform. Mandatory nutrition programs. Mandatory mental health check-ups. Mandatory dental, vision and hearing screening.
It sounds crazy, but that's what is required to fix the system- a huge societal shift that makes the deal that we as a society foot the healthcare bill, but we also hold each other accountable towards maintaining good health.
And this brand of crazy is how it will be on Mars (or space).
Every health service in the world is focused on reactive care because non-reactive care is usually down to the individual.
One of the good things about the US health care system is that it does encourage healthy living for the simple reason that insurance premiums go up if you put on weight and generally let things slide. The only way of keeping people healthy is to provide them with some financial incentive that doesn't require them to think years ahead into the parallel universe of the future. Insurance premiums are a very good way of doing that, because they are directly tied to a person's perceived risk of dying. It gives people a gilt-edged priority to take care of their own health.
It has been my observation that there are two types of American: the squeaky clean types fanatical about health, who look like plastic Barbie toys; and the horrendously obese ones that don't seem to give a shit. The first type pay health insurance, the second type don't. Price signals work. They can appear cruel on occasion, but there is no better way of doing things.
I think this is basically correct - especially the emphasis on mass production. A factory capable of making polymer sheets which include UV protective outer layer and fibre reinforced plastic inner layer, is essentially a factory for producing land. My pet favourite idea was a mass produced steel rectangular frame, which could be covered in loose rock and regolith to counteract internal pressure. I wonder in fact if we could make such items from fired clay, given that the net forces are compressive. Very cheap and simple - just put hundreds of frames into a square lattice, cover them over with soil and bulldoze a gravity dam of soil around the edges.
For domes under tensile stress, cost is proportional to volume. So it would make sense to build relatively small domes and fill the volume with plants and useful structures. For gravity stabilized underground structures, cost is roughly proportional to land area, not volume. Therefore, we would seek to build structures with high roofs, to get the maximum habitable volume for the minimum investment of labour.
Interesting solution to the Fermi paradox presented by Alan Stern:
https://www.space.com/38577-fermi-parad … ceans.html
In short, aside from Earth's surface – all of the potentially habitable environments in our solar system are oceanic and buried under thick shells of ice. These environments are more stable habitats than our planetary surface and hence, there is more time for intelligent life to evolve without disruption. The downside is that any life evolving at such depths would have a very difficult time making it to the surface and becoming space faring.
There is another problem that Stern has not picked up on. The average solar flux at Earth's surface is >100W/m2. The thermal flux exiting the core of a world like Enceladus and entering a slushy mantle is measured in mW/m2. So there is actually remarkably little energy to support a food chain, even if such an environment appears habitable in terms of liquid water and nutrients. This would tend to limit the diversity and complexity of life emerging in buried ocean habitats. It is likely to remain simple, because complex life tends to sit higher up the food chain. Without the ability to harness fire, they would also be stuck in a technological cul-de-sac, as they would be unable to refine metals.
This interesting scenario brings me back to a terraforming concept that we toyed with on this board a couple of years back. The hydrostatic pressure at the centre of a ball of water some 54km in diameter would be exactly 1bar.
http://www.asterism.org/tutorials/tut38 … iation.pdf
What is more, at such low gravity, convection would be a very slow means of removing heat. Heat would need to conduct through the water and ice – which would have thermal conductivity in the 0.5-1W/m.K range. Future human colonists could seek out icy Kuiper belt objects and use the waste heat from nuclear power sources to melt large internal cavities within these bodies. At the centre of gravity, huge inflatable structures a kilometre or more in diameter could be home to low-G ecosystems, with humans housed in rotating buildings. This would be technically quite easy to accomplish, as the same nuclear heat source can be used to melt its way down to the core.
As the cavity gradually expands, silicates trapped in the melting ice will gradually sink to the centre, where they can be extracted and used for construction.
There are many millions of Kuiper belt and Oort cloud objects in this size range and they extend half-way to the nearest star. The far future of humanity in space may end up being a slow migration between the Oort clouds of the galaxy, slowly hopping from one terraformed comet to the next. If we successfully develop deuterium fusion, then these bodies could be semi-permanent homes, potentially lasting for many millions of years. If not, then the power source must be whatever uranium and thorium can be extracted from the silicates. This would limit habitability to thousands of years and the settlers would tend to move on relatively quickly.
Interesting. I wish I had more time for discussions like this, but others here know more than I.
Everything comes down to economics. Is it cheaper to mass produce an expendable craft without the complication and extra weight added by re-entry and landing? Or a fully reusable one that has higher upfront engineering costs, refurbishment costs, reduced payload, but lower unit manufacturing costs?
I think the answer is dictated by launch volume and the proportion of other overheads to total launch costs. If launch volumes are low and design, refit and management overheads of a reusable craft are high, then it makes sense to use it once and then throw it away. The shuttle definitely failed this test.
Reusability doesn't necessarily imply that something has to be used in exactly the same way over and over again. Once a craft is in orbit, it can be dismantled and its components processed into other useful things, like space station modules, cycler craft or just ground up into reaction mass for impulse engines. The analogy would be to buy a jet for $100million, fly it to Australia and then sell it for $99million when you get there.
Louis, you tend to see whatever you want to see. You never critically evaluate anything that you happen to believe in. You oppose any analysis that doesn't give you the answer you want. Solar electricity and electric cars will not be any better or worse solutions because you happen to find them romantically attractive.
We both come from a country where various forms of idiotic idealism have ruined just about everything. It has degenerated into a totalitarian state with nothing but crap political ideals, authoritarian control and no money. Since you are planning to colonize another planet, where life will be harder than anything we have known, isn't it time to dump predispositions and do some decent analysis?
Referencing my earlier posts on EROI, I don't think it's reasonable to say that speculative EROI calculations are anywhere near right or that they should carry much weight in our analyses.
I don't agree. My own efforts are not very robust. But a comprehensive analysis is a good proxy for telling us how the economics of a concept will pan out, if we exploit things like scale economies and if regulatory issues do not exist. EROI tells us how good something might be.
Here's a strange off the wall thought: Could we ever get to the point of making an MCP suit that was easy / convenient enough for human beings to carry out most of their working tasks in it? i.e. about as easy to put on and take off as any other piece of clothing? If so, then we might reasonably spend much of our working time in vacuum. The only air needed would be that we put into buildings, which would be optimised to get the most usable space per unit volume.
Darn! Silly me! At a temperature of -70C (200K) the system will only radiate 90W/m2 into the Martian night.
Earthenware clay is fired at a temperature of 760C.
https://www.goshen.edu/art/DeptPgs/rework.html
Assuming a clay density of 2000kg/m3, a 1m2 x 0.02m thick clay panel would weigh 40kg. If specific heat is 1KJ/KgK, then some 30.4MJ of heat would be needed to heat the clay to sinter temperature. So the embodied energy of the panel is 60.4MJ/m2. That reduces the panel EROI to about 33. Not as good as I originally thought, but still better than PV when storage losses are accounted for and much easier to make on Mars.
According to this link, a SKODA 660MW supercritical steam turbine has a weight of 1000te and an efficiency of 51%.
http://e2010.drustvo-termicara.com/reso … /fiala.pdf
That's 660W/kg. If the ammonia turbine has efficiency of 9.5%, then power density would be 123W/kg - if working fluid energy density and flow rates were the same, which of course they aren't. Since supercritical steam enters the turbine at a pressure of at least 22MPa, it would have roughly 50 times the energy density of ammonia vapour in our system. So the ammonia turbine would have at least an order of magnitude lower power density, although the lower pressure differential may allow thinner blades. If power density is ~10W/kg, then the turbine embodied energy (steel alone) would be about 16% that of the panels. All in all, a whole system EROI of 20 still looks achievable.
I ran a few quick and rough EROI calculations on a Mars built solar dynamic system and was pleasantly surprised by the results.
Anhydrous liquid ammonia has good compatibility with carbon steel:
https://www.calpaclab.com/carbon-steel- … ity-chart/
It is also liquid across a temperature range of -75 to 25°C, the latter requiring a vapour pressure of 1MPa (10bar).
https://en.wikipedia.org/wiki/Ammonia_(data_page)
On this basis, I would propose that anhydrous ammonia would be an excellent working fluid for a solar or geothermal power system on Mars.
A solar thermal collector could be a flat clay plate (no cover glass needed in the vacuum of Mars) with low carbon steel tubes embedded in it, containing liquid anhydrous ammonia. During the day, the collector would collect heat at say 0°C. The cold store would be a tank of saline solution that will melt at -20°C, serving as a heat sink. At night, the cycle can be reversed. The heat sink becomes a heat source at -20°C and the panel will dump heat into space at a temperature of -70°C. At zero Celsius, ammonia boils at 4.3bar. At -20C, it boils at 1.9bar. Could we use a single stage LP turbine? It would have a feed pressure of 4.3bar during the day and back pressure of 1.9bar; and a feed pressure of 1.9bar at night and back pressure of 0.1bar. I don't honestly know. Assuming the device works at 2/3rd Carnot efficiency, the average efficiency of the device would be 9.5%.
If the steel tubes are 1cm in diameter and the steel has a yield strength of 250MPa, then a design factor of 5 would give a tube wall thickness of 0.1mm. If the tubes are spaced 5cm apart, then a total of 20m of tubing would be needed for 1m2 of panel. That would weigh in at 0.5kg steel per m2 of panel, not including manifolds or other pipework. If we roughly double steel mass to include those items and valves, we would need on average about 1kg of steel per m2 of solar plant. Let us assume an embodied energy of 30MJ/kg of new steel. The clay panels would have relatively low embodied energy. The thermal storage tank could simply be a pit, lined with polyethylene and filled with brine. The heat exchanger within the brine would probably consist of polyethylene tubes as these have a relatively low glass transition temperature, will not be corroded by the brine and can be manufactured from Mars-made ethylene gas.
Martian insolation is about 400W/m2 year-round average, close to the equator. If the system runs for 20 years at 9.5% efficiency, then each m2 of solar collector would produce some 8GJ of mechanical / electrical power over the course of its lifetime.
Based upon an energy investment of 30MJ/m2, the EROI of the panels would appear to be ~266. Of course, I have made a lot of simplifications here. I haven't included the energy required to build the thermodynamic plant, the salt water storage pit, or to mould and bake the clay panels with the tubes embedded in them. I have also assumed that the collectors are 100% efficient, whereas in reality, they will probably make half that. But even if EROI is an order of magnitude lower than I have estimated, an EROI of 26 is not bad for a round the clock power supply. As ammonia has good or excellent compatibility with mild and low carbon steels, it should be possible to cast, machine or 3D print most of the components on Mars.
As an aside, this sort of simple thermodynamic system would never be possible on Earth because:
1. Earth has insufficient diurnal temperature ranges for it to be an efficient option and simple brine-based phase change materials would not be useful;
2. Due to the thick atmosphere, Earth-based panels require evacuated glass tubes to build up decent temperatures, which ramps up the required energy investment dramatically;
3. Aside from deserts, Earth based northern locations where most people live do not benefit from persistent periods of direct sunlight. With little cloud cover, Mars would have clear sky most of the time;
4. Earth based panels must be insulated to prevent heat losses to the surrounding air and surroundings due to radiation. Mars based panels will lose no heat to surrounding air and only half as much to radiation; because their operating temperature in full sun will be close to 0°C rather than 50°C.
This is why on Earth; solar power tends to rely on PV. This has high embodied energy and poor EROI, especially when storage is factored in. All in all solar thermal power looks a lot more doable on Mars than it is on Earth. The system works well with low grade easily manufactured materials: baked clay, polyethylene sheeting and pipes and carbon steels. Energy storage is achieved prior to generation in the phase change of brines. These should be cheap on Mars, as water is available as ice and the soils are saturated with salts and chlorates.
Of course, one downside of an extended solar based power system is the large amount of EVA time needed to assemble and maintain the system on the surface of Mars. A 10MWe system would need to cover an area of about 1km2. But it would only need to be built once.
A plasma arc will break down gases into constituent components due to a combination of ionisation and thermal decomposition. But a lot of energy is lost from a plasma arc as radiation and as thermal energy in the expelled gases. Also, the electrodes are subject to erosion. You then need to separate the oxygen from the CO and CO2. Would that require some kind of cryogenic fractionation?
With this in mind, are there any commercial CFD packages anywhere, that can model the interaction between supersonic / hypersonic flows and structures? If they do exist, I am sure that Musk and Co will be using them. My experience of CFD is that it is generally accurate to about 30% in the subsonic region. But I have only dealt with very limited applications. Don't know at all about supersonic. Uncertainties will raise the need for larger engineered safety factors, which will of course add weight and cost.
I am not sure about minimum feasible drop. I don't think heat addition will be a problem, in fact looking at the CO2 phase diagram I would say that for drop heights greater than about 1km, some heating is necessary to prevent the formation of dry ice under static or dynamic pressure. The pipes could conceivably clog up with dry ice if the system is left static for too long.
I know that such a system is unlikely to work on Earth. To liquefy air, one must extract approximately 300KJ/Kg of heat at a coefficient of performance of about 0.33 at 90K. So one must invest nearly 1MJ/kg to liquefy the air, whereas the gravitational potential energy for a drop of 2km, say, would be 20KJ/kg. Even if the device produces net energy, the EROI would be terrible, which means the economics would be terrible.
The unique properties of the Martian atmosphere, i.e. a gas close to its triple point temperature, means that this might be possible on Mars with a much lower embodied energy.
A recent post on Martian compressed air energy storage got me thinking about a possible Martian renewable energy source that has thus far been overlooked. I have not yet performed any sort of detailed analysis of this yet.
https://commons.wikimedia.org/wiki/File … iagram.svg
The idea works like this:
1. Build a compressor station at the top of a mountain. Average Martian temperatures are very close to the triple point of CO2 (217K). This means that with intercooling, very little mechanical work would be needed to compress CO2 into a saturated liquid at typical Martian temperatures.
2. Run the liquid CO2 down the side of the mountain through a steel pipe.
3. At the bottom of the mountain, build a two stage turbine – the first would extract kinetic energy from the falling liquid CO2 much like a hydropower plant here on Earth; the second would boil the CO2 using either ambient heat or stored solar heat and extract thermodynamic work.
Provided the thermodynamic expansion stage provides sufficient energy to cover the energy of compression, kinetic energy of the falling CO2 would result in net energy generation. The idea is sort of like hydropower, but using liquefied CO2 as the working fluid rather than water.
I am inclined to agree with Josh.
High Earth orbit is the most sensible first target to colonise so far as human beings are concerned.
(1) It has ample free sunlight that can be concentrated to high temperatures using concave aluminium foil mirrors. It is available about 99% of the time;
(2) It has zero G and hard vacuum, which are industrially useful commodities;
(3) Gravity and air can be provided where needed, using rotation and pressurisation;
(4) The closeness to Earth has all sorts of advantages. Your transfer vehicle has much better economic performance, as more trips can be carried out in its operational lifetime; less provision is needed for life support, which means better payload; Delta-V is less, again better payloads; you can escape back to Earth in emergencies. It also means that many operations can be teleoperated from Earth and there can be continuous datalinks from Earth. The need for people is limited to assembling and repairing things;
(5) I think best of all, provided we can establish mining operations on other bodies, transport between low Earth orbit and high Earth orbit, should not require rockets. Low thrust propulsion can be established using reaction engines. On this basis, unprocessed space materials or waste materials from manufacturing can be used as reaction mass. That means that after space mining and manufacturing are established, all of the material delivered to LEO can be useful payload – none of it need be propellant.
(6) Mining facilities established on the moon and asteroids can be almost entirely robotic and in the case of the moon, even teleoperated from Earth. Human presence would only be needed when something went wrong and needed repairing.
Overall, high Earth orbit would appear to have an overwhelming economic advantage as the first place that human beings seriously establish themselves in space. Mars would appear to be an end destination that would need to be almost completely autarkic from day 1. It is an interesting place to go for its own reasons, but is not a very sensible first place to colonise.
If the planet can be partially terraformed, i.e. its atmospheric pressure increased by pumped CFCs into the air, it might have a competitive advantage in the production of food for consumption in space. One can then imagine a trade between high Earth orbit and Mars, with HEO providing manufactured goods in exchange for food.
