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The outer crust may consist of clathrates of water ice and various gases (CO, CH4, N2). These have lower thermal conductivity than pure water ice. This will suppress transfer of heat from the mantle to surface, trapping radiogenic heat in the mantle.
Kowloon walled city is widely considered to have been the most densely populated urban area on Earth.
https://en.m.wikipedia.org/wiki/Kowloon_Walled_City
As a Chinese government enclave in British run Hong Kong, it existed as a microstate state within a state. With a population of 35,000 housed on 26,000m2 of land, it had population density of 1.3 million per square km, or 3.76 million per square mile.
I often wonder that this place did not burn down due to some accidental fire. But it does demonstrate that humans can live and prosper in less than ideal conditions when the incentive exists or a choice does not exist. Our first habitats on Mars may be similarly crowded. They will be built underground and the human inhabitants will no doubt efficiently use every cubic foot of volume within the structure.
Another paper on electroagriculture - the conversion of electricity into biomass.
https://www.cell.com/joule/fulltext/S25 … 24)00429-X
Instead of plants synthesising molecules using sunlight, they are fed energy rich precursor molecules which they metabolise into biomass. The authors claim that with present technology (22% efficient solar panels) some 4% of incoming solar energy can be converted into biomass. That is a 4x improvement over natural photosynthesis. That implies that electricity is converted into fixed plant carbohydrates with an efficiency of 18%.
Humans need about 2.5kWh of food energy per day. If that food is produced by plants, yeast, fungi and algae metabolising acetate, then some 13.9kWh of electricity would be used to feed one person each day. That is a constant power of 580W. Here on Earth, we could feed a human being using $1/day of electric energy.
What I find most interesting is that: (1) Acetate can be produced using any electricity source; and (2) Acetate can be stored in solution, allowing us to continue producing food even if the power supply is compromised. The first factor means that we can feed a human population anywhere. A colony on Pluto could be adequately fed provided they take a nuclear reactor with them. The second point means that humans won't necessarily starve if the power goes off. But they would still need reserve oxygen and CO2 scrubbing. Or enough inertia in the system to allow power to be restored before air becomes a problem.
Time for Starmer to come clean on what Net Zero means.
https://www.zerohedge.com/political/tim … strictions
The attack on UK farming is only the beginning.
The fastest stars in the galaxy may be piloted by intelligent aliens, study suggests.
https://www.space.com/space-exploration … r-suggests
The amount of resources and time required to do this makes it unlikely in my opinion. Why would they move an entire star instead of just building a ship?
UK road fuel prices remain high due to retailers margins.
https://oilprice.com/Energy/Energy-Gene … -Drop.html
A couple of things the article fails to mention.
1) Increasing proportions of UK fuel are produced using imported crude as the north sea drops off. The pound has taken a hammering against the dollar. So those costs are going up, even if the dollar price of oil is stable.
2) Electric vehicles are eating into sales of petrol (gasoline). That means the marginal cost of infrastructure needed to distribute fuel is being spread over smaller volumes. So the margin that retailers charge on what they sell has to increase.
Starmer has announced that Labour plan to cut immigration. Down from close to a million a year (the "Boriswave"). We'll see how it goes. Seems though that the Anglosphere is finally closing the main doors; Trudeu has announced Canada will be severely curtailed immigration also.
I mean, maybe we'll still be running at 200k a year. Which is still bad, but nowhere near as bad as 900k a year.
It was 1.2 million last year. And it will be about 1 million this year. We arein the midst of a mass colonisation wave that is rapidly turning the country brown. In just a couple of decades at this rate, the English will be an ethnic minority in their own homeland. Our children and grandchildren will curse us in our graves for failing to prevent this.
Starmer is probably worried about Reform, so is now delivering soundbites to try and contain their political rise. The problem is that every prime minister since Thatcher has promissed to reduce immigration, only to do exactly the opposite. Mass immigration started under Blair, Starmer's predecessor. Starmer is a dogmatic communist who seems to hate the English and would like nothing more than to replace them. He has no credibility in the eyes of the voting public and is widely hated. If he did deliver on this it might go some way towards repairing his reputation. But he is the least likely politician to do anything proactive in this area.
Methanol is water soluble. Starch is insoluble in cold water. I think contamination risks are minimal *if people do their jobs properly*.
One potential problem: Whilst making methanol is relatively easy...
3H2 + CO2 = CH3OH + H2O
...turning methanol into starch involves several process steps using enzymatic catalysts. Where do those enzymes come from? Do they have a reasonably long half life in the system? If we end up having to grow large quantities of gene edited bacteria in agar to make the required enzymes then it is going to put a dent in the whole process efficiency. It wasn't clear from the papers if the energy cost of the enzymes was factored in to efficiency.
I notice that the paper is 3 years old now and there doesn't appear to be any synthetic starch on the market. That means one of two things: (1) A technical bottleneck - difficulty sourcing reagents and scaling the process; (2) An economic bottleneck - more affordable sources of starch elsewhere.
Wikipedia: Photosynthetic efficiency
Photosynthetic efficiency is 11%. One reason is only 45% of light is absorbed, the rest are frequencies it cannot use. You could get fancy, use a prism to split colours, direct colours it cannot use to a photovoltaic cell. But I don't think that's necessary.Calculate total efficiency starting with a photovoltaic panel to convert sunlight into electricity. Is the Chinese method really more efficient?
Not sure. Using PV as the electricity source, they say it is 8.5x more efficient than corn.
https://cen.acs.org/synthesis/catalysis … eb/2021/09
https://newatlas.com/science/artificial … -from-co2/
Here is the video that prompted my interest.
https://youtu.be/e2SsheLN1t8
Here is their paper.
https://www.researchgate.net/publicatio … on_dioxide
Another trick for Mars: artificial flour. According to one research paper, wheat flour is 12.67% moisture, 10.55% protein, 0.94% fat, 74.88% carbohydrate (almost entirely starch). Calcium, iron, and phosphorus measure in mg/100g. That can vary, protein in whole wheat can be up to 15%. Artificial flour could be made by mixing wheat protein from a genetically engineered microbe with starch from chloroplasts. The microbe fed with sugar that comes from treating starch with amylase. Wheat protein is 80% to 85% gluten. Could we engineer a microbe to do this?
Pure starch can be made from methanol. It requires the use of enzymes as catalysts. Chinese researchers estimate that electrical energy can be converted into starch calories at an efficiency of 30%. That is amazing. But the resulting starch has no additional nutritional content. No protein, no carbs, no micronutrients. Those things will have to come from mixing the starch with something else. A genetically engineered bacteria producing protein might work as you suggest. Algae might be an option - chlorella is 51-58% protein. But the flavour is repulsive.
Fine Martian regolith at ambient pressure has about the same thermal conductivity as rockwool.
https://agupubs.onlinelibrary.wiley.com … 21JE006861
You probably don't need to insulate the floor. Convective heat losses will be much lower in the Martian atmosphere. I have some experience with heat transfer using timestep models in spreadsheets. I will look into building a model.
I agree that long, relatively thin polytunnel greenhouses are a more efficient solution than hemispherical domes. The mass of a pressure vessel scales with volume. But the mass of crops produced will be proportional to enclosed land area x average insolation. We therefore want the most enclosed land area for the minimum enclosed volume, whilst maintaining enough head height for human access. A tunnel appears to achieve the optimal balance.
I would agree that natural sunlight is far more desirable than artificial light. Trying to grow plants with artificial light is power hungry and should be avoided unless those plants have particularly high value. Here on Earth, people routinely grow cannabis under LED lights. But no one grows carrots and potatoes that way. That is because the cannabis has high value as a medicinal per unit mass. The carrots don't.
My concern however is more basic. The polytunnels on Mars need to be pressure sustaining structures. As you have pointed out, they also need to be protected by hard but transparent surfaces capable of withstanding abrasion. To grow enough food for 1 person will take about 200m2 of land in temperate environments on Earth. If we assume the same on Mars, that would be a tunnel some 4m wide, 2m high and 50m long. Is that really going to be affordable for each and every colonist? For a city of 1 million, we would need 1 million of those tunnels. How much labour will it take to farm that tunnel to produce food for just 1 person? Maybe we can automate. How much will that cost? Then we must consider heating. Mars is as cold as Antarctica. How much thermal power do we need to heat a 4 x 50m greenhouse on Mars? No doubt we could reduce power by pulling over an insulated shade at night. But that is another design complication that adds cost. Although I don't have exact answers to these questions, pressurised greenhouses don't strike me as an affordable solution for bulk food production. For herbs, spices and specialty fruits and vegetables, maybe we coukd justify the cost. But for staple food we need an arrangement that is energy efficient, compact and labour efficient.
Artificial photosynthesis using acetate solutions as the energy carrying medium, is far more efficient at converting primary energy into calories than natural photosynthesis. It has been a while since I looked at the figures. I will see if I can find them. For production of algae, yeast, bacteria and fungi, we can use vats rather than carefully arranged trays. This is better suited to automation and mass production. Making palatable and nutritious foods out of these ingredients may be more challenging. Many algae are considered superfoods. But the flavour often leaves a lot to be desired. Marmite is a yeast product filled with B vitamins. But it is something you either love or hate. Bacteria make cheese from milk. Microfungi are used to make quorn, which is a meat substitute. I find it inoffensive, but somewhat bland. It disagrees with some people.
It takes about 200 square metres of allotment space to grow enough vegetables (largely potatos) to feed 1 person, under Earth sunlight. On Mars, that space will need to be within a pressurised and heated surface dome. That is a lot of mass per person and a lot of energy needed for heating. It is why I am sceptical that sufficient food can be grown in greenhouses. A portion of food probably will be produced in this way. But the bulk of calories and nutrition need to come from something more efficient. Seperated chloroplasts will produce some. Plants, algae, fungi and yeast grown in acetic acid salts look promissing. That is a form of artificial photosynthesis. We can make food using these ingredients that is actually more nutritious than what most people eat from field agriculture. Synthetic starch looks plausible as well. Meat will be expensive however it is done. Something for special occasions like Christmas.
Practically everything we build on Mars will have to be underground. Whilst the issue of radiation is somewhat overplayed, exposure results in undeniable health risks. Minimising exposure will be desirable. Greenhouses are exposed by their very nature. The cold is an even bigger problem. Mars is as cold as Antarctica. Nuclear reactors will produce waste heat than can be used for keeping these spaces warm. But it is still available in only limited amounts and will be needed for other things. Going underground eliminates almost all of the problems with the Martian environment. But growing things underground in artificial light is power hungry. Growing in acetate solution appears to be much more energy efficient. Starch can be synthesised from methanol using a number of enzymes produced by bacteria. Chinese research suggests that electricity can be converted into starch with efficiency of 30%.
Energy efficiency will be key to the viability of Mars colonisation efforts. Early research assumed that humans woukd need to be fed by plants grown under LEDs in surface vertical farms. This resulted in per capita power requirements of several tens of kW. This was due to the inefficiency of converting power into light and light into fixed calories. The average human needs 2.5kWh of food energy per day. That is a constant power of 104W. Whilst that is a modest amount of power in itself, the inefficiencies involved in natural photosynthesis quickly translate into unworkable amounts of primary energy.
Real underground cities.
https://youtu.be/C-UPTs0zMxc?si=2-5sfL69_6MWQozw
Underground will be where most people live when Mars is colonised.
This pretty young lady sums up how most people feel about politics.
https://youtu.be/9YR0k6DXvvU?si=OVhtj41yQejRb8fs
They are sick of it! If you are a young man or woman trying to support a family, what matters to you is the cost of food, clothing, housing and transport. Whether or not there are gender neutral toilets, or whether drag queens feel that their feelings are respected, is unlikely to be a priority to you. People have been getting poorer for a while now and life is getting harder. People were prepared to tolerate and ignore cultural marxism during times of plenty. But as life gets steadily harder, most people's patience with this sort of thing stretches thin.
This is why Trump prevailed at the last election. He had things to say on issues that people cared about. Whilst Harris' campaign was vague and focussed on cultural issues, Trump talked about jobs, border security, energy, tax cuts and trade. Things that have a big impact on the bottom line for most people. When people are worried about the bread and butter, cultural progressive issues tend to hit a brick wall.
What it means, if indeed it can be scaled up sufficiently, is that humans can live practically anywhere. The main factor that makes it easier to live on Earth compared to say Mars, Ganymede or Pluto, is the simple fact that we can grow food outdoors on Earth quite cheaply. This makes Earth far more habitable than any of the other worlds. But if we no longer need to grow food in sunlight but can instead manufacture it in compact facilities at modest energy cost, it frees humanity from its need for a habitable environment. The same electrolysis that generates the hydrogen needed for starch or acetic acid production, will also produce the oxygen we need to breath.
We no longer need tens of thousands of acres of arable land to supply each city with food. A compact nuclear powered factory will do the job. A group of human colonists can therefore settle anywhere, provided they take a nuclear reactor, food factory and enough uranium or thorium with them. The power requirements of food production amount to a few hundred watts per capita. This is about a 50% addition to the existing per capita electricity production for OECD countries. The reactors will also generate heat needed to keep warm and melt ice into water. So we could likely live in most places without a dramatic increase in per capita energy demand over what we use now. Living in the outer solar system, we would use the waste heat from powerplants to keep living spaces warm instead of simply dumping it into the environment.
The perfection of energy efficient non-photosynthetic food production is likely to change human priorities. If we don't need abundant land to produce food, then the driver for terraforming is much weaker. Actual human living space is an almost negligible fraction of the Earth's total land area. On Mars and other worlds, we can build cities that are quite compact. Dense urban arrangements can be built within pressurised structures or within cavities beneath the surface of other worlds. Reducing the required habitable footprint of human activities makes it much easier to establish and sustain large populations in environments that would otherwise seem hostile.
In the longer term, this development also changes human prospects in the cosmos. We are no longer looking for habitable planets to settle. A rogue dwarf planet wandering through the interstellar blackness, is only marginally more difficult for us than an Earth analogue planet. We won't need habitable land. We don't necessarily need sunlight. Anywhere with tge appropriate balance of physical resources will do. That includes the icy kuiper belt and oort cloud. This development frees humanity to become a truly space faring and space dwelling species.
This youtube video discusses recent Chinese research on the production of artificial starch using hydrogen and carbon dioxide.
https://youtu.be/e2SsheLN1t8?si=Csf-khyGAqfMP668
Chinese researchers calculated a realistic efficiency of producing starch in this way. They assume:
Hydrogen electrolysis: 85%
Hydrogen to methanol: 85%
Methanol to starch: 61%
Additionally, the heat and pressure needed for the reaction steps consume energy, which amount to another 32% energy loss (68% efficiency).
Multiplying all of the efficiencies together, we end up with a 30% conversion efficiency of electricity into starch. Starch is the main ingredient in bread and pasta, which are staples of western diet. The average person needs 2200 Calories to maintain a stable weight. That equates to 2.56kWh. If electricity is converted into starch at 30% efficiency, then 8.53kWh would produce enough starch to feed one person for 1 day. That is equivalent to a constant power of 355W to feed 1 person. At an electricity cost of $0.1/kWh, this would cost $0.85/day. Or to put it another way, a single 1200MWe nuclear reactor with a 90% capacity factor, could feed over 3 million people.
In reality, no one would obtain all of their calories needs from pure starch, because aside from its calorie content it is nutritionally empty. But as an additive to processed food like bread or pasta, this could meet a sizable portion of human calorie needs. This process, assuming it can be scaled to industrial levels of production, has special significance for Mars colonisation. On Mars, it will be impractical to feed colonists with plants grown in acres of pressurised and heated greenhouses. Artificial lighting in vertical farms is also impractical, as it would consume enormous power. This is due to the combination of inefficiency in the light source and low efficiency of photosynthesis.
To produce food affordably, we must side step natural photosynthesis and find methods of efficiently converting primary energy into food. Artificial starch production allows a substantial ingredient of human food to be produced in a compact facility using solar or nuclear energy. We have previously discussed artificial photosynthesis, by growing plants, yeast and fungi in acetic acid salt solutions. By combining both processes, we will ultimately be able to convert electricity into food with high efficiency in compact volumes.
In previous discussions, the power requirements of a Martian colony were found to be extreme: 10s - 100s kW/capita. This was largely driven by the need to grow food using a combination of natural and artificial light under natural photosynthesis. Thermal losses from growing areas also required substantial heating. If artificial photosynthesis and starch production are instead used, then the food, heat and domestic electricity needed by Musk's proposed 1 million person colony could be comfortably powered by a single 1200MWe nuclear reactor or 4 SMRs with a power output of 300MWe each. The BWRX-300 should be operational by 2030. Something like this would be ideal to support Musk's proposed city.
https://www.gevernova.com/nuclear/carbo … ar-reactor
Some 20 tonnes of 5% enriched uranium are needed to produce 1GW-year of electricity. So a single 24 tonne annual shipment of low enriched uranium could replace the need to ship 100,000 tonnes of food from Earth every year.
Why we should NOT terraform the moon.
https://youtu.be/l6ZmbMksv94?si=pFu3pUBTeoaI5kIL
The gist of the video is that the moon is a place we can strip mine without ever worrying about damage to the natural environment, because it has none. The lack of atmosphere makes exporting raw materials relatively easy. Giving it an atmosphere would ruin its value to humanity. This makes sense to me.
Mars is not a good place to colonise.
https://youtu.be/ymtTrwDKnuE?si=eRBNt_nePHppJRHi
The author of this video does make some valuable points. Colonisation will depend upon being able to make things that can be sold back to Earth. The moon is logistically better placed, being much closer. But Mars has far more carbon, hydrogen and nitrogen. The moon is a better source of bulk materials, but it lacks the elements of life. The moon is a good place to establish mining activities. But a lousy place to actually live. Mars is further away. But it has more of what we need to live. Either way, we will be returning to the moon first. What we make on the moon will ultimately facilitate our colonisation of Mars.
Void, you could use thermite to weld your blocks together. Other options would be IR lasers and electron beam welders.
The reaction force needed to drill into the surface could be provided by a cable or net of carbon fibres wrapped around Phobos.
***
Additional: a plasma torch could be used to weld relatively thin ceramic components in vacuum.
One thing that the video misses is that a solar thermal powerplant can be made mostly from iron. Reflectors need a thin coating of aluminium no more than 10 atoms thick. But the reflector shell, receiver, pipework, heat exchangers and most of the power cycle machinery can be made from iron. Iron is by far the easiest metal to make on the moon. It is also the cheapest in terms of energy.
PV requires a great deal of other materials. Making polysilicon on the moon is impractical. The scale of plant needed to make semiconductor grade silicon is immense and mass production on Earth took many years to establish. Using PV would mean shipping polysilicon from Earth. The mass burden would then favour thin film PV. Unfortunately, that would push down efficiency and operating life. That increases the amount of other materials needed per unit power from PV.
The video author is correct in saying that solar thermal plants will need large radiators. However, radiators containing liquid sodium will not need to be massive, as the vapour pressure of sodium is low even at red hot temperature. An S-CO2 turbine is compact enough to be imported. A 1MW turbine is about the size of a tube of pringles. Even a 1000MW unit could be easily accomodated within a Starship payload. The amount of torsion acting on the shaft a turbine that compact must be impressive. Printed circuit heat exchangers can be 3D printed on the moon. Or we can build tube and shell heat exchangers. Both will work. The moon is a very dry environment. So dry in fact that we might even use sulphur dioxide as a working fluid. This may offer even better power density than CO2.
Kbd512 wrote: 'The thin film photovoltaics are already at 60 grams per square meter and thinner than a human hair, so very delicate.'
I find it impressive that we can make films that thin. But even on the airless moon, they would be vulnerable. Rocket engines from spacecraft landing and taking off, will propel dust particles many miles on the moon. We woukd need to build thin film PV a long way from any landing sites.
Pure sulphur found on Mars.
https://www.space.com/nasa-mars-curiosity-sulfur-rocks
If we can find concentrated deposits of sulphur, then we have the key ingredient for manufacture of sulphuric acid. This can be used for acid leaching of ores, allowing metal oxides to be converted into soluble sulphates.
Solar thermal vs solar PV on the moon.
https://youtu.be/3oFi6S-4mp8?si=jvEhmCNcoHujZpzX
The comparison appears to neglect the enormous energy cost of semiconductor grade silicon. Compared to that cost, the energy cost of supporting frames is small.
In "Major Policy Shift" Biden Authorizes Ukraine's Use Of US Missiles To Hit Targets Inside Russia
https://www.zerohedge.com/markets/major … ide-russia
The dementia-ridden, deep state puppet in the White House just greenlighted World War 3 on his way out to the glue factory.
Void, the idea of a repurposable SSTO sounds like a good one to me. It avoids the need to consider reentry in designing such a vehicle, along with the weight and design complication that reentry imposes. A single use SSTO can also get away with slimmer structural margins, as long term creep problems in stressed components are not a concern. The ship needs to survive one stress cycle and then it is done. The engines only need be designed for single use. Maybe ablative lined, pressure-fed engines will do the job, especially if the ship is large. When the ship reaches orbit, different parts of it can be cannibalised for different purposes.
This is a different approach to reusability. But the ship is reused none the less. If you can sell the pieces of it in orbit to customers for about the same cost as you bought it for on the ground, then launch costs for any minimal cargo remain cheap.
Repurpose is arguably more energy and resource efficient than full reuse. Most of the takeoff weight of the vehicle is fuel. A large part of the energy in that fuel is used to accelerate the dead weight of the ship to orbital velocity. That energy then gets wasted and dumped back into the atmosphere when the ship reenters. The way to eliminate waste entirely is to turn the whole ship into orbital payload, i.e your idea.