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Once again, Louis sees what he wants to see.
Lazard's November 2018 analysis of levelised cost of storage for utility grade solar and lithium ion storage, gives a median cost of $124/MWh. This is the most respected and often cited source by green techies of levelised cost of energy, although it does not give us much clue as to where cost reductions are coming from and whether they are sustainable long term. It is really just looking at trends and projecting them into the future.
https://www.lazard.com/media/450774/laz … vfinal.pdf
But note from Lazard's analysis, that Lithium ion battery storage only accounts for about 2 hours of full capacity for utility scale PV and storage. This makes the battery useful for smoothing frequency fluctuations and reducing the slew rate long enough to get enough spinning capacity (natural gas and coal) back online. It is not intended to work as a standalone solution. For that to happen, storage would need to be at least a couple of orders of magnitude greater than is presented here. It would need to cover lulls in solar capacity lasting for days and maybe, dependent upon location, seasonal fluctuations in solar energy abundance.
As the required energy storage capacity increases, the cost per MWh increases geometrically. This is because in addition to being larger, the energy store will fully discharge less frequently and is therefore less well utilised. For example, compare the situation of a two batteries, both designed to produce 1kW of power; one storing power for an hour and the other storing a whole week of power. The first battery will regularly charge and discharge on an hourly basis and over the period of a year; it will have stored and discharged up to 8766kWh of electricity. The second battery operating in the same system will store and discharge exactly the same amount of energy, given that it is discharging at the same rate. But it would need to be 168 times larger and commensurately more expensive to store a week of power. Energy storage in batteries is only affordable in small quantities acting over short periods of time. It is about avoiding crashing the grid before compensating powerplants can be brought online.
It is the need for large volume, long-term energy storage that has led to many green-tech enthusiasts citing liquid hydrogen as an energy storage medium. Although this is relatively inefficient and expensive, it allows energy to be stored in liquid form in insulated tanks and is therefore better suited to long-term storage. Louis's methane-oxygen system is an attempt to do the same thing, but with the extra step of reacting the hydrogen with CO2 in a chemical reactor to make methane, which is then cooled to cryogenic temperatures and stored in an austenitic stainless steel or aluminium tank. None of these things actually happen at present, largely because they are not even close to being competitive with conventional generation. What does happen is the solar power plant runs alongside coal or natural gas burning power plants that ramp up production when the sun isn't shining, or when clouds reduce output. So the solar power plant has the effect of modestly reducing fuel consumption in the coal or NG plant, which is what I was alluding to before. The need to continue using fossil fuels to provide backup for wind and solar, goes some way towards explaining why Germany burns more coal than any other country in Europe. Not very green at all.
https://www.zerohedge.com/energy/where-europe-runs-coal
Is solar power really the cheapest form of energy, before we take into account backup and storage? I suppose that depends upon who you ask. About 80% of solar panels sold in the US market are made in China and the Chinese have faced a number of lawsuits for dumping in order to corner the market and maintain employment back home. Solar is also heavily subsidised and subsidies are largely hidden.
https://stopthesethings.com/2018/08/23/ … subsidies/
Perhaps most telling of all, renewable energy market penetration shows a positive correlation towards increasing electricity cost.
https://wryheat.wordpress.com/2015/08/0 … skyrocket/
If we attempt to carry out a solar energy revolution on Mars, we will have to face all of these problems, on a planet where there are no fossil fuels; where sunlight is about as intense at the equator as it is in Alaska and where we need 10 times more electricity just to survive. Any takers?
A solar power plant in China, is basically a coal burning power plant. The solar plant is useful in so far as it reduces coal consumption in a legacy powerplant by 20%, reducing pollution and stretching coal resources a little further (the Chinese are past Peak Coal). It isn't much of deal, as the coal plant still has operating and maintenance costs, but tye solar power does reduce the fuel bill. All in all, it will be more expensive than the coal plant on its own, but the reduced pollution is something worth paying a little extra for. It's a terrible deal if you have to build the coal plant as a dedicated backup powerplant. The same is true for wind power.
I would have to agree with Spacenut and Louis. The Chinese are geopolitical rivals to the western world, that have stolen huge amounts of intellectual property. They fully intend to dominate the world and spread their authoritarian control everywhere. I would not personally do anything to help these people, nor would I give them anything that I didn't have to.
There is nowhere on Earth a "low-cost" nuclear reactor. There are just differently expensive nuclear reactors, which is why when the market is left to choose it opts for fossil fuels, hydro or, increasingly, wind and solar.
The situation on Mars might be slightly different in that you can perhaps invest less in safety owing to the absence of large human populations (or, so we are told, other organic life). However the incidence of global dust storms would appear to create the risk of radioactivity being quickly spread around Mars.
I really can't see why we would go to the bother of manufacturing or importing nuclear reactors on Mars, when there is a readily available energy source which is practical, cheap and effective ie photovoltaic power (with methane-oxygen as the primary energy storage method).
Lol. The Chinese are doing a very good job of building reactors at low prices. The French did until they started messing with the over-complex EPR. In most major developed economies this is one of the largest sources of baseload electricity and is the cheapest.
Louis wants to build a solar power economy on planet with half of Earthly sunlight, on which we need 10 times as much electricity per capita. If we cannot make this work on Earth, what hope is there for Mars?
The Chinese are developing a low-temperature light water reactor for district heating purposes.
https://www.nextbigfuture.com/2017/12/c … lants.html
This is very cheap, because a reactor that heats water to ~100C does not need a pressure vessel and corrosion rates at such low temperatures are low enough that material selection becomes easy. There is very little danger from a loss of coolant accident, as the whole reactor can be located at the bottom of a deep pool at ambient pressure with huge heat capacity.
A bulk low-grade nuclear heat source on Mars would be a relatively easy thing to build. We could use Mars mined natural uranium to fuel a graphite moderated low-temperature reactor. Cladding and fuel channels could all be made from aluminium if temperatures don't get much above 100C. Because Martian ambient temperatures are lower than those of Earth, a low temperature reactor could still generate electricity at a moderate efficiency, by using something other than water as a working fluid. But a water cooled and entirely heat producing reactor, would be useful in water mining and greenhouse heating activities.
This is primarily for Calliban, and the topic in general ...
Do you buy into the concept that you could become a trillionaire asteroid miner?
If you do, it would make a potentially significant difference in how this topic develops.
Going only from the posts you have provided the global forum audience, I think there is a better than even chance you are worth at least a $2 bet.
That's all I am willing to risk right now, but that could change as this topic advances.
Related to the above is the question of whether you have had a chance to look at the NASA mission planning site that SpaceNut found?
My understanding (or at least first impression) is that the site is designed for serious mission planners, including those who are intending to make proposals to NASA.
You may well have chosen an asteroid to focus upon to the exclusion of all other distractions, but if you have, I missed it.
I was interested in Apophis, but my impression is you have not yet found it compelling. I understand that size of the asteroid you want to select is an important consideration, along with orbit and spectral characteristics.
(th)
Tahanson, I am a middle management engineer who earns before tax, about $100,000 in US money; about £80,000 in UK money. A good wage that allows me to support my family comfortably, but I am not rich by any definition. I am limited on what holidays I can afford on the surface of the Earth. I will not be financing any trips to near-earth asteroids unless there are some much unexpected developments in propulsion technology over the next 20 years; nor would I be a good bet for the asteroid equivalent of Robert Zubrin. I have limited mechanical and nuclear engineering expertise and am respected in the limited circles of my profession, but I am not on the same level as a man like Zubrin.
That said; feel free to share whatever we have discussed here with whoever you like. If it is useful to any real world space agency, then it was time well spent. We have only discussed here some interesting concepts; we have not developed practical mission architecture yet. And I doubt that I have the expertise to take things very much further. Maybe you and some of the others do.
Regarding Apophis, the size of the body would require that we modify the initial concept that I raised. A bag big enough to allow a 300m asteroid to be rotated to provide lunar levels of gravity and 0.5bar internal pressure in any tunnels that we dig; would blow the lift capacity of any heavy-lift vehicle on the drawing board. To make that affordable would require ISRU which SpaceNut has done a good job of expanding upon. I think it would be difficult to mine enough material from Apophis in zero-g and construct a fibreglass bag from the mined material. This is why I suggested that we first focus on a smaller target that can be enclosed with a bag launched from Earth. We could spin up the body to provide gravity and dig tunnels that could be pressurised. We would build our 'bag factory' inside the tunnels, using waste silicates from mining as feedstock. Precious metals would go back to Earth; the bag that we make using waste materials would then be used to repeat the process on a larger asteroid. A staged approach.
The other problem with Apophis is that it appears to be a resource poor LL Condrite that contains little free metal. We cannot be very sure based on spectroscopic data. When it comes to earning money from asteroid mining, the best targets contain an abundance of free iron that contains dissolved platinum group metals and cobalt. These are the things that we have a chance of returning to Earth and selling for profit with the correct mission architecture. So choosing a target that is rich in these things really is important. Other useful materials are volatiles like carbon and water, which are useful for all sorts of things, including life support. Other bonuses include a low delta-v orbit w.r.t Earth. We have also discussed asteroids with orbits that lie between Earth and Mars, which could be used as cyclers.
The thing that leads me to believe that near-Earth asteroids are the best near-term targets for manned space flight is that they appear to be the only destinations that allow space flight to be profitable in a business sense, with realistic investments. There are clearly identified minerals that can be mined and sold with profit with limited outlay. That isn't true for Mars or the Moon.
I concur with Louis in this instance. If real nuclear reactions are taking place, one would expect the emission of gamma rays as excited nuclei relax. It is also difficult to initiate nuclear reactions in a metal without some amount of induced radioactivity, which implies both gamma and beta activity.
If these things are not being observed, it suggests that either nuclear reactions are not the source of any observed energy, or that something unexpected is taking place that challenges our understanding of nuclear physics. I would be more than happy for this to be the case; but it is far fetched at this point.
The RBMK reactor is much maligned in the Western world, due to it's involvement in the Chernobyl nuclear accident. In spite of the known problem of positive coolant void reactivity coefficient; the RBMK had some significant advantages over western light water reactors. These are seldom discussed, but are highly relevant here.
1. The RBMK is a pressure-tube boiling water reactor. This is a direct cycle, in which water boils within the core and steam is dried and passes directly to the main turbines. This means that no steam generators are needed; merely a steam drum.
2. As a pressure-tube reactor, the RBMK does not require a pressure vessel. The fuel is contained in zirconium boiler tubes running through a lightly pressurised graphite moderator stack. The pressure vessel for a PWR or BWR is a very expensive and difficult to fabricate component. It becomes progressively more difficult to construct, the larger it is, as wall thickness increases. To scale up an RBMK, it is relatively simple to increase the size of the moderator stack and simply add more fuel channels.
3. The RBMK is a graphite moderated reactor, with water used for cooling, not moderation. This results in much better neutron economy than a typical Western light water reactor, allowing the use of lightly enriched or even natural uranium as fuel.
These collective advantages allowed the cash-strapped Soviets to build extremely large and powerful reactors quickly and at low cost. The Ignalina reactors were built in the late 1970s and had power of 1500MWe; far more powerful than any western reactor in operation at that time. RBMK units were planned with power up to 2400MWe. Such scales are possible because reactor power can be increased simply by increasing the number of fuel channels. As was noted previously, the economics of nuclear power reactors tend to improve with increasing scale.
Of course, the RBMK has design deficiencies which make it a dubious choice for future power generation. It is noteworthy however, that whilst the positive void coefficient of the RBMK did directly contribute to the chernobyl accident; the real cause had more to do with a complete absence of safe operating culture. The reactor exploded during at experiment, during which control rods were fully withdrawn to burn off a xenon peak and trip settings were deliberately disabled. Most nuclear reactors would be dangerous under those conditions. It is unlikely that a PWR would survive a prompt criticality without significant fuel damage. In a modern design, we would coolant feed water with low temperature trip settings. We would design control rods without graphite follwers and design the control rod motors to allow rapid insertion of control rods into tye core. Most importantly, we would not be reliant on manual operator control.
If we can import enriched uranium from Earth, then we can adjust the concept of a pressure tube reactor to use a calandria filled with light water, rather like a CANDU. This would eliminate the coolant void temperature coefficient problem of the RBMK and would allow a far more compact core, without sacrificing the benefits of a pressure tube boiling water reactor.
In recent discussions it was established that human life on Mars will be very dependent upon abundant, low cost energy. This will be needed in the form of heat of all qualities and electricity.
http://newmars.com/forums/viewtopic.php?id=9187
Initial estimates indicate that that electricity consumption may need to be 10 times greater than North America average, as power is needed for the production of propellant, food, water, metals and the mining of ores. In addition, large quantities of low-grade heat are needed for the production of water from subsurface ice and potentially, the heating of greenhouses. A city of 1million people, as envisaged by Musk by the end of the 21st century; will require up to 10GWe of power on a continuous basis. For such large quantities of power to be affordable in any realistic economy, it must be provided cheaply, for the simple reason that more energy is needed to meet basic functions on Mars.
Power in such large quantities can be provided only by using nuclear reactors. Providing 10GWe of time averaged power on Mars using solar power sources, would require a solar power plant covering several hundred square kilometres. Large scale civilisation on Mars will require the use of nuclear power on a scale that has yet to be replicated on Earth.
I have started this topic to explore how we could develop nuclear power both cheaply and on a huge scale on Mars. Specifically, what technologies we will use; which systems will be imported from Earth; the optimal size of units, etc.
I ran a few calcs using the thin walled pressure vessel equation on how much steel we would need to produce 'cropland' on Mars. My starting assumptions are that we would carry out agriculture in steel-framed tunnels, 2m in diameter; pressurised to 50KPa, with glass, plastic or both providing transparent panes between the steel frames. I have assumed a carbon steel yield strength of 500MPa and a safety factor of 5.
The result: Producing 3000m2 of cropland, would require a tunnel some 1500m long. Some 4.7m3 (36.7tonnes) of steel would be needed for the pressure resisting frames. On Earth, new steel has an embodied energy of about 30MJ per kg. So producing the required steel to feed one person would require some 1100GJ of energy. That is 306MWh – or 35kW continuously for one year, per person. Most of this would be electrical energy input to an electrical furnace and electrical input into an electrolysis cell, assuming that hydrogen is the reducing agent. This assumes that embodied energy is the same as on Earth. Even more embodied energy is needed for the glass between the frames and the hot water pipe that would need to run down the middle of the tunnel to keep it warm under Martian conditions.
It is easy to take for granted the free ride we get here on Earth, with abundant liquid water falling from the sky; air that we can breathe without pre-processing; temperatures that keep water liquid and abundant fossil fuels that can be burned in air to produce heat. Without those advantages, Martian colonists look like they need 10 times more electricity per capita than comparable people living on Earth. To enjoy similar living standards, that electrical energy would need to be 10 times cheaper, presumably. They will need nuclear reactor designs that they can build quickly and cheaply.
Going off topic a bit: Musk is talking about establishing a city with a million people living on Mars by the end of this century. By my estimates, such a city would need to be supported by a power supply of about 10GWe (assuming 100% capacity factor) if they are using synthetic lighting to produce food. With polytunnel agriculture, they would need less electric power but a lot more heat.
A single large nuclear reactor here on Earth produces around 1.2GWe, with around 2.5GW of waste heat. We would need 8 of them to feed and power a 1 million person city. And that is without considering the need for other things, like steel, concrete, air, propellant, mining activities, etc. If Musk is serious about colonising Mars, he needs a plan to build powerful nuclear reactors both cheaply and quickly. A nuclear power source of 10GWe will require some 200tonnes of low enriched uranium or 50 tonnes of highly enriched uranium per year. I would imagine the former would be more acceptable and it would appear most practical to import this from Earth.
Many of the reactor systems will need to be built on Mars, as they will be too heavy to lift from Earth. A careful analysis will be needed to determine which systems need to be imported and which will be manufactured locally. To avoid the need for heavy stainless steel steam generators, some sort of boiling water reactor may be most appropriate. We can manufacture the pressure vessel on Mars from pre-stressed concrete, with an aluminium or stainless steel liner. The high-pressure turbine can be imported. The low pressure turbine and condenser can be made from carbon steels on Mars, with careful chemistry control of coolant water. Control systems will be imported from Earth, as will many components like injection pumps and fuel handling machines. We will be building reactors that are considerably more powerful than their Earth equivalent designs. Larger reactors have better utilisation of materials and are generally more economic per unit power than smaller reactors. And cheap is what we need.
Growing food is a water-hungry activity.
https://www.aboutcivil.org/water-requir … crops.html
Corn requires 4000m3 per hectare per year. Fruit crops require double this. Even with heavy recycling, water requirements are very significant. To irrigate 3000m2 of land to grow corn, some 1200m3 of water are required in 1 year. That is the land we have assumed will be needed to feed just 1 person.
Recall that on Mars, water is a resource that must be mined from ice that is frozen as hard as concrete. Most suggestions seem to focus on mining water by heat injection into buried glaciers. The heat of fusion of ice is about 450KJ/kg. The energy needed to heat the ice from -60C to 0C, accounts for another 120KJ/kg. Taking into account thermal losses, we need about 1MJ of heat for every kg of water that we mine. That is about the same embodied energy as contained in 1kg of concrete on Earth. To mine 1200m3 of water would require 1200GJ of thermal energy. That is 333MWh, or 40kW of heat for nearly a year, per person.
If recycling is less than perfect, then even more energy is needed to make up the losses. If losses are as high as 10% per year, then another constant 4kw of power is needed per person to make up losses. And recycling itself will consume energy.
One option that has been discussed on this board is the use of LED lights to grow food in compact volumes underground. The average human needs to consume about 10MJ of food energy per day. Assuming a generous 2% conversion efficiency of electricity into food energy; the electrical requirement to produce food for 1 person is 500MJ (140kWh) per day. That's a continuous power requirement of nearly 6kWe per person. To feed a thousand people would require a continuous power input of 6MWe.
Life on Mars will be an energy hungry activity and a lot of that energy needs to be in the form of heat. You can count on needing lots of nuclear power to get this done. A 1000 person base will need a power supply rated in the MW, just to produce enough heat for water mining. Any rapid increase in population expands this imperative.
I seem to remember reading that Martian dirt already contains nitrates?
To produce ammonium nitrate, ammonia reacts with nitric acid in an acid-base reaction. According to this source, it takes about 150lb of nitrate to fertilise 1 acre of corn. The energy cost is about the same as driving a car 650miles – about 20 gallons of gasoline, or about 50MJ/kg.
https://www.science20.com/agricultural_ … zer-108036
So to fertilise 1 acre (4000m2), requires an energy investment of 3.3GJ. If the average person is living on 3000m2 with 1 crop per year; that is an energy investment of 917kWh per person, or about 2.5kWh per person per day. A colony of 1000 people would need to invest some 917MWh per year into fertiliser production – the equivalent to a continuous power output of 105kW.
Pricey. And the reality is that we will be manufacturing on a smaller scale than Earth based industry, without the benefit of natural gas as a source of hydrogen. So the real energy cost will be greater. Living on Mars will be an energy hungry activity.
"Only slight problem - we can't master fusion yet."
Yes and no. Fusion can be made to take place in a low cost fusor that you can build in your garden shed and of course fusion yields ample energy in a hydrogen bomb. But achieving breakeven and ignition in low density plasmas is challenging.
Given the difficulty of achieving magnetic fields stronger than 45T; particle density is limited. The easiest way of meeting the lawson criterion is to increase confinement time by increasing reactor size. Hence, the bigger a reactor is, the better its performance. For fusion, it makes far more sense building terrawatt scale machines than it does building 100MW machines. For reactors with cores that large, the plasma will begin to extract energy from neutrons as well.
There was a recent scientific paper that suggested a 3 cm thick covering of transparent aerogel could have a very significant impact in heating up the planet. I did some calculations as regards making enough of that material to cover a large part of the planet...we are talking about billions of tons of material but it's probably still one of the most efficient ways of getting the desired result.
Agreed. About 4 billion tonnes by my estimate for the whole planet. Trouble is you can only work with what's there. If there is only enough CO2 to double or triple atmospheric pressure, then you aren't going to be growing crops under thin polytunnels or building megacities under tents.
Whilst terraforming does not have to imply Earth analogue conditions, it is what we are ideally aiming for. We won't get there without a lot of energy, time or both.
380mb would be more than twice what is necessary for life, and a crazy fire risk.
Most of the benefits of terraforming come from the first, minimal, steps. Some oxygen in the atmosphere, warmer temperatures, better radiation shielding (including an ozone layer), and the ability to grow food on the surface. A ~100mb mostly CO2 atmosphere is a long way from a 1bar O2/N2 atmosphere.
Agreed. If we could build greenhouses that didn't have to be pressurised, the planet would be a lot more habitable. And with surface doserates lower, habitats would be easier to build. The question is whether there is enough CO2 on Mars to do that.
If the higher latitudes of Mars could be warmed using orbital mirrors, then ice would sublime. UV action would dissociate the water vapour into O2 and H2, with the later escaping into space. I would imagine that this process would be slow.
To create a 380mbar pure oxygen atmosphere on Mars; some 1.45E15 tonnes of oxygen would be needed. This could be created by electrolysing some 1.6E15 tonnes (1.6million cubic kilometres) of water. Near surface deposits of ice identified on Mars account for 21million cubic km. So Mars could be terraformed by electrolysing <8% of its detected water reserves. So creating a breathable atmosphere is achievable in principle.
But the energy requirements are intimidating. To produce 1.45E15 tonnes of oxygen through electrolysis (even at 100% efficiency) would consume 2.8E25 joules of energy, or 887million GW-years. That is the equivalent of a million large nuclear reactors, running for 887 years; or all of the sunlight falling onto Mars for 50 years, ignoring any conversion losses.
Basically, to do this in any reasonable human timescale, would take some very big fusion reactors. And the waste heat would be enough to warm the planet up quite substantially. We would probably need to use the polar caps as heat sinks and polar water would most likely be our feedstock. We would probably build a ring of mega reactors around the northern polar cap.
Whilst reactors this size sound enormous, they would probably be on a scale comparable to some of the largest man-made structures on Earth. With a power density of about 15MW/m3 - a spherical fusion reactor producing 1E15 watts of heat would be ~500m in diameter. Powerplants this huge would benefit from large scale economies.
Vapour pressure of ice at different temperatures. At 0C, vapour pressure is 600Pa. Even at -80C, the vapour pressure is 0.05Pa. The ice would need to be contained within an envelope or lightly pressurised cover to prevent it from subliming.
http://www.vaxasoftware.com/doc_eduen/qui/pvh2o.pdf
https://www.lyotechnology.com/vapor-pressure-of-ice.cfm
If the plan is to cover the ice in some way, another option might be to allow an icy body to melt forming a ball of water in space. Even in the meagre gravity of an iceteroid, hydrostatic pressure would reach atmospheric at a depth of several km. A submarine city could be built within an envelope of air, provided that the whole structure was suitably ballasted.
As far as I'm aware, freefall doesn't have the same negative impacts on plant growth as it does on animals. Given the expense and complexity of centrifuges, it doesn't make much sense to incorporate farms (which take up a lot more than that cities do, here on Earth) into the non-freefall section of habitats.
A 500m diameter sphere would have a volume of approximately 60 million cubic meters, and 800 thousand square meters of surface area. If filled with 'air' (probably an O2/CO2 mix) at 50-100mb pressure, it would contain 6000 tonnes of air, which is a sizeable buffer for a small colony. Windows could let light in from the outside for the forest, or lights could be strung inside for the plants (which is what would probably be done further out than the asteroid belt - I'm thinking of the Trojans here). In the middle of the spheres would be the centrifuge towns, where people and their livestock would live. A 100m diameter ring that's 50m wide would have 1.5 hectares, enough space for a few hundred people. Spinning at 4rpm would give you 0.9g, dropping to 0.8g on the third floor/roof. You'd want to pair the ring with another, bringing it up to 3 hectares. Hopefully we'll be able to get away with less gravity, allowing us to drop the spin rate and/or diameter. 25m and 3rpm gives us 0.25g, and 0.75 hectares if scaled down in the other dimension. That's still a colony of over a hundred people, though.
In the outer solar system, the spheres could be built out of ice, using a plastic inflatable mould. Inflate with a little bit of gas, then pump water between the layers and let it freeze. The bag would mass on the order of 100 tonnes? Once the shell is established, it can be further worked on from the inside to insulate it and strengthen it for the full pressurisation. If in the Trojans, the colonies would be quite close to the others, maybe a few million kilometres from their neighbours. A chemfuel spaceship could make trips between them in weeks, even without tether assistance.
A very interesting idea. Given that the shell has negligible gravity, convection within it would also be negligible as a heat transfer mechanism. This would allow a thermal gradient to form, whereby the air at the centre of the sphere is warmer than the air at its surface. The centre of the sphere could be warm without the risk of melting the sphere.
For Calliban re topic in general ...
RobertDyck just posted about using Rhenium as a catalyst for removal of perchlorates from waste water on Earth.
Rhenium is (apparently) rare on Earth, but at the same time it appears (from Google results) to have many significant applications.
By any chance, have you found an asteroid (or other body) that has a measurable amount of Rhenium?
(th)
Some really excellent ideas here. I will comment in more detail tomorrow.
Rhenium is a platinum group metal. It is present as a natural alloying element in free iron within asteroids. Overall platinum group concentrations are 100ppm. That is about 20 times greater than Earthly platinum ores.
Another potential candidate; about the right size (50m) and apparently in a suitable low delta-V orbit (0.81-1.01AU).
https://en.m.wikipedia.org/wiki/1999_AO10#
We could potentially begin by mining a small body like this using a restraining bag brought from Earth (which would weigh about 12 tonnes) and set up a bag factory (for want of a better phrase) within the excavated tunnels, where we would have access to a breathable atmosphere and artificial gravity (by spinning the asteroid) and could assemble the equipment and use excavated material as feedstock. Hence, a bag manufactured from materials mined from 1999_AO10, could then be used to colonize a larger body like Apophis. We could keep boot-strapping like this, using materials mined from one asteroid to begin settling another. Start with tiny bodies and gradually build up to larger ones.
A 50m diameter asteroid like 1999_AO10, would mass around 150,000 tonnes, assuming a stony composition. This is more than enough silicate material to construct a basalt fibre restraining bag for a 300m diameter asteroid like Apophis. A 50m diameter asteroid has volume of 65,000m3. If a sizable portion of this is excavated creating pressurised tunnels and voids; it would appear to provide ample space to set up manufacturing equipment for manufacture of new bags. On this basis, only the very first bag would need to be lifted from Earth. Presumably, this would be relatively small, with all subsequent bags for new missions being constructed in space from materials mined from asteroids. With this in mind, it would be wise to begin with a very small asteroid, such that all of the equipment needed can shipped out using no more than a few heavy lifts, and preferably just one.
We would gradually mine the asteroid until it was just a thin shell of rock. At this point, we would shift production elsewhere.
I did not anticipate that an airtight bag would be a good idea. Even if it started airtight; micrometeors would punch holes in it quite rapidly. The idea was more about providing external compression to the asteroid, such that tunnels could be lined with a thin polymer membrane and pressurised without exploding a rubble pile asteroid. Later, a strong enough bag would allow the asteroid to be spun to provide artificial gravity within the internal tunnels and voids.
I agree that ISRU is a good option for manufacturing the bag. Given that it need not be airtight, a simple woven fibreglass would do the job. Whilst a single sheet could be used, it might be more effective to use a number of hexagonal sections, connected using couplings that can later be tightened. The purpose of the bag is to prestress the asteroid.
The larger the asteroid, the more important ISRU becomes. For a small asteroid <100m in diameter, it is possible to use a heavy lift vehicle to deliver a Vectran bag to Earth orbit and then transfer the bag to its target using electric propulsion. For anything much larger than 100m; the number of launches needed starts to grow excessive.
The feedstock for manufacturing the bag at target would be bulk silicates from the surface of the body. This would presumably be melted, extruded into fibres and then spun into fabric. Apophis, with its ll condrite composition would be a good candidate for this. How it can be done, reliably on a low mass budget, is worth exploring.
I hope that interest builds in placing such a transponder, because it would be understandable if the opportunity to place a probe on the object to collect detailed information about the material it contains. The surface readings may reflect the contents of the entire object, but there might be material of value under the surface.
(th)
Agreed. But without knowing it would be a leap of faith to commit resources to Apophis. On the plus side, even iron magnesium silicates could be a valuable engineering material in Earth orbit. Iron and magnesium are valuable metals and silicate materials can be used to produce semiconductor materials and basalt fibre.
It would be productive to consider options for reducing the required mass of the restraining bag needed to prepare Apophis for mining and colonisation.
An energetically easy to reach asteroid with a diameter slightly less than 40m.
https://en.m.wikipedia.org/wiki/2000_SG344
This is small enough to enclose within a bag weighing just a few tonnes. The asteroid weighs some 71,000 tonnes. It would be interesting to plan a mission that could be carried out using a single heavy lift launch.
GW, regardless of whether you personally like Trump or not, is it really in a America's best interest to see the opposition tie up a sitting president with constant spurious allegations in an attempt to force him out of office? The man does have a job to do. He was elected to do it. If he fails to do it, you suffer.
The Mueller investigation dominated his first term and it ended up finding nothing because the allegations it was investigating, were smears raised by Trump's opponents. Hillary Clinton accused Trump of doing exactly what she had been doing; taking money from the Russians in exchange for political favours. Why is this woman not in prison?