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A 747 can carry well over 400 passengers...whereas the Hindenburg carried 50...so you'd have to multiply your 3.2MW by 8 for a fair comparison I would say, in terms of the energy required to carry x no. of people.
Of course Louis. I reference the Hindenburg only as a very loose example of engine power needed. We would not replicate it precisely today. Frames would be built from carbon fibre reinforced polymer instead of aluminium; gas cells probably the same and the outer cover some sort of fibre reinforced polymer. We would also use CFD and CAD to determine a more optimised shape. All in all, a modern rigid the size of the Hindenburg would carry a lot more passengers. But I think freight is a more likely use for such a vehicle.
Hydrogen would still have to be used as lifting gas. There isn't enough helium on the planet to roll out the airship as a mass market solution in the quantities needed.
The undoing of the airship is its slow speed. Not only is this inconvenient for passengers, but it means that an airship will deliver far fewer passenger miles than a jet aircraft of comparable capacity in its lifetime. To put it another way, a 747 carrying 400 passengers, could cross the Atlantic perhaps 5 times (2000 passenger journeys) in the same time as it would take any airship to cross it once (400 passenger journeys). Unless fuel is very expensive, it will be difficult for an airship to compete, as both options have capital costs.
I ran a few numbers for solar power satellites.
Northropgrumman manufacture lightweight space solar power systems.
https://www.northropgrumman.com/Capabil … tsheet.pdf
From their graph, an ultraflex system capable of delivering 700kW (presumably in full sun, at Earth orbit) would weigh some 7000kg. That works out at 100W/kg. Due to UV light, all panels have a decline rate in power output. Thicker cover glass reduces decline rate, but also increases weight. Since I do not know, I am going to model SPS lifetime as 20 years with no decline. You get the same results if you assume a 40yr lifespan with a linear decline rate to zero after 40 years.
If we assume that the solar power producing elements of a SPS constitute roughly half its mass, and that attitude control, fuel and microwave antenna contribute the other 50%; power density in GEO would be about 50W/kg. So, a 10,000MWe SPS would weigh some 200,000 tonnes. It would take several thousand Falcon Heavy launches to deliver it to GEO.
Over a 20 year lifespan, each kg of satellite mass will yield 8766kWh of electricity. Assuming microwaves are used to transmit power to a ground receiver rectenna; about 50% of the electricity will be lost either as losses in the atmosphere or in power electronics. So each kg of satellite will deliver 4383kWh into the grid.
Using the Falcon Heavy, launch costs to GEO are about $3000/kg. So ignoring all other costs, launch costs would be $0.68/kWh of electricity delivered to the grid. So, Earth launch satellite solar power is not economically competitive and it is very unlikely that it ever will be. Furthermore, it would be logistically difficult to maintain enough launch capacity to deliver it.
However, SPS is a far more workable option if its heavy components can be manufactured in space, using materials mined from the moon or asteroids. A single 100m diameter stony NEO, would weigh some 1.4million tonnes. That is enough material for perhaps 2x 10GWe SPS, each weighing 200,000t and the reaction mass required to deliver them to Earth orbit. On a neighbouring thread, it was determined that such a body could be enclosed in a polymer net or bag, allowing pressurised tunnels to be excavated within it. Furthermore, the body could be imparted with a spin, to allow modest lunar levels of gravity within the tunnels. The restraining bag or net to allow for this would weigh about 100 tonnes for a 100m diameter body– about three orders of magnitude less than the weight of a single SPS.
http://newmars.com/forums/viewtopic.php?id=9110
Presumably, the optimum arrangement would be to ship mining equipment and manufacturing equipment to the NEO and assemble this equipment within the excavated tunnels within the NEO. It would be necessary to manufacture the SPS in small modular segments, which are then assembled in space into a single large structure. The required mass of the manufacturing, mining and life support equipment is difficult to determine. But let us assume that for SPS to be economic, the mass of equipment delivered to the NEO must be 2 orders of magnitude less than the total mass of the two SPS delivered to GEO. This puts the total mass delivered to the NEO no greater than 4000t.
Could we carry out a NEO mining and SPS manufacturing operation, within a mass budget of 4000 tonnes? That is an interesting question. The restraining bag would consume about 2.5% of that mass budget. We would need all sorts of mechanical and chemical processing of excavated material, to convert it into iron, aluminium and doped silicon, before we would presumably either 3D print or cast the required components. And of course, we would need crew and habitation space for the crew, along with a vehicle to get them there and supplies to support them for what will probably be a mission lasting several years. It is an open question.
On the plus side, if an SPS delivers 5000MWe to a ground based grid and the operator is paid a constant $100/MWh; then the SPS will deliver some $87.7bn over its lifetime, or $44,000 per kg of equipment mass delivered to the NEO. This suggests that finished goods delivered to Earth orbit, are probably a more profitable endeavour than mining platinum. And most of the mass of those goods is basic elements like iron, aluminium and silicon, which can be found on most asteroids.
erica1E - another spammer.
I've seen no reports of electric propulsion for lighter-than-air craft, but that certainly doesn't mean folks aren't working on them.
(th)
Airships generally have greatly superior performance compared to aeroplanes, in terms of MJ/tonne-mile. The price to pay is much lower speed ~100km/h.
In terms of power requirements, from memory, the Hindenburg was powered by four diesel engines with power about 800kW each - so that's about 3.2MW at cruising speed. By contrast, a 747 at take-off needs about 200MW, with somewhat less power when it reaches cruising speed.
So a large airship needs not much more than 1% of the power of large jet, but it must be sustained for a lot longer. Probably a good candidate for compact passively safe nuclear reactor. We aren't so bothered about power density, but energy density needs to be high for long trips, as fuel mass eats into payload allowance. By contrast, a nuclear powered aeroplane would require a reactor producing 100+ MW of thrust power; the mass of shielding makes it impractical.
When the world starts to run short of liquid fuels and jet travel becomes expensive, airships powered by compact modular reactors are a very workable alternative, at least from an operational perspective. Politics is always another matter.
For Calliban re #5 ...
Thank you for adding to this topic!
I agree that (from all I have read so far) supercapacitors have a lower power density than batteries, but I'm not sure (at this point) if the difference is by volume or by weight. Please comment upon this quote from the article:
The Sián's 48-volt e-motor, built into its transmission, uses a supercapacitor as its power reserve. Lamborghini has not provided the exact specifications for its supercapacitor, but it has revealed that it's three times more powerful than a lithium-ion battery of the same weight.
I'm unsure of the meaning of "powerful" in this context.
The comparison of weight is a useful marker.
The implication might be that for an aircraft with volume to spare, a supercapacitor of this new design might be able to store three times as much "power" as a comparable set of lithium batteries, without the risk of fire, or (presumably) the cost of materials.
That last is another point of uncertainty, since the materials used for the new capacitor are not revealed.
An aircraft type with "volume to spare" would be lighter-than-air craft.
I've seen no reports of electric propulsion for lighter-than-air craft, but that certainly doesn't mean folks aren't working on them.
(th)
Power is a measure of energy delivered per unit time. Super capacitors are far more powerful per unit weight than chemical batteries, as they do not need to rely upon chemical reaction kinetics between a reactant and a surface. They just discharge stored charge. This makes them useful for driving the acceleration of a vehicle, where modest amounts of energy need to be delivered in a very short time.
Energy density is a measure of total energy stored per unit mass or volume. By this measure, super capacitors are inferior to practically any chemical battery, which is in turn inferior to any IC engine. A pure supercap powered vehicle would have awesome acceleration, but pitiful range.
By the same measure, explosives have enormous power density, because their stored energy is released in milliseconds. But their energy density is typically an order of magnitude lower than chemical fuels.
If a printer can reliably produce complex parts from low-carbon steel or aluminium, it would be very useful. 3D printing would appear to be all about compact manufacturing of novel parts, without the need for casting and milling.
On Mars, we could produce large pressurised spherical volumes, from repeatable hemispherical steel segments that are bolted together.
Low energy density: about a fifth to a tenth that of a lead acid battery. But a very high discharge rate, leading to very high power density.
https://en.wikipedia.org/wiki/Energy_density
Useful for smoothing power transients, but not so good for bulk energy storage. If you are relying upon diesel backup for a small wind turbine and you need a few minutes to start it and run it up to speed, supercaps are a good option for smoothing the transient and avoiding tripping the system by frequency drop, because of their high and rapid discharge rate.
They could be useful in regenerative braking as well, where modest amounts of energy are needed to accelerate a vehicle, delivered at high power. Engines, fuel cells, nuclear reactors; all require finite time to start or change power level, as they require fluid injection (fuel and cooling) and have mechanical and thermal inertia.
Supercaps are also frequently discussed as components for rail guns, coil guns and direct energy weapons, where very high discharge rates are needed. They would be useful components in mass drivers.
Helenalxu appears to want an audience quite badly.
Do they know something we don't? Yep...if you use free prison labour to build nuclear reactors you can build them more cheaply...
Seriously, take a look at this projection from BP:
https://www.bp.com/content/dam/bp/busin … -china.pdf
The analysis states "Nuclear increases by 7.3% p.a. from 2017 to 2040, and China accounts for 37% of global nuclear power generation in 2040. Renewables expand rapidly, rising by8.5% p.a. to 2040, and accounting for 26% of global renewables by then" - so renewables are growing at a faster rate than nuclear. Do you think that means they know something else?
Yes. The Chinese have a lot of legacy coal plants, with capital cost long paid off. The only costs are fuel and operating labour. Trouble is, Chinese coal production has peaked; coal prices are rising and air pollution in China kills a couple of million people per year. Although winfd and solar plants are not cheap, it makes economic and societal sense to build them and use the coal plants as backup power plants. This reduces fuel consumption and pollution, which outweighs the wasted operating costs.
The trouble will come when the coal plants reach the end of their lives and need replacement. Building a few wind turbines to reduce coal consumption in an old plant is one thing. But building a state of the art coal powerplant to function as dedicated backup is quite another. At a stroke, it doubles the cost of power. So renewables make sense as a short-term strategy, but not so well in the long run, because two power plants are needed instead of one. If storage is used, make that 2.5 power plants. Not many countries can afford that. Which is why the Chinese are building nuke plants as quickly as they can. You only need one nuke plant to produce a GW of power. No need for backup. No one ever escapes the second law of thermodynamics.
Maybe the moral of the story here is not to believe all the crap you see on Youtube! You have no way of verifying the provenance of what you are seeing. And as I have said before, wanting something to be true, does not make it so.
We might be heading into a recession - that can't be discounted. But we are not heading towards some sort of economic armageddon because of depletion of high quality fossil fuels.
The real issue with energy is how much labour goes into each unit of energy. Try this thought experiment...There's a huge PV field in the desert. This powers a factory that makes machines that can mine and otherwise source all the raw materials required by industry.
Some machines make the factories that make the machines and some make the PV arrays that power the whole industrial area.This is pretty much the way we are headed and it is all powered by a "fuel" - solar radiation - that is free and requires no transport to the energy generation facility. In terms of the EROI, this is huge.
The economy is an energy system that runs on surplus energy. That is to say, the energy that is left over after the energy invested in getting the energy out of the ground or building your solar plant. The smaller the energy surplus, the higher the cost and the less energy left over to both consume within the economy and invest in replacement infrastructure and new infrastructure for new growth. The increasing energy cost of energy of fossil fuels, has been slowly crushing new economic growth in the developed world since the 1990s. Japan was the first domino to fall. It has now reached levels that are crushing new growth in the developing world as well.
The ECOE of renewable energy sources has been declining as scale and slow technological improvements have improved economics. But ECOE of renewable energy will never reach the low levels of fossil fuels in their heyday, because low power density means that renewable energy is relatively heavy on capital infrastructure. It take about 20 times more steel to produce a unit of wind energy compared to a kWh of nuclear energy. For gas turbines, the disparity is even greater. This sets a floor beneath which ECOE for renewable energy cannot fall.
What Tim Morgan doesn't address is the energy cost of storage. Comparing renewable energy to nuclear or fossil fuel energy, is like comparing apples to oranges. One is controllable and responds to demand, the other is not. When the energy cost of a storage plant is factored in (it is after all, a whole other power station) and losses are included; the ECOE of renewable energy roughly doubles. It goes from being a weak option, to being an unworkable option.
Well worth a read.
https://surplusenergyeconomics.wordpres … ding-down/
We are heading into a recession. There is nothing particularly unusual about that - typically recessions occur once every decade. But for the last 10 years, central banks around the world have inflated enormous debt bubbles and have printed money in a desperate attempt to maintain economic growth. The result is that total debt burden is roughly 5 times worse than it was on the eve of the Great Recession. The next bust, which may arrive in 2020, will likely rival the Great Depression, as fiat currencies are now in danger of a crisis of confidence.
It is noticeable that everything the American Left touch (and the left everywhere to be honest) seems to turn into shite. It isn't long before anyone interested in the future just wants to get away from any place where these people hold power. They use unrestricted immigration to deliberately dilute White Americans into minority status.
https://www.zerohedge.com/political/con … red-states
They seem determined to turn America (and the world) into a giant multiracial version of Soviet East Germany. The above article describes the exodus of White Americans out of California. Declining living standards, rising taxes, overcrowding, excrement in the streets and ethnic minority status, do not, for some reason, seem to appeal to most White Americans. Ironically, many of those leaving probably voted Dem in the past and some of them will be moronic enough to do it again, even after the effects of that decision literally drove them from their homes.
China produced 23% more electricity from nuclear power, 253.53TWh, between January and September than in the same period last year, according to figures released by the China Nuclear Energy Association. This represents 4.8% of China's total power generation during the first three quarters of 2019.
https://wna.informz.ca/informzdataservi … IyMDY2MTg4
China's nuclear generating capacity is growing at a rapid pace of 18.6% growth per year (in 2018). If that growth rate continues for another decade, the Chinese will be generating about a quarter of their present electricity consumption from nuclear energy and will have around 3 times as much nuclear generating capacity as France.
Do you suppose these people know something that we don't?
Solar power for asteroid mining and mineral processing would appear to have excellent power-weight ratio, as it can be in sunlight 100% of the time and no storage is needed. At Earth orbit with 1350W/m2 insolation, a thin film space solar panel weighing 0.1kg/m2 would deliver 2-3kW/kg.
The only downside is that it does limit operations to asteroids that have relatively circular orbits with apogee not too far beyond Earth orbit around the sun. Many candidate NEOs have highly elliptical orbits that go beyond the orbit of Mars. But these wouldn't be our first choice anyway, as the dV requirements to match orbit with them from Earth would be much higher.
We could cast nickel into hollow spheres, sputter it with some sort of molten oxide as a re-entry shield, and drop them either onto land or into the ocean. Ideally, we want the terminal velocity on impact to be low enough that they survive intact. Aluminium might be a more profitable asset for building space based structures, at least initially. It takes 20kWh of electric power to produce 1kg of aluminium. So a 10m2 solar panel, weighing 1kg, could produce about 8766 times its own weight in aluminium over a 10 year lifespan. Even if we have to transport the solar panel from Earth, that sort of ratio could make space based aluminium production quite profitable.
Economy of scale states that (crudely) for every increase in size of a device, capital cost increases to the 0.6 power.
https://en.m.wikipedia.org/wiki/Economies_of_scale
Let us say we want to build a fusion reactor on Mars that delivers 887million GW-years of energy in 100 years. That equates to a power of 8.87million GW. Compared to a 1000MW device, the capital cost would be 14,750 times greater. The per unit capital cost would be 0.0017 of the 1000MW unit.
There are other factors that favour very large fusion reactors. The larger the reactor is, the longer the confinement time of particles. It takes a finite period of time for a particle to cross the containment vessel. For a given plasma density, the larger the vessel, the more likely an ion is to collide with another ion before reaching the edge. Finally, there is the cube/square law. Leakage is a function of surface area, whereas power is a function of volume. All things considered, it will be much easier to reach the Lawson criterion in a very large reactor.
A Martian civilisation of a sufficient size could build mega reactors to power industry on a scale that is so far unknown on Earth. Without oceans, Mars is effectively a single huge continent, making it relatively simple to distribute power all over the planet using superconducting cables. If we assume a Martian population of some 4 billion people, each consuming power at a rate of 10KWe, then a total reactor power of 40,000GW would be needed. To terraform Mars with a breathable atmosphere in just 100 years by the electrolysis of water; about 100 times more power would be needed.
This amount of heat ejected by the system over this timescale would begin to rival the power of sunlight reaching Mars and would warm it considerably.
In terms of volume: ITER plasma would have a core power density of about 10MW/m3 following plasma ignition. To produce 8.87million GW implies a plasma volume of 887million cubic metres; or a spherical confinement chamber some 600m in radius. This sounds achievable, as it amounts to about two-thirds of a mile in diameter. Extracting heat from the reaction might be difficult at this size range. Heat loading would amount to nearly 2GW/m2 of the reaction vessel. Even boiling liquid metal would struggle to remove that much heat. So a fleet of 100 reactors some 2 orders of magnitude smaller would be more practical. They would likely be build in a ring around the Martian north pole.
One thing that could be problematic if we attempt to rapidly terraform Mars is structural stability. The crust of the planet is likely full of water ice and frozen CO2. If this were to rapidly melt it would probably imperil any structures on the surface.
If stainless steel production peaks, then humanity would be in serious trouble.
http://newmars.com/forums/viewtopic.php … 63#p161863
You can't make food without fertiliser. You can't make fertiliser without nitric acid. And you can't make nitric acid without stainless steel. Less stainless steel means less food. The day may not be long off, where asteroid nickel mining is the difference between life and death for a lot of people.
Peak stainless steel?
https://link.springer.com/article/10.10 … 019-0056-9
“This study shows that there is a significant risk that stainless steel production will reach its maximum capacity around 2055 because of declining nickel production, though recycling, and use of other alloys on a very small scale can compensate somewhat. The model in this study assumes business as usual for metal production and fossil fuel supplies (though the authors note that energy limitations are likely in the future, which will limit mining). If oil begins to decline within 10 years, as many think, shortages of stainless steel and everything else will happen before 2055.”
Nickel is naturally present in meteoritic iron at concentrations of about 10%. It can be separated using carbonyl chemistry. It is of more than academic importance that asteroid mining is perfected relatively soon. It could make the difference between a prosperous future and a poor one.
One thing I have occasionally wondered about is the possibility of life based on different DNA nucleotides. All life that we know is based upon two pairings, C-G and A-T. Are different nucleotides possible?
Like I said before, the 2¢/kWh is the cost after subsidy, hidden or otherwise. It is not representative of the real cost of electricity.
https://wryheat.wordpress.com/2015/08/0 … skyrocket/
Mars needs cheap electricity. Basic living space and agricultural land must be encased in a pressurised shell of steel, which is reduced from ore using electrolytic hydrogen. Water must be mined from the ground using as much energy as it takes to make concrete on Earth. This is not something that can be done with solar panels.
The problem is that the batteries can only provide a few hours of storage at most. They are there to prevent sudden changes in output from crashing the grid due to frequency changes. It is a relatively expensive way of storing energy, but has the advantage of rapid discharge rate and can therefore respond well to short-term peaks and troughs. Large scale energy storage typically relies on pumped hydro, CAES or thermal storage. Hydrogen has been discussed, but isn't really very practical. It is difficult to scale any storage solution to cover days worth of lulls without pushing costs to ridiculous levels, which is why wind and solar plants need to be paired with backup power plants, usually running on natural gas. Even before storage, solar panels are only as cheap as they are, because of hidden subsidies and dumping.
We cannot make this work as a scalable solution here on Earth. There is no fossil fuel on Mars and even if there were, there is no air to burn it in. A Martian civilisation would need about 10 times as much electrical power to provide food, water and manufacture habitation space. Musk's proposed city of 1million people would need round the clock power of about 10GWe. This energy needs to be delivered cheaply if Martians are to enjoy a decent standard living. And sunlight is half the intensity that it is on Earth. This would suggest to me that solar power is only suitable as a small scale supplemental energy source, where we need modest amounts of power without a grid connection and cost is not the driving factor.
If nuclear fusion comes online in the timescale of Musk's vision, then it may be the solution to the problem. If not, then the Martians will need to build powerful nuclear reactors, cheaply and quickly. I raised the idea of building RBMK reactors, burning natural uranium mined from Mars. But there are other concepts that could work as well. RBMK is a graphite moderated, pressure tube boiling water reactor. No steam generators or pressure vessel is needed; it can burn natural uranium and it can be scaled to virtually any power level necessary by adding more fuel channels and increasing the core diameter. Hence this reactor can provide large amounts of electricity very cheaply. We need to design these reactors to be safe of course. I don't think that there is any need to repeat the design mistakes of the Soviet union.
From my limited understanding: an SSTO is a non-optimised launch concept, because it means accelerating to orbital velocity a lot of mass that doesn't need to be accelerated to orbital velocity. Most of the dV required to reach orbit is required to achieve orbital velocity. That implies a lot of kinetic energy. It also means that the same engines must be used for takeoff at Earth surface (1bar, low propulsive efficiency) as are used to accelerate to orbital velocity in a vacuum. A better question would be, what is the optimum division of propulsive requirements between the lower and upper stage? Does the lower stage need to achieve enough dV to reach orbital altitude, so that the upper stage is built to focus on attaining orbital velocity? Or would a minimal design be better, whereby the lower stages pushes the upper stage so far as the stratosphere, where the upper stage engines get better expansion ratio; most air resistance is gone and a significant portion of gravity losses are already accounted for?
Fake comment above from someone that wants to use your site for free advertising. The comment should be deleted and the user banned.
This is an interesting topic. Anything in contact with solid ground on Titan would lose heat rapidly due to conduction. So you want to stay above, or remain under the ground. The atmosphere of Titan is almost pure nitrogen at a temperature of -180C. At these frigid temperatures, at a pressure of 1.5bar, nitrogen would have a density of about 5kg/m3. A vessel containing ordinary air at standard temperatures, would experience substantial lift. Titan cities could actually be balloons of air, tethered to the surface. The outer surfaces would be lined with aerogel. A nuclear reactor on the ground, would pump hot nitrogen through a central column, maintaining internal temperatures.
For Calliban re topic ...
If you are willing to pick an asteroid from all you have considered to date, or perhaps a new one, I'll see if I can make head or tails of the NASA mission planning site. My understanding is the site is pre-loaded with a number of Solar System objects, so the asteroid you pick may already be in the list. That would help if the listing includes orbital elements, which seems likely, if the object is listed at all.
(th)
I think it needs to work the other way round. We decide what we are looking for and search the minor planet database for a match.