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Mars_B4_Moon,
Gloucestershire Police "just" need to spend more money on gigantic batteries. Maybe if the entire car was a gigantic rolling battery, with the officer sitting on the roof of the car, then it would be truly equal to a 10 gallon gasoline tank.
Since that bit of "derp" obviously didn't work, I have an even better idea that also won't work:
Let's force the public to use battery-powered Ambulances and Fire Engines.
After enough of these "batteries are the future" religious zealots die because they never make it to the hospital or their houses burn to the ground after the fire engine quits pumping, then perhaps the rest of them will have a "crisis of faith" in their new religion.
It's a pity that all the normal people will suffer as well, but the religion's dogma must be satisfied.
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Even emergency vehicle carries with them a power generator. So, buy one and put it in the trunk.
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SpaceNut,
EVs don't carry a power generator with them. Do what normal people do and put that generator under the hood of the vehicle where it belongs. If you need to carry a backup power generator with you, then that means a pure battery powered vehicle doesn't work. The reason it does not work is math. Math is the foundation of all valid science.
1 gallon of gasoline weighs 6lbs / 2.7223kg and stores 33,700Wh of energy. You can get half of that from a constant speed combustion engine. The rest is lost as heat. That means the energy density of a gallon of gasoline is 16,850Wh per gallon, or 6,189.6Wh/kg. A 16,850Wh battery, at 160Wh/kg. A Tesla Model 3 has a 75kWh battery pack that weighs 478kg, so 156.9Wh/kg. That's a difference of 39.45 TIMES. The energy densities figures for all the various other battery pack capacities all fall within about 5Wh of each other, provided they use the same cell type and chemistry.
No amount of wishful thinking can overcome that power-to-weight deficit on the part of batteries. I know combustion engines have come quite a long way since their invention, but there has been no 40X improvement in power density per unit weight using a fuel 40X more energy dense than batteries. A 2X to 5X on power-to-weight is about where you max out at, excluding rocket engines, since rockets will never power practical land motorized vehicles, much like batteries. Modern engines are not 10X lighter than the engines of the early 1900s, let alone 40X lighter. That's about where batteries would need to be to provide equivalent power-to-weight. Something tells me that probably won't happen, because it hasn't happened in the past.
Modern 4-cylinder turbocharged engines generate about 825W/kg of weight. A Ford flathead V8 generated about 330W/kg of weight. That's a factor of 2X, maybe 3X improvement over time if you don't care about engine lifespan. In other words, no night-and-day difference to be had. If you skimp on engine materials, then your engine doesn't last very long. Ford flatheads will outlive both of us. That turbocharged 4-banger will be trash in 10 years or less. The 3-banger in Nissan's e-POWER series hybrid system is 60mpg. The Ford flathead V8 was 12mpg to 17mpg, possibly up to 25mpg with EFI since it's a 100hp motor. That's a 2X to 4X improvement over existing engines.
At best, future batteries might see another 2X to 3X capacity improvement / weight reduction over existing models, hopefully within our lifetimes. The electric motors are already 96% to 98% efficient. The power conversion electronics are around 95% efficient. The battery charge / discharge efficiency is already near 100%. There's nowhere significant for battery or electric motor or power inverter efficiency to go. It's already maxed out or nearly maxed out. Those last few percentage points of improvement won't yield any dramatic results.
Some of the lab example Lithium-ion batteries of the early 1990s were achieving 100Wh/kg. Now they're at 250Wh/kg and only completely different cell chemistries plus some packaging efficiencies can greatly improve upon that. Tesla exploited the latter, and of course, "solving" the geometry problem worked. Good for them, because that was very low-hanging fruit. However, it's not possible to "solve" the gravimetric energy density problem that way more than once. They can't improve much on energy density by making the individual cells larger, because then we have larger and larger void spaces between individual cells, which are not batteries, available space is not unlimited, and making the vehicle much larger also makes it heavier.
We saw a 2.5X cell capacity increase over 30+ years. If we could sustain that rate of capacity improvement, which we can't, which is why Tesla used cell packaging geometry instead of cell chemistry changes to achieve their latest gravimetric and volumetric energy density improvement, then we might see 500Wh/kg by the time I'm in my 70s. Total battery pack gravimetric energy density is about 64% of individual cell gravimetric energy density, so 320Wh/kg at the pack level vs 160Wh/kg, or a 2X improvement. They can't do much more to improve aerodynamics or rolling resistance without drastically changing the car, but even if they did, it doesn't net much improvement because weight is what kills performance at city to highway speed ranges.
Lightyear Zero is the same weight of a normal 4-seat passenger car of its size class at 3,471lbs, whereas Telsa's Model 3 is a subcompact car with the weight of a Chevy Silverado light duty pickup truck from about 10 years ago, or about a 4,250lbs. One uses 105-110Wh/km and the other is 250Wh/km. Both vehicles can drive about the same distance. Lightyear Zero ($265,000 USD; promise of $175,000 USD for production models) has a 60kWh (344 miles of driving range) battery and Tesla Model 3 ($58,000 USD) has a 82kWh (358 miles of driving range) battery. So, 3X to 4.5X the cost for a 27% energy efficiency improvement. Any bets on how breathtakingly expensive a 2X to 3X better battery will be?
Assuming we could even achieve a 2X to 3X gravimetric energy density improvement over existing batteries, what does that yield?
Unfortunately, not much. Gasoline is still 20X more energy dense than batteries that don't exist.
Could you ever make a car 20X heavier to provide equivalent range and payload carrying capabilities, but still use less energy?
That's a hard "no", even if the car is riding on rails, but then it's not a car, it's a miniature train.
Why is that?
This universe has rules concerning weight and power. I didn't invent them for sake of argument. The universe did not consult with me before that decision was made, either. If it had, then the rules would be considerably more flexible.
Did the universe conspire with "big oil" to crush your "green dreams"?
Not as far as I can tell. If you want to blame something, then blame math and physics.
This will likely never work the way you want it to, because it requires battery tech that's decades and maybe centuries beyond what we know how to design and build. Maybe AI can make magic happen, but I doubt it. They've had AI and computational electro-chemistry software working on this specific problem for years on some of the world's most powerful supercomputers. It's yielded a few interesting finds, but no real game changers.
What does this all mean?
As near as I can tell, there is no future without gasoline and diesel and kerosene. We can use a lot less of it, but for society to continue to feed everyone and take them to work, it will never be zero or anything close to zero. That is why recycling is required. I don't make things up to argue or because I'm bored. I'm telling you that you can't get to where you want to go from where you're at. If you have the personal integrity to admit this to yourself, then share it with the people you tend to vote for and ask them what they know about this issue, because it's every bit as real as climate change and will accelerate climate change if pursued to its logical maxim. Alternatively, a lot of people will starve to death. If the way we "save the planet" is by killing half the people living on it, then that's not a good trade from my perspective.
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NASA plans mini nuclear reactors for moon, could power lunar colony
https://www.businessinsider.com/nasa-pl … ony-2022-7
US Regulators to Certify First Small Modular Nuclear Reactor Design
https://www.extremetech.com/extreme/338 … tor-design
The Space Race is Going Nuclear
https://www.counterpunch.org/2022/08/11 … g-nuclear/
The American Nuclear Society describes itself as comprised of “10,000 members dedicated to advancing nuclear science and technology.”
Last edited by Mars_B4_Moon (2022-08-12 13:02:18)
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Maybe there will be progress or maybe not and if some politically crazy were to send everyone back to steam power?
'It’s the end of the car as we know it'
https://www.vox.com/recode/23333356/ev- … on-driving
“Modern machines are in themselves useless,” Appleyard told Recode. “They have to be connected. There’s no point to a computer that’s not connected now. That connection is not yours — you don’t control it. Cars will be like that.”
As Appleyard sees it, the end of the car as we know it may be on the horizon.
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Molten Salt Reactors: Maritime’s Nuclear Option
https://www.marinelink.com/news/molten- … ear-499681
old vid of Black n White photos uploaded to a social media channel in 2009
'Ford Nucleon Atomic Cars'
https://www.youtube.com/watch?v=bdL9rAti_fI
Our SpaceFlight Heritage: Project Orion, a nuclear bomb and rocket – all in one
https://www.spaceflightinsider.com/spac … mb-rocket/
The Ford Motor Company went so far as to come up with a car they called the Ford Nucleon
Last edited by Mars_B4_Moon (2022-10-09 17:30:35)
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That is one heavy old timer Ford car.
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If NASA and the US Navy make progress with the lattice confinement fusion fast fission systems that they are developing, then something like the Ford Nucleon is at least technically possible. The reactor would not need any plutonium or enriched uranium. It would consist of a number of hollow slugs of depleted uranium, with titanium deuteride inserts. These would sit within a cast iron block, which would contain cooling channels, shielding and would provide a heat sink. Such a device would produce maybe 20 kilowatt of heat and a small brayton cycle engine would raise 5kWe (~8HP). Units this small would be passively safe. The engine block would have sufficient surface area to lose full power heat by radiation and convection.
I can see units like this being very useful on Mars for a huge range of applications. They are small and compact enough to power vehicles without excessively bulky shielding solutions. They are non-radioactive until activated. So there should be no issues with launch.
On Earth, such units have applications as remote power sources. The military applications are obvious. They provide easy offgrid power in the kW range. Could they be used to build an infinite range tank? That is an interesting idea. Such a vehicle would be slow, but would have no fuel limitations. Starting from a base in Poland, you drive it all the way to Vladivostock!
For bulk energy applications, this discovery allows us to build pressure tube boiling water reactors, that run on natural uranium fuel and achieve high burnup. That is a revolution in nuclear power, that will make it possible to build new reactors quickly and cheaply.
Last edited by Calliban (2022-10-09 19:53:15)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Will the Moon or Mars have its humans drive the first Nuclear Space-Car?
New funding for space projects using Moon’s resources and nuclear power
https://www.independent.co.uk/news/uk/u … 95388.html
The projects could revolutionise the ability to journey deeper into space.
The UK Space Agency has announced new funding to support space exploration using the Moon’s resources and nuclear power.
China has made a breakthrough in plans to acquire capability for nuclear power generation in space. The 801 institute under the 6th Academy of CASC has developed closed Brayton cycle thermoelectric generator technology. US & Russia have this tech already
https://twitter.com/AJ_FI/status/1634517124520484864
New Nuclear Fission Concept Could Power Future Rockets in Space
https://www.inverse.com/science/nuclear-fission-rocket
Besides the typical argument between solar sails and chemical propulsion lies a potential third way.
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Rolls-Royce won a bid to put a nuclear reactor on the moon
they are involved in Car Manufacture, Aerospace, Boats and controllable-pitch propellers
Rolls–Royce given £2.9m to explore nuclear power for future Moon bases
https://www.express.co.uk/news/science/ … moon-bases
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With changes to a market of energy attitudes to 'Nuclear' are changing? China has previously said its lunar base would likely be powered by nuclear energy, Perseverance, nicknamed Percy with its helicopter, the Rover a similar design to its predecessor rover, Curiosiy uses a 110 watt radioisotope thermoelectric generator.
In news we see possible changes to attitudes with Nuclear power in space
Europe wants to build a nuclear rocket for deep space exploration
https://www.space.com/european-space-ag … propulsion
NASA has sights set on Mars with help from a nuclear rocket engine
https://www.nbcnews.com/science/space/n … -rcna84060
A conventional spacecraft powered by burning liquid fuel typically takes around seven or eight months to reach the red planet. Scientists have said nuclear rocket engines could shave off at least a third of that time.
On newmars topics users have discussed Betavoltaic Cell device, new Designs for liquid fluoride thorium reactor, Atomic Radioisotope battery or Atom Battery
The use of Curium-242, curium-244, Tritium, nickel-63, promethium-147, technetium-99
Calliban as an interesting link on Strontium-90 RTGs
https://newmars.com/forums/viewtopic.php?id=7025
older article on Vehicles for Titan and Europa
The autonomous submarines would roam above the ocean floor, taking high-resolution images that will be combined into a 3D map of the seafloor, looking for traces of life in the process.
https://www.space.com/orpheus-ocean-aut … technology
Robot Submarine on Jupiter Moon Europa is 'Holy Grail' Mission for Planetary Science
https://www.space.com/14997-jupiter-eur … robot.html
Titan Submarine: Exploring the Depths of Kraken
https://www.nasa.gov/content/titan-subm … of-kraken/
other discussions
US developing different versions of lunar nuclear power
https://newmars.com/forums/viewtopic.php?id=9772
Dust Blowers on Probes
https://newmars.com/forums/viewtopic.php?id=5698
Last edited by Mars_B4_Moon (2023-05-27 07:10:37)
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Pentagon Awards Lockheed Martin $33.7 Million for Nuclear Spacecraft Project
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Nuclear power on the moon: Rolls-Royce unveils reactor mockup
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MMRTG 110 watt
NASA’s Perseverance Rover Hits the Mark – “This Is the Kind of Rock We Had Hoped To Find”
https://scitechdaily.com/nasas-persever … d-to-find/
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Thaks to Mars_B4_Moon for reminding us that the nuclear powered rovers are indeed "nukemobiles"
I went back and checked the early days of this topic, and it started out with a vision of huge reactors, and plenty of alternatives.
One poster suggested RTG's and that poster was rewarded with a critical comment by someone else.
The fact is... NASA has had nukemobiles on Mars for quite some time now, and they performed well and Perseverance is ** still ** performing well.
I asked Google for an update on the 110 watt system in Perseverance ...
https://www.jpl.nasa.gov/news/press_kit … gy%20(DOE).
What Is an MMRTG?
Perseverance's power system works essentially like a nuclear battery. The MMRTG converts heat from the natural radioactive decay of plutonium-238 into a steady flow of electricity. The power system will reliably produce about 110 watts (similar to a light bulb) at the start of Perseverance's mission, declining a few percent each year in a very predictable way. The MMRTG doesn't just power the rover; excess heat from it keeps the rover's tools and systems at their correct operating temperatures.The MMRTG also charges two lithium-ion batteries, which are used during daily operations and when the demand temporarily exceeds the usual electrical output levels. Perseverance's power demand can reach 900 watts during science activities.
The MMRTG, located on the aft of the rover, weighs about 99 pounds (45 kilograms) altogether. It contains 10.6 pounds (4.8 kilograms) of plutonium dioxide as its heat source.
The two batteries weigh a total of 58.4 pounds (26.5 kilograms) and each has a capacity of about 43 amp-hours.
More details on the MMRTG can be found on this electrical power page.
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To crawl at a fraction of a mile per hour, you need only watts of power to move. That's what falls in the output range of the radioisotope decay generator, which is big and heavy for only several watts worth of output. Bear in mind that for wheels rolling in soft dirt, friction coefficients often approach, and sometimes exceed, 1.
For a metric ton-mass of vehicle on Mars, that's a rolling friction force on the order of 0.38 metric ton-force (near 3.8 KN), to be overcome. At slow speeds where you can neglect aerodynamic drag, power-at-the-drive-wheels is rolling friction force x speed. If speed is 20 mph (about 30 km/hr = 8.3 m/s), the required power at the wheels is around 30 KW. By the time you overcome driveline frictions and inefficiencies, you are looking at a 35-40 KW "engine" of some kind.
If you intend to drive multiple tens of miles per hour, say 30 mph, like a dune buggy in sand, this so very clearly takes 10's of KW of propulsion power. That's way out of range for a radioisotope generator, thus requiring real fission taking place in your nuke, plus the requirement to reject waste heat effectively FROM A MOVING VEHICLE when the air is too thin on Mars to receive it effectively, by convection.
Waste heat will be larger than the useful power it produces, and by far, because converting heat to electricity in large amounts is only done with heat engines. And heat engines have conversion efficiencies that are substantially lower than the Carnot efficiency, which rarely exceeds 40% in designs small enough to be mobile. There's only convection and thermal re-radiation as the means to dump the waste heat from your vehicle.
Crudely speaking, for 30-something KW of electric drive power, you must be rejecting something on the order of 100 KW worth of waste heat from the nuclear fission-powered heat engine that creates the electricity. Now just how do you do that on a moving vehicle, when the only available means is a thermal re-radiation panel? It's going to be awfully big and heavy, is it not? These things are plumbers' nightmares, not at all like solar panels.
Food for thought.
GW
Last edited by GW Johnson (2024-05-09 09:25:08)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #181
Is there any reason you can think of why Mars air can't provide all the cooling you need?
The air is thin, so you'll need a fan to blow the air past radiator fins.
This discussion needs to be lifted out of the hand waving category.
If a reactor generates 30 Kw, and 100 kw of thermal energy needs to be dissipated, and the density of the atmosphere is:
Per Google:
The atmosphere of Mars is much thinner and colder than Earth's having a max density 20g/m3 (about 2% of Earth's value) with a temperature generally below zero down to -60 Celsius. The average surface pressure is about 610 pascals (0.088 psi) which is less than 1% of the Earth's value. Atmosphere of Mars.
Then it should be possible to compute the amount of that 30 Kw that needs to be invested in driving the fan to achieve the needed cooling.
This forum tends to generate a lot of hand waving.
Let's try to steer a course toward solid numbers that a Mars Mission planner can use to design equipment.
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For a given temperature difference, the heat transferred by convection is the temperature difference multiplied by the heat transfer coefficient of the device. Heat transfer coefficients are roughly proportional to atmospheric density, for a device transferring heat to the local air. Mars density is ~0.01 that of Earth. Which means your (automotive-type) cooling "radiator" (a real misnomer, but traditional for over a century), must be ~100 times larger on Mars! There is no fan, and no fan stream speed, that is going to overcome an effect like that. Traditional cooling "radiators" of the type well known on Earth, simply CANNOT work on Mars, unless they are ~100 times bigger! It's just physics. You cannot argue with it. Is that "numbers" enough for you?
Thermal re-radiant panels work as well on Mars as they do on Earth. That's just a panel area times its spectral emissivity times Boltzmann's constant times a temperature-to-the-fourth-power term. But you will be fairly limited by the coolant you must use, as to the average effective radiation temperature of that panel, meaning your panel will end up being quite large. The environmental sink temperature is a bit lower on Mars, and that helps a tad. Things cooler than about 1200 F (glowing red) do not radiate much power per unit of area because of the T^4 effect. Your coolant won't be anywhere near that 1200 F / red glowing hot! So your thermal re-radiation panel must be large, although likely not as large as the convection panel (traditional automotive-type "radiator"). That's the closest to "hand-waving" I have to offer here.
Cooling with convection requires both a coolant pump and a fan to drive the airflow. Cooling by thermal re-radiation requires only the coolant pump. Twice the absolute temperature is a 16 times smaller panel (real numbers!), that's the T^4 effect. But you won't be able to operate anywhere near that hot! Closer to 500 F average across the panel (maximum!!) than that glowing-red 1200 F. Plus, it cannot be inlet temperature-hot all the way across the panel! That's just heat transfer physics! And unless the temperature drop across the panel is big, your coolant flow rate and pipe sizes get enormous! Also real physics.
There's no simple way to "estimate" this. It requires real engineering design, by a specialist in that application.
GW
Last edited by GW Johnson (2024-05-09 14:54:51)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #193
This sure would be a good time for Calliban to join the flow here....
Calliban has often written about nuclear power plants, and even more often about the problems of cooling.
In the absence of Calliban, I will accept your prediction that a radiator would need to be physically larger to deliver thermal energy to the atmosphere of Mars, and your equally informed prediction that increasing airflow at Mars cannot make up for the density.
That leaves onboard cooling as a possible solution.
If you were given a contract to design a vehicle for Mars, and you were given a 130 Kw reactor, you might consider alternatives to the cooling methods you've already considered.
One available option unique to Mars is dry ice.
If you designed a system with a wagon load of dry ice for use as a coolant, then I would ** hope ** you could design a solution that is compact and able to operate efficiently with that 30 Kw of power.
One possible benefit of this scenario is that if you are heating all that dry ice to cool your reactor, then you would (presumably) have gas available to operate simple mechanical machinery, rather than just exhausting the gas to the exterior.
I ** would ** like to see some numbers...
There should be data available on the performance of radiators in varying gas density situations.
It should be possible to find experimental data that shows the effect of lower atmospheric density on the effectiveness of cooling fins, such as those used for piston engines operating at 30,000 feet or greater, as we done at one time.
The cooling in those cases was achieved by moving the radiator through the available atmosphere.
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Tom:
I think what you really have to do is build the re-radiation cooling panel, which is much more of a "radiator" than the convection heat exchangers that we call "radiators" on cars and trucks. These things look very much like solar thermal panels (and not at all like solar photovoltaic panels).
Assuming an average panel temperature of 500 F (960 R) and an emissivity of 0.9 (very "black") plus a surroundings temperature of about -50 F (410 R) as "typical", and using the US customary units I am familiar with, I get about 1267 BTU/hr-ft^2 of re-radiated infrared. I'm honestly surprised it was that high. Converting to metric, that is 3997 KW/m^2. To re-radiate 100 KW worth of waste heat would require about 0.025 sq.m worth of radiator panel, or only some 0.27 sq.ft (crudely 6 or 7 inches by 6 or 7 inches). I am very surprised indeed it s that small! It won't be as light as a standard car radiator of that size, though.
You can't achieve that temperature with water as a coolant except at thousands of psi pressure, so the coolant must be a liquid metal, of say specific heat capacity nearer 0.3 BTU/lbm-R than water's 1 BTU/lbm-R, and a specific gravity near maybe 10. If the temperature drop across the panel were 20 F, so that the hot edge was about 510 F and the cold edge about 490 F, then the coolant massflow would be about 211 lbm/hr-ft^2, or 0.059 lbm/sec-ft^2, or 0.027 kg/sec-ft^2. The pump size and power could be reasonable.
If you consider water-as coolant, then the average panel temperature is nearer only 200 F (660 R) with surroundings near -50 F. That gets a panel re-radiation power of 249 BTU/hr-ft^2 = 785 KW/m^2. Your panel size is nearer 0.127 sq.m = 1.37 sq.ft, much nearer what I might have expected.
I probably did something wrong, so do not bet these results are good. The basic message here is the re-radiator panel is not as large as I feared, but does not resemble an Earthly car radiator, it more closely approximates a solar thermal panel. The coolant actually could be water, or maybe silicone oil would be more appropriate for Mars.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #195
Thanks for taking the risk of possibly making a mistake in a first try at something.
The size of the "radiator" is indeed surprising, but I have the advantage of not knowing anything about the subject.
We have an opportunity for Calliban to help out here.
While we wait for Calliban, or someone else willing to review the first draft results in Post #195, I'd like to encourage you (and whoever else feels qualified to participate) to see what you can do with a reactor that produces 130 Kw, of which you can use 30 Kw for electrical devices.
Let me ask if you could do something useful with that radiating panel?
Could you bake regolith, for example?
You could make bricks out of Martian regolith, if you can produce enough thermal energy.
I hate to see all that perfectly good heat going to waste.
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