New Mars Forums

This graphite based thermal battery can store heat at 2000°C.
https://youtu.be/cwDly9pjSJg

This device could have a number of potential applications.

1. For electricity storage, the inner surface of the casing is lined with infrared photovoltaic cells, which convert heat into DC electricity.
2. For industrial heat applications, the storage temperature of 2300K is high enough for most applications.  Glass manufacturing requires temperatures >1000°C.  Blast furnaces >1200°C.  Steel production ~1600°C.  Cement production >1200°C.  Heat can be transfered efficiently by radiation.  There are numerous other direct heat applications at lower temperatures, which could actually work as part of a hybrid scheme using this device.
3. The high operating temperature could make this useful for mobile applications.  We could potentially power ships using a bank of these batteries, which would run along the bilge line.  An S-CO2 powerplant would then convert the heat into shaft power.
4. A neat side benefit of thermal energy storage is that units can be stacked close to population centres.  Waste heat leaking from these devices can then be used to supply district heat networks.  This works well in Europe and Asia, where urban settlements tend to be quite dense.

At temperatures above 1200°C, graphite has specific heat of 2.2KJ/Kg.K.  Density (room temperature) is 1.6 - 1.8 tonne/m3.

Between 2200 and 1200°C, the heat stored would be:

Q = 1600kg/m3 x 2200J/kg.K x (2200-1200) = 3.52GJ/m3 (978kWh/m3)

A block of graphite 3m aside, could therefore store 1MW-day of energy in the form of high grade heat.  Graphite is a relatively cheap material that can be manufactured from any carbon containing material.  The blocks can presumably be used for decades.  The only limitation that I can see is that high temperature gradients could result in cracking.  Provided this problem is managed, graphite thermal energy storage would appear to me to be a cheap and scalable solution.  It works best if it can be coupled with a low grade heat load.

A Million People On Mars
https://www.zerohedge.com/news/2026-06- … eople-mars

A Bonus Plan From Another Planet
Since SpaceX (SPCX 0.00%↑) went public, the stock has been on a tear.

The IPO pop was big. The Monday follow-through was big too. But the most interesting part of the SpaceX story isn’t just the stock action. It’s the scale of what Elon Musk is trying to build.

In an X article published yesterday, Marc Andreessen and Michael McGuiness of the venture capital firm Andreessen Horowitz highlighted the first milestone in Musk’s SpaceX bonus plan: a $7.5 trillion market cap for SpaceX and a self-sustaining city of 1 million people on Mars.

A million people on Mars.

That’s not a normal growth-stock target. It’s not even a normal space-company target. It points to how large the investable space economy could become if even part of that ambition starts to look plausible.
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My understanding was that Musk had postponed his 'Humans to Mars' plan in favour of development of a lunar base?

Meet the nomad prepping for doomsday with sheep!
https://youtu.be/4gEczsNlkGM

This is quite inspiring.

Almost any material could be used as propellant.  The propellant does need some conductive material within it.  But once it is heated beyond it's first ionisation temperature, any material is conductive, because it is a plasma with free charge carriers at that temperature.  That includes any oxides that we could, for example, mine from the Martian moons.  Metals would be preferable, but unless you have a convenient supply of them i.e. as waste, oxides will be the dominant materials available naturally.  The problem is that oxides break down into a mixture of metal and oxygen ions.

Thanks SpaceNut.

Overall, the mechanical wind power project has not worked very well.  I have been able to use it to polish stones.  But even in this limited application, it is slow compared to an electric tumbler and its work rate is highly dependant on weather conditions.  Some lessons learned:

1. Given the limited power output from a machine of this size, a homemade windmill is only worth building if the majority of materials used to build it are free.  Most of the material inputs to my machine were recycled wood and recycled aluminium from old drink cans (for the blades).  The bearings, stainless steel thread, screws, epoxy glue and some fastenings were purchased components.  Overall, the financial cost of the machine was ~$US500.  The time input was huge.

2. From the outset, the machine was intended to generate mechanical rather than electrical power.  Electrical generation would have improved the utility of the machine, but would have at least doubled it's cost.  However, mechanical power transmission was not successful.  Much of the problem was due to difficulty assembling the machine at height, which resulted in the pulley being mounted unevenly on the rotor.  The rope frequently slipped off, making power transmission unreliable and requiring constant attention.  The rope also suffered excessive wear.  Metal rope did not work well either, as it did not grip the pulley properly and caused damage when it slipped off.  The rope drive also added a lot of friction.  This further reduced the operating window of the machine, as the turning force had to overcome static friction in order for rotation to start.

3. The siting of a small wind machine has a critical impact on its viability.  For the machine to work well, it must have open space in front of it for at least a few hundred metres in the dominant wind direction.  If your space is surrounded with trees or buildings that attenuate wind at the hub height, performance will be poor.  This is a problem in the UK, because most homes are crowded together and only a minority have free space around them.  So a wind machine will only be useful in a minority of situations.

4. Building a horizontal axis machine turned out to be a mistake.  Without the ability to track the wind (which adds a lot of design complication) the machine is idle a large percentage of the time.  When I started the project, my assumption was that facing the machine west south-west, was an acceptable design compromise, because on a time averaged basis, about 80% of annual wind energy comes from that direction.  But that decision reduced the operating time of the machine.  A vertical axis machine could have operated using wind from any direction.  Although vertical axis would be slightly less efficient, the ability to harness wind from any direction without tracking, means that a machine of comparable swept area would generate similar power over the year.  However, this power would be spread over more operating hours, which is valuable.

5. The machine was difficult to build and I had to modify the design several times.  Modifying the machine meant working at height and on two occasions, I had to lift the rotor out of its cradle.  Everything is more difficult when working at height.  Designing a machine that allows the rotor to be easily lowered to ground level would make maintenance easier.

6. A vertical axis machine would have been simpler and easier to build.  It would also have made mechanical power transmission easier.  Instead of the unreliable rope drive, a bevel gear could have attached directly to the rotating shaft at ground level.

7. The machine now incorporates tumbling boxes at the end of (four of) the blades.  This eliminates the need for power transmission and eliminates the friction imposed by the ropedrive.  However, the machine cannot be used for any task now other than stone tumbling.

8. The machine proved to be under-powered and poorly sited for many of the tasks I wanted to use it for.  I estimate that average power is ~300W.  However, friction consumed a great deal of power and what remained was generally insufficient and too intermittently available to support other mechanical loads.  The power available to a wind machine is proportional to swept area.  Doubling the length of the blades would quadruple power output.  But the cradle design did not allow that.

At some point in the future, I may try again.  If I do, I will choose a different design to the one that I built.  It was a pig to build and the results were far more limited than I had hoped.

DOE estimates that there is enough hydrogen underground, to power humanity for 170,000 years.
https://oilprice.com/Energy/Energy-Gene … Years.html

Due to its low density and low boiling point, transporting hydrogen is problematic.  But if we can find a natural hydrogen deposit that can be tapped relatively cheaply, i.e $1/kg, then it can be used to produce liquid fuel using CO2 extracted from seawater or air.  This can be done using a plant that is assembled close to the well head.

2H2 + CO2 = CH3OH

Liquid methanol can be used as a fuel directly, or can be converted into longer chain hydrocarbons through addition reactions.  Everything starts with cheap hydrogen.  Even if hydrogen sources are relatively remote, they could still be useful for liquid fuel production.  Liquid hydrocarbon fuel can be piped across land to sea ports, where it can be loaded onto tankers.

A hydrogen extraction cost of $1/kg, is equivalent to $43/barrel in energy terms.  Present oil prices are oscillating around $100/barrel.  Capturing CO2, chemically synthesising liquid fuel and transporting the fuel will have additional costs.  But if oil prices remain moderately high, synthetic fuel produced using mined hydrogen could provide a substitute for our gradually depleting oil based liquid fuels.

Presumably, the same geological processes that produce geological hydrogen on Earth will also be active on Mars.  The low geological activity of the Martian surface should mean that hydrogen is trapped more efficiently.  We won't know until we go there and start drilling.  But if we do find abundant hydrogen on Mars, it will be a huge boost to colonisation of the planet.  It would make the production of liquid fuel, steel and polymers much cheaper than it would be if everything had to be produced using electricity.  We could even use the hydrogen to make food by synthesis of acetic acid.

For a body some 1500km in diameter (63% Pluto diameter) and mass 25% of Pluto, my spreadsheet indicates that a nitrogen atmosphere with a 25KPa surface pressure would lose 1% of its mass every 80 days.  For a mass this small, there is no exobase within the gravitational influence of the body, resulting in bulk escape of atmospheric gas.  The atmosphere is also very massive, with a column density 89.1 tonnes / m2.  So a dense, gravity confined atmosphere would appear to be impractical for a body this small even in interstellar space.  Maybe a more complex model accounting for real gas properties will change things.  But getting the required data is difficult.

Void, that is interesting.  It suggests that we can likely build temperature gradients within the atmosphere.

I decided to build a spreadsheet to model the atmosphere of a body the same mass and diameter as Pluto.  My assumption is that this body is far enough away from any star that the top of the atmosphere is dominated by non-ionised N2 at 40K temperature.  The spreadsheet models the decline in pressure vs height using the standard scale height equation.  This is based on ideal gas properties, which makes it pessimistic, as nitrogen gas will be more compressible beneath its critical point (126K).  This will result in a more compact atmosphere with a higher escape velocity in the exobase.  So any results calculated here will be bounding for real gases.  My assumption is that the atmosphere is heated from the bottom, with little or no heat arriving at the top.

Some assumptions and starting conditions.

1. The model calculates atmospheric properties at increments of 100m and extends from the surface up to the exobase at 1242.8km.
2. The temperature at the surface is taken to be 68K, which is the saturation temperature of nitrogen at 28.481KPa.  This is above the triple point for N2, allowing liquid N2 to flow on the surface.  It is also a high enough pressure for human breathing, meaning that habitats will not need to be pressurised.
3. Temperature is assumed to be constant at 68K, until a height of 27.4km.  At this point, pressure drops to 12.6KPa, which is the triple point pressure of N2.  The assumption is that temperature declines to 63.2K at this point.  Temperature remains constant w.r.t height until pressure drops to 10KPa at 34.7km.  For pressures <10KPa, I was able to derive an equation for saturation temperature as a function of pressure, based upon the phase diagram for nitrogen.  The fitted equation is:

Tsat ~ 7LOG(P/1.93E-5)

Using this equation iteratively, I was able to model a declining temperature vs height, reaching a temperature of 40K at 243km.  Beyond this height, temperature is assumed to be a constant 40K until the exobase.

4. The local scale height was calculated using a value of g that was calculated using Newtons universal law of gravitation:

g = GM/((r+h)^2)

Where: g = gravity at height, h, above the surface; G = 6.67E-11; M = Mass of body (kg); r = radius of body (m); h = height above the surface.

The scale height was recalculated for each 100m element within the atmosphere.

Local escape velocity is given by: Ve = (2*g*(r+h))^0.5

Results

The main question that we wish to answer with this exercise is whether such an atmosphere could be stable for any length of time.  For a body as small as Pluto, with an escape velocity of ~1.2km/s at ground level, is it possible to sustain an atmosphere with enough pressure for human breathing for a long timescale?  This was the question I wished to answer.

The escape velocity at the exobase is only 846m/s.  However, at a temperature of 40K, the root-mean-square speed of N2 molecules is only 189m/s, about 4.5x smaller than escape velocity.  I used an online tool to calculate the Maxwell-Boltzmann distribution for N2 at 40K.  Amazingly, only ~5E-7 of the molecules (i.e. 1 in 2 million) attain a speed of 846m/s.  I conservatively doubled this number to estimate the integral of the curve at all speeds higher than this.

The mass flux escaping from the exobase can be approximated by multiplying the number density of escaping molecules in the exobase by their average escape velocity.  The pressure at the exobase is 7.39E-9Pa.  Solving the ideal gas equation gives a mass density of 6.23E-13kg/m3.  Assuming 1 in 1 million of these has sufficient energy to escape, allows escape flux to be calculated:

q = (6.23E-13/1,000,000)*846 = 5.25E-15 kg/m2s.

Multiplying by the surface area of the whole atmosphere at the exobase (7.428E13m2) gives a whole planetary mass loss rate of 0.039kg/s.  The total atmospheric mass is 9.18E17kg.  It will therefore take 7.46 billion years to lose 1% of the atmosphere via Jean's Escape.  I would therefore expect cosmic ray sputtering to be a more important atmospheric loss mechanism than Jean's escape.  Suffice to say, the atmosphere should be stable over geological timescales.

Interesting facts:
1. Although the atmosphere is extensive, some 75% of its mass is within 50.2km of the surface.

2. The column density of the atmosphere (mass per unit of surface) is some 51,700kg.m-2.  This is ~5x the column density of Earth's atmosphere, yet surface pressure is only 28% Earth sea level.  This is a direct consequence of the low gravity of the body.  It also suggests that building such an atmosphere is only likely to be achievable if the nitrogen is already in place at or close to the surface of the body and can be vaporised by adding heat.

3. Assuming all heat is radiated into space from the top of the triple point layer, the total radiant heat flux ejected into space is 1.7E13W, or 17TW.  Present human civilisation uses some 19TW per year.  So the terraformed world could support a large civilisation, but there are clearly limits to population and power consumption before waste heat becomes a problem.  If we assume that the bulk of human food is produced via artificial photosynthesis, which turns electrical energy into calories with 20% efficiency, then providing 10MJ of food energy per day requires 50MJ of electrical energy.  This in turn, would require the generation of 100MJ of heat in the powerplant.  If we assume that each human needs an extra 1kWe for other (non-food) energy needs, then each human will need a continuous 3kWe of power production, implying some 6kWth of nuclear heat production.  This implies a maximum practicable population of 2.83bn for this dwarf planet.  That is 160 people per square km.

If human beings do find rogue Pluto sized bodies in interstellar space or the Oort cloud, it is possible in principle to terraform these worlds, at least from the point of view of providing surface pressure sufficient for humans to breath.  Humans would still need to live within habitats that are hotter than the surface.  But these could be thin tent like structures, as there would be no effective pressure difference between the inside of the habitat and the surface.  Something like a polymer membrane draped over a steel frame, would be sufficient to separate warm breathable air inside, from cold nitrogen gas outside.

My next iteration of the spreadsheet will explore how small a world would need to be before this terraforming approach is no longer viable.

TH, the link in the original post has gone inactive.  One problem with fuel cells is that surfaces are vulnerable to contamination, especially with sulphur.  Historically, there have also been issues with weight, cost and fragility of ceramic membranes in SOFCs.  If we want to burn coal in an engine, the traditional approach was to gasify the coal with partial combustion with steam, to produce carburretted water gas.  This gas can then be burned in a spark ignition engine or gas turbine.  This is old technology now.  It has been used in road vehicles.  It could be used in trains and ships.

In ships, it might find a niche, because such a ship could be powered using coal, raw biomass, crop residues, forestry wastes and even trash.  The fuel wouldn't require much processing aside from being chopped into pieces of the right size.  Any plant material available would work.  This option hasn't been popular up to now because of the logistics of handling solid fuel, the need for pre-burning furnaces on board the ship (which would take up space in the hull), the cumbersome nature of solid fuel injection into furnaces and the lower energy density of biomass fuel.  But this is an option that coukd be made to work if the world finds itself enduring a prolonged shortage of liquid fuels.

I keep getting this message when attempting log-on:
'Bad CSRF hash. You were referred to this page from an unauthorized source.'

Any idea what this means?

Interesting discovery of atmosphere on 2002_XV93.
https://en.wikipedia.org/wiki/(612533)_2002_XV93

This little world is just 470km in diameter and surface gravity is ~1% Earth normal.  So even a thin atmosphere should dissipate quickly.  The authors suggest complete escape in 100 - 1000 years, depending upon composition.  The source of the atmosphere is most likely an impact exposing buried volatiles, which subsequently sublimate.

By my estimation, the escape velocity of this body is less than 200m/s.  Even at the low temperatures present in the Kuiper Belt, I am surprised that an atmosphere could survive as long as 100 - 1000 years.  The gases most likely to be present, N2, CO, CH4, also have relatively low molecular mass.  If we take nitrogen as an example gas and assume an atmospheric temperature of 50K, the median gas molecule velocity is 177m/s.
https://cfm-calculator.com/calculator.p … ulator.php

That means that around half of the molecules in the atmosphere will be moving at velocity that exceeds escape velocity.  How is it that these gases are not lost on a timeframe measured in hours or days rather than years?  How could any atmosphere survive for centuries?
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Additional: I think the reason that the atmosphere can hang around for so long is due to inertial confinement.  The particles that escape first are at the top of the atmosphere, where the mean free path starts to exceed the scale height.  The particles beneath are confined by collision with particles above them.  This deflects them downward, confining them.  Even so, it isn't clear to me why the lower layers wouldn't just expand, pushing the upper atmosphere into space.  How escape can happen so gradually is not something that I can explain.

Thanks. It is good to see the forum up and running again.

I think my original e-mail has gone inactive.  I will update with a new one this week.