New Mars Forums

Why we should build with stone again.
https://youtu.be/VVaWmEI9O1w?si=CxF-SIoXZi83faGe

Interestingly, some quarries are entirely electrically powered.  The manufacturing supply chain for stone is much shorter than reinforced concrete, which requires several mined components.  Natural stone is typically stronger than concrete as well.  But unlike reinforced concrete, stone cannot take tensile forces.

On Mars, underground stone mines could be useful space.  Whereas an open cast mine will require robotic or pressurised vehicles, underground can be a shirtsleeve environment.  Also, the voids created by room a pillar mining, can be sealed off and used as habitation space.  Mars appears to lack the large carbonate stone deposits that are necessary to make portland cement.  Stone may ultimately be a cheaper option on Mars.

Not everyone reading this board will be happy with the election result.  Politics varies, because life experience varies. But within the (relatively) narrow interests of this board (space colonisation) this is the best US administration since John F Kennedy.  Better in fact.  A return to the moon and onwards to Mars, fits the MAGA ethos perfectly.  And Trump's new bestie and principle technical advisor is none other than Elon Musk.  So far as Mars is concerned, this confluence of political outcomes may be a truly pivotal moment in history.  It is analogous to the passion for exploration that gripped the Iberian peninsular in the 15th century.  That ultimately led to the discovery and settling of America and a worldof wealth and technology that our ancestors could not have imagined.  Maybe we stand at the cusp of something similar right now?  I dare to hope.

Direct fission based propulsion systems are the only ones that can generate the power needed to deliver high ISP and high thrust simultaneously.  ISP x thrust = power.  The sort of torchship drives that you see on the expanse, capable of exhaust velocity in the 100s km/s whilst accelerating at several gee, are only possible using fission or hybrid fission fusion propulsion.  That is because that combination of high thrust and high ISP requires GW to TW of power for a reasonable sized ship.  There is no way of doing that aside from direct conversion of nuclear energy into kinetic energy.  The fission fragment rocket is one such example.

What stands in their way is politics.  If Trump enters the white house with Elon as his trusted advisor, things like this might really be on the table.  If we could truly unleash the potential of fission for spacecraft propulsion, it would unlock the solar system.  We have known that all along on this board.  In a few hours, we may know whether such dreams will be possible or not.

CO2 is far more soluble in water than most other gases, due to the formation of ionic carbonic acid.
https://en.m.wikipedia.org/wiki/Carbonic_acid

Strangely enough, carbonic acid is unstable in the presence of water and decays back into H20 and CO2 quickly.  But the finite halflife of H2CO3 in even a liquid medium results in a high solubility of CO2 at any particular partial pressure.  It is more soluble because it forms covalent bonds with water molecules.

Of course, water on Mars exists as either ice or saturated brines.  Both will be extremely cold, which will extend the half life of H2CO3 and increase CO2 solubility even further.  We know this because colder temperatures mean lower molecular speeds even if carbonic acid decomposition has no minimum activation energy (I don't know if it does or not).  H2CO3 is also denser than water and pure ice, so will tend to sink within solution under gravity.  This explains why deep ocean water is CO2 enriched.

I wonder how this behaviour has played out on Mars over aeons?  Did the formation of carbonic acid result in gradual stripping of the atmosphere as CO2 sank into the porous outer crust?  Will we find pressurised CO2 pockets as we drill into the surface?  Or was the planet's atmosphere sequestered as carbonates deeper within the crust.  It is surely no coincidence that the current atmospheric pressure on Mars is close to vapour pressure of water at its triple point.  A CO2 based atmosphere is unstable on an igneous planet in the presence of liquid water.  This has many implications, both good and bad, for terraforming.

The Nobel prize for chemistry has been awarded to a group of scientists who developed AI software that is capable of accurately predicting protein structure.  It is even possible to design proteins with specific shapes to fit specific applications.  Some of these do not exist in nature.
https://youtu.be/5i2U67TVsRI

This is an incredible achievement that would have been considered sci-fi until a decade ago.  It could herald a new era of designer drugs and even artificial organisms.  But it also tells us something else.  To be able to accurately predict the shape of something as complex as a protein, our understanding of atomic physics must be very close to being complete.  Even subtle errors in our understanding of orbital structure and bond length would throw the results off.  For such a model to work, there can't really be any unknown physics remaining at the atomic level.

Void, that is an interesting idea.  Keep in mind that stone is brittle, has relatively low thermal conductivity and likely to crack if subject to thermal gradients.  Those gradients create shearing stresses within the material due to differential expansion.  This is why sensible heat storage schemes tend to rely on crushed materials in which the lumps are no bigger than hand sized.

I don't think keeping warm will be that much of a problem on the moon.  Inhabited structures will be covered in at least 2m of regolith for cosmic ray shielding.  Fine regolith has a better insulation value than rockwool under vacuum conditions.  Keeping cool may turn out to be a problem.  Without heat rejection systems, habitats may end up cooking due to internal heat accumulation.

Kbd512, good post.

If Mars does indeed contain large amounts of trapped methane, it will make the job of building up solar thermal capacity a lot easier.
https://www.science.org/doi/10.1126/sciadv.adm8443

We can reduce powdered iron oxides to iron metal by blowing methane over it at 800°C.

4Fe203 + 3CH4 = 8Fe + 3CO2 + 6H2O

The iron powder can be converted into mild steel using an electric furnace.  We can also use methane to make acetic acid.  That would allow food production without sunlight.  A large chunk of the 100GWe that was calculated as being needed to support a million people is needed for food production.  The original plan was to grow plants under LED lights.  If Mars fossil methane can be used to support food production through acetate production, then we avoid the need for a huge chunk of power supply.  Martian natural gas is a game changer, if we can find it.  Even without atmospheric oxygen to burn it in, natural methane would be an enormously useful resource on Mars.

Whilst solar powerplants may be visually unappealing, a larger problem on Mars is the materials needed to build them.  On Earth, photovoltaics are the most resource intensive energy source that we have by a significant margin.  On Earth, solar PV has experienced almost miraculous price drops since the turn of the century.  A large part of this is due to the use of very cheap coal-based energy, mass production and use of slave labour.  None of those things exist on Mars and sunlight is only half as intense.  That means to produce the same power at any lattitude, the plant must be twice as large.  Using solar thermal power, most of the material inputs can be steel or cast iron, which are much less energy intensive than silicon-based PV.

Power density will still be low, requiring a lot of refined metal for each MWh of electricity or heat.  This presents a significant problem on Mars because refined materials will be expensive.  The high energy density of uranium makes it a more desirable optionmeven if nuclearfuel must be imported from Earth.  A single gram of uranium will yield some 21,000kWh of heat in a fission reactor.  This pretty much guarentees that fission will be the dominant energy source on Mars because the powerplant needs only a few percent of the materials needed to build a comparable solar plant.

This video discusses metal production and seperation from lunar regolith.
https://youtu.be/xH4Ki6TxRTs?si=TnEn9ER04HanhaZ_

The same process could work with the various silicates present in stony asteroids.  One major advancement that the video discusses is the use of iron-chromium alloy electrodes for magma electrolysis.  As both iron and chromium are relatively abundant on the moon, this removes a potential bottleneck from magma electrolysis.  Previously, carbon based electrodes were expected to be used.

There is more discussion on the use of calcium as a reducing agent.  Calcium oxide bonds with silica, yielding calcium silicate which floats on top of the melt.  Calcium can also be used to remove different metals.  By adding selective quantities of calcium metal, different metals in the mix can be selectively reduced and seperated.  The electrolysis cell can then focus on reducing calcium oxide back to metal.

Melting the various oxides is energy intensive.  The author expects this can be achieved by solar concentrators, which will reduce the amount of electricity needed to produce metals.  If metal reduction is accomplished using calcium, then calcium oxide electrolysis is the only part of the process that needs electricity.  Everything else is done using concentrated solar heat.  In free space, this gives us a significant advantage.  Concentrating solar heat is cheap and easy and requires focusing a concave mirror at the sun.  Electricity will be more expensive, as we need either photovoltaics or turbomachinery.

I have to admit, I was sceptical about the chops sticks idea of catching the super heavy booster on decent.  It looked to me like it would result in heavy point loads on the air frame.  It also requires very precise alignment to be able to work.  But they tested it and it did work.  Well done SpaceX!

Observations from the New Horizons probe confirm that no new physics is needed to explain the amount of background light in the universe.
https://youtu.be/4SZHy54vyrI?si=-c98ms6tV2fEYhgq

Increasingly, what we observe in nature is well predicted by our theories.  The LHC confirmed the existence of the Higgs Boson.  Its mass was almost exactly what was predicted by the standard model.  Recent measurements of mass of the W Boson, are also exactly what was predicted by the standard model.  There seems to be very little room for new physics beyond what is already understood.  Our model of the universe, whilst not complete, is certainly approaching completion.

That statement is fundamentally false.  I will explain why.

Firstly, human technology has very definitely peaked since the 1960s.  Peaked does not mean halted of course.  But there is a definite and noticable slowing of pace.  What we are seeing now is refinements, rather than fundamentally new technologies.  Microelectronics are the significant outlier that have seen great progress in the past three decades.  But this is now reaching physical limits.  A transistor cannot get smaller than a single atom.  This is a good example of how physics imposes ultimate limits that are simply impossible for us to cross.  This isn't a problem that results from failure of imagination.  It is a constraint imposed upon us by the fundamental nature of matter.  It is not negotiable or traversable.  It is an ultimate impasse, a hard limit that no amount of optimistic thinking or inventiveness will get past.  Not now or at any point in the future.

The same is true of many other things.  There are limits to the ultimate strength of materials.  The strength of any new material that we develop in the future, will be constrained by the strength of electrostatic force between protons and electrons.  There are limits to the melting point of materials, that ultimately come from the same place.  It isn't a coincidence that our strongest materials have high melting points.  There is a fundamental speed limit to the universe.  Limits to achievable energy densities.  These aren't things that new technologies can get past.  Indeed, technology is constrained to forever work within them.  We will never be able to build warp drives if doing so requires energy density comparable to a black hole.  It isn't possible to build things like that out of materials that we can use.  Likewise, the Heisenburg uncertainty principle tells us we can never build a Star Trek style transporter.  It is impossible with technology we have now and we know it will remain impossible with any technology that we may develop in the future.  We will never have Star Trek style tractor beams, for the simple reason that standard model physics doesn't allow us to produce beams of gravitons.

The laws of physics are finite.  There are only so many ways that particles can interact.  This tells us that no area of science can be infinitely complex.  The more we discover, the less there remains to be discovered.  Given that technology works within the bounds of physics, it follows that there are a finite number of permutations that we can develop.  Technology can continuously adjust to new circumstances, but it cannot grow infinitely complex or capable, because it can only operate within the bounds of the physical laws of the universe.  This tells us that the huge growth in new technology that we have seen this past 200 years, is likely to be a historic, one-time transition rather than being characteristic of a continuous state.  Technology is still developing in its complexity, but this is showing diminishing returns.  The 1950s bought us jet engines, for example.  The 2000s brought us new and improved jet engines, with better efficiency.  It didn't bring us compact micro-fusion reactors.  The laws of physics constrains what we can build.