New Mars Forums

This is the kind of machine that I would choose to build if I could repeat the process.  A much simpler machine, easier to build, able to accept wind from any direction and although slightly less efficient, it has more starting torque than the horizontal axis machines.  That is important, because the rope drive and any machinery attached to the clutch, will have considerable internal friction.  So efficiency is about more than just aerodynamics.

Update: Today I attached the rope drive and the clutch.  It seems to be working as intended.  Aside from cosmetic changes and the balancing of the machine, it is now finished.

The rotor is turning now.

There remains much to do.  The rotor must be balanced, the bearing caps must be installed and any damaged surfaces must be painted.  Finally, the rope drive must be installed.  This is going to take a while.  I would like to finish by next sunday.  I will see how it goes.

A currency based upon non-perishable commodities would appear to me to be a good idea.  Metals are an obvious choice.  They have value because of the energy needed to mine and refine them.  Fiat currencies are prone to inflationary pressures.  This tends to destroy the value of long term investments, because the rate of return always has to exceed baseline inflation.  If inflation were always guarenteed to be zero, then people could confidently make investments knowing that their grandchildren will reap returns.  That will be important for projects that take a long time to finalise, like terraforming for example.  Or building capital intensive but long-lived infrastructure.

Any sort of cash based financial system is cumbersome, but it has the advantage that transactions are private from overbearing authorities that wish to control people.  These may be financial institutions or governments themselves.  In both cases, human liberty is at risk.  Remember how easy it was for that snake Trudeau to freeze the bank accounts of the truckers?

TH, that is marvelous!  It captures the concept perfectly.

The idea of a layered city does somewhat undermine the original design intent of providing residents with an open, expansive environment.  But the cost of the dome may necessitate compromise.

This video by Dami Lee discusses the fortress tower cities in the fictional Lord of the Rings series.
https://youtu.be/K0sRNqfiwfw

Whilst these cities are fantasy, her video did get me thinking about vertical stacking of infrastructure in real cities that we might one day build on Mars.  Our proposed catenary dome will be 200m in diameter.  Although we have yet to determine its exact shape, it will likely be similar in height.  It will make sense to use the enclosed volume as efficiently as possible, given the high cost of building the dome.

The lower gravity of Mars offers opportunities in this.  It is possible to stack cities as a series of layers, as shown in the image below.

Each layer would be built on a slab of concrete or glued rock about 1m thick and would be supported on stone pillars, transfering load to the layer beneath it.  About 10m above the slab would be the base slab for the next city layer.  On the underside of the upper slab, we would put a transluscent blue tinted glass ceiling.  Under the glass, a blend of coloured LEDs would simulate an Earth sky colour and solar spectrum.  The 10m between the two rock slabs is sufficient for a dense pedestrian town consisting of 2-3 storey buildings, with enough space under the ceiling for roof gardens.  The drawing shows some 17 layers, each of which would house a town with its own artificial sky.

The drawing shows each layer terminating some distance from the edge of the brick dome.  There are options to consider here.  We could allow a substantial gap and turn the edges of each town into a sort of hanging garden.  Or we could extend the layers all the way to the edge of the dome.  This would be the most resource efficient solution, because it fully utilises the internal volume of the dome.

How many people could we ultimately house in this way?  I am going to estimate the volume of our catenary dome as 0.5 x base area x height.  For a 200m high, 200m wide dome, this would give an internal volume of 3.14 million cubic metres.  Dividing by a 10m gap between city layers, gives an internal buildable surface area of 314,000m2.  If we take the population density within city layers to be comparable to the pedestrian medina of Fez, total population of the dome could be as high as 17,500.  By making optimum use of internal volume, a 200m dome could therefore house a small city, built up in vertical layers.

There are complications with packing so much infrastructure into a single volume.  One complication is fire.  Our city must have excellent fire extinguishment and containment capabilities.  Another problem with stacking layers of urban infrastructure is waste heat.  Without some means of venting heat to the Martian environment, our city would cook in its own radiated heat.

This blog is an excellent resource for anyone wishing to better understand masonry construction.
http://masonrydesign.blogspot.com/

The ideal site would be:
(1) Not too far from the equator, avoiding extreme cold in winter and at night.
(2) Close to a source of geothermal energy.
(3) Nearby access to liquid brine or at least easily accessible water ice.
(4) Would allow easy excursions to other parts of the planet, i.e avoid deep ravines and other natural barriers.
(5) Would have low altitude, maximising atmospheric shielding and atmospheric braking potential.
(6) Lower susceptability to impact by dust storms.

Whilst we could in theory build a base anywhere, I suspect there are few locations that meet all of these criteria and there may indeed be none.

Criteria 1 is important, as a base too far from the equator would experience extreme cold and darkness for half of the year.  If we are planning on using surface domes or polytunnels for agriculture, that is undesirable.
Criteria 2 is a nice bonus.  It allows heating of surface structures, provides a source of low grade heat for multiple activities and adds an option for power production.
Criteria 3 is essential.  Don't bother considering sites that don't have access to water.  Liquid water, even if salty and cold, would be far more useful than ice.  But abundant accessible ice is a minimal requirement.
Criteria 4 is important both for scientific exploration and for the city to develop as a hub for resource development.  We are going to need minerals of every element on the periodic table.  A lot easier if we aren't stuck at the bottom of a ravine.
Criteria 5 makes shipping resources from Earth easier and also makes surface activities less risky.
Criteria 6 is essential.  A base site that is regularly engulfed in dust is a bad place to do anything.  Solar panels stop working, crops stop growing, dust gets blown into moving parts and people will get lost and die.

I would probably build a much simpler vertical axis machine were I to do it again.  Efficiency is lower, but the ease of construction and assembly make it more practical overall.  Above all else, the design needs to minimise the need for working at height.  If there is a rotor that needs maintenance or adjustment, then there needs to be a capability of lowering it down the pole for work, without having to work at height.  Working at height means putting up scaffold and introduces problems of working in confined space, confined angle and having to avoid vibration.  It slows things down dramatically.

One important thing I have learned is that the best solution is very dependant on local conditions.  Midwest farms on flat land with a consistant wind direction, are well suited to the jumbo type ground mounted wind machines.  Locations with variable wind directions are better suited to vertical axis designs that can make use of wind from any direction.  Locations with a cluttered near surface environment need towers to overcome surface attenuation.  If there is limited space, a horizontal axis machine offers greater efficiency.  Local geography can sometimes be used to focus the wind.  The availability of materials will have an impact as well.

The new CatGen catalyst bed technology promisses more compact and fuel efficient GT engines.
https://youtu.be/-TDoteS9QZA

I can see a number of problems with this idea in practice.

1. Whilst the catalyst allows efficient combustion in a compact volume, its presence limits combustion temperature to the melting point of the catalyst and substrate.  This places limits on cycle efficiency.
2. The catalyst bed adds weight.
3. The compressor must force air through the narrow channels of the cataylst bed, which increases pumping losses through the engine.  In a conventional GT, compression already consumes at least half of the energy produced by the turbine.
4. Although the video talks about the tolerance of the catalyst to different fuels, the reality is that fuels containing sulphur or soot will poison the catalyst.

In spite of these problems, this engine concept may offer value in burning lean fuel mixtures that would not otherwise support combustion.  In the Martian context, we know that the Martian atmosphere contains small amounts of CO and O2.  If CO2 can be seperated from the bulk air, the remaining gas mix could be preheated and passed through a catalyst bed to extract energy.  Given the small concentration of CO, this is unlikely to be a net energy producing reaction.  But assuming we are inputting energy to extract specific gases from the Martian atmosphere, this reaction would allow some portion of input energy to be recovered.  It also scrubs CO out of the N2/Ar gas mix, which is important if we are gathering life support gases.

GW,
Out of interest, what would you estimates the rate of return on your investment to be?

A man has been jailed in the UK for 'possessing rightwing music'.
https://youtu.be/kKrBDsFBlxw

TH, impressive image.