Technology needed for Mars

SpaceNut · 2019-08-13 20:08:53

Seems that we have yet another use for Carbon Nanotubes as these Damaged hearts rewired with nanotube fibers

Researchers at Texas Heart Institute and Rice University have confirmed that flexible, conductive fibers made of carbon nanotubes can bridge damaged tissue to deliver electrical signals and keep hearts beating despite congestive heart failure or dilated cardiomyopathy. Thin, flexible fibers made of carbon nanotubes have now proven able to bridge damaged heart tissues and deliver the electrical signals needed to keep those hearts beating.

tahanson43206 · 2019-10-08 08:54:41

For SpaceNut re topic ...

I let a newsletter offer tempt me into subscribing recently.

This item may be of interest to a forum reader down the line:

http://www.ti.com/lit/an/sboa344/sboa344.pdf

You have to sign up to see the full article but subscription is free.

Kirby Kruckmeyer
ABSTRACT
Historically, satellite programs have used space grade, hermetically sealed, QML-V qualified components
for enhanced reliability and radiation hardness. With the emergence of “NewSpace,” there has been more
interest in using plastic encapsulated microcircuits (PEM) in space for a variety of reasons. NewSpace is a
loosely defined term covering some of the trends in the space ecosystem, including the emerging private
spaceflight industry and programs that have reduced reliability, lifetime, and radiation requirements. PEMs
become more attractive because leading edge products are not available as space qualified products and
PEMs generally have smaller footprints and are lighter than the ceramic packages used in space qualified
products. It has been recognized that there is a quality and reliability risk in using commercial-off the shelf
(COTS) products and some space programs have been investigating using automotive grade AEC-Q100
products with more stringent qualification requirements. However, the extra qualification steps in Q100
parts do not meet all the requirements of a space application, even for those space applications with
reduced requirements. For instance, commercial low earth orbit (LEO) applications with a projected three
year life still have to meet radiation goals that many PEM products do not survive. One of the biggest
challenges for a satellite program is finding and then testing those products that meet the radiation goals.
Although radiation performance may be biggest obstacle to using some COTS or automotive products in
space, there are a number of other risks and factors to consider, such as tin whiskers, copper bond wires,
rated temperature range, and package outgassing. How is a customer to know if a product has the right
stuff to even be considered for a space mission?

I have omitted the name of the corporate underwriter to fit with forum tradition.

(th)

SpaceNut · 2019-10-08 16:53:29

Some of the once damaging effects of radiation have gotten less as the parts get smaller and with much more testing after coating the parts with conformal coatings they are pretty much sealed from anything that would cause corrosion or moisture to get into the circuits.

tahanson43206 · 2020-01-06 19:17:08

For SpaceNut ...

The link below is from Lizard King of luf.org

It applies to more than one topic, so I'll be posting it where it seems to fit.

https://www.sciencemag.org/news/2019/09 … iquid-fuel

In this case, a Mars expedition would use this technology to capture water vapor and CO2 from the atmosphere.

(th)

tahanson43206 · 2020-07-18 15:17:37

For SpaceNut re Topic ...

I was looking for an existing topic where the suggestion which follows would fit...

It would fit just as well in a topic "Technology needed for Earth" ...

There is a business opportunity with multiple avenues for earning income while providing needed services.

When Magellan set sail for his Around the World venture, he included a barber in his crew. That was 500 years ago, and the niceties of proper appearance were known to the aristocrats of the time, but in Magellan's case, I'm of the opinion he included a barber for ALL the members of the crew, and not just for the captains and other officers.

In the case of an expedition to Mars, I do ** not ** expect there will be a manifest slot for a barber.

Instead, a technology to allow individual crew members to trim their own hair would seem (to me at least) a reasonable capability to include.

This is the first time I've thought about what members of the ISS do about keeping trim.

It would not be surprising if a bit of hair trimming is a part of the responsibility of crew members.

In any case, what this post is about is the business opportunity for Mars, ** and ** for Earth, for people to be able to cut their own hair.

There is a product or system called "Magic Mirror" that is (apparently) available for download from the Internet.

A local computer group gave a presentation on the system, and it is available for viewing on YouTube. I'll post the link if anyone is interested.

However, "Magic Mirror" turns out NOT to be what I was hoping for.

What I am imagining is a robot with a capability of maneuvering an electric clippers in one "hand" and a comb in the other, while the operator views a (presumably large) computer screen in order to guide the motions of the robot arms.

The potential market opportunity for Earth seems significant.

But ** here ** is the angle that I'm hoping you (in particular) SpaceNut will appreciate ...

I am interested in designing this system so that ** real ** barbers can operate the equipment remotely.

Thus, the potential exists to provide gainful employment for the thousands of Earth humans who have mastered the art of barbering, while at the same time eliminating travel time from the schedules of countless customers.

SpaceNut ... in the past, when I have offered suggestions for teleoperation, you have (on occasion) translated the suggestion into something involving AI level robotics! This is ** not ** intended to be any such thing.

I am looking for opportunities to provide gainful employment for thousands of people alive today, and an ** not ** interested in eliminating jobs, as an AI level robot would do.

(th)

Last edited by tahanson43206 (2020-07-23 08:32:02)

SpaceNut · 2020-07-18 16:33:08

Sort of an extension of the hand controls that allow the operator to sit in a booth and to work the controls so that the tools move to the places that we are telling them to move to. Sort of like a tactile suit to save movements to a computer program for later use.

The barber angle would mean comradery of crew such that they care for each others appearance.
There are lots of other activity which include medical that we would want to learn how to do for others...
A Floby was the vacuum cleaner like attachment that was used to groom hair but you are correct that having another person around that would want to do the hair could not be something that all would want to do for each other so a tactile computer interface to control robotic arms that would make use of the tools would seem quite challenging for the person that fears being cut by the tools.

kbd512 · 2020-07-18 17:00:41

tahanson43206,

Out of necessity, Mars will have at least 10 "remote maintainers" to support each colonist braving the new frontier, at least initially. This is no different than how our military functions. For each person in our military, there are at least a dozen people directly employed, full-time, to supply all of the food / fuel / depot level maintenance of the machines, etc. We can easily create standing armies of gainfully employed support personnel to supply our space exploitation / colonization endeavors. This is how the endeavor will ultimately "pay for itself" (creating gainful employment to produce the goods and services that the colonists need to survive), not absurdly expensive trinkets or gaudy advertisements on rockets (things that are merely "here and there" bonuses if/when someone out there is willing to pay for them).

I can justify increased head count to provide engineering and maintenance support services in the form of someone who remotely provides expert guidance to a colonist to maintain a life support system or rocket engine, for example, but I can't justify putting someone on Mars to make watches or collect rocks for rich people. Some of that stuff will inevitably happen and I'm not against it at all, but only after the basic necessities of life have been taken care of. Our starting point on Mars must take us from nothing at all to a self-sustaining society, which means all the fundamentals that technologically advanced human civilization here on Earth requires are still required on Mars. If we could put a million people on Mars, then I can see employing around 15 million people to keep everyone supplied / supported. We would also have to create the education / health care / transportation support to support the maintainers. If the US, EU, and Asia all did this, then I can see how we could guarantee the employment of at least a quarter of a billion in high-technology jobs with middle class salaries and benefits.

We're going to build a supply chain of maintainable, rather than replaceable parts, from Earth-to-Mars, using the military's system for maintenance / support of technologically advanced equipment. The military keeps sophisticated equipment operating for decades through continual disassembly, inspection, re-machining or cleaning, and re-assembly of parts. Some spares are required, but more often than not, complicated machines have their parts maintained rather than completely replaced. Overhaul maintenance is a different proposition, as SpaceNut is aware, and a significant number of parts must be replaced at that time. We'll have to figure out how to do that remotely. In any case, the military's maintenance and supply system has proven itself capable of sustaining a forward deployed force for many decades now. Mars is clearly an extreme case where the force in question has been forward deployed to another planet.

Calliban · 2020-07-19 09:57:53

A high breeding ratio, fast breeder reactor. Mars appears to have a poor abundance of fissile fuels. However, a fast breeder reactor yields so much energy from such a small amount of fuel, that it hardly matters. I would propose a gas-cooled fast reactor, with an S-CO2 direct cycle. The reasons are:

1. A harder neutron spectrum than a sodium cooled FBR, resulting in a shorter doubling time. For a sodium FBR, doubling time is typically 30 years. For a fast growing Martian colony, we would want to get that down to a decade of possible.
2. Direct cycle means no bulky heat exchanges.
3. The S-CO2 power generation equipment is very compact. When combined with a high power density core and a direct cycle, this allows very high system power density.
4. CO2 is non-corrosive, so all parts of the system (minus perhaps the fuel) can be made from low carbon steel, with a pre-stressed concrete pressure vessel.
5. A relatively low temperature cycle might be compatible with metallic fuel, that is suitable for electro-refining.
6. A high temperature cycle could drive thermochemical hydrogen production through the sulfur cycle. This would be the basis of synthetic fuel production, plastics and a Martian steel industry.

This probably wouldn't be the first reactor built on Mars. We would probably start with light water reactors burning enriched uranium. But as base power requirements grow and the spent fuel accumulates, we would eventually have enough plutonium to start an FBR programme.

Last edited by Calliban (2020-07-19 10:03:48)

kbd512 · 2021-06-10 15:36:31

Calliban,

If the CO2 is extremely pure, with no O2 and H2O vapor from the Martian atmosphere, then it should be compatible with low carbon steel. However, even trace amounts of O2 or H2O will quickly corrode unprotected low carbon steel. If the steel was coated with Nickel, possibly sourced from Nickel-Iron asteroids found on the surface of Mars, then I could see a CO2-cooled reactor being more practical. Otherwise, Inconel is quite good at resisting high temperature driven oxidation from hot gas with impurities mixed in. Incidentally, they tried this (using cheap low carbon steel) in Colorado in the gas-cooled reactor at Fort Saint Vrain, but ran into the same problems with impurities in the coolant gas corroding the steel used in that reactor. They did eventually resolve the coolant's O2 and H2O contamination problems through strict process control for purifying the coolant gas (I think they used Helium, not CO2), but the reactor was subsequently shut down due to cost overruns shortly thereafter. The nuclear core was removed and then they started burning natural gas in the same system to generate commercial electric power.

The new diffusion-bonded Printed Circuit Heat Exchangers (PCHEs) are not nearly as bulky and can be designed for very low pressure drops. They're at least 5 and possibly 6 to 8 times smaller than traditional heat exchangers. These are typically made from stainless or Inconel, so they'd probably have to be imported from Earth. Anyway, it's better to keep the power generation loop separate to avoid radioactive contamination of the power turbine for ease of maintenance, since sCO2 gas turbines contain service life-limited consumable parts that must be periodically replaced, especially if the bearings use oil as a lubricant. The benefit I see to the PCHE and sCO2 gas turbine tech is that it applies to both Earth and Mars, it applies to nuclear thermal, solar thermal, geothermal, and oxy-fuel combustion heat engines. A Mars colony of any significant size will need one of those technologies to supply power at night, since batteries are impractical at the scale required and technologically demanding to maintain. The low-cost thermal batteries suitable for grid scale application are all using hot liquid salts anyway, and Professor Donald Sadoway said that power can still be transferred via gas turbines if the thermal photovoltaics prove impractical.

If extreme power density is desired, why not opt for a liquid salt or liquid metal coolant with a sCO2 thermal power transfer scheme on the non-nuclear side of the plant?

I have a counter-proposal for consideration that's very similar to what you proposed:

The reactor containment building will use a Sulfur-based concrete mixed with an Iron Oxide aggregate, both collected right off the surface of Mars. The reactor vessel itself will be cast ductile iron with a Nitride coating to inhibit oxidation. The coolant and fuel will be molten salt, so that the reactor vessel itself is not pressurized and the salt-based fuel can have fission products chemically separated without shutting down the reactor. The secondary loop will be a PCHE that's literally cast into the walls of the iron reactor vessel, to transfer thermal power to a sCO2 gas turbine. It's an "almost direct cycle", or an "integrated heat pipe" design. The radioactive fuel salt doesn't touch the power transfer fluid (sCO2), so there will be fewer complications than there otherwise would be with having hot CO2 in direct contact with the fuel.

My reasoning is that minimal processing of all the materials used in construction is required to produce the proposed reactor, most of these materials can be locally sourced from Mars, rather than imported from Earth, so only the nuclear fuel and complex precision machined parts like sCO2 gas turbines and electric generators would need to come from Earth. Since the turbine and electric generator are relatively small and lightweight, it's feasible to import these machines with little effect on the overall colonization effort. While the ability to produce cast iron is tantamount to steel production, in pretty much every case here on Earth, producing cast iron is easier, less labor-intensive, and therefore cheaper than producing steel.

Calliban · 2021-06-10 16:18:37

I agree that an indirect cycle, using liquid metal coolant, is a better idea than a direct S-CO2 cycle with the development of compact heat exchangers. Typical S-CO2 cycle inlet pressure is 20-30MPa. At this pressure, volumetric heat capacity is reasonable even in a gas and the low viscosity of CO2 means good heat transfer coefficients and relatively low temperature drop needed across heat exchangers.

The contamination issues that you mentioned are only partially avoidable when CO2 is used as a reactor coolant. The problem is that under high neutron and gamma flux, the CO2 breaks down to produce CO and oxygen radicals. The oxygen then attacks metallic surfaces. At the relatively low temperatures in Magnox reactors, it wasn't a big problem. But in AGRs, corrosion became a concern and the graphite moderator suffers progressive loss of density after a couple of decades. To attempt to mitigate the problem, British AGRs inject methane into the coolant to mop up oxygen radicals. But that isn't a satisfactory option in a fast reactor.

Sodium is generally accepted to be the best overall fast reactor coolant. It has excellent thermal properties, low viscosity, it is light enough to avoid eroding fuel surfaces when pumped and although it is a relatively light element, it does not soften neutron spectrum to an unacceptable level. It does not require pressurisation, even at high temperatures up to 800°C. Sodium cooled reactors, with metallic tube-in-duct fuel assemblies may achieve very high breeding ratio, which is what we want on Mars. They are also very compact, with high power density. With S-CO2 as secondary power generation fluid, the usual need for intermediate heat exchangers should be avoided. The result would be a nuclear system that has high power density and high efficiency. Two important drivers for low generating cost.

Calliban · 2021-12-19 16:46:42

Link to Casey Handmer's book: 'How to Industrialise Mars'
https://docs.google.com/document/d/1pxQ … tn4186ugy9

One thing that I note is how exceptionally difficult it is for any nation on Earth to come close to self-sufficiency in all of the industries that make up the products of our high tech modern society. Places like Cuba and North Korea, have been forced into positions approaching autarky. Both have generally failed to achieve self-sufficiency in complex goods. They have populations of 11 million and 25 million, respectively. And they do not face the extreme environmental challenges that a Mars colony would face. In North Korea, the climate is cold. But there is breathable air, liquid water and fertile soil. The entire surface of North Korea is a shirt sleeve environment. Not so on Mars. Elon Musk's city of 1 million, would be attempting to achieve a high level of self-sufficiency, with a population much smaller than North Korea and within a far tougher environment. Which begs the question of why anyone would expect this to be possible on Mars, when it is clearly extremely difficult for much larger nations living on Earth? Even a country like South Korea, with 51 million people, is not functionally self sufficient here on Earth. Could South Korea survive if transplanted to Mars? It seems unlikely. Mars is a much more difficult environment.

This raises important questions about the efficacy of Mars colonisation. We are travelling to a planet that is much colder than Earth, with a thin poisonous atmosphere. Food must be grown in a pressure vessel. Water must be mined. Air must be made in a chemical reactor. Any living space must be shielded from cosmic radiation and the Martian night, which falls to temperatures of -90°C. Visionaries expect to create thriving colonies, that grow rapidly and eventually achieve economic independence from Earth. Why would anyone expect that to be possible on Mars when it so often fails to work in much easier environments here on Earth?

Last edited by Calliban (2021-12-19 16:56:48)

Calliban · 2022-05-01 08:51:08

In-space manufacturing could help humanity fight climate change, startup says

https://www.space.com/in-space-manufact … -footprint

"Space provides a much, much better manufacturing baseline for almost any material," Western said. "Going into space enables about a billion new alloy combinations through a combination of microgravity, high-purity vacuum (without the need for multistage pumps), and accessing extremes of temperature of plus to minus 260 degrees Celsius [plus 500 degrees Fahrenheit to minus 436 degrees Fahrenheit] just depending on which way your platform is orientated."

"The applications that we're focused on at Space Forge are really in the advanced material sphere," Western said. "And that allows us to develop new types of semiconductors, new types of composites that can leapfrog the state of the art about 100 times in terms of performance through improvements in thermal capacity and power handling."

It turns out that there are alloys and materials that can be made in microgravity that aren't possible to make on Earth.
https://www.space.com/40552-space-based … arted.html

Last edited by Calliban (2022-05-01 09:06:00)

Void · 2022-05-01 11:00:46

Very wonderful stuff Calliban. The idiots that criticize the human space effort, are like people who look down on plumbers, but still want to poop. And in many cases that is all they produce other than obnoxious word formations.

I think SpaceX has it right to try to size a ship that can just bring a bunch of stuff to the surface of Mars and refuel. If you can do that, then there is so much more you could do, such as service a microgravity based industrial activity, and many other things.

Done.

SpaceNut · 2022-05-01 19:51:40

Yet we make nothing onboard the ISS and that is the near applicable location to what is needed.

Calliban · 2022-09-13 03:51:50

Magnetic gears.
https://m.youtube.com/watch?v=DAWVetrtD9U

I had heard of magnetic bearings before, but not gears. You learn something new every day. Air and magnetic bearings and magnetic gears, are all relevant to design for Mars and other low pressure environments, where oil based lubricants would suffer evaporation due to low pressure, or waxing due to low temperature. A non-contact solution does not require lubrication and will not suffer wear, so in theory at least, a magnetic gear box should have infinite service life. Impressive when you consider that gear boxes are usually the first things to wear out in vehicles and are the most significant repair item for wind turbines.

For a Martian surface vehicle, we will be operating at relatively low speeds, but will require high starting torque to get tracks moving. A diesel-electric type system would appear suitable here, with a diesel engine powering a DC generator and the generator powering motors that drive the tracks. DC motors have excellent starting torque. This is why electric vehicles have set world records for acceleration, even if they fall short when it comes to speed and range. A magnetic gear box would sit between the engine and the generator and allows us to eliminate a high wear component and a source of waste heat.

Last edited by Calliban (2022-09-13 03:54:58)

Calliban · 2023-05-19 17:26:52

Can we make solar PV and electric power systems generally, more sustainable propositions? One potential avenue is to reduce the demands that they place on rare metals.

Interesting description of the skin effect.
https://en.m.wikipedia.org/wiki/Skin_effect

When using AC, a conductor does not provide uniform conduction of charge throughout its cross-section. Rather, most of the conduction takes place in the outer skin of the conductor.

In the past, I have attempted to explore the possibility of using iron as a power conductor, instead of copper or aluminium. This extract explains why iron cannot be used to conduct AC currents, although it works well for DC.

**************************************************
'Skin depth also varies as the inverse square root of the permeability of the conductor. In the case of iron, its conductivity is about 1/7 that of copper. However being ferromagnetic its permeability is about 10,000 times greater. This reduces the skin depth for iron to about 1/38 that of copper, about 220 micrometers at 60 Hz. Iron wire is thus useless for AC power lines (except to add mechanical strength by serving as a core to a non ferromagnetic conductor like aluminum). Skin effect also reduces the effective thickness of laminations in power transformers, increasing their losses.

Iron rods work well for direct-current (DC) welding but it is impossible to use them at frequencies much higher than 60 Hz. At a few kilohertz, the welding rod will glow red hot as current flows through the greatly increased AC resistance resulting from skin effect, with relatively little power remaining for the arc itself. Only non-magnetic rods can be used for high-frequency welding.'
**************************************************

Iron rods could be used to transmit DC electric power. Solar PV panels produces direct current and are coupled in series to produce a voltage sufficient to allow large arrays to be served by distributed inverters. We could potentially replace some of the copper used in PV solar farms with plated iron rods.

Concrete may allow a reduction in usage of aluminium for PV panel casings and steel frames. This would substantially reduce embodied energy and would reduce capital cost. Unfortunately, it would make panels heavier and more difficult to assemble.

One innovation that could reduce the amount of copper and transmission infrastructure needed, would be to fit each array of assembled panels with a hydraulic pump, driven by a DC motor. This allows power transmission through steel pipes. It allows generation of AC is a central generating station. Using hydraulic power transmission also allows energy storage to be integrated into solar farm using raised weight hydraulic accumulators. No one appears to have studied or even considered by possibility of a solar farm employing hydraulic power transmission. But this may be a way of improving the long term viability of PV.

Last edited by Calliban (2023-05-19 17:50:20)

Steve Stewart · 2023-05-20 11:09:45

Calliban #41

I think we could use iron to transmit power on Mars. I've been thinking along the same lines as you, as iron is much more abundant than other metals. One way to alleviate the skin effect problem with an iron bar, is to use an iron pipe instead. Current will travel throughout the iron in the pipe, and the hollow middle does not cause much loss in current flow, due to the skin effect. When I was in college, I remember a class that mentioned the outer part of a power line is primarily for conduction and the center is primarily for strength and low weight.

As I recall, there are two types of power lines. "Transmission lines" are used for moving large amounts of power over long distances. They usually have a very high voltage (100,000 volts and higher). They are used to carry power from where it is generated to a large city. The tower shown above is a high voltage transmission line.

Another type of power line is a "distribution line". These are the lines that run through neighborhoods and businesses. Substations are used to convert the high voltage from transmission lines to a lower voltage for distribution lines. I used to work for a company called "Cellnet", that automated the reading of electric meters. I worked closely with the utility company, and I'm thinking distribution lines had a voltage of less than 10,000 volts. I'm thinking around 3,000 to 8,000 volts. I don't remember the exact voltage.

I learned that the voltage varies from one city to the next, there isn't any one standard voltage for distribution lines. The transformers you see hanging on a pole, in neighborhoods with overhead lines, convert the distribution line voltage down to 110V (in the USA) for a home or local business. 220V is created by connecting between two 110V phases. (Most houses I know of have two phases, the utility creates power with three phases). Utilities can provide higher voltage for businesses (such as 440V, and higher) if needed. They do this by installing a different transformer that converts the distribution line voltage to 440V (or whatever is needed).

How much power that can be carried by a conductor is limited by the current, and not so much the voltage. The power (Watts) is equal to volts times amps. Doubling the voltage on a power line will double the amount of power it carries (assuming the current remains constant). This is why voltage is so high on power lines. If the voltage is 10 or 100 times greater than it is in a home, then 10 to 100 times more power can be carried on the lines.

AC is used on power lines because it's easy to step the voltage up and down with AC. All that is needed is a transformer. Transformers don't work with DC. A transformer looks like a short circuit to DC current. This is why AC (Nikola Tesla, George Westinghouse) beat out DC (Thomas Edison, JP Morgan) in the famous "War of the currents".

When talking about solar panels that produce DC, the voltage can be increased by connecting them together in series, as you mentioned. I think flat silicone solar panels made on Mars could be installed between bars of iron, propped up off the ground with rocks or bricks. The iron would serve as both a support and a conductor for the panels. There are ways of converting DC to AC if a higher voltage is desired, for transmitting over long distances.

tahanson43206 · 2023-05-20 11:32:41

For Steve Steward re #42

Thank you for this concise package of insights about power distribution on Earth, and suggestions for Mars!

The hollow high voltage pipe might serve as a conduit for liquid, but I don't know how practical that idea would be in the context of Mars.

It might turn out that brine is unsuitable for transport in pipes carrying AC, and brine is most likely to be what is mined on Mars and shipped elsewhere.

SearchTerm:Transmission lines on Earth
SearchTerm:Distribution lines on Earth
SearchTerm:Power distribution systems on Earth with possible Mars options

(th)

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#26 2019-08-13 20:08:53

Re: Technology needed for Mars

#27 2019-10-08 08:54:41

Re: Technology needed for Mars

#28 2019-10-08 16:53:29

Re: Technology needed for Mars

#29 2020-01-06 19:17:08

Re: Technology needed for Mars

#30 2020-07-18 15:17:37

Re: Technology needed for Mars

#31 2020-07-18 16:33:08

Re: Technology needed for Mars

#32 2020-07-18 17:00:41

Re: Technology needed for Mars

#33 2020-07-19 09:57:53

Re: Technology needed for Mars

#34 2021-06-10 15:36:31

Re: Technology needed for Mars

#35 2021-06-10 16:18:37

Re: Technology needed for Mars

#36 2021-12-19 16:46:42

Re: Technology needed for Mars

#37 2022-05-01 08:51:08

Re: Technology needed for Mars

#38 2022-05-01 11:00:46

Re: Technology needed for Mars

#39 2022-05-01 19:51:40

Re: Technology needed for Mars

#40 2022-09-13 03:51:50

Re: Technology needed for Mars

#41 2023-05-19 17:26:52

Re: Technology needed for Mars

#42 2023-05-20 11:09:45

Re: Technology needed for Mars

#43 2023-05-20 11:32:41

Re: Technology needed for Mars

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