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#1 2021-12-12 17:40:24

kbd512
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Registered: 2015-01-02
Posts: 5,842

Nuclear Powered Crawler-Transporter for Mars

I'm starting this topic to discuss using stainless steel Starships that land on Mars, into mobile nuclear powered bases by repurposing all the stainless steel in Starship, into a NASA / Marion Power Shovel crawler-transporter vehicle.

NASA's crawler-transporter (CT) vehicles are approximately the size of a baseball diamond and weigh 2,721t / 5,997,084lbs.  The Earth-bound models are powered by a pair of 2,750hp ALCO diesel locomotive engines that supply electrical power to 16 375hp locomotive electric traction motors, 4 per track.  Each new model track shoe (NASA recently redesigned the shoes using a proprietary 4320 steel alloy to support the crushing weight of SLS) weighs in at a hefty 2,100lbs.  There are a total of 456 track shoes per CT.  The track shoes alone weigh 435t (434,483kg), which would have to be transported to the surface of Mars after being cast here on Earth.

Each track shoe measures 90" long by 25" wide, so 2,250 square inches of ground contact are per shoe.  There are 17 shoes in full contact with the ground at any given time and 8 tracks per CT, so 136 track shoes making full contact for 306,000in^2.  If we figure on a 5,000t payload, then the vehicle is supporting 7,721t / 17,021,871lbs, so ground pressure with a full load, on Earth, is 55.63psi.  The astute amongst you will note that Mars only has 38% of Earth's gravity, so the vehicle effectively "weighs" 6,468,311lbs on Mars, for a ground pressure of just 21.14psi, and an unladen ground pressure of 7.45psi.  A 200 pound man walking on Earth exerts about 16psi of ground pressure, or 6.08psi on Mars, thus the unladen weight of the CT is very comparable to a human, especially one carrying the additional weight of a space suit.

Fine sand has a bearing capacity of approximately 3,000lbs per square foot, meaning 20.8psi (pounds per square inch), so there may be places on Mars where the CT's laden weight must be reduced in order to accommodate very soft ground.

The following article describes the design and fabrication process NASA went through to produce new track shoe castings for the CT:

NASA CT Track Shoe

The jacking and leveling equipment (JEL) and steering gear would also have to be fabricated here on Earth and transported to Mars.

The plate steel and I-beam chassis construction would make use of the hulls of the Starships themselves to supply the source material.  The propellant tanks for each Starship are high grade stainless steel (304L alloy), suitable for operating in the cold of Mars.  The Raptor engines on the upper stage / Starship weigh somewhere between 9,000kg to 12,000kg, so if we surmise that the TPS tiles are 5,000kg, then we likely have some 80,000kg of 304L source material to work with.  Additionally, Starship's non-reusable payload is quoted at 250,000kg / 250t, which means each Starship could potentially supply 330t of source material to use to construct a NASA CT.

If we figure on 286t of vehicle mass (I just pulled that number out of my butt and need to do more research on the weight of the installed equipment for JEL and propulsion) being devoted to the vehicle's electric motors / control electronics / jacking gear (to level the platform) / life support equipment, then that means we need to fabricate 6 sacrificial Starships that provide plate steel for the vehicle.  We need a further 3 Starships to carry the 721t of Earth-fabricated special equipment to the surface.

Rather than using a pair of V-16 locomotive diesel engines and another pair of Cummins diesel engines for electrical power, since there is no diesel fuel available on Mars, these vehicles will be powered by small nuclear reactors, specifically Aqueous Homogeneous Reactors (AHRs) that have the fuel salts dissolved into water in a roughly spherical cavity containing heat transfer pipes to transfer thermal power to a gas turbine that produces electrical power.  AHRs operate at low temperatures and pressures, with a low total fissile inventory in the core, amounting to about 10 kilos at any given time for 5,593kW / 7,500hp electrical power output, approximating the total propulsion and supplemental electric generating capacity of the original diesel powered CT used by NASA.  The total reactor weight, including sufficient radiation shielding to enable a human to walk right up to the edge of the shield, is around 200t.  For redundancy and supplying additional propulsive power, a pair of such reactors would be installed on the Mars-bound CT.

AHRs have the best neutron economy and fuel burnup of any type of nuclear reactor actually built, and they have been built and currently operating for creating medical isotopes and for experiments supplying electrical or thermal power.  Since neutron poisons are continuously removed from the liquid core and there are no fuel rods to crack and become unusable, they can and do operate continuously for years at a time, with fuel salt added in small quantities as thermal power is gradually extracted.  Whereas the fuel rods in PWRs and BWRs crack after 2% of their potential thermal power output is extracted, AHRs hover around 50%.  Most "nuclear waste" is cracked fuel rods containing 98% of their original / potential energy content, so "burnup" is quite low.  The temperatures and pressures produced by AHRs are also very modest, approximately the same as a conventional diesel fueled boiler on a ship or a locomotive.  Despite the lower achievable electrical power output, overall efficiency at minimal cost is still top notch.  They are not particularly suitable for producing Plutonium for nuclear weapons, thus they were not favored by countries that developed dual-use nuclear power / nuclear weapons capabilities.  However, they will still readily transmute fertile Thorium 232 into fissile Uranium 233.

It's reasonable to think that these nuclear powered vehicles could achieve 2mph to 4mph on Mars, fully laden.  That speed is none too impressive for exploration purposes, about the same walking speed of a human child, but this heavy haul vehicle could literally circle the planet in 276 days.

That brings us to why we would want such vehicles to begin with.  What purposes would they serve?

Vehicle #1: Polar water extraction and transport for Starship refueling (water buffalo)
Vehicle #2: Sabatier reactor for LOX/LCH4 production / mobile launch platform for return of Starships to Earth (fuel refinery / space launch)
Vehicle #3: Regolith mining and smelting for local steel / concrete / glass production (mining / smelting / forging / casting)
Vehicle #4: Base construction equipment power plant and site preparation / habitable structures fabrication (construction / machining)
Vehicle #5: Temporary habitation during base construction (mobile habitat / mass transport between colonies)

Obviously such a vehicle could do all 5 jobs with appropriate equipment refits / equipment transported to Mars from Earth, but it would be more useful to have several vehicles dedicated to different tasks.  Eventually, one of these vehicles would help construct a water pipeline to melt polar ice and then transport the melt water from the poles to the equator, where temperatures still fall within the realm of habitability for normal structures and space suits.

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#2 2021-12-12 18:20:25

kbd512
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Re: Nuclear Powered Crawler-Transporter for Mars

In case the point isn't clear, the "sacrificial" Starships will be constructed of thicker gauge stainless steel sheet or plate, so that the body / propellant tank of the ship itself is the payload.  The point of doing this is to supply source material and eventually permanent storage tanks for LCO2 / LOX / LCH4 and other cryogenic liquids used power / propulsion / backup power for bases, etc.

To avoid the hassle and expense associated with totally re-creating all of our technology on Mars, the specialty equipment like the hydraulic cylinders for the jacking gear, the electric motors, track shoes, and nuclear reactor equipment will be imported from Earth and assembled onsite using power provided by rollout solar panels and KiloPower portable nuclear reactors.

It's important to note that the Mars-bound CT can also be considerably lighter than the Earth-bound CT for equivalent carrying capacity and durability, because its fully laden weight is only nominally above the empty weight of its Earth-bound cousin.  NASA also built their CTs with cost being top-of-mind, rather than performance in hostile environments.  A 304L stainless or 300 series maraging steel has considerably higher tensile strength and is far less brittle at the very low temperatures encountered on Mars, as compared to the low alloy carbon steels used to fabricate the chassis of the CT by the Marion Power Shovel Company, using what was essentially 1960s locomotive technology.  Casting and welding stainless and maraging steel (merely a special type of high-strength / highly corrosion resistant low carbon alloy steel) is still relatively easy to do, but the end result is far more durable components at a lower weight.

Regarding the track shoe, here's another article on it:

Engineered Casting Solutions - Casting of the Year

I see I was off by 100 pounds on the track shoe weight, at least according to the article above, so an additional 20.7t of weight added to the total.  The stated track shoe weights seem to vary between 2,000lbs and 2,200lbs.

An article on the JEL (Jacking / Equalizing / Leveling) gear (hydraulic load leveling cylinders):

New JEL Cylinders Give Youth and Vitality to NASA’s Old Crawler Transporters

Edit:

Google Books - Crawler-Transporter Forged Steel Parts

According to the book, each CT contains 270 tons (541,520lbs) worth of forged steel parts, to include 176 steel rollers (the CT's equivalent of a tank's "road wheels) that weigh 2,010lbs each and 8 forged steel guide tubes that weigh 23,470lbs each.

Last edited by kbd512 (2021-12-12 18:26:20)

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#3 2021-12-12 18:50:48

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear Powered Crawler-Transporter for Mars

Excellent new topic - I will comment in more detail tomorrow.  Having a truck that can transport a thousand tonnes of equipment, ice or mineral ores over thousands of km, without placing a fuel burden on the base, would certainly be valuable.  The same for a vehicle that supports base construction.  If most habitable volumes are built underground, we need a vehicle that can shift a lot of dirt.  If it can work continuously without placing a burden on base power supply, then that is ideal.

One thing that sticks in my mind about AHRs is that heat rejection temperatures will be about 300K.  The engine power of the truck will ultimately be limited by the rate at which heat can be rejected by radiating surfaces.  If we are carrying ice, then some amount of waste heat can be used to melt the ice and warm the resulting water.  Likewise, heat could be absorbed into dirt or minerals as a partial heat sink.  If we are shifted dirt over a new base complex, we don't really care if that dirt gets heated to 30°C in the process.

One interesting thing about the AHR is that although operating temperatures are relatively low (~200°C), power density could be as high as a PWR.  A spherical reactor vessel capable of delivering 5MW, should be only half a metre in diameter.  Hence shielding can be compact.

Last edited by Calliban (2021-12-12 19:07:05)


"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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#4 2021-12-12 18:51:24

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear Powered Crawler-Transporter for Mars

I think this is a great idea, I also thought a discussion of Large Nuclear powered Transport in another topic but the ideas were different to yours.

kbd512 wrote:

That brings us to why we would want such vehicles to begin with.  What purposes would they serve?

I've thought about something similar to this topic but a migration lifestyle when Mars has a larger population, a bit I discussed moving something like a Giant Juggernaut Convy or maybe something as big as a ship with a convoy of people behind, maybe inside their 'car' Giant Village sized Cars/Tanks. You could have maybe Lunar/Mars type vehicles and wagons or bikes would scout ahead or follow behind but also use a Giant transporter to move all Heavy Material, some might have been working on Biodomes or some kind of rail system but resources get less in winter.

You could have nomadic people on the move all the time, in one Nothern Summer they work on mines or farms and whatever needs to be done to keep a colony well stocked, a small skeleton crew is left behind with robots as winters approach. Then everyone moves South to the Southern Summer and again works on the Souther colony. I didnt do much research on numbers but I was thinking about starting connecting something 85 miles (137 km) eventually the nomadic peoples would establish a profitable permanent colony at equator with networks running North and South to support a nomidic migratory working peoples that would travel on the surface of Mars.

kbd512 wrote:

Obviously such a vehicle could do all 5 jobs with appropriate equipment refits / equipment transported to Mars from Earth, but it would be more useful to have several vehicles dedicated to different tasks.

I like the idea of a vechile being a swiss-army knife of sorts but I also have some reservations that's why I suggested a convoy of people annd other vehicles travel either with it or travel ahead or follow behind, while STS Shuttle was an amazing craft I think one of its flaws it tired to do too many things, a place to repair satellites, testing new ideas for a new crew compartment and travel in space, a space hotel for people who might one day do tourism, a space to launch satellites, a mini space station, Spacelab etc I do agree it is great to have a swiss army knife but sometimes it is also good to have the correct tool for the right job.

kbd512 wrote:

The jacking and leveling equipment (JEL) and steering gear would also have to be fabricated here on Earth and transported to Mars.

I understand high tech equipment will be costly and have to be transported from Earth but there is a possible future where one day we figure out how to build a 3-d printing factory of sorts on the Moon or Mars and be able to manufacture low tech products on the planet rather than paying to get stuff shipped from Earth.

Last edited by Mars_B4_Moon (2021-12-12 18:57:50)

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#5 2021-12-12 21:17:01

SpaceNut
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Posts: 25,943

Re: Nuclear Powered Crawler-Transporter for Mars

Recycling "sacrificial" Starships 100mT of materials into crawler means lots of additional equipment to reprocess this materials into what we need to make on mars if the items are not part of a planned payload delivery.

The list of vehicles are for sure a short list of what we would want.

We know that going nuclear with mostly unmanned use is the means to conquer mars.

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#6 2021-12-12 22:06:58

tahanson43206
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Registered: 2018-04-27
Posts: 10,760

Re: Nuclear Powered Crawler-Transporter for Mars

The Zoom meeting is still in progress at UTC 04:01 .... RobertDyck and kbd512 have been conducting an in depth discussion of many aspects of the Mars venture.  I've been just listening (via radio audio) for the past three hours, while attending to chores.  These are two very well informed folks, supplementing their discussion with Internet lookups as needed, and I've found the discussion interesting throughout.

I decided to post here in Nuclear Powered Crawler (following the post #5 by SpaceNut) because kbd512 has covered the topic in detail.

If anyone (limited to NewMars members) would like to listen to the discussion, you can ask SpaceNut to request a link to the YouTube video.

(th)

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#7 2021-12-13 13:54:16

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear Powered Crawler-Transporter for Mars

Martian soils contain a much higher concentration of manganese than Earth soils.
https://ntrs.nasa.gov/citations/20000110466

The Martian soil is also very iron rich compared to Earth based soils.  The materials needed to make high manganese carbon steels are present in abundance on Mars. These steels remain tough and ductile at temperatures as low as -100°C.  High manganese content stabilises the austenitic phase in the steel.
https://www.totalmateria.com/page.aspx? … =KO&NM=537

If we can ship the required equipment to Mars to produce high purity iron, then the track segments and chassis can be cast or drop forged from high manganese carbon steel.  Stainless steels can then be reserved for reactor components, which really cannot be made from anything else.  To reduce stainless steel thickness, we could heat steel to temperatures of ~700°C and then hot roll it.  Temperature control is important, because if temperatures rise too high, grain boundary precipitation becomes a problem.

Welding on Mars should be much easier than on Earth, thanks to the thin atmosphere.  No shielding gas or flux should be needed.  Lasers or electric arcs can provide the required heat to join the metals without need for argon shield gas.

Ordinary carbon steels can be used for some applications at temperatures down to -29°C.
https://www.piping-world.com/minimum-te … -materials

However, these are only suitable on parts of the vehicle that receive limited tensile stress and impact forces.  Alternatively, given that these vehicles are nuclear powered and those nuclear reactors will generate a great deal of waste heat, we can use that waste heat to keep carbon steel components warm enough to avoid brittle fracture problems.  But austenitic steels must be used for track segments, which are in contact with the cold ground.  Not sure about track wheels. Carbon steels may be acceptable here.

If we are using AHRs to generate power, then we need steam turbines, steam dryers, a condenser and condensate return lines.  These components would ideally be stainless, or at least stainless clad, even in the low reduced oxygen environment of Mars.  The reactor pressure vessel should be stainless steel clad, low alloy steel.  Low alloy steels are preferred in this situation because of their ductility.  The turbine shafts would ideally be crome vanadium molybdenum steel.  The turbine and condenser casing can be carbon steel, but carbon vanadium steel is more resistant to crack growth under pressure cycles.  As temperatures and pressures are relatively low, there is probably little point trying to achieve a multistage turbine with interstage reheat.  We are probably looking at a single stage turbine.  This at least makes the power generation machinery relatively simple.  Unfortunately, it will be relatively bulky for the power it produces.

A sodium cooled fast reactor can reach temperatures needed to superheat steam or generate power through an S-CO2 cycle.  This isn't possible with an AHR, as water passes its supercritical point 340°C.  Uranium salts won't be anywhere near as soluble in supercritical water and the required pressure makes pressure vessels increasingly difficult to fabricate.

Last edited by Calliban (2021-12-13 14:55:17)


"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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#8 2021-12-13 17:49:24

kbd512
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Registered: 2015-01-02
Posts: 5,842

Re: Nuclear Powered Crawler-Transporter for Mars

I'm mostly concerned with minimizing the total cost of transporting the materials and equipment there.  We're going to have a small contingent of Mars-based fabricators available who have lots of time on their hands, relatively simple fabrication equipment for welding and cutting of metal, and lots of high quality steel to work with.  Towards the end of our conversation, we talked about the cheapest possible methods for delivering steel, literally allowing metal with minimal reentry heat protection to impact the surface in the most extreme case, because the end goal is to furnish steel to be transformed on-site into parts for the vehicle.  Parts that require very specialized machinery to produce will be fabricated on Earth and transported to Mars using gentler delivery methods.

The overriding reason behind expending the resources to fabricate gigantic mining type vehicles is that constructing a colony on another planet requires massive quantities of steel / concrete / glass.  Here on Earth, whenever we want to make that stuff, we use giant machines for sake of efficiency and ultimately total cost.  If it was more efficient to haul ore using a fleet of pickup trucks, then at least one mining operation would use a fleet of pickups hauling ore out of the pits or perhaps run a series of small smelters, yet none do, because that's not the most efficient way of mining / transporting / refining thousands of tons of ore.  All actual mining operations use a handful of monster trucks that haul ore from the mine to gigantic ships or barges that transport the ore to a large smelter.  Through volume of production, we minimize energy inefficiency and total cost and labor.

There are no oceans on Mars to transport bulk materials, no diesel fuel, and half the sunlight received by Earth, so in a practical sense we're limited to nuclear powered pipelines and giant mining trucks to transport materials in an efficient way.  For equivalent power generation per day of 144MWh, we would need 100,174m^2 of solar panels to generate the same output as a 200t nuclear reactor (all-up weight, including shielding).  I've never seen or heard of a 100,000m^2 mobile solar array, so that clearly won't work.  Mars InSight's 3.2m^2 of triple-junction solar panels generated 4.6kWh/day (1,437.5Wh/m^2) on Sol #1, but less than 3 years later, it was only generating 0.7kWh/day, so the atmospheric dust is also clearly a serious problem.  The Silicon wafers for such an array may only weigh 34,285kg, but what about a suitable support structure for an array spanning 316.5m (3 American football fields) per side?  That can't be lightweight.  1kg/m^2 seems reasonable for a CFRP and Nomex honeycomb panel reinforcement, so 100t to 120t for the array without wiring.  To that, we would need to add at least 72MWh worth of Lithium-ion battery storage, which would weigh 288t assuming a pack level gravimetric energy density of 250Wh/kg.  That's considerably more than the weight of the reactor / shielding radiator array.

AHRs are capable of 25% electrical conversion efficiency and a fuel burnup of around 50%, so each kilo of U235 (24GWh original energy content) provides approximately 3GWh of electrical power.  In other words, the fuel consumption rate is 1kg per 20.83 days at full power output (6MW), so each vehicle requires 32kg of fuel per year.  In reality, it's more than this, because we need to maintain at least 10kg in a moderated and reflected core at any given time, but 10kg initial load plus 32kg per Martian year of operation (668 Sols) seems quite reasonable.  A single cubic foot of U235 is 539kg, or enough fuel for more than 16 years of continuous full output.

In reality, we don't want to load any more U235 than absolutely necessary, and it would be better to start with U233.  We want enough U235 to start the reactor and then we want to consume Th232 transmuted into U233 inside the reactor so that 80%+ of the fission products generated are storage-safe outside of substantial shielding in less than 1 year.  At that point, a single 55 gallon steel cask with walls several inches thick can safely hold the minor quantity of remaining radioactive waste products for the next 300 years.  Th232 is only 331kg per cubic foot, which provides enough energy for more than 10 years of operation.  However, the reduction of long-lived radioactive byproducts from the very limited Trans-Uranic isotope production (mostly Neptunium) and shorter-lived daughter products from fission is worth the energy output penalty per unit weight of fuel.  While both Uranium and Thorium are present on the surface of Mars, including 1 cubic foot / 331kg of Th232 to supply 10 years of full power output is merely "very faint noise" within the context of the total mass budget associated with a Mars colonization effort, or indeed the mass of this vehicle concept.

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#9 2021-12-13 18:02:44

kbd512
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Re: Nuclear Powered Crawler-Transporter for Mars

Calliban,

At $3,000USD/t for American-made 304L, 2,721t of 304L would cost $8,163,000.  If you're going to "save money" somewhere, then for goodness sake don't save money on steel capable of surviving the mildly cryogenic Martian winters.

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#10 2021-12-13 18:11:21

kbd512
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Registered: 2015-01-02
Posts: 5,842

Re: Nuclear Powered Crawler-Transporter for Mars

Mars_B4_Moon,

We're trying to avoid having to ship convoys of vehicles to Mars.  Taking care of a single vehicle is enough work on its own.  That said, CTs will have a pair of nuclear reactors to provide redundant power, 16 electric drive motors, and 8 tracks.  A single CT already "counts" as its own convoy.

We may have some smaller vehicles for milling about around the much slower moving CT.  RobertDyck says we can have electric ATVs or dirt bikes and pressurized pup tents for short exploration missions on our way to important objectives, such as fresh water supplies, ore resources, or potential sites of establishing colonies.  We don't know exactly which locations would be most suitable for establishment of the first colonies / settlements, and won't ever know that without a lot of exploration.

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#11 2021-12-13 19:02:28

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear Powered Crawler-Transporter for Mars

kbd512 wrote:

Calliban,

At $3,000USD/t for American-made 304L, 2,721t of 304L would cost $8,163,000.  If you're going to "save money" somewhere, then for goodness sake don't save money on steel capable of surviving the mildly cryogenic Martian winters.

I'm thinking more about steel that we could feasibly make locally, without having to ship it from Earth at a cost of $1million per tonne, or thereabouts.  At some point it becomes cheaper to ship a steel foundry to Mars than to attempt to deliver steel from Earth.  How much steel do we need before that becomes true?  Probably quite a lot.  But we need thousands of tonnes just to start and millions of tonnes for the sort of city state vision Musk has in mind.

I am reasonably confident that we could make carbon steels on Mars, by reducing iron oxide in dirt and putting the resulting crude iron into an electric furnace and then burning off sulphur, phosphorus and silicon impurities by pumping oxygen through the molten iron.  If we can produce high purity iron, then carbon manganese steels aren't that much more difficult.  Maybe we can make stainless steels as well, if we find an abundant source of chromium.  But carbon manganese steels are relatively easy.  The stuff is already there in the dirt.  The slag can be molded into compressive columns for our underground habs.  The steel can be hot rolled into sheets and strip and then cut and welded.  But not all of the steel needs to be austenitic.  We are talking about mounting a nuclear reactor on this vehicle.  Why not use the reactor to keep it warm?  We have to dump the heat somewhere.  And decay heat will continue to be generated even when the reactor is shut down.

I think you are correct about the need for a lot of nuclear power.  Making steel is an energy intensive process.  On Earth, the embodied energy of finished steel is estimated to be about 30MJ/kg, or 67MWh per cubic metre.  That means a 1MWe nuclear reactor could produce only one third of a cubic metre of steel per day.  Trying to make steel using solar panels will be absolutely unworkable.  Producing 2000 tonnes of steel, requires about 2MW-years of electricity.  Instead of shipping steel to Mars, we should be shipping steam turbines and steam generators for our 1000MWe AHRs!  As energy hungry as that steel is, it would cost around $2billion to ship it to Mars.  A 1000MWe power plant could produce up to 1 million tonnes of steel each year.  Many times its own weight.  To ship that much steel to Mars would cost $1trillion.  No one could afford that.  These are the volumes needed for a rapidly growing colony, that needs to grow food in heated, pressurised greenhouses.  A colony on Mars will need tonnes of steel per capita and a city of 1 million will need millions of tonnes of steel.  Our ability to make steel basically foretells our ability to make everything else.

Storing waste in steel drums is a good idea.  In the US, low decay heat spent fuel is stored in concrete silos, where air cooling is provided by natural convection.  Something similar could work on Mars.  The Martian soil contains a lot of highly basic oxides.  These could be concentrated and mixed with Martian regolith, along with mixed carbonates.  Fission products injected into this material will melt it into glass at about 900°C, which can then flow by gravity into steel casks.  The casks will be placed within a steel liner, within a compressed regolith silo.  There will be slots in the silo that face into the Martian wind, allowing the wind to blow into the slots, around the steel linear and up out of the top of the silo.  This will remove residual decay heat.  The Martian atmosphere has density of about 0.015kg/m3 at datum level.  Specific heat of CO2 is about 800J/kg.K and let's say average wind speed is 5m/s.  If the CO2 heats up from -50°C to 100°C, then each square metre of slot will remove around 9kW of decay heat.  Sounds about right.  As decay heat declines, the molten regolith in the casks will solidify into glass.

With all that I have said about the importance of steel, I am going to invest some time exploring what would be needed to establish a steel foundry on Mars.  Cast irons are useful class of materials as well.  This is especially the case if we intend to build our city underground.  We need structural members that are capable of withstanding high compressive loads.  High silicon cast irons are highly corrosion resistant.  There are applications where we need corrosion resistant materials.

Last edited by Calliban (2021-12-13 19:51:54)


"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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#12 2021-12-13 21:35:50

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 25,943

Re: Nuclear Powered Crawler-Transporter for Mars

Another very large item to include is a Crane capable of a vertical stack up of not only a Starship but for other stuff.

I have seen a tractor trailer haul them in and have a smaller crane aid in its reassembly onsite.

18000-MAX-ER-1.jpg

Manitowoc.jpg

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#13 2021-12-14 18:53:23

kbd512
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Re: Nuclear Powered Crawler-Transporter for Mars

Calliban,

We're starting from a point of extreme energy and resource poverty.  The nuclear waste casks / drums are going to serve as hot water or space heaters, they're not going to be tossed out like trash.  We need to import at least one vehicle from Earth, in order to start going after the resources.

RobertDyck says that there are hematite concretions on Mars that are nearly pure Iron, due to the way they formed.  More importantly, they're located on the surface.  Beyond that, the debris fields of Nickel-Iron asteroids are reasonably close to being maraging steel.  The bulk Iron ore that will be mined later will require more extensive refining and associated energy input.  Oddly enough, we will have to add Carbon because there's not enough Carbon in the ore.

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#14 2021-12-14 19:20:36

SpaceNut
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Re: Nuclear Powered Crawler-Transporter for Mars

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#15 2021-12-15 08:30:18

Calliban
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From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear Powered Crawler-Transporter for Mars

kbd512 wrote:

Calliban,

We're starting from a point of extreme energy and resource poverty.  The nuclear waste casks / drums are going to serve as hot water or space heaters, they're not going to be tossed out like trash.  We need to import at least one vehicle from Earth, in order to start going after the resources.

RobertDyck says that there are hematite concretions on Mars that are nearly pure Iron, due to the way they formed.  More importantly, they're located on the surface.  Beyond that, the debris fields of Nickel-Iron asteroids are reasonably close to being maraging steel.  The bulk Iron ore that will be mined later will require more extensive refining and associated energy input.  Oddly enough, we will have to add Carbon because there's not enough Carbon in the ore.

Good points.  I remember a discussion over a year back on these boards around using strontium fission products as a radio-thermal heat source for inertial confinement fusion engines that NASA has proposed.  If we are using AHRs, then fission products will mostly be in the form of dissolved nitrate salts.  At some point, we would build a processing plant to extract the elements we have specific use for.  Strontium-90 is a pure beta emitter.  Some shielding would be needed to reduce doses from bremsstrahlung radiation.  But Sr-90 could power a compact Brayton cycle that would power the engines of a ship.  A contender propulsion system for Robert's large interplanetary ship.  Cs-137 is more problematic, as it is a strong gamma emitter.  It has niche uses in non-destructive examination of welds and could be used as a portable heat source for a remote base, where shielding can be provided by placing it at the centre of a barrel that is filled with regolith.

On the topic of blue berries: presumably, these contain iron (II) oxide and should have magnetic properties.  I wonder if a vehicle could mine them from the soil by driving over them with an electromagnet mounted on the chassis?  That would make the process of gathering the materials particularly easy.

Last edited by Calliban (2021-12-15 08:43:17)


"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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#16 2021-12-15 11:34:20

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,858
Website

Re: Nuclear Powered Crawler-Transporter for Mars

I'm sure y'all probably know this,  but Sr-90 and Cs-137 are two radioisotopes with very high multipliers that make REM very much higher than Rads.  Those are the two that were accumulating in the atmosphere,  which had the most dangerous effects on people,  and were the proximate cause of the atmospheric test ban treaty.  They are why we were warned not to eat snow ice cream in the winter of 1962-1963,  until the test ban could have its effect.   And no one worried about the fact that we were eating snow ice cream all during the 1950's when those atmospheric tests were made (because back then,  nobody knew any better).

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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#17 2021-12-15 12:06:56

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear Powered Crawler-Transporter for Mars

The problem with strontium is that it mimics calcium in the human body.  It is therefore absorbed into human bone tissue, where it has a long biological half life.  Beta emissions do not have a particularly high RBE, but because of the long biological half life, each unit of activity absorbed can result in a relatively high tissue dose over a period of years.  My advice: don't eat the stuff.


"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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#18 2021-12-15 20:38:17

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 25,943

Re: Nuclear Powered Crawler-Transporter for Mars

Magnetic? https://en.wikipedia.org/wiki/Hematite
Magnetic Properties Experiments on the Mars Exploration Rover mission

Caliban is correct on the type content

The dominant iron type present in the rock forming minerals on Mars is Fe(II). The iron in the Martian dust and soil is mainly present as Fe(III)-ions.

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#19 2021-12-15 20:55:46

kbd512
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Registered: 2015-01-02
Posts: 5,842

Re: Nuclear Powered Crawler-Transporter for Mars

We will take any reactor operator's Cesium or Strontium off their hands, encase it in enough maraging steel that whatever radiation produced won't make it through the walls of the cask, and then use it to provide warmth to our colonists.

Again, we're starting from a state of energy and resource poverty.  If nuclear waste can provide hot water and space heating without additional energy input, then we're not going to look that gift horse in the mouth.  We will keep these casks outside the habitat modules and use conduction to transfer the heat.  Similarly, we will use the natural environment for refrigeration.  Heating and cooling would otherwise consume vast quantities of power that we could not economically afford to supply.

As far as steel production using nuclear heat is concerned, the Japanese did quite a bit of development on this process:

The assessment of nuclear hydrogen cogeneration system application for steel industry

A bit more detail on the process:

Study of a nuclear energy supplied steelmaking system for near-term application

Take note of the cost ($628/t) and CO2 emissions (13.8kg/t).  A 650MWt gas cooled high temperature reactor running at 85% capacity can produce 628,000t per year, at $628/t of steel, along with 109t of H2/day, 870t of O2/day, and 8,666.4t of CO2 per year.  The traditional methods of making steel produce 1,161,800t of CO2 per metric ton of steel, on average, or 134X more CO2 per ton of steel produced.

This presentation comes from OSTI's library:

Sustainable, Net-Zero Carbon Steelmaking Utilizing Nuclear and Renewable-based Integrated Energy Systems

On Mars, we need to economize on CO2 for an entirely different reason because there's not enough Carbon in the Iron ore, but any minimization of waste, which reduces energy expenditure on resource collection, is most welcome.

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#20 2021-12-16 08:35:44

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,955

Re: Nuclear Powered Crawler-Transporter for Mars

Kbd512, these are impressive technologies.  I notice that one of the intermediate products in the iodine-sulphur cycle is sulphuric acid.  This is an important end product in its own right.  It is very useful for mining elements from diffuse ores, as it frees metal ions in the form of sulphate salts.  This is probably how we will mine uranium and thorium on Mars, as the planet appears to lack concentrated ores.  In Namibia, insitu acid leaching is used to accomplish this.  Acidic water is injected into low grade ore bodies and satellite wells are then drilled to extract the sulphate solution.  We would need to raise the temperature of the ore bed for this to work on Mars.  We would do this using the steam injection technique described by GW.  We may also need to hydraulically fracture the rock bed.

Mobile AHR units are essential for this kind of operation.  We need to generate high pressure steam to force the acid solution through the fractured ore bodies.  What we do with the sulphate bearing liquids is a point of discussion.  Do we boil them down to solids on site, or do we pump the solute back to our base through a plastic pipe?  We could simply pump the solution into a pond and allow the ice to sublime.  But that means wasting a lot of water that could be reused.

Oldfart1979 is an industrial chemist.  Maybe he is in a better position to detail how best to convert an aqueous sulphate solution into separated compounds.

As an aside, I found this:
https://www.powerstream.com/vapor-pressure.htm

The atmospheric pressure on Mars is above the vapour pressure of most liquid metals.  The CO2 atmosphere is also quite inert.  This suggests to me that our metal foundries do not need to be in pressurised envelopes.  We can pour and mold steel, aluminium and magnesium alloys under ambient Martian atmosphere.  On Earth, magnesium would need to be cast under an argon atmosphere.  So would uranium and many other reactive metals.  Not so on Mars.  And there is enough atmospheric pressure to prevent boiling and sublimation.

Additional: I notice that it is decomposition of sulphuric acid that requires a temperature of 850°C.  When accounting for the temperature drop across heat exchangers, an outlet temperature of 950°C is required from the reactor.  It is extremely difficult to find materials that will stand up to these temperatures.  Helium must be used as coolant.  CO2 is too reactive at these temperatures.  Argon and nitrogen absorb too many neutrons and decompose into solids that will deposit in heat exchangers.  Steels are about as strong as caramel at these temperatures.  Graphite is used as both fuel cladding and moderator.  Some more details on materials choices for different components:
https://inldigitallibrary.inl.gov/sites … 559926.pdf

Last edited by Calliban (2021-12-16 11:14:49)


"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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#21 2022-06-28 08:17:29

Mars_B4_Moon
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Registered: 2006-03-23
Posts: 3,212

Re: Nuclear Powered Crawler-Transporter for Mars

I recall seeing Musk reply to tweets that saying on twitter Starship will only stack vertical and can not be put down flat and transformed into a Base lying down on its back or in prone position, perhaps events have changed.

I remember seeing photos of the Soviet Shuttle Buran on its crawling transport rail car. I believe it had two rains underneath, there are two train engines under a transporter and unlike NASA's spacecraft, Soviet era space vehicles were transported in a prone position and lifted into a vertical position, the Soyuz still operates this way. The Soviet Union had a road network of 1,757,000 kilometres (1,092,000 mi), of which 1,310,600 kilometres (814,400 mi) were paved and 446,400 kilometres (277,400 mi) were dirt roads. There would often be political hardships and economic collapse, maybe far worse outside of Russia and by 1975 only 0.8 percent of households owned a car. Communist Soviet economists who argued that transferring some 100 million tons from the railways to road transport would save up to 120 million rubles. But in 1975, road transport was 27-times more expensive than railway transport, due to long distances between starting points and destinations. There was also the Space Program failure of the Polyus battlestation StarWars ColdWar era spacecraft, Russians were experimenting with all sorts of strange locomotive vehicle types designed to keep axle load to a minimum, they also had a Grasshopper Transporters originally built for the failed N1 Moon Rocket. https://www.flickr.com/photos/martintro … 4241700123 Abandoned https://www.istockphoto.com/photo/aband … -245937148

NASA's 'Phenomenal' Crawler Rolling Out 2,600-ton SLS Moon Rocket Explained
https://www.newsweek.com/nasa-crawler-s … -2-1689341
Put simply, SLS is heavy. In its most basic configuration it weighs 5.75 million pounds, or around 2,600 metric tons. It therefore needs a powerful vehicle to transport it—the Crawler-Transporter 2 (CT-2).

Crawler-Transporter
https://apollo11space.com/the-nasa-crawler/
They were initially used to bring the Saturn V and Saturn IB rockets during the Apollo, Apollo–Soyuz, and Skylab programs. They were then used to move Space Shuttles from 1981 to 2011.

Weight: About 6.6 million pounds or the total weight of around 15 Statues of Liberty or 1,000 pickup trucks.
Height: Varies from about 20 feet to 26 feet, based on the jacking, equalization, and leveling cylinders.
Load Capacity: Capable to transport 18 million pounds or the total weight of more than 20 fully loaded 777 airplanes.

It sounds like some sorts of new ultra super SuperHeavy Starship is needed to send any kind of such huge vehicle, material to Mars, maybe in the future vehicles could unfold like JWST or a local 3-d printing factory facility could make many of the parts for larger vehicles.
The sooner 3d printers and AI and  robots are sent to Mars, the Moon or Europa to build stuff there instead of sending people and Cars there, the sooner everything gets cheaper, who not have your domes and car one day built on Mars, it is about Mass efficiency:  How much usable habitable volume you get for each tonne of Starship hull. How do you fit all those parts for people and vehicle and having to add in stairs, extra floors & ceilings, etc.? Should robots and factory go first or do you truly need people on the surface yet and having one large pressure vessel, instead of several small ones. Is the heavy equipment to lift whole Starships, then build your cars and crawler factory a lot more mass than to disassemble them or print most of it on Mars with local material? Labor efficiency will local Mars rbots build faster and better and how much work is it to safely lower and partly bury or cover your human habitat while you create these giant crawler on Mars.

When your crawler is made, maybe it will have an important function as some sort of mobile base factory with living quarter?


Handle the heavy loads with our Transport Crawler
The PT series of transport crawlers is designed to efficiently and economically relocate your crushing stations, conveyor drive stations and other open-cast mining equipment. We customise each model we build, tailoring it to your operation for precise balance and stability during the transport of your heavy equipment.
https://www.flsmidth.com/en-gb/products … rt-crawler

The lifting and load-carrying capacities of this heavyweight hero ranges from 150 to 1,500 metric tons (165 to 1,650 short tons). It effortlessly handles rough terrains, and can travel up or down steep grades of up to 20%, while keeping your load stable and safe.


Nuclear Powered Trains
http://large.stanford.edu/courses/2015/ph241/sanders1/

The concept of nuclear powered trains first surfaced seriously in 1950s when the idea became an official technical goal of the Ministry of Transport of the USSR. The talk of nuclear powered trains were very real and encouraging. The idea seemed reasonable at the time because the dangers of nuclear reactors were not widely known. Locomotives have been a constant resource for transportation of all kinds of goods, useful both in speed and in amount of cargo transported. They are used in every country in the world. Unfortunately, these useful machines use fossil fuels and thus leave a carbon footprint every time they operate. The concept of a nuclear powered train has the potential for reducing both costs and CO2 emissions. The possible benefits of having nuclear powered trains include economic and transport efficiency, lower emissions, and ease of hauling cargo over great distances. Rail is already the greenest method of long-haul transportation. But is going greener worth the trouble? Is it a good idea to have a moving bomb on rails?

Transport of Radioactive Material
https://www.world-nuclear.org/informati … rials.aspx
The objective of the regulations is to protect people and the environment from the effects of radiation during the transport of radioactive material, both routinely and when transport accidents occur. The fundamental principle is that the protection comes from the design of the package, regardless of how the material is transported. More specifically, protection is achieved by:

    Containment of radioactive contents.
    Control of external radiation levels.
    Prevention of criticality.
    Prevention of damage caused by heat.

Radioactive material defined as Class 7  material in the UN Model Regulations on Dangerous Goods is not unique to the nuclear fuel cycle. Radioactive substances are used extensively in medicine, agriculture, research, manufacturing, non-destructive testing, and minerals exploration, and it is estimated that just 5% of radioactive material shipped globally each year relates to nuclear power production.a Regulatory control of shipments of radioactive material is independent of the material's intended application.

The Secret 'White Trains' That Carried Nuclear Weapons Around the U.S.
https://www.history.com/news/nuclear-tr … s-cold-war
For as long as the United States has had nuclear weapons, officials have struggled with how to transport the destructive technology.

PDF
papermodelingman.com/apollo480/crawler-transporter.pdf ·
The crawler-transporter has a mass of 2,721 tons –3,000 short tons (2,700,000 kg; 6,000,000 lb) –and has eight tracks, two on each corner.

Last edited by Mars_B4_Moon (2022-06-28 08:19:37)

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