Aluminium Smelting in Space: What Would it Take?

Void · 2016-10-29 19:58:32

I would go with the electromagnetic cannon sir.

I would also be looking to manufacture smart loads with their own mini propulsion capabilities and computer brains.

O'neills original vision had sacks of dirt to be launched from the Moon's surface and to be collected in a sort of spinning cup.

I think we can do much better than that with current technology.

It should be possible to create loads to shoot which can further propel themselves, and also have the computer powers to navigate themselves to a location of value, where they would be recycled to a purpose. A sort of mass production of these temporary robots.

Last edited by Void (2016-10-29 20:03:20)

JoshNH4H · 2016-10-30 08:18:04

Hey Void,

It's all a question of investment vs. return. A rocket system may cost $100 million to develop and cost $5/kg (marginal) to launch. The electromagnetic gun might cost $1 billion to develop and build (If you cap your acceptable total acceleration at 20g and use a circular track, it will be about 115 km long in total, if you're curious about how I got to that number I encourage you to inquire) but only $0.50/kg to use. A space tether might cost $10 billion to make and $0.05/kg to use. Don't take my numbers as facts as they are optimistic and also made up.

One other problem with electromagnetic launchers that you don't have with other systems is the high accelerations. It's not clear that rocket components can withstand 20g, or anything else besides raw materials. Therefore with this technology you probably need substantial, in-space assembly.

SpaceNut · 2016-10-30 09:28:00

I was think shortage as being created like OPEC oil shortages in which the price is driven up by controlled restriction of the commodity by the largest producer. This the speculator controlled market and not the demand to availability.

JoshNH4H · 2016-10-30 09:42:09

Something like that would definitely make aluminium smelting profitable sooner but that's definitely not something we can count on

GW Johnson · 2016-10-31 09:14:31

Stuff that accelerates at high gee has to be very hardened. For example, the average acceleration of a 5-inch/54 shell is around 20,000 gees. But there's absolutely nothing about that projectile that is lightweight. And nothing in it made of aluminum or plain iron/steel, either.

If you do your mining on an asteroid instead of a planetary body, there's no gravity well you must climb out of, there is only a modest delta-vee to get on a transfer orbit back to earth. You could do this with a simple MMH-NTO thruster, which also gives you terminal guidance adjustments as you approach free-return entry.

If your cargo is a load of aluminum ingots, say, then all you need do is contain weakened metal at 300-400 F during entry. If you don't allow it to get that hot, then you need no containment. Just band the ingots together.

Now the heat shield need not be very sophisticated. In fact it can be dense urethane foam, as long as it is thick enough for a 3 minute transient. The only real risk here is controlling where this load actually comes down. It will need a chute not to shatter on impact.

If your propulsion is more sophisticated, say a solar-electric rig of some kind, then don't do free return, do a capture into LEO, and send supplies and materials back to the mine with the SEP rig. If you return the ingots from LEO, you have a lot more control over where they come down, and you need a lot less urethane for the heat shield.

GW

Last edited by GW Johnson (2016-10-31 09:15:54)

JoshNH4H · 2016-11-01 16:11:34

You make a good point about asteroid mining, but we know even less about the asteroids than we do about the Moon!

The other thing about asteroid mining is that the high solar flux on the Moon/outside of Earth's orbit is the only reason this makes any sense. At 3 AU the solar flux is actually lower than it is on Earth so there's really no reason to do any Aluminium production there.

Platinum Group Metals, Gold, and Titanium make sense though.

SpaceNut · 2016-11-01 22:21:51

Here is the possible lunar export:
Mirrors made of thin aluminized PET film for Mars to increase the total insolation it receives for the greenhouse.

JoshNH4H · 2016-11-02 08:19:04

SpaceNut,

Who exactly do you expect to pay for those mirrors, and why do you expect them to pay that?

SpaceNut · 2016-11-02 19:02:42

Well nasa will not need any mining of the moons aluminum as they will not be going and that is most likely the case for mars as well. I was looking down the road of developement when man not connected to government sponsored flight will need the more easily mining moon aluminum as compared to what is available on mars.

These will be corporate flights where people will have paid there way to settle the Moon or mars and if there is a sponsored missions from government such as the Red dragon its going to be more like a ride along package for science there will be a few rides that will happen to sort of fund the corporate direction of moving people into space.

So will mars people need mirrors of aluminum from the moon sure if the price is right for the martian colonist as they will not have the tools to make them or the ore to do so for quite some time down the road. Just speculating that a rocket from the moon will be cheaper than one from the earth filled with the processed commodity that will aid in solar concentrating. Also speculating that it will be quite some time before equipment would be sent on made on mars to process any level of ore let alone send the equipment to mine for it as these are both very heavy.

Ya I am reading a crystal ball but who knows what the future will be if prices for trips drop off this world.

JoshNH4H · 2016-11-03 08:10:28

What I was driving at is that all you've really done is shifted the problem. Space colonies will need to be able to sell things to Earth in order to buy things from Earth. If the Moon is engaging in trade with Mars instead of trade with Earth, what is Mars selling to Earth?

These are really vital questions that need to be answered for space colonization to happen.

SpaceNut · 2016-11-03 08:19:52

Not sure how long a need on earth will be for the moons He3 or even for any precious stones that man may find once we start mining let alone gold if its there. There is little that earth does not have.... I see space colonies trading more with each other as they lack what the other has especially once we have venus as well as mars and moon journeys in full swing.

RobertDyck · 2016-11-03 13:15:34

I've said before that I doubt there will be a market for ³He. Or much of a market. I said once fusion is achieved, it would be ignited with the easiest fusion fuel mixture: Deuterium and Tritium. That's ²H and ³H. Once ignited, nuclear fusion will increase temperature and pressure sufficiently to ignite double-deuterium reaction. That doesn't produce as much energy as D-T or D-³He, but byproducts are T and ³He. Since ignition temperature and pressure for both D-T and D-³He are lower than D-D, those other reactions will occur as soon as the isotopes are produced. Secondary reactions will produce most of the energy.

Ps. I got the squared and cubed symbols from the character map.
Windows XP: Start -> Programs -> Accessories -> System Tools -> Character Map
Windows 7: Start -> All Programs -> Accessories -> System Tools -> Character Map
Windows 10: Start -> All Apps -> Windows Accessories -> Character Map

Of course my assertion is based on the assumption of a continuous reaction. A pulse reactor is completely different. Tritium does not occur in nature, it's half-life is too short. It's a byproduct of a heavy water fission reactor.

Once your reactor requires nothing but Deuterium as fuel, itself producing everything else it needs, that's a lot easier. Deuterium is extracted from every drop of water on this planet. You have to start with fresh water, but could desalinate seawater to get that.

RobertDyck · 2016-11-03 13:20:15

Earth is exponentially increasing consumption of precious metals for industrial purposes. As I said, now that lead solder is banned, solder is still 60% tin, the remainder is a mix of copper and silver. Contacts for computer cards, iPhone data and power contacts, and all other electronic contacts are gold plated. Oil refineries use platinum group metals to break crude oil into gasoline, diesel, naphtha, etc., but catalytic converts also sue platinum group metals, and hydrogen fuel cells do too. So demand for all precious metals will increase. And these are not plentiful on Earth. Iron is, precious metals aren't.

JoshNH4H · 2016-11-04 08:02:05

Helium 3 is definitely a red herring as far as the Moon goes. While the isotope may technically be more plentiful there than it is here on Earth it's still exceedingly rare and exceedingly rarefied. Processing a billion tons of material to extract a few hundred grams of fuel for fusion reactors that don't work yet doesn't seem like something to base a space economy off of.

Precious metals definitely are a valuable import from space. They'll probably come before Aluminium, even. For comparison, here is the (approximate) market price of several different materials:

Steel: $0.35/kg
Crude Oil: $0.50/kg
Aluminium: $1.80/kg
Copper: $4.80/kg
Nickel: $9.90/kg
Titanium: $16.50/kg (Grade 5 Titanium)
Silver: $600/kg
Palladium: $16,000/kg
Platinum: $34,000/kg
Gold: $40,000/kg

Please be aware that these prices are approximate, change daily, and should not be regarded as authoritative.

Of the expensive metals, I think Platinum and Palladium are most likely to retain their high prices as supply goes up. Gold has commercial uses but is mostly ornamental and is primarily valuable for its scarcity. Silver is sort of the same. Copper, nickel, and titanium are also very useful metals. Aluminium is more of a long-term "reach" goal, but I think it's pretty interesting to talk about how it could happen.

JoshNH4H · 2016-11-04 09:10:27

As I said before, I think our ability to ship the Aluminium back to Earth is really the crux of the question of whether you can produce Aluminium in space economically. For this reason, I want to go in-depth with a few possible transportation options.

The four options (In order of decreasing marginal cost) are:

Chemical Rockets
Nuclear Rockets
Electromagnetic Launcher
Space Tether

I would like to review these possible options in depth and throw some guesses out as to the range of possible costs.

The first and probably most important assumption I'd like to make is to assume high production rates. Assuming the price of aluminium remains constant around $1,775/tonne and that the all-in cost of Aluminium production is $1,000/tonne, you need to ship about 3,500 tonnes per day to profit a billion dollars per year. Call it 4,500 tonnes per day including re-entry equipment.

What I'm getting at is that this is a very, very high volume operation that needs to be done at a very low cost.

Once in Low Lunar Orbit, the material is going to need to be transported down to LEO, and then the craft back up. Assuming this happens with a solar electric tug, the cargo will also need to come with some amount of fuel.

I'm going to assume the solar electric tug has approximately the same mass as its cargo and an Isp of 3000 s. The one-way delta-V for a low-thrust transfer from LLO to LEO is about 6 km/s (2 km/s if you use aerocapture). Going back it's 6 km/s no matter what. It's important that this is a low-thrust transfer and not a high-thrust transfer because low thrust transfers have higher delta-V.

Assuming a mild aerocapture (3 km/s down and 6 km/s up), the mass ratio going down needs to be 1.1, and the mass ratio going up needs to be 1.22. This means that (assuming the craft doesn't carry anything up, or more accurately assuming that the cost of doing so is not counted towards the transportation costs of Aluminium), the initial craft will be 27% fuel by weight, and that for each kg of cargo you send to space you also need to send up 0.66 kg of fuel.

These solar tugs are interesting and important, but I'll look at them more in-depth later. My next post will be a systemic review of the possibilities for chemical propulsion on the Moon.

GW Johnson · 2016-11-04 10:22:33

$0.20/kg for steel? I wish I could buy it that cheap. That's lower than wholesale.

Last time I bought half a ton of mild steel for building farm implements a few months ago, I paid retail $0.70/lb = $1.5/kg for plate, bar, and tube stock. A few years ago, when Chinese demand peaked, steel was running retail about $1.00/lb = $2.2/kg.

Because of competition, the wholesale-to-retail markup is a factor closer to 2 or 3. It ain't a government-imposed monopoly the way pharmaceticals are, with markup factors from 10 to 10,000 or more. So that's $0.50-$0.70/kg for wholesale carbon steel. Non-mild steel alloys are more expensive.

Crude oil at 42 US gallons per standard barrel (I know it's a 55 gal drum, but they're not dead-level full) is running $30-40/barrel on the wholesale market, according to the evening news. At sp.gravity ~ 0.9, that's about 7.5 lb/gal for 315 lbm = 143 kg per barrel. That works out to a wholesale price per unit mass in the vicinity of $0.24/kg, not too far from the quoted 50 cents above.

That's wholesale. A retail finished product is gasoline, currently in the vicinity of $2/gal at 6 lb/gallon in the US. That's $0.33/lb or $0.73/kg. It's been over twice that high before. Also fairly close to the 50 cents quoted above.

So I have to wonder about the quoted price for the steel. It appears to be wrong by a factor on the 5-10 range, not 2-or-less.

I cannot comment on the other prices.

GW

JoshNH4H · 2016-11-04 14:17:04

Hey GW,

The price of steel was actually the hardest one for me to get. Most other metals are traded on a commodity market, but it doesn't seem like Iron or Steel are traded as one commodity but instead (Because the market is so huge) are traded on different markets for each alloy. I had seen $200/tonne somewhere and ran with it.

Doing more research, this website gives the trading value of steel, although it doesn't specify which kind. It seems that over the past 10 years, Steel has traded at between $90 and $1200 per tonne. Looking at the period after the 2000s commodity boom, it's generally fluctuated between $100 and $600, with the average lying probably somewhere around $350. I will update my post to reflect this.

Half a ton of steel isn't a whole lot as far as the steel market is concerned. They build bridges and skyscrapers out of the stuff. 1000 pounds is chump change, and you probably paid a pretty high markup over what a bigger player would pay.

Regarding crude oil, I assumed a price of $60/barrel, 42 gallons per barrel, 3.78 L/gallon, and 0.8 kg/L. That works out to $0.47/kg, which I rounded up to $0.50 because of the large error bars on the future price of oil. $45/barrel is the average over the last two years, but just before that the price was hovering above $100/barrel. We have no idea where it'll be in twelve months, or even in one month.

The other prices are obtained from various websites that list the commodity prices of metals. Titanium was hard to get. The numbers are approximate, change daily, and should not be regarded as authoritative.

SpaceNut · 2016-11-04 19:28:18

Trade value and comodity pricing have nothing to do with the cost to mine or process it as those things appear to be written off here on Earth and that is not the case for lunar efforts to create an export business as it will bare the cost of rockets and so much more to even begin to mine anything on the moon. This is the same for food as what the farmer gets to charge for it is not what we pay for it.....

The question of how to return the shipment of any item via the suggested means must also look at how it get to the surface as well which introduces even more cost to the cargo.
The moose bailout would work but it would need to target areas where there is little chance to hit a populated area. To accomplish that would mean to have a direct hit in an ocean of maybe the poles. Making what ever it comeback in reuseable with just a simple battery change and fuel probably not going to happen.

GW Johnson · 2016-11-05 13:28:15

So, think outside the box. How about some sort of end user for space aluminum (and the other metals) not down on Earth? If it becomes feasible to make duralumin alloys in bar, tube, plate, and sheet stock on the moon, where would these be most useful? How about some sort of assembly shipyard in orbit somewhere in cislunar space?

If somebody else is making propellants off-earth, you can start to think about a transportation system between planets that would cost a lot less to fuel and run.

I've heard somewhere there's more crustal water near the surface of Mercury than there is on the moon. But I'm going to guess that Mars has even more. Mercury and Mars have about the same gravity wells, but transport costs at Mars are lower, because you can aerobrake away about 3/4 of the needed delta-vee to land from orbit. Mercury is straight rocket burn stuff both ways.

Even so, there's gobs upon gobs of solar energy available at Mercury. Think power as an export from Mercury, in the form of H2 and O2 liquids made from local water. Could that be worthwhile? With Mars and the moon as customers? Using ships and containers made from materials from the moon and assembled in those orbiting cis-lunar facilities?

On Mars, you can use the H2 and the local CO2 to make methane, and even transform that into other organics. There's also likely to be easily-recovered iron on Mars. Mars could export both methane/methane products and steel materials to the moon and those cis-lunar facilities.

But none of that goes home to Earth, which already has all those things. There's the metals like platinum that are hard to get on Earth, which might be what the off-world colonies could export to Earth. All those colonies are going to need things that they cannot get locally, but which are plentiful on Earth. Somehow the up-transportation cost needs to be reduced to (1) make this feasible, and (2) allow it to bootstrap into being.

Ultimately, the rare metals may be easier to obtain from the asteroids than the moon. And then there's Ceres, which has lots of water and who-knows-what-else?

Just the lunatic ravings of an otherwise trained mind.

GW

JoshNH4H · 2016-11-05 15:11:30

I have a counter-challenge to you: Think inside the box. Money up less than or equal to money down. Solve that equation and space will happen. Keep suggesting we sell things to the Martians (Which incidentally do not exist) and it won't.

SpaceNut · 2016-11-05 20:54:53

So is it cheaper to send the materials from earth or from a lunar processing plant for a space shipyard....

A Population in space and lots of space locations to go to will drive the space economy, these are a combination science, tourist and manufacturing at these locations for it to work.

JoshNH4H · 2016-11-13 22:36:01

1. Chemical Rockets

__________________

This is going to be a long post. I have a tl;dr at the bottom below the line
__________________

Chemical rockets are the simplest and most well-developed of the propulsion options I mentioned. Their behavior is well-characterized and we have experience with them going back to the 1920s (And even further back than that, depending how you think of chinese fireworks and artillery).

Launching to Low Lunar Orbit is a mission to which Chemical rockets are very well suited. The delta-V is low (Lunar orbital velocity is 1.7 km/s so launching to lunar orbit should be 2 km/s or a bit less), lunar gravity is low (meaning you can skimp on engines), and you're in a vacuum the whole way, which means no air drag and that you get the highest possible specific impulse from your rocket engines.

We want to be able to send things up to LLO for probably about $0.05-$0.10/kg or less. If that sounds like an absurdly low number for space travel it's because it is. It's about 5 orders of magnitude cheaper than a Falcon 9. But how cheap can we get these rockets?

Right off the bat, we know they have to be reusable. There's no way you can get to that price point when you're throwing your rocket away each time you use it.

The rockets will probably be made primarily on the Moon from Lunar materials. Incidentally, rockets are made mostly from Aluminium so rocket manufacturing sort of complements that (Will the Moon/L4/L5 be the solar system's shipyard? Maybe!).

A big, open question is what fuel the rockets will use. There are tons and tons of options, some of which are suited to the Moon. We have strong evidence that there is hydrogen (almost definitely bound up in some chemical compound) in the perpetually shaded craters on the Moon.

However we have no idea what form it takes or how much of it there is. Both are important at the scales we're looking at. Launching 4500 tonnes per day could exhaust the supply of Hydrogen pretty quickly if it's limited. In that case, you would probably need to import it from a comet or asteroid. That's not a dealbreaker (Before you start trying to profit off Aluminium, you're already probably going to be extracting nickel and other valuable elements from the asteroids, so you would be adding onto already existing capabilities rather than starting from scratch). As far as that goes, you'd probably be looking to send frozen water to L4 or L5, depot it there, and have the crafts refuel in Lunar orbit instead of on the surface of the Moon.

Provided there are substantial amounts of Hydrogen, it will probably be in the form of Water, Ammonia, Methane, some combination of the above, or chemical/mineral hydrates (Or ammoniates or methanates, which are generally not observed on Earth but may exist).

The following table contains information on the density, exhaust velocity, and storage temperature (at 1 atm) of various fuel/oxidizer combinations.

fuel information table

One of the benefits derived from vacuum operation is a lower chamber pressure. This enables pressure-fed rocket engines which are simpler and more robust. The Apollo lander had a chamber pressure of just 7 bar.

I built a model designed to compare how different fuels would affect this mission. The assumptions that went into the model are as follows:

Fuel/Oxidizer combos have the properties given in the above table
Tanks are composed of two spheres, one containing the fuel and the other containing the oxidizer.
Tanks are pressurized to 1 MPa
Pressurization is the dominant force on the tanks and is substantially more important than the weight and inertia of the propellants contained within
Tanks are made from 6061 Aluminium alloy with a factor of safety of 2.5
Rocket engines have a thrust to weight ratio of 800 N/kg
Liftoff thrust to weight of the craft is 5 under lunar gravity, or 8 N/kg
Upwards delta-V (with cargo) is 2.25 km/s and downwards delta-V (without cargo) is also 2.25 km/s
Structural and functional elements besides engines and tanks are 35% of the combined mass of those two

I have summarized the results in the following table. For each fuel/oxidizer combo, the table lists the following results from the model:

Payload Fraction
Fuel Fraction
Structural Fraction
Tank Efficacy (Ratio of the mass of the stuff inside the tank to the mass of the tank itself)
Landing T/W (Thrust to weight ratio of the rocket with no payload and no remaining fuel)

These results will be the same regardless of the actual payload of the rocket.

Basically, H2/LOX and Methlox are better propellants, and Ammonia/LOX and AlOx are worse propellants.

I would love to create a cost model to estimate how much it would cost to launch from the surface of the Moon using these propellants, but any cost model I made would be unreliable and guess piled upon guess.

Instead, I will provide the following table. For each fuel combination, the table gives:

Engine Ratio: Kg of engine mass per kg of payload mass
Tankage Ratio: Kg of tank mass per kg of payload mass
Other Structure Ratio: Kg of non-engine and non-tank dry mass per kg of payload mass
Fuel Ratio: Kg of fuel mass per kg of payload mass

In general, engines are more complex and expensive than tanks kilogram per kilogram, while “other structure” is a general category with a range of values.

I want to focus on fuel costs because these are somewhat better constrained than the other contributors to cost. For the purposes of this analysis, I'm going to assume that mining and resource extraction on the Moon is comparable in cost, although somewhat more expensive, than on Earth. This is a prerequisite technology for the development of Lunar Aluminium production, so this isn't a much bigger additional claim.

Fossil fuels on Earth are pretty close to a best-case scenario for low-cost production. In areas gifted with large, easily accessed oil reserves, it will simply come out of the ground. I've heard Saudi Arabia can produce oil at a cost of $20/barrel, which works out to about $0.15/kg.
Methane is the closest to this ideal. If there is methane frozen on the Moon, it is probably of cometary origin. This means that it would probably be mixed with other ices (water, ammonia, possible carbon dioxide), and possibly with rock, dirt, or dust in permanently shaded craters near the lunar poles. When these ores are collected and heated nearer to room temperature (Or really even to 120 K) the Methane will boil off and can be re-collected in a nearly pure form. I will therefore price methane at $0.20/kg.

The next closest is ammonia. Should a mix of ices exist at the lunar poles, Ammonia will probably be one of the components. However, unlike methane ammonia is completely soluble in water, so that multiple distillations will be required to purify it. I will therefore price ammonia at $0.25/kg.

Most of the propellant by mass in both of these cases is Oxygen. This oxygen has to come from somewhere and will not be produced as a byproduct of making methane or ammonia. However, it will be produced as a byproduct of producing Aluminium. This Oxygen would otherwise not be that useful, because it's way more than is needed for breathing. If you're producing 3500 tonnes of Aluminum per day, you will also produce 3100 tonnes of Oxygen. This is about as much as is consumed by Los Angeles or Brooklyn.

With methlox propellant, producing aluminium will also create 92% of the amount of Oxygen required to launch the aluminium into Low Lunar Orbit. With ammonia/LOX, the number is 90%. Because this oxygen would otherwise go to waste, the only additional process is liquefaction, so I will price this LOX at $0.05/kg.

The rest of the LOX is going to have to come from somewhere else. I'm going to say it comes from using hydrogen to smelt iron oxides to produce iron, then electrolyze the water produced to get oxygen. I will price this LOX at $0.20/kg.

H2/LOX fuel will need to first be mined as water and then electrolyzed to its components and liquefied. I will price it at $0.40/kg. The mining process is comparable to ammonia, but on top of that it needs to be electrolyzed and liquefied.

AlOx will naturally be produced by Aluminium electrolysis. However, there needs to be a stoichiometric excess of LOX. 44% of the LOX will be produced with the Aluminium, and, if the payload is also Aluminium, another 47% can be produced from that. The remaining 9% (Or 56% if the payload is not Aluminium) will be produced as described previously. LOX produced from Aluminium will be priced at $0.05/kg. Aluminium will be priced at $0.80/kg. LOX not produced from Aluminium will be priced at $0.20/kg, as above.

A table describing these results is below. Please be aware that the figure for $/kg of payload is only money spent on fuel. This is a lower limit on the price but does not include the cost of building, maintaining, operating, fueling, or recovering the rocket.

I want to point out a few things from this table. Firstly, it's cheaper to send Aluminium up than non-Aluminium payloads. You can think of this as the aluminium foundries having a reciprocal relationship with the launch companies where the foundries sell the launch companies oxygen and then apply the revenue to launches. Secondly, I'd like to point out that methlox is the cheapest fuel followed by ammonia/LOX followed by H2/LOX followed by AlOx.

While methlox is the cheapest, we have no verification that there are reserves of methane on the Moon. If there's no methane there's also likely no ammonia. There may be water, but if there's not enough to fuel very regular rocket trips then AlOx will be the fuel of choice.

It is reasonable to expect that the total transportation cost would be some multiple of the fuel cost. For cars, the multiple is about 3. For airplanes it's about 6. I stated earlier that I would like to have the capacity to send 4500 tonnes up per day to ship 3500 tonnes of Aluminium. This increase of 30% is for the reentry vehicle. I also noted that you need to multiply the earthbound payload by 1.66 to account for ion engine fuel. Therefore each kilo of aluminium will have an associated 1.15 kg of non-aluminium payload. Provided you also produce oxygen when producing ion engine fuel (reasonable), and that you use methlox with a multiplier of 3, you're looking at a minimum launch cost of $0.71/kg of Aluminium. This pretty much blows our entire budget on this one leg, so it's too high.

_______________________________

tl;dr:

Fuel options in order of best to worst performance: H2/LOX, Methlox, Ammonia/LOX, AlOx
Fuel options in order of lowest (estimated) total cost to highest (estimated) total cost: Methlox, Ammonia/LOX, H2/LOX, AlOx
We don't know which of those will actually be available to use because we've never gone and looked for them
Launch costs with chemical rockets will almost definitely be too high to profitably ship Aluminium from the Moon to Earth

kbd512 · 2016-11-14 02:42:25

Josh,

When superconducting thrusters achieve operational capability, we'll start mining operations on the moon and on asteroids. At that point, it will rapidly become too costly and too much of a hassle to conduct mining operations on Earth. Who in their right mind would sift through billions of tons of rock in a war-torn country when a robot could be sent to an asteroid made of pure or nearly pure platinum that you could cart off without bribing the local war lord, dealing with environmentalists going bananas, or paying import/export fees to governments?

Chemical rockets are too costly to use for off-world mining. Nuclear rockets are also too costly for off-world mining. People freak out any time the word "nuclear" is mentioned, too. Rail guns and light gas guns are impractical for all but a handful of very specialized uses. A space tether might work after the space around Earth is cleaned up, otherwise it's like flying through a shooting gallery.

The requirement for reaction mass is the fly in the ointment of limitless off-world resources. Once that fly is removed, our solar system has resources galore available to anyone willing to invest a little bit of their time prospecting. There's so much good stuff in the main belt that there won't even be a point to fighting over any of it.

JoshNH4H · 2016-11-14 08:45:43

Hi kbd512,

When superconducting thrusters achieve operational capability, we'll start mining operations on the moon and on asteroids.
[...]
The requirement for reaction mass is the fly in the ointment of limitless off-world resources.

You appear to be implying that some kind of superconducting thruster will enable in-space transportation without the use of reaction mass. This might be viable in space (I like the M2P2 concept, or even better the "dusty" M2P2 concept, where the magnetic field contains particles that absorb some of the incident sunlight, thus acting as a solar sail), but in any gravity well you're going to need something more substantial to push back on.

We agree that chemical is too expensive. I'm about to write a post on the topic, but nuclear is probably also too costly.

There are no asteroids made of pure platinum.

SpaceNut · 2016-11-14 21:35:56

Thanks Josh for all the work to that little question I asked.
That alone is the basis for a Thesis of why space transportational systems need to go way down in costs and the power to move payloads need to be much greater than anything we have even built plus greater in size to carry as much mass a possible in one shot.

Fuel from Earth is a fixed price but Fuel made insitu is of a greater level of cost if there is no means to replentish it. Earths supply is vast but its the unknown of insitu that we need to get better measurements of.

In the words of GW we need to Drill deep.....

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#26 2016-10-29 19:58:32

Re: Aluminium Smelting in Space: What Would it Take?

#27 2016-10-30 08:18:04

Re: Aluminium Smelting in Space: What Would it Take?

#28 2016-10-30 09:28:00

Re: Aluminium Smelting in Space: What Would it Take?

#29 2016-10-30 09:42:09

Re: Aluminium Smelting in Space: What Would it Take?

#30 2016-10-31 09:14:31

Re: Aluminium Smelting in Space: What Would it Take?

#31 2016-11-01 16:11:34

Re: Aluminium Smelting in Space: What Would it Take?

#32 2016-11-01 22:21:51

Re: Aluminium Smelting in Space: What Would it Take?

#33 2016-11-02 08:19:04

Re: Aluminium Smelting in Space: What Would it Take?

#34 2016-11-02 19:02:42

Re: Aluminium Smelting in Space: What Would it Take?

#35 2016-11-03 08:10:28

Re: Aluminium Smelting in Space: What Would it Take?

#36 2016-11-03 08:19:52

Re: Aluminium Smelting in Space: What Would it Take?

#37 2016-11-03 13:15:34

Re: Aluminium Smelting in Space: What Would it Take?

#38 2016-11-03 13:20:15

Re: Aluminium Smelting in Space: What Would it Take?

#39 2016-11-04 08:02:05

Re: Aluminium Smelting in Space: What Would it Take?

#40 2016-11-04 09:10:27

Re: Aluminium Smelting in Space: What Would it Take?

#41 2016-11-04 10:22:33

Re: Aluminium Smelting in Space: What Would it Take?

#42 2016-11-04 14:17:04

Re: Aluminium Smelting in Space: What Would it Take?

#43 2016-11-04 19:28:18

Re: Aluminium Smelting in Space: What Would it Take?

#44 2016-11-05 13:28:15

Re: Aluminium Smelting in Space: What Would it Take?

#45 2016-11-05 15:11:30

Re: Aluminium Smelting in Space: What Would it Take?

#46 2016-11-05 20:54:53

Re: Aluminium Smelting in Space: What Would it Take?

#47 2016-11-13 22:36:01

Re: Aluminium Smelting in Space: What Would it Take?

#48 2016-11-14 02:42:25

Re: Aluminium Smelting in Space: What Would it Take?

#49 2016-11-14 08:45:43

Re: Aluminium Smelting in Space: What Would it Take?

#50 2016-11-14 21:35:56

Re: Aluminium Smelting in Space: What Would it Take?

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