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I posted an article with illustrations on "icecrete", over at http://exrocketman.blogspot.com, dated 3-11-12. There are still serious questions, but I was able to pose a list of credible experiments needing to be done. I am still very enthusiastic about such a material.
GW
Well, following Spacenut's links, it appears that water-based paints can be applied to ice, at least here on Earth. Hmmmmm.
Maybe the experiment is really to see what happens to a bucket of (water-based) wet paint in vacuum. If there is no bubble formation, then we can paint poured "icecrete" structures once they are frozen, in vacuo.
The second test is to see if that coat of paint stops the sublimation.
If both tests are successful, then we have a way to create structurally-useful materials and construction parts on Mars, on the moon, or on any other celestial object that has both ice and regolith.
As to color, I'd suggest a highly-reflective white or aluminum pigment, to reduce the absorption of solar energy that could melt the ice. Or, just keep the stuff in the shade. The paint might have to be an imported item, but the paint on a pre-stressed "icecrete" beam weighs a lot less than the beam.
GW
Thanks, Midoshi. I had forgotten the distinction between the vapor pressure above the ice vs the "air" pressure above the ice. Had been thinking vacuum-only, as for spacesuit compression issues so long, I got stuck in that rut.
BTW, "hi". Long time no see, crash and all that.
So, since Mars's atmosphere is generally very dry, the water vapor pressure in that atmosphere would be pretty near zero, regardless of the atmospheric pressure. Summer temperatures in the equatorial regions will get close to the standard freezepoint (triple point), so we can't count on very-cold-ice vapor-pressure reduction. Yep, "icecrete" will need a tough sublimation coating. That material will not know Mars from the vacuum of the moon or space.
I was hoping for some sort of paint coating we could spray on and "cure" right in place on the dirty-but-not-wet cold ice surface. Maybe an evaporating solvent cure with linking residuals like some oil-based paints here on earth.
Hmmm, some sort of water-based latex paint might even work, if it could be kept from boiling before it dries.
Does any body have a bell jar and a vacuum pump? Two ice cubes, one painted at below-freezing conditions with latex house paint, the other not. Maybe three: try an oil-base hardware paint, too. (Maybe even Krylon clear sealer spray - ha ha.) Paints will take a long time to set-up in the kitchen freezer on a not-wet icecube surface, but that's what we need.
Here in central Texas it's never cold enough to do the painting successfully outside, although I have a couple of good freezers. Maybe somebody in snow country?
GW
If Gingrich does get the nomination, which I doubt, he would still have to beat Obama, which the polls indicate as a lower probability, at best.
But, if Gingrich did become president, why should anyone believe he would make good on his promises as regards space (or anything else)? His decades of history in Congress, and as an influence peddler/lobbyist advisor, indicate pretty strongly that he typically tells people what they want to hear, then just does whatever he thinks is best for him personally.
Of course, that kind of misbehavior is no different from all the rest. But, Gingrich is the only one talking bases on the moon while in Florida, but nowhere else. See the pattern? Again?
GW
If you have something from which to build the mirrors, a solar concentrating furnace makes a lot of sense for melting things. I know the ones here are made using mirrors of silvered glass, and with a big-enough field of actively-steered mirrors, can melt steel.
Where do we get silvered glass, or an effective substitute, on Mars? Where do we get the materials from which to fabricate mirror towers than can be steered? Where do we get the electronic/electric controls? We're talking substantial-horsepower electric motors here, and gears to boot.
Looks to me like, initially at least, a lot of this gear has to come from Earth. Chicken-and-egg problem.
GW
I'm still thinking about a coating for "icecrete" to prevent sublimation. If the local pressure is 6+ mbar, then a coating is not needed. But, if it is, then I am not sure PVA (polyvinyl acetate?) or any other organic plastic will be easily obtainable on Mars or the moon.
Re: Mars atmospheric pressure: I have my doubts as to northern lowland pressures really being 6-7 mbar per Viking 1 & 2. Why? Because the recent northern polar lander (Phoenix) saw ice that it exposed while digging sublimate, and fairly quickly. If the pressure really were 6+ mbar in the polar lowlands, that would not have happened. Basic physics.
So, I really think we need an anti-sublimation coating. I'd like the coating to be local materials, and I'd like to avoid the energy expenditure of melting local rock or dirt. This is going to be some sort of chemistry thing. If we find one, it would work at 0.00 mbar on the moon, too. "Icecrete" is a pretty nice thing to have, so the anti-sublimation coating for "icecrete" is really a very important item.
For reinforced "icecrete", any material with tensile strength would do for the rebar substitute. Basalt (or any other rock) fiber would do, braided into a coarse-textured rope. I dislike the energy expenditure of melting the rocks to do it, but it seems unavoidable, since no one has ever spotted an active volcano on Mars or the moon. Ideas?
Does anyone know the elastic modulus of a braided basalt-fiber rope? (It would not the same as the individual fibers, not by a long shot, no real composite material ever has the properties of the individual fibers.) If the rope's effective modulus is near that of steel (30 million psi = 207 MPa), such a rope might in some way be tensioned very hard, thus serving as the pre-stress member in a pre-stressed "icecrete" beam. Not worth dreaming up, if the modulus is too low, though.
Having pre-stressed beams available is nice for bridges and buildings. Good for resisting bending, such as in pressurized habitats. Very important.
GW
A dark horse nobody is talking about is XCOR. Their Lynx should be flying for the first time by year's end. Suborbital flights, single stage, HTO/L on simple tricycle gear at very ordinary lightplane speeds, with a simple delta-wing rocket plane. Ground crew of 3 or 4 to refuel and fly again, multiple times a day. Stick and rudder flying, like a piper cub, just very fast straight up and back down. I've sat in their mockup. Even I could fly the thing.
Mark my words, it's people like that who will solve the practical space plane-to-orbit problem. Extremely tiny logistical tail, just like Spacex. Combined with true reusability, just like Spacex is trying to do. Very impressive. In some ways, they're ahead of Spacex, as regards designed-in reusability and long life airframes.
That kind of thinking did not (I repeat, did not) come out of a government lab. The real smarts is out there in the innovative companies. And it's not all science, either. I'm fond of saying "rocket science" ain't just science, it's about 40% science, 50% engineering art, and 10% blind dumb luck. Because it's true. The government labs have the science, but little or none of the art.
GW
That 6 mbar vapor pressure at 0C is a very nice result. I calculate about 3.8 inches or 10 cm dirt cover will stop all sublimation once the water freezes, and that's in total vacuum. If we use liquid water very near the freezepoint, the vapor pressure is not much higher, so a maybe a foot or 30 cm of dirt cover over a plastic tarp would do nicely while the ice concrete "sets up". That's figured at 0.38 gee, too. It's only 1.5 inches of dirt at 6 mbar here on Earth, inside a hard vacuum chamber.
That means casting ice concrete and getting it solidified without evaporation loss will be relatively easy. Simple backhoe work. Nice. We're going to need an electric backhoe.
My understanding of Mars's atmosphere is that the surface pressure is 2-4 mbar over most of the planet. The 6 mbar is down in the bottom of a very deep hole: Valles Marineris. That's pretty close to vacuum conditions in any practical sense for most of the settlement locations.
You're quite right, some foundations need no forms, only a shaped hole. It depends upon whether you want the top of slab above grade or not. For the rest, sheet metal and maybe rods or tubes as stakes will likely do. Be nice if it was scrap needing re-use. Any sort of building is going to need a foundation to be stable. Unsupported walls sink into and tip over if just set upon dirt. Slow, but fatal to the structure. Takes less than a year here to tear up a loose cement block wall in the garden.
Still thinking about preventing sublimation from exposed ice. Sure would be nice to build bridge beams from water, dirt, rocks, cheap plastic pipe, a few steel rods, and some nuts and washers. Your idea of some sort of plastic paint is very interesting.
GW
The electric furnaces they use for steel-making are using scrap steel as an input. That just a remelting thing.
Making steel directly from pig iron and coke is an enormously power-hungry combustion-driven process. There is a hollow furnace stack fed compressed air and fuel at the bottom, which burn to create heat at the bottom, percolating up through the stack with lots more air injection. There are alternating layers of pig iron, coke, and limestone filling the stack. The coke and the added air burn, the 3000+F temperature melts the pig iron and the limestone, and the molten limestone is a liquid slag coating the puddles of iron so that it does not oxidize.
That's the slow, relatively "energy-efficient" way (LOL). For the fast, not-so-efficient way, look at a Bessemer converter. It's really quite spectacular when they turn on the oxygen lance to burn out the excess carbon. Those processes don't sound very amenable to solar PV to me. It'd be hard to make that kind of chemistry happen at 1200 MWe direct from a nuclear plant here on earth.
What's needed on Mars is a different set of chemistries reflecting the availability of atmospheric CO2 instead of O2. No one knows what that is yet. Maybe we'll be lucky and the yet-to-be-defined process won't be such an energy hog. I wouldn't hold my breath about that, though.
Do we yet know if Mars has both uranium and thorium reserves in deposits accessible on the surface? If there are deposits like that, the entire thorium breeder cycle could be bootstrapped into operation locally with HEU as the starter. The machinery to refine the materials would either have to be imported or built from parts and supplies locally. The smarts to do it is intellectual property shipped electronically from earth. The whole thing is dependent upon supplies of alloy steels locally.
Sort of a chicken-and-egg thing. Those situations always require a kick-start of some kind.
GW
Now there's an idea I hadn't thought of: solar PV with the panels on the freight cars. Neat.
Heat engines on Mars should use something that will react with a CO2 atmosphere. If you have to carry both reactants, that's like rocket vs airbreather: a real disadvantage. Magnesium will, but it's awfully smoky. Raw soot carbon plus solid mag oxide for the "exhaust".
Batteries? Not very energy-dense compared to chemistry of liquid reactants generally, but lithium ion seems to work the best.
GW
If it's unmanned, slow is OK. Use fuel cell electric, water and sunlight are all over Mars. Just load enough H2 and O2 bottles to make the trip.
GW
Why not think some sort of paved roadway, and a rubber-tired truck-trailer-trailer-***-trailer rig? Extremely simple.
We've been talking about concrete substitutes in some of the other threads. We just need a minimally-paved fairly-smooth surface for rubber tires.
The tractor/locomotive unit could be electric, steam, chemical fuels, whatever turns out to be best. It's train, just no tracks. They run 3 and 4 trailer trucks on the highways in Australia, as I understand it.
GW
Is Paul Webb's elasticspacesuit.com site still in operation? He had some good stuff up there, when I was last there months ago, including video clips from old movie footage. That was 1969-vintage stuff that they demonstrated with 6 or 7 layers of the then-new-technology pantyhose material.
Part of the problem MIT is having is the NASA requirement for 1/3 of an atmosphere counterpressure. That's coming from the 1/3 atm they customarily use in the O2 gas suits. Been standard for years like that. That's just about 253 mmHg, or 338 mbar.
But it's more oxygen than we get here on Earth at sea level, which is 159 mmHg or 212 mbar. You don't really need 1/3 atm pressure on pure O2. You don't really even need sea level oxygen. Most of us do fine up to 10,000 foot altitudes. Some higher.
One has to account for the displacement of oxygen by water vapor inside the wet lungs, and should account for exhalation CO2 displacement of O2, but that's a minor effect. I did numbers like that and posted them over on http://exrocketman.blogspot.com, as an article dated 1-21-2011.
The upshot is that 20-25% of an atm's compression will do. That's 152-190 mmHg, or 203-253 mbar. 190 mmHg (253 mbar) is what Paul Webb used in 1969, so he and I got the same answers decades apart.
MIT's suit design can already supply compression like that. What is holding back immediate success is the unnecessary higher compression requirement. How stupid is that?
GW
Ballutes are very interesting stabilizers and decelerators. For use at high-subsonic and low-supersonic speeds, I found round ribbon chutes superior in stability. But chutes cannot be used successfully during re-entry. There is the possibility that ballutes can.
If some sort of ablative coating could be added to the ballute, a gas-inflated conical ballute could be used as a decelerator and stabilizer drogue during re-entry. On the end of a long ablative-protected line, it could add deceleration capability over and above what the basic object's heat shield does. How much, I dunno. Up close, none.
If the ballute is really big, part of it will protrude outside the object's wake into freestream flow, even up close. Then it could really produce a lot of decelerator effect, at the cost of very high surface pressures on the freestream-exposed surfaces. It just needs a high-enough inflation pressure. Don't count on ram effect for that, you won't get it.
GW
GW
RobertDyck:
Bad memory goes with the gray/white hair. Mine is getting pretty bad. I have to write everything down or it's lost.
I quite agree about absolutely idiotic, wasteful spending. Politicians ought to be the targets of the missiles that cannot hit the other missiles. Stationary targets, easier to hit. Their political window-dressing projects are just wasteful crap.
I cannot think of any politicians since JFK and LBJ that were actually really serious about any sort of space projects. JFK was just sort-of, he did the moon thing as a race with the Russians. It wasn't about the moon, it was about just beating the Russians at something big. Going to the moon was just a convenient "big" thing. But, I give him credit: once he decided, he stuck with it.
LBJ was actually a spaceflight hobbyist. By chance, we got him as VP, then Pres. He was in there just long enough to get done the follow-through necessary to actually carry out the plan, and thus actually go to moon. The next one, Nixon, killed it before we could make all the planned landings (all the way to Apollo-22 not just Apollo-17). Nixon thought spaceflight was useless.
All the ones since have been window-dressing projects, not properly formulated or funded. Botching the shuttle into a dangerous side-mounted cluster, just to hold down some yearly budgets, is really why two crews died. Nixon was part and parcel of that. His executive order didn't just kill Apollo, he killed all spaceflight outside LEO.
And NASA responded by killing the nuclear rocket program, which was just ready to fly. The official thinking was "why build the rocket if we aren't going to go?" How short-sighted and idiotically-foolish was that?
And, where is the medical centrifuge on the ISS that determines how much gee is enough to stave off microgravity illness? They had a module for that, but cancelled it! ISS as it is, will never give us that absolutely crucial answer for long space voyages. Very expensive window-dressing, as it is.
Reagan's X-30 scramjet in the 1980's had no hope of being feasible, even if scramjet had been ready for application (it still is not): airbreathers alone do not have the frontal thrust density to climb that steeply in air that impossibly-thin (at 100,000+ feet, the Mach-15+ compression of near vacuum is still near-vacuum). Several $B got spent to find out what we already knew. No craft ever flew, of course. Political window-dressing (it was never really intended to fly). Expensive. But just crap.
The smarts isn't in the government labs, and most certainly not the politicians themselves. The real smarts is out in the contractors, and the breakthroughs will not come from the long-time favorites that have been on the payroll so long. Example: The real breakthroughs in LEO access are coming from Spacex, not ULA.
Problem is, this is government-led stuff, because exploration and blue-sky R&D is generally not what business CEO's invest in. They do it only when paid to do it. If the government lab is too hide-bound to foster some new contractors for the breakthroughs, they won't happen. And the smarts that was in the unfunded contractors is lost: they die/retire/go elsewhere and do something completely different.
That third outcome is what happened to me personally. I was once one of about a dozen or so all-around experts in ramjet propulsion, in the whole US. Most of us are dead now. I haven't done ramjet since 1994. Now I teach math in a 2-year tech school.
Not very smart of the government. Penny-wise, pound-foolish, as the adage has it.
GW
I don't know a lot about the details of nuclear reactors, but I have heard of the U-233/Thorium-232 breeder cycle. The Indians are actually trying to do this. You have to use a normal enriched-uranium reactor (involves U-235 fission and the inevitable U-238 breeding to Pu-239) with Th-232 also inserted, to be bred into U-233. You do this until you accumulate enough U-233 to shut down the uranium plant and just go with a straight U-233 reactor, breeding its own fuel from Th-232. This may take a small number of years (I dunno exactly). The waste products of U-233/Th-232 are much more benign than the U-235/238-Pu-239 cycle.
I kinda think that's something we ought to bootstrap into operation down here right now, and just ship U-233 product to space settlements, for direct breeding of local thorium into U-233 fuel. It saves having to ship two breeder reactors, if we could just get it started here first. Thorium is a lot more plentiful here on Earth than uranium, and I rather suspect that's true elsewhere, too.
Also, a U-233 reactor could also be a nuclear rocket. Even in open-cycle gas core designs, the radioactive plume is a lot less objectionable than a uranium or mixed-oxide reactor basis.
Just a thought.
There's a a natural timing here. If we could get the technology started now, it would be ready as we plant settlements soon, and they need atomic power for whatever the local industries might prove to be, not long after.
After all, you simply cannot make steel powered by solar energy.
GW
About the only three things I can think of RE: "ice concrete" are:
1. Boiloff of water into the near-vacuum that is the Martian atmosphere. It'll be in a stout form. I guess lay some relatively impermeable tarps over the freshly-poured material's free surface, and quickly bury that with local dirt several inches to a couple of feet deep (that's just a wild guess). The overburden pressure should stop most of the boiloff until the thing can freeze solid.
Fixing the wild guess: Somebody with a steam table handy could find the vapor pressure of water at 32 F (0 C), and convert that to dirt depth at a typical loose dirt effective specific gravity of 1.68 and 0.38 gee on Mars. I don't have one here.
2. What do we use for forms? No lumber on Mars. Old spacecraft shell plating?
3. Exposed ice concrete structures will be subject to slow sublimation into the near vacuum, reduced somewhat by the aggregate. Dirt cover should stop that. Based on the probe and rover results to date, maybe 3 inches (7-8 cm) of dirt will do. Maybe even less.
I'd use this stuff for in-ground foundations and building structures that get buried or built underground and buried.
For roadway-trackway uses, it'll need a few inches of the dirt cover on top of exposed surfaces. But it should be the same hell-for-stout heavy structural material that concrete is here at home.
Makes me wonder if there is a coating we could apply that would stop the sublimation? Ideas? That would make exposed bridge beams possible. Sort of important.
For rocket landing pads, in some locations just grade off the dirt to expose bedrock. Land directly on that.
Other places where the bedrock is irregular or too deep, that's where the mortared basalt blocks come in real handy. If you find an old lava flow, just saw them out quarry-style. Why waste the energy to melt basalt you already have to cut? It doesn't even need to be basalt. Actually, almost any rock will do.
GW
The way I had in mind to make the suggested martian "ice" concrete would be to mix liquid water, local sand, and local rounded rocks (yep, rounded, no sharp edges or corners), and pour that into a form the same we do ordinary concrete here. Then just let it freeze solid. The liquid water would freeze to the aggregate and stick there, just like the little boy's tongue on the subzero light pole.
In such a formulation, the water ice takes the place of the Portland cement in concrete here. The other two components (sand and rocks) are the same. Here, concrete has both the sand and the rocks, and tests in compression as much stronger than mortar mix, which is just Portland cement and sand. Both are way stronger than Portland cement alone without the sand. There's something about a particulate embedded in a matrix that is far stronger than the matrix alone, even without any fibers.
As for reinforced martian "ice" concrete, you rig the basalt fiber braided ropes, or the steel rebar, inside the empty forms, then pour the concrete in to fill the forms. This embeds the reinforcement inside the structure.
To do pre-stressed beams, rig the forms and reinforcement, plus the empty pipes or tubes from one end to the other. Then pour your concrete mixture. Once fully hard, slip the pre-stress rods through the tubes, add thrust washers on each end, add the nuts, and tighten savagely, but to an engineered torque (so that the tensions in the rods are what was intended).
I see very little difference between doing this with Portland cement here and water ice there. Except that it takes about 30 days for Portland cement to reach full cure strength here. I doubt it takes that long to freeze the water and lower the ice temperature to below -20 or -30 C there. Once that cold, the stuff should be very stout.
Plus, ice composites are harder to melt than straight ice. The dirty snowbanks of plowed snow beside the road are the last to melt.
Rounding sharp edged rocks merely requires tumbling them in a drum with some steel hammer shot.
GW
I had the weight statements and delta-vee figures worked out for Dragon with a "modest dumb tank" inside the unpressurized cargo space. I had 2.3 km/sec total delta-vee that way. You could do a bigger tank, it just needs to dock somehow to the rear. These would be minor mods to the existing design.
The figures I caloculated are in figure 11 of the posting-version of my convention paper. It's over at http://exrocketman.blogspot.com, dated 7-25-11. The by-date navigation tool on the left can take you right to it. This stuff was reverse-engineered from the data posted on Spacex's website.
I haven't done anything for Falcon-Heavy yet, but Falcon-9 I reverse-engineered into a weight statement and some delta-vee estimates in the posting on "exrocketman" dated 12-14-11. It's the first figure in the article. That's the posting on re-usability in launch rockets. Falcon-Heavy is a Falcon-9 with two extra first stages strapped on. The key to their design is propellant cross-feeding among the three 9-engine units. The center one is still nearly full when they drop the outer two off, yet all 27 engines have been burning.
The data I calculated for Dragon should be pretty realistic, unless what I found does not take into account the cosine correction for the canted Draco thrusters. I'm not sure on that one.
What I did for Falcon-9 should be really close.
GW
I remember two Project Plowshare shots named gasbuggy1 and 2, if memory serves. I thought it was natural gas they were after. But you're right, it was too radioactive to use. Those underground shots all have the total mass of the bomb fragments (and the weapons guys SOOOOO love to go with plutonium), plus all the induced secondary radioactivity in all the debris and surrounding rocks. It stays lethal down there for many many, years.
There are a couple of caves that might contain the volume of a test or two, pressurized. But you can't leave it that way, you have to depressurize the cave or it'll leak. That still means cleaning the gas of radioactive debris. Might as well just build the rig to do it on-site as an artificial structure.
By the time you pay for building such a facility, you could have sent the whole kit and kaboodle to the moon. It's pretty expensive stuff. After about the first test or so, it'll begin to pay for itself in spite of the space travel costs, seeing as how with open-plume tests, you get to concentrate your funds on the testing, not the cleanup operation. On the moon, those plumes shoot straight out into space, never to return. The exhaust velocities are way far beyond lunar escape.
GW
Now you're thinking outside the box. Good show, Rune.
GW
I agree with Rune that the sooner we get over our irrationality and apply nuclear propulsion, the sooner things will get affordable, no matter the destination. Don't forget, NERVA-type nuclear is not the best that could be done, it was just the only thing that actually ever got done. Big distinction there.
I disagree that the way to test a nuclear engine is flying somewhere out in space. Nope, chemical or nuclear, you start testing on a stable thrust stand somewhere. If every test has to be a flight test, nothing will ever be done. Because it simply cannot be done that way. Engineering reality.
I suggest we start testing nuclear stuff in a deep crater on the moon. Safe place to do it, and close enough to be reached without nuclear power or gigantic rockets. We can do it with what we already have going. Flying to the moon will prove cheaper than building a facility on Earth that can capture and clean the plume from a nuclear rocket engine that leaks radioactivity. Open plume nuclear tests on Earth are no longer allowed.
GW
Back to using Falcons and Dragons to go to the moon. You will need a lander of some tonnage, probably not unlike the old Apollo lander. You might even build it out of a Dragon with extra tanks, or maybe a from-scratch design. Whatever.
But, I don't see why you need a Centaur or any other departure stage. You don't need any more engines, you just need delta-vee. The Dragon will have the new Super-Draco thrusters on it with 120,000 lb of axial thrust, according to their website. There's eight of them, plenty of redundancy there. Just add a big dumb propellant tank, and plumb it up to the Dragon's system. Use the Dracos for all the delta-vee from LEO to lunar orbit, and back, sucking from the big dumb tank.
Launch the lander on one Falcon-Heavy, launch the Dragon and the big dumb tank on the other. Rendezvous in LEO, and dock the big dumb tank to the rear end of the Dragon, and the lander to its nose. Make up your plumbing connections. Then go to the moon.
Lots of minor details to work out, but I don't see any show stoppers here.
GW
If you are building colonies, build more than one. I'd put them in the northern lowlands, which were once ocean beds. There will be whopping amounts of water ice buried deep. That's ice mining. Put one colony much nearer the north pole for dry-ice mining, and build a railroad between them. Use local ice/basalt fiber/local rock aggregate to form the concrete track for the rail line. Use rubber tires on the train cars. If you can ensure by careful design that the tracks never see much bending or tension, then plain ice-aggregate unreinforced "concrete" will do. (Basalt fiber manufacture is likely to be rather energy-intensive, unless you can find a local active volcano with a basaltic type of lava, not the silicic type.)
To quickly and easily get CO2 gas at 1-10 atm, haul in mined dry ice by rail to your processing plant, and put it in a pressurizable space of limited volume, then apply solar heat, and vaporize the dry ice. It will pressurize the closed space quite easily, no machinery required! Use that pressure to transport the gas down a pipe to where you do whatever you want to do with it.
If you just want raw solid carbon, I've heard tell that Phobos is a carbonaceous chondrite. There's a carbon mine. But you do have to fly it down to the surface to use it.
It's some kind of iron ore, plus a massive energy source, that will be needed longer-term. I'm thinking steel-making, which is extremely energy-intensive. But steel is the key to the future of any viable technologically-based society. Steel and concrete. We've already seen it here.
GW
In the other conversation under "3D Printers", I just today described an ice-matrix Mars concrete, including how to form the basalt fiber rebar, and how to pre-stress beams for bending resistance, the same way we do here. That conversation had veered into concrete, too.
GW