Iridium, asteroid mining and space elevators

 

If iridium were common and cheap, would it make almost impenetrable armor or would it be too heavy?

Short answer: probably not good armor, even if it were cheap. The two problems would be weight and brittleness.

First, density. The element Iridium is one of the densest materials known, about 22.6 g/cm³. For comparison, typical armor steel is around 7.8 g/cm³, and Tungsten—already considered extremely heavy—is about 19.3 g/cm³. So an iridium plate thick enough to matter would weigh roughly three times as much as steel armor of the same size. On a vehicle or a person that becomes impractical very quickly. Even tanks struggle with weight limits, which is why engineers obsess over strength-to-weight ratios.

Second, and more important, mechanical behavior. Iridium is very hard and extremely corrosion-resistant, but it is also brittle. Armor materials need toughness—the ability to absorb energy and deform without shattering. When a projectile hits armor, the metal must bend, mushroom, and spread the force. A brittle material tends instead to crack or spall, which is exactly what you do not want.

That is why effective armor tends to use things like:

• tough steels

• layered composites

• ceramics backed by ductile metal

• sometimes very dense metals like Depleted uranium or tungsten alloys, not pure elements

Even tungsten, which is far tougher than iridium, is usually alloyed because pure tungsten is also too brittle for many armor roles.

So if iridium suddenly became common and cheap, engineers would probably still not use it as the main armor material. At most it might appear in small alloying amounts or specialized coatings where corrosion resistance or extreme temperature stability mattered.

If you’re curious, there’s an interesting twist: in armor design, being extremely dense is not always an advantage. A material that is slightly lighter but much tougher can actually stop projectiles better because it spreads and absorbs the impact energy instead of cracking. ⚙️

If you'd like, I can also tell you which materials are closest to the theoretical “best possible armor” engineers can currently make—some of them are quite surprising. 🧠

What about in space as protection from radiation where you don't need to accelerate?

In that situation, density actually helps, so Iridium would perform quite well as radiation shielding—but it still would not be the most practical material.

Space radiation mainly comes in three forms:

1. Charged particles (protons and heavy ions) from cosmic rays and solar storms.

2. Gamma rays (very energetic photons).

3. Secondary radiation produced when the first two strike shielding.

Dense, high-atomic-number materials—like iridium, Lead, or Tungsten—are very good at stopping gamma rays, because heavy nuclei interact strongly with high-energy photons. In that sense, an iridium wall would indeed block a lot of radiation.

However, spacecraft designers have learned something slightly counter-intuitive. Very heavy elements can make cosmic radiation worse. When high-energy cosmic particles slam into heavy nuclei, they tend to produce particle showers—secondary neutrons and fragments that spread through the spacecraft. Lighter elements produce fewer of these secondary cascades.

That is why materials rich in light atoms, especially hydrogen, are often preferred for space radiation protection. Hydrogen slows and absorbs energetic particles effectively while producing fewer dangerous secondary fragments. Water, plastics, and fuels are actually excellent shields. (For example, Hydrogen-rich polyethylene is often studied for spacecraft shielding.)

In practice, the best shielding strategies proposed for long missions include things like:

• Water tanks arranged around crew quarters.

• Fuel or food stores placed in the walls of the habitat.

• Plastics rich in hydrogen.

• Lunar or Martian regolith piled over habitats.

So if iridium were abundant and cheap, it might be useful for gamma shielding in special situations, but it would still not be the optimal all-purpose radiation shield for space. Ironically, water or plastic can outperform dense metals against cosmic rays.

There is an amusing implication of this: the best emergency radiation shelter in a spacecraft might be the pantry or the water storage area, not a metal vault. 🚀

Except for expensive spark plugs that last a lot longer and can power more faster engines, how would it be used?

If Iridium were suddenly abundant and cheap, its unusual combination of properties would make it useful in several places where engineers currently wish they could use more of it but cannot justify the cost.

One major use would be extreme-environment components. Iridium has one of the highest melting points of any metal (about 2446 °C) and is extraordinarily resistant to corrosion. That means it survives chemical and thermal conditions that destroy most materials. Today it already appears in tiny amounts in high-temperature crucibles used to grow crystals for electronics and optics, but if it were cheap you would likely see entire crucibles, furnace parts, and chemical-processing equipment made from it. It resists attack even by very aggressive chemicals that dissolve metals like Iron or Nickel alloys.

It would also likely become common in electrical contacts and switches. Iridium is very resistant to erosion from electrical arcing. That is why alloys of it with Platinum already appear in high-reliability electrical contacts. If price were no issue, many relays, breakers, and precision switches could use iridium contacts that last vastly longer than copper or silver ones.

Another area would be chemical catalysis. Iridium is an extremely effective catalyst for certain reactions, especially those involving hydrogen and oxidation. At present chemists often avoid it simply because it is so expensive. If the price collapsed, it could become widespread in industrial reactors, fuel-cell technology, and specialized chemical synthesis.

You would probably also see it used in precision instruments and wear surfaces. It is hard, extremely stable, and resists oxidation even at high temperatures. That combination is rare. Bearings, measurement probes, and scientific equipment that must not corrode or deform over decades could benefit from it.

There is also an interesting niche in space hardware. Iridium survives intense heat and oxidation, which is why it already appears in protective layers on the plutonium fuel pellets used in radioisotope generators for deep-space probes. If it were cheap, engineers might use it more broadly for heat shields, rocket engine components, or parts exposed to extreme atmospheric reentry heating.

What probably would not happen is widespread structural use—beams, armor plates, machinery frames—because iridium is too dense and somewhat brittle compared with steels or titanium alloys. Even at zero cost, engineers usually choose materials based on mechanical properties first and price second.

So in a world where iridium was common, it would likely become the go-to “indestructible” metal for hostile environments, much the way stainless steel became the everyday corrosion-resistant metal once chromium alloys became affordable.

There’s also a delightful historical footnote: iridium was originally discovered as an almost useless impurity in platinum ore because it was so hard and chemically stubborn that chemists couldn’t dissolve it to analyze it. That same stubbornness is exactly what makes it valuable today.

When people talk about mining asteroids, they talk about all the gold and nickel and such but never mention iridium or osmium.

That’s a perceptive observation, and the reason is mostly economics and demand, not geology.

Asteroids—especially metallic ones—almost certainly contain large amounts of the platinum-group metals: Iridium, Osmium, Platinum, Rhodium, and others. We know this because many asteroids are thought to be fragments of differentiated planetary cores, and meteorites that reach Earth often contain these elements in much higher concentrations than Earth’s crust. In fact, the famous global iridium spike associated with the Cretaceous–Paleogene extinction event is one of the key pieces of evidence that an asteroid impact occurred.

So in principle, asteroid mining could yield enormous amounts of iridium and osmium.

But when people discuss asteroid mining commercially, the focus tends to fall on gold, platinum, and nickel for three main reasons.

First, market size. The global demand for iridium and osmium is tiny. Only a few tons of iridium are produced each year on Earth. Osmium production is even smaller. If an asteroid miner returned even a few dozen tons, the market price would likely collapse almost instantly because there simply aren’t enough uses.

Second, industrial familiarity. Gold and platinum already have large, established markets—electronics, jewelry, catalytic converters, investment bullion, and so on. Nickel is valuable because it is a major industrial metal used in stainless steel and batteries. Investors understand those markets.

Third, technical difficulty and toxicity issues. Osmium in particular forms a compound called Osmium tetroxide, which is extremely toxic and volatile. Handling large amounts of osmium safely would complicate processing operations.

If asteroid mining ever became routine, the story might change. A sudden large supply of iridium, for example, could enable technologies that are currently limited by cost—high-temperature equipment, advanced catalysts, extremely durable electrical contacts, and so forth. In other words, the applications might expand to match the supply, just as aluminum went from being more valuable than gold in the 19th century to a cheap structural metal once extraction became easy.

There is also an interesting twist: some asteroid-mining proposals actually emphasize iron and nickel instead of precious metals. Those are not valuable on Earth, but in space they could be extremely useful for building structures without launching material from Earth. In that scenario, iridium and osmium would simply be minor by-products of processing metallic asteroids.

Your observation is a good one: the reason they are rarely mentioned isn’t that they aren’t there—it’s that the present-day economy has very little capacity to absorb them.

What about in the building of bunkers and other bomb proof structures: not a large use, granted, but a politically significant one?

For bomb-resistant structures, extremely dense metals like Iridium or Osmium would still not be very attractive, even if they were cheap. The limiting factor in blast protection is usually energy absorption, not simply density.

When a bomb detonates, the main threats to a bunker are:

• Blast overpressure (a powerful shock wave)
• Fragments or penetrators
• Ground shock transmitted through soil and concrete

Materials that perform best against those threats tend to be tough and somewhat deformable, not brittle and ultra-dense. Reinforced concrete and steel work well because they can crack, bend, and absorb energy without shattering catastrophically. Very dense, brittle metals would tend to fracture or spall under a powerful shock wave.

Even today, the most hardened bunkers rely on combinations of:

• reinforced Concrete

• structural Steel

• large amounts of earth or rock overburden

Earth is actually one of the most effective protective materials simply because you can pile up enormous thickness cheaply, and it absorbs shock well.

Another practical issue is that bunker protection scales mostly with thickness. A meter or more of reinforced concrete is common in hardened facilities. If that were made of iridium instead, the mass would be almost three times greater, which creates serious structural problems for the rest of the building and its foundations.

Where extremely dense metals do matter in military engineering is not usually the defense, but the offense. Dense metals like Tungsten or Depleted uranium are used in penetrators because their density helps them maintain momentum and punch through armor or concrete.

So even in the bunker context, abundant iridium would likely be used only in specialized components—perhaps very durable electrical systems, high-temperature parts, or corrosion-proof hardware inside the structure—rather than as the main protective material.

There is also a broader strategic point: modern “bunker buster” weapons work less by brute penetration and more by precise delivery and delayed detonation inside the structure, which means that simply switching to a denser material would not dramatically change survivability.

If you're interested, there’s actually a fascinating hypothetical engineers sometimes discuss: what material would make the “ultimate bunker” if cost didn’t matter at all. The answer turns out not to be a metal at all.

What I hear is that asteroid mining will be more important for space travel than for Earth, and while critical uses would be found they would not be revolutionary.

Yes—what you’re hearing reflects the current mainstream view among space engineers and economists. The real value of asteroid mining is expected to be in space itself, not in shipping materials down to Earth.

Launching mass from Earth is brutally expensive because you must climb out of the gravitational well of Earth. Even with modern reusable rockets, every kilogram you launch costs a great deal in fuel, engineering, and logistics. If raw materials already exist in orbit or on small bodies, they can be used without paying that gravitational “tax.”

So most serious proposals focus on resources that are valuable for operating in space, especially:

Water from carbon-rich asteroids. Water is extremely important because it can be split into Hydrogen and Oxygen for rocket propellant, or used directly for life support and radiation shielding. In effect, water becomes fuel depots, breathable air, and shielding all in one.

Structural metals such as Iron and Nickel from metallic asteroids. Those could be used to manufacture beams, pressure vessels, and large structures in orbit without launching the mass from Earth.

Bulk materials like rock or regolith for radiation shielding or habitat construction.

In that framework, the precious metals—gold, platinum, iridium—are almost incidental by-products. They might eventually be shipped to Earth if transport becomes cheap enough, but that is not the main economic driver in most realistic scenarios.

There’s also a subtle economic point. If a mining operation returned huge quantities of rare metals to Earth, their price would collapse, just as aluminum went from a luxury metal to a common structural material once extraction technology improved. That means asteroid mining would tend to create new uses rather than simply enrich existing markets.

So your summary is very close to the consensus: asteroid mining would likely be transformative for space infrastructure—fuel depots, construction materials, radiation shielding—while on Earth it would mostly lead to incremental or niche applications, rather than a dramatic technological revolution.

The analogy people often use is early coal mining in Britain. At first coal wasn’t exported very far; it mainly powered local industry where it was mined. Only later did it reshape global trade. Asteroid resources may follow a similar pattern—first powering a space-based economy, and only secondarily affecting Earth. 🚀

You seem to have missed the point that a lower price creates new uses, which was kinda my thread all along.

You’re quite right—that was the key point in what you were driving at, and I didn’t push it far enough.

When a material becomes dramatically cheaper, engineers start using it in places that previously seemed absurd. The history of materials is full of this. Aluminum is the classic example: in the mid-19th century it was more valuable than Gold because it was so difficult to extract. Once cheap electrolysis appeared, aluminum suddenly became the material of airplanes, power lines, beverage cans, and window frames—uses nobody would have imagined when it was precious.

If asteroid mining flooded the market with platinum-group metals like Iridium or Osmium, the same process would likely happen. The present uses are tiny only because the price forces engineers to treat them like jewels. If the price collapsed, people would begin designing technologies around their properties instead of around their scarcity.

A few examples where abundance could genuinely change design choices:

Electrical durability.
Iridium resists electrical arc erosion extremely well. Today only microscopic amounts appear in contacts because of cost. If it were cheap, high-power switches, motors, and power-grid components might use it routinely, dramatically extending lifetimes.

Extreme-temperature machinery.
Iridium’s combination of high melting point and chemical stability is exceptional. Cheap iridium could transform high-temperature industrial processes—furnaces, glass production, crystal growth, chemical reactors—because the equipment could run hotter and last far longer.

Catalysis.
Catalytic processes are often limited by the price of the catalyst. Large quantities of iridium could open up new industrial reactions or make hydrogen-related technologies more efficient.

Electrochemistry and energy systems.
Iridium oxides are among the best catalysts for water electrolysis. Cheap iridium could significantly change the economics of large-scale hydrogen production.

Precision components and wear surfaces.
Anything that must survive decades of heat, corrosion, or electrical wear might shift to iridium alloys.

None of these individually sounds world-shaking, but collectively they could produce the kind of quiet technological shift that cheap aluminum or stainless steel produced. Not a sudden revolution—but a broad redesign of equipment once engineers stop worrying about the price.

Your instinct is exactly how materials science usually progresses: availability drives imagination. Once a material becomes abundant, designers start asking not “Where can we afford to use this?” but “What can we build now that we couldn’t before?”

And with iridium or osmium there’s a particularly intriguing possibility: their properties are so extreme that we may simply not yet know the best uses, because nobody has ever had the freedom to experiment with them in bulk.

I'm aware of the radiation problem of space elevators preventing human use, but couldn't they still in the not-too-distant future be used for getting objects into space?

Yes—quite possibly. Even if a full passenger-capable space elevator turned out to be impractical for humans, versions of the idea could still be very useful for moving cargo.

The basic concept of a Space elevator is a cable extending from the surface of Earth up past Geostationary orbit. Climbers move along the cable using electric power rather than rockets. The theoretical appeal is enormous: once built, lifting mass would require energy but not propellant, making it vastly cheaper than rockets.

The difficulty, as you noted, is that the elevator would pass through the Van Allen radiation belts. Humans lingering there for hours or days during a slow climb would receive dangerous radiation doses. Cargo, however, doesn’t care. Electronics could be hardened or shielded.

So in principle an early system might work exactly as you suggest:

• Cargo only, no passengers.

• Shielded containers for electronics or sensitive equipment.

• Bulk materials—fuel, metals, construction components—moving up and down continuously.

There are two other serious technical problems besides radiation.

The first is materials strength. A cable long enough to reach geostationary orbit must support its own weight over tens of thousands of kilometers. Ordinary materials such as steel fail by a huge margin. The only candidates that come close are extremely strong materials like Carbon nanotubes or possibly Graphene fibers, but manufacturing them in defect-free lengths of tens of thousands of kilometers remains far beyond current engineering.

The second is orbital debris and micrometeoroids. The elevator cable would pass through regions crowded with satellites and debris traveling at several kilometers per second. A large impact could sever it.

Because of those challenges, many engineers think intermediate systems might appear first. One example is a rotating skyhook or orbital tether—essentially a shorter cable that dips into the upper atmosphere and grabs payloads launched by rockets. Another is a lunar elevator on Moon, where gravity is much weaker and the materials problem is far easier.

So your intuition is sound: even if a classic Earth space elevator proves difficult for people, cargo-only use could still be extremely valuable—and versions of the idea may well appear within this century if materials technology advances enough.