Calculations

Timing

A realistic timeline for the terraformation puts the scrub in the last third of the 21st century.

It should be noted that the engineering requirement is not the same having all these resources ready from 2066.

The average number and performance of the robotic scrubbing tadpoles, which will do the majority of the work, will come about in the latter half of the production cycle.

After a parabolic increase in production and productivity will be occuring about this “average” sometime in the 2080s, 60 years from now.

The “sticker-shocked” should take this intervening development time into account.

The Planet Now.

Consider a square metre of the Venusian surface.

Above this square metre is 1043 metric tons of atmosphere.

The atmosphere is 96.5% CO2, so there is 1007 tons of CO2 to get rid of, per square metre.

This proposal would combine that tonnage of CO2 with an equal molar amount of CaO from below the surface, to make CaCO3, or lime.

This scrub has already occurred, over geological time, on Earth, where the atmosphere was once about a third CO2.

Here the reaction has been facilitated by the solvent, water.

CaCO3 weighs 100g/mol, 44g of which is the CO2, and 56g of which is CaO. So, the 1007 tons of CO2 will combine with 1281 tons of CaO from the crust, to make 2288 tons of lime.

It is assumed the CaO makes up more than 10% of the Venusian crust.

This volcanic crust weighs in at 3.5 tons/cubic metre.

This puts the tonnage (per square metre) of crust to be processed to obtain 1281 tons of CaO at around 12,000.

The depth of crust that will yield this is 12,000 tons per square metre over the density of 3.5 tons per cubic metre, or about 3400 metres.

Many, if not most, of the tadpoles will dive past this depth before finishing.

The surface area of Venus is 4.6x10exp14m2.

The robots’ mission is to, therefore, turn over 5.52x10exp18 tons of Venus’s crust.

Five and a half billion, billion tons. Nobody’s saying it is going to be easy.

To The Moon

Fortunately, Earth has an enormous resource in the form of the moon.

On the moon, mining, manufacturing and launching industries will perform of the work required to put tadpoles on Venus.

The low gravity and vacuum environment are blessings for manufacturing.

Launch services will consist of magnetic rail tracks, many circular, which will accelerate the tadpoles to the moon’s low escape velocity of 2400 metres per second, unimpeded by an atmosphere.

Tadpoles

The tadpoles, so called because they have large heads and tapering tails, will tend to be rectangular at the ‘face’.

Flat sides will allow them to join with neighbouring tadpoles, and they will be launched, and will travel laterally through the crust, in strings.

This way the tadpoles will share resources such as intake/exhausts, power, heat and refrigerant.

Let’s say each tadpole is 20×30 metres face-on.

A 600 square metre cross section melting through a metre of 3.5 ton/m3 crust turns over 2100 tons of crust.

There’s plenty of crust on Venus, 30 to 50 kilometres’ worth, but the tadpoles will turn to the horizontal, and only convert the first few kilometres, as necessary.

A good range will be expected of them, more than 3000 kilometres. So a single tadpole will get through 6300 million tons of crust.

So the scrub, working on CaO alone, needs 876 million tadpoles.

A notable extra may take the scrub’s ‘crustal turnover depth’ shallower than the 3400 metre figure if there is a significant yield from ferric and magnesium oxide, which can also absorb CO2 in carbonates.

Depending on the robots’ yield, this may put the average depth requirement down to 1500 metres or less, and the number of required tadpoles down to 400 million.

If strings of 400 tadpoles are launched at a time, a million such launches will be required over the 33 year scrubbing effort.

Split between a hundred lunar launchers, that is a manageable one launch per day, per rail-gun.

The strings may carry loads of colonists to the Venusian clouds with them.

Each rail-gun will have, associated with it, a factory output of 400 tadpoles a day, not unlike Volkwagon’s Wolfsburg car plant, which can make 3800 cars a day.

Again, this output will occur at a ‘productivity half-way point’ in the mission, shall we say, 60 years from now (2024).

Producing 400 million units of anything will have unprecedented economies of scale, and the resulting product will come in cheap.

Each component will have its own supply huge network, and competition will ensure value.

For individuals buying tadpoles in the expectation of an average of a 50 hectare pay-off, the average price of one must be in the order of one hundred thousand 2024 U.S. Dollars, making the per hectare price about $2000.

Total costs, multiplying this average tadpole unit price with the required number of units, $100,000 x 400 million = $40,000,000,000,000 or 40 trillion dollars.

Hey, that’s the price of a planet these days.

This is about the same as the U.S. public debt, but the similarity ends there, as $40 trillion of value will be created, as opposed to $40 trillion of waste.

For reasons not unrelated to the U.S. debt, the medium of exchange and measure for Venuzians must be gold.