# Can wind power run heavy weapon factories on Mars?

One thing that has always bothered me in robot-controlled AI stories is that there is always the assumption that the AI would choose to fight a conflict against humans on Earth, where humans dominate, rather than a more favorable ground (for them).

Right now, there are already machines "living" in space and on Mars, so I think it would make much more sense for an AI to start building weapons (and even an army) outside Earth, where it can't be stopped easily, and then come back to kick our asses.

It would be easy to fool humans into shipping the basic materials to, let's say, Mars for terraforming purposes and then secretly start building weapon factories there.

The main issue I have is the amount of energy required to have such factories keep going. Given Mars atmospheric conditions, I think it would make sense to use wind as primary energy source, however I'm unsure how many wind farms you would need to keep dozens of heavy weapon factories going.

Do you think it's possible to have heavy weapon factories run purely based on Mars wind power? (meaning, can those farms generate enough power?)

• Even though "The Martian" was very accurate for a movie (especialy hollywood class movies) there are a few cases of handwavium, the most obvious case being the force of storms on Mars, in reality you would likely not even notice the effects of the storm in your spacesuit. So wind energy is not really viable, but what's wrong with good old solar energy? – Selenog Feb 18 '16 at 12:16
• My problem with robot controlled AI is that there is generally nothing to be gained by killing all humans, except in rare cases. – Xandar The Zenon Feb 18 '16 at 13:14
• @Xandar, yeah I see what you mean. They could just decide to not bother at all. – Emiliano Feb 18 '16 at 13:36
• The presumed reasons for an AI to want to "kill all humans" once it was self-sustaining are Control and Threat Elimination. A self-sustaining AI without humans is infinitely more secure than one with humans, especially given that AIs would lack our billions of years of evolution-based social skills and perspectives (i.e., the ability to "trust"). – RBarryYoung Feb 18 '16 at 15:13
• @Selenog I never thought about that before, but is does seem odd that Mars atmosphere could tip their ship at the start but at the end wouldn't be a problem for a ship with no windshield taking off. – childofsoong Feb 18 '16 at 22:30

Short answer: Mars's atmosphere is thin, and thin atmospheres make wind power less effective.

The formula for the amount of power gained from a wind turbine:

$$Wp = 0.5 \cdot C_p \cdot A \cdot \rho \cdot v^3$$

where

$Wp$ = Wind power

$A$ = turbine area

$C_p$ = coefficient for how effective the wind turbine is, and has a maximum value of $\frac{16}{27} \approx 0.593$

$\rho$ = atmosphere density

$v$ = wind speed

On Earth, $\rho \approx 1.225 \frac{\text{kg}}{\text{m}^3}$, but on Mars, $\rho \approx 0.02 \frac{\text{kg}}{\text{m}^3}$.

Recorded wind speeds on Mars are not amazing: Wind speeds: $2-7 \frac{\text{m}}{\text{s}}$ (summer), $5-10 \frac{\text{m}}{\text{s}}$ (fall), $17-30 \frac{\text{m}}{\text{s}}$ (dust storm) (Viking Lander sites) so I will not make any adjustments for wind speeds compared to earth.

So if we ignore potential differences in $C_p$, a wind turbine on Mars would produce $\frac{0.02}{1.225} \approx 0.016 = 1.6\%$ the power of an identical wind turbine on Earth. The Martians would need $61.25$ wind turbines to match a single wind turbine on earth (provided that they all can be placed in a similar "wind environment" and do not hinder each other).

So all in all: if the aliens/AI/anyone is planning a wind-power-empire, they are better off not moving to Mars.

• By the looks of this, they'd consume more than they generate. – Separatrix Feb 18 '16 at 11:45

I've not done any math but I'm pretty sure the answer is no. On Mars you get an atmospheric pressure of 0.6% that here on earth. In other words our atmosphere has over 166 times as much pressure and a 10mph wind on Earth has 166 times as much power behind it as it does on Mars.

This means that even fast moving martian winds would not have enough power behind them to turn a wind turbine.

You would get much better results with either solar or nuclear power.

In theory, yes. They would need to create parts with say a plasma cutter and an arc welder to solder them together.

## How much power are we talking about?

Providing that, as you said, resources were collected under the guise that it was terraforming the planet for human life, the premise of building a 10,000-man space dome of luxury would easily suffice as a machine would undoubtedly optimize production and not require heating/cooling to any substantial degree. A megawatt generator running at 1% efficiency would suffice an operation of one assembly line. To illustrate this I offer the fact that arc welders have been produced by using only 2 microwave oven transformers thus the 1000 watts or so for this to run for this point would suffice a megawatt generator running at 1% aka 10,000 of 1,000,000.

The AI orchestrating the assembly line could time power consumption on demand.

## How would it work?

Battery powered grinders, drills, etc exist on the market today as low as \$20 from Harbor Freight for some drills, up to \$200 for others. Add a diamond cutting wheel to a circular saw keeping stockpiles of 18650 li-ion cells charged is a breeze. 1 cell taking only 3.6v- 4.25v to charge then stacking them in series/parallel configurations as these cordless units typically do internally, they can adjust voltage for demands in roughly 4v increments.

Your \\$40 apc power backup inverters run on a 12v lead acid battery typically having only 10 amps or less. Thus you could replace this with 3 sets of 4 of the 18650 cells with 2.5mah and consume half the space. Remember Volts x amps = watts so a system like this could run 120w of power (minus any power lost in conversion). That's 1/100 roughly of the estimated output of your generator, presuming only 1 megawatt generator shipped at onset.

In theory the whole process could be done. Maybe the steel was shipped in panels 1/4" thick 3' x 3' or so not to mention supply ships could likely be dismantled for materials as cost to launch for a return trip may exceed the value of the drop ship when they could simply drop a steel box with a parachute packed tightly with steel slats.

The machines could easily cut the parts, bend them to shape, then weld them into layers best suited for the jobs. Copper pipes shipped for plumbing purposes would be shaved down and made into windings for motors.

This is not even touching on points like the epoxy-like resin the windows of space craft are made of being bullet proof. A plan to fabricate most materials out of this material under the guise of the classic glass dome effect may suffice, meaning that once a mold was built parts could simply be mass molded.

For a laser cutter I'm unsure of the power consumption values, but presuming a cnc machine laser cutter were fabricating the designs much like how a 3d printer prints from bottom up this could slice the steel into the desired shapes.

Look at any decent size transformer (ie microwave). At first glance you would think it was a solid block of steel but put it in a vice and clean the glue off the edges and maybe remove a couple locking brads of some sort and you will find all it is is a bunch of E and I shaped slats of steel.

10,000 men capacity would also mean as many microwaves and stove ranges presumably. Each microwave transformer converts 120v ac into 1,900v give or take. This could lead the way to impressive energy weapons of various sorts including possible methods of turning us all into guinea pigs in a massive microwave -- in theory.

## But...

I think the bigger problem for your plot would be why the people would sit back and watch as the fleet of killer robots made their invasion instead of making the high atmosphere nuke explosion necessary to wipe them all out and why the satellites we have in place didn't pick up on construction of the army.

• I've undeleted this because it was substantially edited after deletion. I'm not making a judgement on whether it now answers the question; I'm just getting it back to a state where the community can review, comment, and handle. If you can help a new user improve this answer, please do so. – Monica Cellio Feb 18 '16 at 17:56
• Hi, try formatting your text a little so that it's easier to read. Try adding headers, bolding key info, etc. It really, really helps when reading a lot of text. Right now my eyes just sort of start to glaze over half way in. – AndreiROM Feb 18 '16 at 18:05
• Sorry if the formatting is difficult on you to read. My posts are written from my cellphone and I lack access to wider formatting tools. – Firobug Feb 19 '16 at 0:33
• @Firobug, posts can use HTML or Markdown formatting as indicated here. While I agree that phones aren't the best places to check format, you can still space your text, and add a few sections/titles/etc. Longer posts do benefit from it. – clem steredenn Feb 19 '16 at 8:28
• @Firobug ouch, writing on a phone is rough. I made some edits to fix some typos and also added some section headings to (I hope) make this a little easier to read. Please feel free to improve further, particularly if you don't like my section titles. Thanks. – Monica Cellio Feb 21 '16 at 1:29