# How many windmill rotations does it take to send a rocket to Mars?

I want to live in a pollution free world, where all creatures can breath clean air.

I also want to live in a high-end space civilization, where its possible to travel to other planets in our solar system (e.g. Mars).

I therefore need a lot of clean energy, and I'm researching the best source.

This question is related to wind energy.

Question: How many rotations from an average-size land windmill does it take to produce the energy needed to travel to Mars?

The rocket used for Mars travel would be something like SpaceX's "Big Fucking" Mars Rocket

EDIT

To simplify things a bit: The wind-mill produces the rocket fuel on site (no power lost in transmission and storage). The fuel is liquid oxygen and hydrogen.

• First, you need to define how efficient is your storage. Then, energy output depends on more than size and count of turns. And last, pollution-free rocket system is something we don't really have, so it's quite ard to calculate. – Mołot Nov 22 '16 at 12:16
• I have edited the question. Pollution from rockets are tolerated until a better alternative is found. – Vingtoft Nov 22 '16 at 12:24
• I suppose in such a world the technology for near loss-less energy storage has to exist. There are further assumptions to make, how is that energy used to propel the spaceship? Rockets are basically fuel tanks that are pointed in the right direction and then lit at one end, thus the comparison to the SpaceX rocket is mostly useless because it mostly lifts itself. The question is basically about the energy per kilo efficiency of your energy storage and propulsion system which determines how to reach escape velocity. – Helmar Nov 22 '16 at 12:25
• Once in orbit the energy to reach Mars is near zero, unless you set a time frame you can push your space ship to Mars given time ;) – Helmar Nov 22 '16 at 12:26
• Please see edit. The rocket im referring to is not electrical, its powered by normal rocket fuel. The rocket fuel is produced by power from a windmill. – Vingtoft Nov 22 '16 at 12:29

# In 2 years, 8 months (or 9 hours if you go nuclear)

To electrolyse water, you need at least $286 kJ/mol$

Liquid oxygen has a density of $1.14 g/ml$

Oxygen has an atomic weight of 16, i.e. $16 g/mol$

So for every liter of Oxygen — and its corresponding amount of Hydrogen — you need to use $19.1 MJ$, which is $5.3 kWh$.

The Saturn V used about 1.6 million liters of liquid Oxygen for its first, second and third stages. Assuming we then use Hydrogen and Oxygen in all stages (the Saturn V did not but let us play at that) this lands us on about $8.5 GWh$.

A 1.5 MW wind turbine at 25% capacity factor would produce that amount of energy in about 2 years and 8 months. This gets you as far as the Moon, not Mars, but now you know what ball park you are in.

Oh... and as a side note: a bog-standard 1000 MWe (*) nuclear reactor — which is cleaner than wind power (pages 16 to 18), and also safer — generates that same amount of energy in 8.5 hours.

(*) MegaWatt electrical

• It seems that Vattenfall solved the deconstruction and long term storage issues. A shame they don't actually implement this tech. – Burki Nov 22 '16 at 13:27
• @Burki The application for long term storage — the KBS-3 solution — has been handed in to the Swedish authorities and is in the process of being approved. Finland has already approved it. The start of construction and acceptance of the first storage capsules for both countries is expected within a decade. skb.com/news/swedish-method-gains-approval-in-finland-2 – MichaelK Nov 22 '16 at 13:31
• And how is this taken into account in your "nuclear power is cleaner" calculation? Could you provide some insights there? – Burki Nov 22 '16 at 13:53
• The document I linked to — corporate.vattenfall.com/globalassets/corporate/sustainability/… — addresses decommissioning as well. It is a Life Cycle Assessment and in that decommissioning is required to be included. – MichaelK Nov 22 '16 at 13:56