Gigapress
Trying to be less wrong
I had been reasoning from physics first principles that this would be the only reasonable way to get atmospheric CO2 (on Earth or on Mars) converted to methane for Raptor propulsion.
Elon said just last week in the Tim Dodd/Everyday Astronaut interview:
- Minimizing the fully considered cost per ton to orbit is the only goal for designing the launch system
- When Starship/Superheavy is fully and rapidly reusable, the propellant (methalox) becomes the largest portion of the cost structure
In December Elon had Tweeted:
Even as far back as 2018 he said:
Drew Baglino in his recent Stanford interview was discussing the importance of hydrolysis technology for making hydrogen, although not in a SpaceX context. However, that indicates that one of Elon’s closest colleagues who was representing Tesla publicly believes electrolysis is the path for green hydrogen. Assuming solar cost trends continue, I agree with him because I don’t see any other physically and economically viable option.
But then, after seeing your question I remembered where I first heard about this: the famous 2016 SpaceX presentation for Making Humans a Multiplanetary Species. Here we have clear confirmation that they’ll use water electrolyzers and Sabatier reactors. I probably originally got the idea from this and forgot about it.
The part that remains my speculation is:
- Lime calcination kilns will be used for the CO2 capture, at least on Earth
- Generally the same industrial process and supply chain used for making cement (releasing 2.5% of human CO2 emissions in the process)
- There are other options but this one is simple and energy-intensive and requires no exotic materials, making it ideal for exploiting cheap solar energy
- SpaceX is so good at engineering that they’ll be the strongest player in the CO2 capture, H2 synthesizing and CH4 synthesizing industries
- If SpaceX can produce the most H2 and CH4 at the lowest cost, SpaceX will leverage that strength into selling these commodity chemicals in the broader market and possibly will integrate into existing petrochemicals industry in Texas and neighboring Louisiana, with Fischer-Tropsch synthesis of other chemicals being a long-term potential
- Increase economies of scale and innovation (Wright’s Law)
- Increase probability that civilization on Earth survives because the goal isn’t just Mars, it’s actually making life multiplanetary
- Get lots of $$$ to fund Mars terraforming
- This will require a lot of energy per kg of methane produced, mostly from making the H2
- At scale of current natural gas and petrochemicals industry this would require at least an order of magnitude more electricity than humans use today
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