3 ms·
Sorry, I skipped some steps in my calculation. The chemical reaction is indeed CH4 + 2 O2 -> CO2 + 2 H2O. So, for each 16 grams of CH4 you get 64 grams of O2,
by credit_guy 6y ago
Sorry, I skipped some steps in my calculation.
The chemical reaction is indeed CH4 + 2 O2 -> CO2 + 2 H2O. So, for each 16 grams of CH4 you get 64 grams of O2, that's a stoichiometric mass ratio of 1:4.
The fuel ratio for the Raptor engine is 22:78, according to Elon Musk's tweet. So, for each 100 g of propellant mixture you get 19.5 g of CH4 to burn using 78 g of O2 and you are left with 2.5 g unburned CH4.
I simply neglected the H2O resultant from the reaction because, while H2O is a very potent greenhouse gas, it has a fast cycle in nature (rain, etc). Also, I have no idea how to account for it as a greenhouse gas.
- bryanlarsen 6y agoFrom what I've heard there is a significant fraction of carbon monoxide in the exhaust, so there will be a lot less CH4 in the exhaust than you have calculated. CO is only a weak greenhouse gas.
- credit_guy 6y agoThat is very interesting. Do you happen to have a link? I'm not doubting you, I think you are right, but a link that goes into this type of detail would be a very interesting one to read.
- bryanlarsen 6y agoI probably heard that here: https://everydayastronaut.com/rocket-pollution/ https://everydayastronaut.com/rocket-pollution/ Otherwise it would have been in a comment on an Eric Berger Ars Technica article.