RP-1 is much less toxic than Hydrazine, but toxicity is not the same thing than pollution. One is qualitative, the other both qualitative and quantitative.
Burning a huge amount of kerosene is polluting.
For comparison a Boeing 747 (4 engines) consume 2,8 kg per second, while a Saturn V 1 first stage burns 13,600 kg per second, nearly 5000 times the amount of the Boeing 747.
I hope for a breakthrough in rocket engines, but I am quite sure it will not happen. We need something new.
Yes, but the Merlin engine doesn’t burn hydrazine, it burns RP-1 just like the F-1. I fail to see the environmental benefit.
Also, how energy efficient is the production of hydrazine? Non-fossil processes for making fuels tend to be pretty wasteful, take hydrogen from methane compared to hydrogen from electrolysis for instance.
SpaceX’s starship and superheavy are planned to use Methane rather than RP-1. The exhaust is much cleaner. It’s not as clean as just using Hydrogen, but that’s quite difficult to store at cryogenic temperatures, far less dense, and not as suited to long duration missions.
Yes, this is the whole reason they designed Raptor and get methane via the Sabatier reaction [1]. If you want to get back from Mars, you won't find tanks of RP-1 but you can make methane from abumdant CO2 and water (with solar arrays) which is available on Mars
Sabtier doesn't make H2, it makes CH4. You'd need to convert it at about 300degC with a catalyst (so that takes lots of energy). Then the byproduct would be CO, whilst that isn't a bad direct greenhouse gas it interact with hydroxyl radicals in the atmosphere. Hydoxyls ineract with other greenhouse gases to reduce their power, so it would have no net effect, if anything it could be worse. Just combust the CH4 directly, it's got better energy storage capacity anyway.
I hope for a breakthrough in rocket engines, but I am quite sure it will not happen. We need something new.