[lukealization]

I agree space is cool. But why do you think the "space is cool" mantra is more important than ensuring that for the 8 billion humans that call this planet home—we have somewhere sustainable and safe to live?

Your asteroid mining for profit is arguably meaningless if we have no ozone layer.

[golol]

So Starship+Superheavy have about 4.6kt of propellant which should mean about 1kt of methane. That's about 2.5kt CO2 per flight which yields 2.5mt CO2 annually for 1000 launches. The US releases around 4.4Gt CO2 annually so you end up with around 0.05% of US emissions. I actually thought it would be more so I hope I didn't miss an order of magnitude somewhere. Quick search says US airliners release less than about 200mt annually so you're looking at less than 2.5% of that. Annually about 850 million people fly in the US so if you imagine a Starship flight having 100 passengers then in some weird way flying with Starship is maNe about 200 times more CO2 intensive than flying with a plane.

Now high-altidude effects would increase the greenhouse effect of these emissions by some factor I don't know. At the same time a large amount of fuel is actually burned by the booster at below airliner altitudes. Another mitigating effect is that some of this methane could be produced renewably.

I haven't heard about Ozone depletion from spaceflight except for the case of reentering Aluminum burning up. Well this wouldn't be an issue with Starship flights.

So you know overall, let's just give it a lot of conservative margin and imagine we are looking at about 10% of the US airline or 0.2% of total US greenhouse impact. That is on the scale of a whole new industry, yes, but if you can imagine a world which has attained a sustainable rquilibirum surely you can also imagine one which has a bit of margin left? And this is only for the US!

What do you gain? Three of the points I mentioned have potential direct benefit for people.on earth: asteroid mining, L1 solar shield and brilliant pebbles.

Asteroid mining "for profit" also means that the economy profits, unless you believe that capitalism doesn't work. I read that less than 200t platinum are produced annually. Say your asteroid mining crashes that economy. I found some figure of 20kt of CO2 for each ton, so 4mt in total. That is more than your 1000 launches emit! Now my calculations are of course wrong but it seems plausible that the orders of magnitude could match. So you should definetly consider that your asteroid mining operations might stop other mining operations from happening which reduces your greenhouse impact.

Then you have the solar shield. It is certainly possible, although of course difficult and has some risk. But it's good to have a backup plan, no?