1. In an anarchist country in a world where there are still capitalist countries, how would it defend itself cohesively if invaded?
Call it what you will. A Peoples War with a libertarian tinge, workers militias, ect.
2. In worldwide communism, is total abolition of the state really necessary, especially as we venture out into the universe?
Its Necessary to abolish the state otherwise communism doesn't exist.
3. Would scientific progress be important in a communist society, e.g. space exploration?
We are all about moving society forward materially, science is srs business
"Treason to whiteness is loyalty to humanity" - Noel Ignatiev
"Oogle pride!" -Spook Rat