>Solar energy is "free", asteroids are "free".
The rocket equation says that if you want to do anything besides sitting in one place, it's super expensive. Moving mass around requires throwing huge amounts of mass away.
The rocket equation says that if you want to do anything besides sitting in one place, it's super expensive. Moving mass around requires throwing huge amounts of mass away.
Throwing rockets' worth of water away seems wasteful, but if we have it then it isn't that expensive.