[AlexanderHowl]

That does not work for the requirements of supporting 30 billion people earning an average of GURPS$47,000 per year on the Earth though. The energy requirements far outstrip anything we are familiar with and rapidly increase to a K1 level. It just becomes much cheaper and more more efficient to expand throughout the Sol System. Even supporting our current population at TL8 at GURPS$31,000 would require energy expenditures that would exceed global GDP because of the exponentially increasing energy costs.