While he was teaching, O’Neill became excited about humans living in outer space. He wrote about the O’Neill cylinder in “The Colonization of Space”. This was his first paper about people living in space. He met with other scientists at Princeton in 1975. There he talked with them about manufacturing in outer space. O’Neill built his first mass driver with help from scientist Henry Kolm in 1976. Mass drivers were part of his plan to mine the Moon and asteroids. His book "" won an award and got people excited about outer space. He died in 1992 after a seven year fight against leukemia.