Entering Space: Creating a Spacefaring Civilization is a nonfiction book by Robert Zubrin, published in 1999. The book details Zubrin's ambitious plans for space exploration, with an eye towards colonization. It starts with an overview of the current status of space exploration. It then goes into detail about exploration of the Moon, Mars, the outer solar system, and beyond. The book uses engineering and mathematical concepts that are explained in layman's terms.