For decades, the aerospace industry has sought to build a fully reusable rocket launch system to bring down the cost of ferrying people and payloads into orbit. Despite dozens of concepts and millions of dollars directed at that goal, no truly reusable system has been created yet.
What does it take to build one?
Because of our planet's gravity, getting into low-Earth orbit from the ground is a daunting task, even for rockets that are designed to burn up in the atmosphere, never to be reused again.
This month, at a conference in New Mexico celebrating the 20th anniversary of a reusable rocket prototype, the Delta Clipper Experimental, or DC-X, aerospace engineer Jim French joked that if humans were intended to go to space, they would have been born on Mars. (Gravity on the Red Planet is 38 percent of Earth's gravity.) [Reusable Rockets: How They Work (Infographic)]