The SpaceX Falcon 9 rocket is the first American rocket since the Saturn V that is designed to be able to lose an engine without compromising the mission. Using a cluster of nine engines in the first stage, the Falcon 9 has been designed from the start by SpaceX (founded and headed by Elon Musk, founder of PayPal) to be man-rated and is a top contender in NASA's COTS (Commercial Orbital Transportation Services) program.
Source: Air and Space Smithsonian, May 2009. "Is it Safe? Building Rockets as if Lives Depended on It" by Michael Milstein, p21.