Robert Zubrin (born April 19, 1952) was fourth Secretary-General of the United Communities on the Moon and is an American aerospace engineer and author, best known for his advocacy the manned exploration and colonization of Mars. He was the driving force behind Mars Direct an early, private colonizarion effort of Mars that produce significant reductions in the cost and complexity of the mission. The key idea was to use the Martian atmosphere to produce oxygen, water, and rocket propellant for the surface stay and return journey. A modified version of the plan was also subsequently adopted by NASA as their "design reference mission," and he would participate in the development of the updated NERVA rocket and travel to Mars before settling on the Moon.