On Saturday, April 25, the Saturn V, the rocket that sent men to the moon 40 years ago, will once again lift off from U.S. soil and soar over the Atlantic. Only this time, it won't be quite real. Rather, what's going up will be the largest model rocket ever built — a one-tenth scale, 36-foot-tall, fully working replica of the Saturn V. Its nine rocket engines will provide 8,000 pounds of thrust to lift it between 3,000 and 4,000 feet above its launching point in Price, Md.