World's Biggest Rockets

The Ares I-X rocket is poised to launch on a suborbital test flight on Oct. 27 and rolled out to its launching pad earlier this week. It stands about 327 feet high — 14 stories taller than NASA's space shuttles — and is equivalent in height to its namesake Ares I. The Ares I booster is designed to launch NASA's Orion spacecraft slated to replace the shuttle fleet. (NASA)

Sept. 11: In NASA Kennedy Space Center's Vehicle Assembly Building High Bay 3, NASA's Ares I-X rocket undergoes its first power-up. Not since the April 1981 test flight of NASA's space shuttle Columbia has NASA test launched a new rocket designed to carry astronauts into space. (NASA)

The 327-foot-tall Ares I-X rocket sits perched atop Launch Pad 39B at NASA's Kennedy Space Center in Florida for an Oct. 27, 2009 test flight, but it's not the tallest structure there. On either side of the pad are 100-foot fiberglass lightning masts mounted atop 500-foot towers. The rotating service structure, or RSS, was retracted from the rocket at midday on Oct. 22. (NASA/Kim Shiflett)

Standing 235 feet tall, the Delta 4 Heavy made its launch debut in 2004, but suffered a sensor glitch that prevented it from reaching its intended orbit. The problem was promptly fixed. The rocket most recently launched a classified satellite for the National Reconnaissance Office in January.<br> The Delta 4 Heavy is actually a group of three boosters, each called a Common Booster Core, arranged in a line to give it a three-column look. At least two more Delta 4 Heavy missions are expected on the books for future classified satellite launches, according to Spaceflight Now. (US Air Force)

Two giant Soviet N1 Moon rockets appear on the pads at Tyura-Tam in early July 1969. The N1 was designed for the Soviet space program human lunar missions. The giant rocket stood nearly 345 feet tall, had five distinct stages and resembled a huge, tapering cone that was about 55 feet wide at the base. (NASA)

A Saturn V rocket on its crawler carrier as it rolls out to the launch pad at the Kennedy Space Center in Florida during the Apollo era between the late 1960s and 1970s.  (NASA)

A concept image shows the Ares V cargo launch vehicle. The giant rocket could reach a skyscraping height of 381 feet, surpassing the Saturn V and set a new world record. The rocket is designed to launch 207 tons of cargo to low-Earth orbit and 78.5 tons to the moon. (NASA/MFC)