The U.S. space agency readies the first test flight of the vehicle destined for the moon.

One of the largest structures in the world, the vehicle assembly building at Kenned­y Space Center in Florida is the last stop for the space shuttle before it is rolled out to the launch pad. But with the shuttles scheduled to retire in 2010, the massive building has already become home to NASA's next launch vehicle.

Steel pieces that make up most of Ares I-X are clustered in High Bay 4 of the assembly building. The five cylinders represent the interstage and upper stage of Ares I; the final piece is the dart-shaped mock-up of the crew capsule. (See more images.) Credit: John Loomis

The Ares rockets are a crucial part of the Constellation program, NASA's plan for new manned flights to the moon and possibly to Mars and beyond. Unlike its predecessors, the Ares will use separate launch vehicles to transport cargo and crew. Ares I will carry humans to space, while Ares V will transport large-scale hardware such as items needed to establish a lunar base.

Ares I-X, the first launch vehicle to be tested in nearly four decades, sits in immense pieces in the assembly building, awaiting a test flight scheduled for late August. "This flight will allow us to nail down the design of Ares I and eliminate uncertainties, so that everyone will feel more comfortable when the first rocket flies with humans on it," says Jon Cowar­t, deputy manager for the Ares I-X project at Kennedy. The main goal is to gather data during the first two minutes of ascent, when the rocket is most vulnerable to failures. To that end, the I-X includes a mix of real and simulated systems and is equipped with around 700 sensors that will measure load, pressure, vibration, temperature, acoustics, strain, and movement at different points on the rocket and at different stages of flight. The sensors will gather information on the rocket's performance in the roughest parts of the atmosphere, on the separation of its stages, and on the recovery of its boosters.