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.

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.

In Pieces
Entering High Bay 4 is like walking into a giant indoor stadium. In the middle of the bay sit five large steel cylinders, called stacks, that will be assembled into Ares I-X. Surrounding them is a seemingly haphazard assortment of cranes, toolboxes, laptops, and rolling chairs.

The first stage of Ares I will include a single, five-segment solid rocket booster. Its design is derived from the shuttle, which uses two four-segment solid rocket boosters, and it will burn the same specially formulated propellant. "We didn't want to start over," says Steve Cook, manager of the Ares project office at NASA's Marshall Space Flight Center in Huntsville, AL. "We took the best from the past and combined it with modern technology." Ares I-X will use only a four-segment reusable solid rocket booster, with a dummy fifth segment stacked on top. The mock segment marks the beginning of the first stack and lies in several similarly sized pieces, all solid white. (The fifth rocket motor will allow Ares I to lift more weight and reach a higher altitude, but it's not needed for the test flight.)

Near the bottom portion of the fifth-­segment simulator is the first-stage avionics module, which will control the components of the booster and communicate with the upper stage. For example, the module will send the signal to fire the motors, control the vehicle's flight path by moving the motor nozzle, initiate the booster separation sequence, and command the parachute recovery system. The module will also gather important test flight data, specifically on the performance of the flight control system. In the final design, however, the avionics will be housed in the upper stage of the rocket, since propellant will fill the fifth segment.