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.

Mounted on top of the fifth-segment simulator are the forward skirt and its extension, which hold the parachute recovery system; it will allow the first stage, after breaking away from the upper stage, to safely splash down in the ocean, where it can be recovered for reuse. The system consists of a computer that triggers separation, a small explosive charge that cuts the metal, and five parachutes.

Ares’s boosters are heavier than the space shuttle’s boosters and will drop from a higher altitude, so they will be falling faster. To compensate, the launch vehicle’s parachutes are much larger and stronger but, thanks to new materials, lighter. The parachutes will deploy in three stages, starting when the rocket boosters reach an altitude of about 4,500 meters. The staged deployment will not only slow the boosters for splashdown but also maneuver them into the appropriate position to prevent damage.

At the very top of the 24-meter-tall stack rests the interstage, which marks the beginning of the upper stage and holds the system designed to control the forces that cause the rocket to rotate during flight. The interstage of Ares I will also carry the rocket’s J-2X engine, which will power the upper stage; it will not be simulated for the test flight, though its weight is accounted for.

The next three stacks simulate the shape and weight of the rest of the upper stage. Stack two, which is the shortest, represents the liquid oxygen tank. Engineers used steel ballast plates to account for the fuel’s weight. Stack three, which is almost 14 meters tall, sports the NASA logo and three emblems that identify the mission. For the test flight, this stack is purely structural and will remain empty. In Ares I, however, it will house most of the liquid hydrogen tank, as well as the flight computer and avionics that control all aspects of flight. Stack four, which displays the U.S. flag, stands for the rest of the hydrogen tank, which will span both stacks; it is also filled with steel ballast plates.

The final stack of Ares I-X is the dart-shaped mock-up of the Orion crew module and launch abort system. The upper stage and crew module will make up a quarter of the assembled rocket’s height; for the Ares I-X flight, it will carry many of the most critical sensors. However, after separation the engineers will have gathered the data they need most, so these portions will fall uncontrolled and splash into the Atlantic Ocean.

Some Assembly Required
Inside the assembly building, Ares I-X will come to life. By the time they finish, engineers will have spent several weeks stacking the rocket’s components, delicately maneuvering one piece on top of another with massive cranes. The completed Ares I-X will be nearly identical to Ares I from the outside: a sleek, two-stage rocket with the crew module on top, as far away from the propulsion system as possible. To make the test-flight data as accurate as possible, it will also be similar in mass and size, standing approximately 99 meters tall, varying from 3.7 to 5.5 meters in diameter, and weighing about 816,000 kilograms when fully fueled.

Three more unmanned test flights are planned after the August launch. Ares I-Y will be identical to the final rocket–nothin­g simulated–and is tentatively scheduled for launch in 2013. The Orion 1 and 2 launches, designed to test the crew module, are planned for the following year, and the first manned launch of Ares I is set for 2015.

NASA is staking its future on long-term exploration, moving beyond low Earth orbit and using the Ares rockets to get there. “The space shuttle has been a great machine, but we need a vehicle [with] better safety and reliability, and with more capabilities,” says Cook. Ares I will have greater range than the shuttle and will cost less to maintain and launch, he says, so it will be possible to venture farther into space, and more often. When Ares V is completed, NASA hopes to build an outpost on the moon, sustaining a human presence there by 2020. The base will allow them to research and test new technologies useful for manned exploration of Mars. Says Cook, “This is what we came to NASA to do.”