Behind the Scenes: How Rockets are Built at the United Launch Alliance Decatur Factory


United Launch Alliance (ULA) has been producing reliable rockets for years, and their factory in Decatur, Alabama, is a marvel of modern engineering and manufacturing. This article provides an in-depth look into the intricate process of constructing rockets, detailing each step from raw materials to the final assembly and launch.

The Importance of Trust and Security

Building rockets involves sensitive technologies, some of which are shared with ballistic missiles. Due to this, the knowledge about rocket construction is protected under International Traffic in Arms Regulations (ITAR). This means filming or sharing detailed information about the factory operations usually isn’t allowed.

Introduction to ULA’s Rockets

At the heart of ULA’s operations are three key rockets: the Atlas V, the Delta IV Heavy, and the new Vulcan rocket. The Atlas V is ULA’s workhorse, a reliable and versatile rocket used for numerous missions. The Delta IV Heavy, known for its significant lifting capability, was used to launch the Parker Solar Probe. The Vulcan rocket is the newest addition, boasting 30% more lift capability than the Delta IV Heavy and incorporating advanced technologies.

United Launch Alliance Atlas V Launch
United Launch Alliance Atlas V Launch

Raw Materials to Rocket Parts

The process begins where raw materials enter the factory. Giant plates of 7000-series aluminum arrive at the factory, ready to be transformed into rocket parts. These plates are machined into barrel sections, starting as flat pieces and ending as curved rocket segments. The machining process is critical, removing more than two-thirds of the material while retaining most of its strength.

The raw materials are brought in through a massive door and move through a detailed manufacturing process. The first step is planing the large plates to make them perfectly flat. This is essential for ensuring that the subsequent machining processes are precise. Skilled technicians inspect the machined plates, looking for any imperfections. They use various tools, including end mills and side mills, to achieve the desired dimensions.

7000 series aluminum alloy
7000-Series Aluminum Alloy

Craftsmanship and High-Tech Machinery

The process at ULA’s factory is a blend of advanced technology and skilled craftsmanship. While high-tech CNC machines handle much of the material removal, skilled technicians inspect and perfect the machined parts by hand. This combination ensures precision and quality in every rocket component.

One of the most fascinating aspects of the machining process is the use of isogrid patterns. These patterns, characterized by triangular grids, provide strength while minimizing weight. The design of the isogrid pattern was influenced by the computational tools available in the 90s. Today, ULA uses orthogrid patterns for the Vulcan rocket, which are more efficient and faster to produce.

United Launch Alliance Isogrid Pattern
United Launch Alliance Isogrid Pattern

The Bending Process

After machining, the flat panels are curved using massive 25-ton brake presses. This step is crucial for forming the cylindrical sections of the rocket. Skilled technicians manually guide the panels through this process, ensuring the correct curvature and structural integrity.

The bending process requires a tremendous amount of force, especially for the long panels used in rockets. The technicians use a combination of hand-guided operations and precise measurements to achieve the desired shape. The process is repeated multiple times, with the technicians making small adjustments to ensure uniform curvature.

Chemical Processing and Anodizing

Next, the machined and curved panels undergo chemical processing and anodizing. This involves cleaning the aluminum, etching it for a consistent surface, and creating a thick oxide layer for corrosion resistance. Anodized aluminum has a distinctive bronze color, seen on Atlas rockets on the launch pad.

The chemical processing facility at ULA is one of the largest in the world. The panels are thoroughly cleaned to remove any contaminants from the machining process. They are then etched using sulfuric acid, which helps to create a uniform surface for anodizing. The anodizing process involves immersing the panels in an electrolyte solution and passing a current through them. This creates a durable oxide layer that provides excellent corrosion resistance.

The plating facility at ULA is an impressive sight. Here, panels are methodically processed through various tanks and rinsing stations to ensure they meet the exacting standards required for rocket components. The process involves multiple steps of cleaning, etching, and anodizing, with each step carefully monitored by skilled technicians to ensure optimal results.

Friction Stir Welding

A critical part of the assembly process is friction stir welding. Unlike traditional welding, which melts materials, friction stir welding heats and stirs the materials together without melting them. This results in stronger joints and lighter rocket parts. Longitudinal and circumferential welds are performed to join sections into complete rocket barrels.

friction stir welding tool
Friction Stir Welding Tool – Credit: NASA

Friction stir welding is a fascinating process that uses a rotating tool to generate frictional heat. The heat softens the materials, allowing them to be stirred together and form a solid-state joint. This method produces welds that are stronger and more reliable than traditional fusion welds. The process also minimizes distortion and eliminates the need for filler materials.

In the ULA factory, the friction stir welding process is performed on large, specialized machines designed specifically for this purpose. These machines ensure precise control over the welding process, resulting in consistent and high-quality welds. The panels are carefully aligned and clamped in place, with the welding tool moving along the seam to join the sections together.

Building the Centaur Upper Stage

The Centaur upper stage, the final component of ULA rockets, is made from incredibly thin stainless steel. These parts are precision-machined and resistance-welded, creating a lightweight but strong structure. The Centaur is known for its high performance, taking payloads to their final orbits.

ULA Atlas V Centaur Upper Stage
United Launch Alliance Atlas V Centaur Upper Stage – Credit: NASA

The stainless steel used in the Centaur upper stage is less than half the thickness of a dime. Despite its thinness, it is incredibly strong and capable of withstanding the extreme conditions of space. The construction process involves cutting the steel into precise shapes, stretching it to the desired dimensions, and welding it together to form the structure of the upper stage.

The construction of the Centaur upper stage requires a high degree of precision and skill. The stainless steel sheets are carefully handled to prevent any damage or contamination. The pieces are then meticulously aligned and welded together using resistance welding techniques. This process ensures that the joints are strong and reliable, capable of withstanding the stresses of launch and space travel.

Final Assembly and Launch

In the final assembly area, rockets are put together with all their components. Engines are mounted, plumbing is installed, and insulation is applied. After thorough inspections and tests, the completed rockets are transported to the launch site via the Rocketship, ULA’s custom transport vessel.

united launch alliance "Great Hall of Rockets"
United Launch Alliance “Great Hall of Rockets”

The final assembly process takes place in a massive hall known as the “great hall of rockets.” Here, technicians carefully assemble each rocket, ensuring that every component is perfectly aligned and securely fastened. The assembled rockets are then subjected to rigorous testing to verify their readiness for launch. This includes pressure tests, X-ray inspections, and other quality control measures.

The Rocketship

One unique aspect of ULA’s operations is the Rocketship, a specially designed vessel used to transport rockets from the factory to the launch site. The Rocketship navigates through several rivers, up the Mississippi River, and down to the Gulf of Mexico. From there, it heads to the launch pad, ensuring the safe delivery of the rockets.

United Launch Alliance RS Rocketship
United Launch Alliance RS Rocketship

The Rocketship is a vital part of ULA’s logistics, allowing them to transport fully assembled rockets across long distances. The vessel is equipped with specialized cradles and securing mechanisms to keep the rockets stable during transit. This method of transportation minimizes the risk of damage and ensures that the rockets arrive at the launch site in pristine condition.

The Rocketship’s journey is a testament to the complexity and coordination involved in space missions. Navigating through rivers and open seas requires careful planning and precise execution. The vessel’s crew works tirelessly to ensure that the rockets are securely fastened and protected throughout the journey, demonstrating ULA’s commitment to excellence and safety.

The Role of Technology and Innovation

ULA’s approach to rocket building is a perfect example of how technology and innovation drive the aerospace industry. The use of advanced materials, such as 7000-series aluminum and high-strength stainless steel, combined with state-of-the-art manufacturing techniques like friction stir welding, highlights the cutting-edge nature of modern rocketry.

Additionally, the implementation of sophisticated computational tools and simulations ensures that every component is designed and manufactured to exacting standards. This level of precision is critical in the aerospace industry, where even the smallest deviation can have significant consequences.

A Personal Touch

Walking through the factory, one can’t help but feel a sense of awe and excitement. Seeing the raw materials transformed into complex rocket components is like watching a work of art come to life. The smell of the machine shop, the sound of the tools, and the sight of the massive machinery all add to the experience.

Meeting the people who make it all happen is equally inspiring. Their passion for their work and dedication to excellence are evident in every step of the process. From the technicians inspecting the machined plates to the engineers overseeing the assembly, everyone plays a crucial role in building these incredible machines.

One of the most memorable moments is seeing the technicians at work. Their expertise and attention to detail are apparent as they carefully inspect and machine each component. The blend of high-tech machinery and skilled craftsmanship is truly impressive, showcasing the level of precision and quality that goes into every rocket.


Exploring ULA’s rocket factory reveals an unforgettable experience. The blend of technology and craftsmanship, the dedication of the workforce, and the sheer scale of the operation are truly impressive. It’s no wonder that ULA has a reputation for producing some of the most reliable rockets in the world.

Understanding the detailed process of how rockets are built, from raw materials to final assembly, provides insight into the complexity and precision required in the aerospace industry. Each step, from machining to welding to final assembly, involves meticulous attention to detail and a commitment to excellence.

Thank you for joining this detailed look at how rockets are built at ULA’s Decatur factory. The fascinating world of rocketry is brought to life through the intricate processes and skilled workforce that make space exploration possible.

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