What is a Body Tube?

The body tube is an aerodynamic component that protects the internal parts of the rocket from external influences. It maintains the structural integrity of the rocket. The body tube typically hosts the fins and the nose cone at its ends. Inside, it contains the internal structure components, payload, electronic systems, and the rocket motor. Due to its cylindrical shape, it is referred to as the body tube.

How to Design a Body Tube?

Before designing the body tube, the materials and components that will be housed within it must be determined. This helps in defining the material selection, length, and wall thickness of the body tube. The design must also account for avionics systems and the rocket motor, offering multiple alternatives for the body tube. Consequently, it is not the first component designed in a rocket. There are two primary considerations in body tube design: The body tube must withstand pressure, friction, and impact to protect the internal components. The body tube should have a geometry that does not adversely affect the rocket’s flight performance.

To achieve a stable rocket that reaches higher altitudes and can accommodate heavier internal components, the body tube should be as lightweight as possible. For stable flight, the body length should be at least ten times the diameter. A narrow and short body tube minimizes the surface area in contact with air, enhancing flight stability. The rocket’s stability can be calculated using tools like Rocket Fx’s “Stability” page. To balance internal and external pressure, the body tube should have several small holes, typically 3 to 4 mm in diameter. For rockets launched from rail launchers, launch lugs must be mounted on the body tube. Suitable holes or slots must also be created for the fins.

The body tube can consist of two or three segments for ease of placing and removing internal components. These segments can be joined using an integration section and may include holes and pins for attachment if they are to separate mid-flight. After determining the body tube’s length, the wall thickness should be decided, ensuring manufacturability and optimal protection for internal components.

Body Tube Materials

Once the body tube design is finalized, a suitable material must be selected, considering manufacturability, cost, availability, required dimensions, durability, weight, and rigidity. Composite materials, such as fiberglass and carbon fiber, are commonly used due to their ease of shaping. Aluminum and other metals are also used for high-speed, high-altitude rockets or those with heavy internal loads, as cardboard, is often insufficient. Material selection should also consider manufacturability, durability, and signal permeability. After designing, the body tube can be painted or coated, paying attention to potential changes in wall thickness, center of gravity, and surface integrity. For more detailed information on materials and manufacturing methods, refer to the “Materials Used in Model Rocketry” page.