An airframe, or body tube, gives an aerodynamic shell to the interior of the rocket. It also transmits the thrust loads of the rocket from the motor up to the nose cone, and holds together under compression from the thrust and drag forces.
The materials of the airframe vary depending on how large the rocket is and how much thrust the motor is providing. Below are some options for materials for body tubes (in order of strength from left to right).
| Material | Cardboard | Phenolic | Quantum Tube | Phenolic overwrap | Fiberglass | Carbon Fiber | Aluminum |
|---|---|---|---|---|---|---|---|
| Max OD | 7.5" | 7.5" | 4" | 7.5" | None | None | None |
| Max Speed (Mach) | 0.7 | 2.5" and below - Mach 2 Above 2.5" - Mach 0.85 | 0.85 | Depends on the diameter. Usually not recommended for much above mach 1. | The speed of your epoxy (Usually 3-4, unless you use ablatives) | The speed of your epoxy (Usually 3-4, unless you use ablatives) | None |
| Notes | Low speed, easy to work with | Use for motor mount tubes. | Polymer-based. Do not use for motor mount tubes. | A bit heavier than the previous three, but excellent strength. Easier layup than full composite. | More difficult to make, requires filament winding or full layup. | Highest strength-weight ratio of composites. Layups are difficult. Not RF-transparent. | Ductile, easier to machine than CF. |
| Price | Cheap. Buy in bulk for HPR's. | Cheap | A little less cheap. Cardboard is usually fine. | Medium | A lot | A lot | A lot, though often less than Carbon Fiber |