How to: Choose a Nose Cone

There are three important characteristics to determine when choosing a nose cone: material, fineness ratio, and shape.

Material:

For low power rockets through some Level 2 high power rockets, plastic nose cones are common. For rockets with greater loads on the nose cone, a carbon fiber or fiberglass nose cone would be better.

Fineness ratio:

The fineness ratio is the ratio of length to base diameter. For supersonic rockets, a nose cone with a larger fineness ratio decreases wave drag. However, a larger fineness ratio requires more material and more mass. OpenRocket simulations or experimental data (there’s some in references 1 and 3) can help determine the optimal fineness ratio.

Shape:

This website gives a detailed description of common nose cone shapes and their equations.

For subsonic flights, the shape does not have a significant impact on the drag of the rocket. Common nose cone shapes are ogive and Von Kármán, but the drag reduction from these shapes over a simple cone is small. A curved shape will cause the least drag for a subsonic rocket. Once the rocket reaches Mach 1, a pointy nose cone will have the least drag (5). The wave drag of the nose cone is a significant factor, becoming more important as the speed increases.

Von Kármán (L-D Haack) nose cones are calculated to have the theoretical minimum wave drag, but the assumptions make it most valid for low supersonic values and large fineness ratios (2). These are optimal for rockets traveling most of their flight in a Mach 1 – 1.2 range. For rockets traveling above Mach 1.5, the hypersonic optimum shape is the best (1). The following two graphs provide useful data for choosing a nose cone for a supersonic rocket.

(4)

(1)

Useful links:

Child pages

How to: Choose a Nose Cone