Nose cone design

Given the problem of the aerodynamic design of the nose cone section of any vehicle or body meant to travel through a compressible fluid medium (such as a rocket or aircraft, missile, shell or bullet), an important problem is the determination of the nose cone geometrical shape for optimum performance.

For many applications, such a task requires the definition of a solid of revolution shape that experiences minimal resistance to rapid motion through such a fluid medium.

The full body of revolution of the nose cone is formed by rotating the profile around the centerline C⁄L.

While the equations describe the "perfect" shape, practical nose cones are often blunted or truncated for manufacturing, aerodynamic, or thermodynamic reasons.

The sides of a conic profile are straight lines, so the diameter equation is simply: Cones are sometimes defined by their half angle, φ: In practical applications such as re-entry vehicles, a conical nose is often blunted by capping it with a segment of a sphere.

The tangency point where the sphere meets the cone can be found, using similar triangles, from: where rn is the radius of the spherical nose cap.

Half angles: Next to a simple cone, the tangent ogive shape is the most familiar in hobby rocketry.

The popularity of this shape is largely due to the ease of constructing its profile, as it is simply a circular section.

The tangency point where the sphere meets the tangent ogive can be found from: where rn is the radius and xo is the center of the spherical nose cap.

Then the radius y at any point x as x varies from 0 to L is: If the chosen ρ is less than the tangent ogive ρ and greater than half the length of the nose cone, then the result will be a secant ogive that bulges out to a maximum diameter that is greater than the base diameter.

This shape is popular in subsonic flight (such as model rocketry) due to the blunt nose and tangent base.

[further explanation needed] This is not a shape normally found in professional rocketry, which almost always flies at much higher velocities where other designs are more suitable.

The parabolic series nose shape is generated by rotating a segment of a parabola around a line parallel to its latus rectum.

The power series shape is characterized by its (usually) blunt tip, and by the fact that its base is not tangent to the body tube.

The power series nose shape is generated by rotating the y = R(x/L)n curve about the x-axis for values of n less than 1.

While the series is a continuous set of shapes determined by the value of C in the equations below, two values of C have particular significance: when C = 0, the notation LD signifies minimum drag for the given length and diameter, and when C = 1/3, LV indicates minimum drag for a given length and volume.

The Haack series nose cones are not perfectly tangent to the body at their base except for the case where C = 2/3.

The aerospike creates a detached shock ahead of the body, thus reducing the drag acting on the aircraft.

[4] This chart generally agrees with more detailed, but less comprehensive data found in other references (most notably the USAF Datcom).

For example, an F-16 Fighting Falcon nose appears to be a very close match to a Von Kármán shape.