Most incoming potential meteorites spin and tumble as they plummet through the atmosphere. Occasionally, one will maintain a fixed orientation towards the surface of our planet, causing the leading edge to ablate into a shield, nose cone, or bullet shape. When meteorites ablate, some of their mass is removed as a result of vaporization. Meteorites which display such features are quite rare, highly collectible, and are described as oriented. Oriented meteorites were studied by early NASA spacecraft designers and the leading edges of such meteorites are reminiscent of the heat shields on Mercury, Gemini, and Apollo space capsules.