Cooling Requirements
In most of the cases listed in Table 1 the heating is
so strong that cooling is made necessary to protect the structure. The maximum
temperature that the skin of a space vehicle or ballistic missile can reach is a
technological limit, which may move upward with further progress in material science
and configuration design.
Blunt Nose.
An important parameter is the geometry of the nose. A basic result of hypersonic
theory shows that the heat transfer at the nose is inversely proportional to the
radius of the nose, Fig. 1.
Shooting Stars
Another case, though not technological, is the atmospheric penetration of
meteors, which occurs as speeds estimated between 20 km/h and 70 Km/s. The meteors
look as luminous objects (shooting stars) because of the high temperature
reached. Their vaporization starts at temperatures around 3500 °K. Small meteors
disintegrate before reaching the lower atmosphere.
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