Reference no: EM132415993

When NASA's space shuttle descends from orbit it must pass through the upper reaches of Earth's atmosphere where the air is extremely thin. In this upper atmosphere, there are enough air molecules colliding with the space shuttle to cause significant heating, but there are too few air molecules to transport thermal energy away from the shuttle. The primary mechanism for cooling the shuttle is emission of blackbody radiation. The shuttle has a heat shield on its underside (see the black panels in the photo at the bottom of the page). This heat shield reaches a temperature of 2000 K. The topside of the shuttle stays cool (~ 300 K).

a) At what rate is blackbody radiation emitted from the space shuttle's heat shield when its underside reaches a temperature of 2000 K? Give your answer in J/s. Note: the space shuttle is about 35 m long, and has a wingspan of 25 m.

b) Apply the First Law of Thermodynamics (conservation of energy) to estimate the fastest rate that the space shuttle can safely descend through the upper reaches of Earth's atmosphere. Give your answer in terms of elevation drop per unit time. Express your answer in units of m/s.

Note: The space shuttle mass is about 100,000 kg (similar to the mass of 100 cars). The change in kinetic energy is negligible compared to change in gravitational potential energy. The friction from the upper reaches of the atmosphere starts to become significant approximately 130 km above sea level.