Heating of satellites is treated in connection with flight in planetary atmospheres and in interplanetary space. Heating during entry into the earth’s atmosphere is generally more severe than that encountered during launch or exit, although it can be substantially reduced by employing blunt shapes and small entry angles. Decelerations and heating rates during entry can be further reduced by employing lifting satellites. These techniques in combination with known radiation, heat-sink, and ablation cooling techniques appear adequate to handle the entry problem at speeds up to escape speed. Return flights from distant planets like Saturn and beyond may be characterized by much higher entry speeds, and more advanced techniques for coping with the heating problem may be required. Heating during entry into the atmospheres of planets neighboring Earth tends to be more or less severe than that in the earth’s atmosphere depending on whether the planets are larger or smaller than Earth.
Heating in interplanetary space due to solar radiation becomes severe only if a satellite approaches to within a small fraction of an astronomical unit of the sun, or if the vehicle has an inefficient radiation shield. A cooling problem is encountered in the outer portion of our solar system, and an auxiliary power source may be required to supplement the reduced amount of heat from the sun. The sputtering or erosion of material from the surface of a satellite, caused by impact at hypervelocities with small particles in space, may also pose direct or indirect heating problems. Further research is required to assess the magnitude of these problems.