Solar/Infrared Aerobots for Exploring Several Planets

A report discusses a class of balloon-borne robotic instrumentation systems that have been proposed for use in exploring Venus, Jupiter, Saturn, Uranus, and Neptune. The balloons would be of the Montgolfier type; that is, buoyancy would be achieved through heating of atmospheric gases contained in the balloons at ambient pressures. However, unlike the familiar fire-heated hot-air balloons invented by the Montgolfier brothers, the proposed balloons would be heated primarily by the Sun during the day and by infrared radiation from relatively warm planetary surfaces at night. The proposed balloons would be modified versions of solar/infrared-heated Montgolfier balloons that were flown in the upper stratosphere of the Earth by the French space agency CNES during the 1980s. The lower parts of those balloons were made of infrared-transparent polymeric materials to admit infrared radiation from below, the upper inside surfaces were blackened to maximize absorption of the admitted infrared radiation, and the upper outside surfaces were aluminized to minimize radiation of heat to outer space. During the day, the balloons would rise high due to solar heating. At night, the balloons would sink lower, with the descent slowed by heating due to compression of the contained gasses, as well as by heating from lower planetary radiation.