LOW-COST BALLOON MISSIONS TO MARS AND VENUS
* While the "great age" of manned balloon flights into the stratosphere is history, balloons continue to be important tools for scientific research. Unmanned stratospheric balloons are used for astronomy and climate studies, and balloons are also potentially an important tool for exploring other planets.
* Although manned high-altitude scientific ballooning died out in the 1960s, high-altitude unmanned balloon research remains alive and well, with the US a leader in the effort. The US Air Force never really abandoned unmanned high-altitude balloons, with the Air Force Research Lab currently conducting about a half-dozen flights a year from the municipal airports at Santa Rosa, New Mexico, and Holbrook, Arizona.
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After the success of the Venus VEGA balloons, Blamont focused on a more ambitious balloon mission to Mars, to be carried on a Soviet space probe. The atmospheric pressure on Mars is about 150 times less than that of Earth, though the gravity is only about a third that of Earth. Under such conditions, a balloon with a volume of 5,000 to 10,000 cubic meters (178,500 to 357,000 cubic feet) could carry a payload of 20 kilograms (44 pounds), while a balloon with a volume of 100,000 cubic meters (3,570,000 cubic feet) could carry 200 kilograms (440 pounds).
Early concepts for the Mars balloon featured a rozier dual balloon system, with a sealed hydrogen or helium-filled balloon tethered to a solar montgolfiere. The light-gas balloon component was designed to keep the montgolfiere off the ground at night; during the day, the Sun would heat up the montgolfiere, causing the balloon assembly to rise. Eventually, the group decided on a cylindrical sealed helium balloon with an envelope made of mylar, and with a volume of 5,500 cubic meters (196,000 cubic feet). The balloon would rise when heated during the day and sink as it cooled at night.
Total mass of the balloon assembly was 65 kilograms (143 pounds), with a 15 kilogram (33 pound) gondola and a 13.5 kilogram (30 pound) instrumented guiderope. The balloon was expected to operate for ten days. Unfortunately, although considerable development work was performed on the balloon and its subsystems, Russian financial difficulties pushed the Mars probe out from 1992; then to 1994; and then to 1996. The Mars balloon was dropped from the project due to cost constraints, and the probe was lost on launch in 1996 anyway.