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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The exploration of the solar system has proceeded in several phases beginning with flyby missions, proceeding to orbiters, then to probes and landers and finally mobile vehicles that operate on the surface and in its atmosphere.
Until quite recently, the only practical means to control balloon buoyancy, and thus altitude, required consuming large amounts of fuel or the limited venting of helium balloons and/or dropping of ballast. With recent discoveries at JPL, novel long-life, balloon buoyancy techniques have been discovered that for the first time allow balloons to float in the primarily hydrogen atmospheres of Jupiter, Saturn, Uranus, and Neptune (using ambient fill-gas), and by using renewable energy sources, allow multiple controlled landings on Venus (using atmospheric temperature differences), Mars (solar heat), Titan (RTG heat), and Earth (planet radiant heat).