posted on Sep, 12 2003 @ 05:02 PM
Galileo is powered by a Radioisotope Thermal Generator, or RTG. This is not a reactor in the classic sense, that reacts 2 subcritical masses for
thermal energy to be converted into steam, and generate electricity with a steam turbine. Such a system would be far too large and heavy for a space
Instead, an RTG uses a thermocouple to convert the thermal energy produced by the natural decay of radioactive masses directly into electricity. It is
less efficient and far more expensive than a standard reactor, but it is compact and lightweight, and offers long term power output for such space
Because Voyager had to fly so far from the Sun (which appears virtually as a bright point of light from the distance of Neptune), it could not rely on
sunlight for energy. Instead, it was powered by heat from the radioactive decay of plutonium -- all this occurring safely, without the slightest
mishap, in a component of the spacecraft called an RTG, for "radioisotope thermoelectric generator."
Galileo also will be powered by radioactive plutonium. There is no alternative. To power Galileo by solar panels, the spacecraft would have to be as
big as a house; to power it by batteries would add so much weight that the mission would never fly -- at least on any U.S. launch vehicle in existence
or now under development. But plutonium can be deadly, and the Galileo RTG's have now begun to alarm many people. A lawsuit has been filed in Federal
District Court in Washington, D.C. -- by the Washington-based religiousaffiliated Christic Institute and other organizations -- to stop the Galileo
launch on the grounds that it may pose a serious danger to public health. Meanwhile, the White House, after considering the dangers, has given the
go-ahead for launch.
The U.S. Department of Energy (DOE) has provided radioisotope thermoelectric generators for space applications since 1961. These generators provide
electrical power for spacecraft by direct conversion of the heat generated by the decay of plutonium-238 (Pu-238) oxide to electrical energy. The
first generator was used on the Navy Transit 4A spacecraft launched on June 29, 1961. Between 1961 and 1972, DOE provided power systems for six Navy
navigational satellites. In addition, DOE provided power systems for two Air Force communications satellites, LES 8 and LES 9, both launched together
on March 14, 1976.