The Phoenix Project actually gets its start in the late 40's. It was an attempt to control the weather using information and technologies derived from the work of Dr. Wilhelm Reich, an Austrian scientist.
Reich is said to have been a brilliant man, credited with discovering the highly controversial "orgone" energy. Orgone energy is also known as "life" or "orgasmic" energy and is very different from more ordinary electromagnetic energy. Reich supposedly proved the existence of orgone energy in various laboratory experiments, and wrote up his findings in several scientific journals. He claimed that orgone energy could cure cancer, a finding that didn't find wide acceptance with his colleagues. Reich also stated that orgone energy has related to "cosmic energy" and with the Newtonian concept of the "ether". Needless to say, his theories where widely criticized by his fellow scientists.
The "ether" is a Victorian concept that refers to a hypothetical substance that suffused all of space. It served as a medium for light and other forms of radiant energy. This ether was a popular concept and was used by more than one science fiction writer as a way to explain space travel. For example, E. E. 'Doc' Smith sprinkles references to the ether all through his Lensmen novels.
With further research, Reich found that orgone energy was responsible for storms and bad weather. "Dead orgone" or "DOR" was the term used to describe the "dead energy" found within violent thunderstorms and hurricanes. This dead energy was also found within people as well. Active people had plenty of orgone energy, while those who were depressed or sullen had an excess of DOR energy.
After extensive research, Reich finally developed a device that would break up concentrations of DOR energy. When set up with a weather balloon, this device would dissipate or deflect thunderstorms. Armed with Reich's storm-buster, the US Government created a device called a "radiosonde". This device consisted of several sensors and a transmitter that could broadcast across several bands to either build up orgone energy or to disrupt DOR energy. With it the government could control the weather.
It should be pointed out that any device capable of transmitting both orgone and DOR energy could be used to affect people as well. It is possible that the Phoenix Project was also looking into methods of population control. Supposedly, the Soviet Union had conducted extensive experiments on select populations by broadcasting orgone or DOR energy into the area to try and alter the emotion content of the population.