What are heat sources in DS1?
During almost all of the mission, internal electrical power generation and direct solar energy (radiation from the Sun) are the only heat sources. The solar panels on DS1 are 22% efficient, which means that 22% of the sunlight that comes into them is made into electricity. The rest of the solar energy turns into heat. Heat also comes from the current traveling through the wires in the electrical system. The ion engine is a significant source of heat, getting to temperatures as high as 300 degrees C during peak thrusting, but almost no heat from the ion thruster dissipates back through the spacecraft. There is an 18 inch separation between the back of the thruster and the rest of the spacecraft, and the spacecraft side of the thruster is blanketed with insulation. Since heat radiates in the direction of the greatest difference in temperatures, and space is hundreds of degrees C colder than the spacecraft, the heat radiates almost completely into cold space, rather than back through the
