Electric Propulsion System

The IX-6315 "Dawn" Electric Propulsion System is a tiny-sized engine which runs on electricity and xenon gas propellant. It's modeled after the real-world Hall effect thruster.

This engine has a phenomenal fuel efficiency (4200 s Isp), but very low thrust and requires a substantial amount of electricity to operate. Xenon gas is provided by xenon containers like the PB-X50R Xenon Container, PB-X150 Xenon Container or PB-X750 Xenon Container. Electricity can be obtained using solar panels, radioisotope batteries (RTGs), and fuel cells. 

Solar panels are recommended in this case, however RTGs are very efficient when traveling to far distances such as Jool and Eeloo. The amount of electricity needed to keep one ion engine running at full thrust is roughly equivalent to half the output of one Gigantor XL Solar Array (however one array will power two engines only near peak sun exposure around Kerbin), 6 Fuel Cells, 12 PB-NUK Radioisotope Thermoelectric Generators, or 25 OX-STAT Photovoltaic Panels at peak outcdput. 

When pairing with solar panels, it is highly recommended to bring more than it needs (slightly less than 9 Ec/s). Not all panels are at peak output during operations, and maximum available power falls of with the square of the distance from the star.

Batteries can be used to store the electricity since there may be times the solar panels will be blocked from the Sun by objects or the dark side of celestial bodies. For extended burns in the darkness the fuel cells happen to be a good choice. When the power is provided by the fuel cells the majority of the mass flow (about 69.2%) is liquid fuel and oxidizer used by the fuel cell. 

Thus the ion engine powered by the fuel cell may be seen as having much more modest but still impressive effective Isp of 1293 sec. However if the burn doesn't take more than a couple of hours the stack of RTGs providing the same amount of power (and thus thrust) tend to be heavier than the fuel cell array and its fuel tank. The RTGs should be reserved for very long low-thrust burns in the deep space.  READ MORE...