The Solar Electric Propulsion project is dedicated to developing critical technologies to enable trips to further away destinations such as Mars or asteroids. NASA needs to reduce the cost of these ambitious exploration missions. High power and high efficiency SEP systems will require much less propellant to meet those requirements. The new system will use xenon propellant energized by electric power from solar arrays and use 10 times less propellant than a chemical propulsion system like the engines on the space shuttle.
Large Solar arrays and high power thrusters are being developed for flight into space. Compared with current systems, they will launch at weight 2 times less and use 4 times less storage for electricity produced, and will be able to withstand 4 times more radiation. SEP solar arrays must stow into very small, lightweight packages for launch and then unfurls to cover a very large area to capture enough solar energy to produce high levels of electrical power. They also need to be durable so that they can operate for a long time in places like low Earth orbit and the Van Allen radiation belt. SEP also uses electrostatic Hall thrusters instead of a chemical rocket engine. A Hall thruster uses electricity from a solar array to emit electrons from an external cathrode. Those electrons create ions as they colloide with an inert gas like xenon. An electric field accelerates the positively charged ions back into the exhaust plume of the plasma that races out of the back of the thrusters and propels the spacecraft forward. Hall thrusters can rapidly accelerate xenon ions to over 65,000 miles per hours!