SIFT's Joseph Mueller Appears on The Science Channel

Dr. Joseph Mueller was interviewed recently on "NASA's Unexplained Files", a new TV show for science buffs and NASA enthusiasts that is now airing its second season on the Science channel.

Dr. Mueller discussed the unique capabilities of electric propulsion and its role in future manned missions to Mars. Historically, spacecraft have utilized chemical propulsion to perform large orbital maneuvers. The thrust produced from the chemical reaction (typically Hydrogen reacting with Oxygen) is applied over a short time, causing an impulsive change in the velocity and thereby placing the spacecraft on a new orbit. For a manned mission to Mars, chemical propulsion becomes impractical for two main reasons: 1) The propellant mass required to achieve the necessary orbit transfers is too high, especially considering that all of the propellant for the return trip must be carried along. 2) The corresopnding orbit transfers involve long coast times, which lengthens the mission -- this means more supplies to sustain the astronauts, and more radiation exposure. The only viable way to send humans to Mars and back is to use electric propulsion -- sometimes called "ion-drives" or "ion-engines" -- where a small thrust is produced continuously with much less propellant. The spacecraft is constantly accelerating (or decelerating), using solar radiation as an energy source to drive the engine. Bottom line: a lighter propulsion system, and a faster mission.

Portions of his interview were aired over two different episodes (episode 2 on March 1, and in episode 7 on April 5). Selected segments of NASA's Unexplained Files can be viewed online at

Dr. Mueller is also an adjunct faculty member in the Aerospace Engineering department at the University of Minnesota. He teaches dynamics, orbital mechanics, and spacecraft design.