Goddard Space Flight Center, Greenbelt, Maryland 20771

ENGINEERING COLLOQUIUM

Monday, October 4, 2004 / 3:30 PM, Building 3 Auditorium

Franklin Chang-Diaz

"VASIMR: Mars in Four Months"

ABSTRACT -- The Variable-Specific-Impulse Magnetoplasma Rocket (VASIMR), currently under development at the Johnson Space Center's Advanced Space Propulsion Center, may be able to reduce travel times to Mars to as little as four months. The system uses radio waves to ionize and heat a plasma, which is then confined and directed by a series of superconducting magnets.

Unlike conventional rockets, which get their energy from the chemical reactions of the propellants, VASIMR gets its energy from electricity. Thus, VASIMR is an electrically powered propulsion system, like the more familiar ion engine. One disadvantage of ion engines, and other electric and magnetic drives, is that some mechanical parts are in direct contact with the propellant, and can be damaged over time. In VASIMR, however, this problem does not occur, because the plasma is confined by magnetic fields. Even the nozzle is a magnetic field, rather than a mechanical object.

Another advantage of VASIMR is that it can be throttled by adjusting the energy input and the magnetic fields. Thus, to leave Earth orbit and start on an interplanetary trajectory, VASIMR could be throttled up to maximum thrust. While between planets, however, VASIMR could be throttled back to a low thrust, high specific impulse (high efficiency), setting. Over the days, weeks, and months of an interplanetary voyage, a continuous thrust, even a small one, can greatly increase speed and reduce travel time.

SPEAKER -- Dr. Franklin Chang-Diaz has had an adventurous life. He arrived in the United States in 1968 from Costa Rica, as a high-school student with $50 in his pocket and very little English in his vocabulary. In 1973, he graduated from the University of Connecticut with a bachelor's degree in mechanical engineering. In 1977, he graduated from the Massachusetts Institute of Technology (MIT) with a doctorate in plasma physics. After graduation, he joined the Charles Stark Draper Laboratory, where he worked on control systems for fusion reactors. While there, he developed a novel concept for guiding fuel pellets for an inertial fusion reactor chamber. In 1980, Dr. Chang-Diaz was selected by NASA for the astronaut corps. He has flown on seven Shuttle missions. On STS-111, he performed three EVAs to help install the Canadian Mobile Base System to the station's robotic arm. While serving as an astronaut, Dr. Chang-Diaz has worked to form closer ties between the astronaut corps and the scientific community. He started the Astronaut Science Colloquium and helped form the Astronaut Science Support Group, which he also directed. Dr. Chang-Diaz also worked as a visiting scientist at the MIT Plasma Fusion Center, leaving in 1993 to become Director of the Advanced Space Propulsion Center (ASPL) at the Johnson Space Center. His work there revolves around the Variable Specific Impulse Magnetoplasma Rocket (VASIMR), a propulsion system that could lead to greatly reduced travel times to Mars, and for which he received the AIAA's Wyld Propulsion Award. Dr. Chang-Diaz's other awards include two NASA Distinguished Service Medals and three NASA Exceptional Service Medals, as well as honorary degrees from schools inside and outside of the United States. Dr. Chang-Diaz has been involved in rehabilitation for drug abusers. His hobbies include hiking, flying sailplanes, scuba diving, and soccer.