Science Seminars

What is the Pu-238 Supply Issue and Why Should You Care?

Speaker: Ralph McNutt, Jr., Applied Physics Lab, The Johns Hopkins University
Date: Wednesday, Jan 18, 2012
Time: 4:00 PM to 5:00 PM
Location: LSTB-299, Auditorium

Seminar Abstract:

Most commercial, military and research satellites today have power systems that run from solar energy via solar cells with battery backups for eclipse periods. This type of power systems runs the gamut from small satellites to commercial broadcast satellites up to the International Space Station itself. However, this was not always the case, and, more importantly, for many important future locales in deep space exploration, ranging from Europa in Jupiter’s radiation belts, to the Ice Giants of Uranus and Neptune, to long lived missions to the surfaces of the Moon, Mars, and Venus, as well as other locales, solar illumination is inadequate to do the job. For other 50 years, the alternative has been the use of radioisotope thermoelectric generators (RTGs), producing electricity from the radioactive decay heat of the rare, artificial isotope plutonium-238 (Pu-238). Some of the most important – and scientifically productive – space missions have been enabled by RTGs including the Pioneer 10 and 11, Voyager 1 and 2, and New Horizons missions to the outer planets and the space beyond, the Galileo and Cassini orbiters of Jupiter and Saturn, the Viking 1 and 2 landers and the Mars Science Laboratory MSL) to Mars and the Apollo Surface Experiments Package (ALSEP) left by Apollo crews on the Moon. Many future space exploration missions – including many put forth in Vision and Voyages for Planetary Science 2013 – 2022, the recent planetary “Decadal Survey” – are enabled by such power supplies, that is, in their absence, these missions simply cannot be carried out. Yet there is, potentially, an acute shortage of the critical Pu-238 fuel, and much of the future of planetary exploration is in jeopardy. How the U.S. Space exploration program has come to such straits is a complicated story of physics, chemistry, technology, politics, money, and policy split amongst NASA, the Department of Energy and its precursors, and multiple Administrations and Congresses. Why there are no alternatives and what is being done will be discussed, along with why no one interested is space exploration should be breathing easily – and likely not for quite a few years to come.

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