Since the dawn of the space age more than fifty years ago, nuclear power systems have been used for many long duration missions. While these technological systems made possible a myriad of accomplishments in space, especially the successful flights to the outer planets, controversies surrounding the propriety of using space nuclear power sources have periodically arisen and enraged the public. This paper will analyze the use of this technology to power spacecraft and the public debate over its employment.

For the first decade and a half of space nuclear power the public, even though it had an interest in the risk nuclear systems portended, did not register serious misgivings about the use of this technology in space. This changed rather dramatically in the later 1970s in response to two incidents, the 1978 the Soviet Cosmos 954 accident which spread radioactive debris over more than 100,000 square km in Canada and the 1979 Three Mile Island nuclear power plant accident. Accordingly, support for the use of nuclear power in any setting quickly eroded.

Since that time every American space mission—of which there have been six—that used some type of nuclear system elicited important protest efforts. The first example came with the deployment of the Galileo probe to Jupiter in 1989. Because of Galileo’s deployment from the Space Shuttle, it would only be able to reach Jupiter using a gravity assist trajectory that required it to pass close to Venus and have two swings past Earth before sling-shotting on to Jupiter. The possibility for Galileo’s uncontrolled reentry into the Earth’s atmosphere on one of its flybys added to other concerns. Protesters had a point, Carl Sagan, agreed: “there is nothing absurd about either side of this argument.”

Such has remained the case to the present. The launch of the Mars Science Laboratory on November 26, 2011, is only the most recent example of this longstanding debate. This paper will discuss and analyze this issue of the use of nuclear power systems for spacecraft engaged in scientific pursuits.