The plutonium threat in orbit



The plutonium threat in orbit

The US National Aeronautics and Space Administration launched the Cassini spaceship on October 15, 1997, on a seven-year mission to study the planet Saturn, purportedly in the hope of "understanding the birth and evolution of our solar system". But by using 32.8 kilos of radioactive plutonium to run Cassini's 740-watt instrument panel, NASA created the possibility of unspeakable disaster for our own planet.

NASA plans to accelerate Cassini by using Earth's gravitational field; on August 18, the space ship will approach Earth in a so-called "fly by" at a velocity of 16 kilometres per second. NASA claims that the odds of the spaceship entering our atmosphere are one in a million. But there is important evidence showing that NASA has seriously underestimated the possibility of human or equipment error — and the potential danger of any accident during the fly by manoeuvre.

The Jet Propulsion Laboratory, for example, in May 1997 reported 18 different types of malfunctions that may occur, including electrical short-circuits, meteors or space debris striking the space probe and erroneous ground commands. If the craft does veer from its course even slightly, Cassini could plunge into Earth's atmosphere and burn up like a meteorite.

Cassini is carrying the isotope plutonium 238 which, because of its shorter half-life, according to physicist Dr Kai Petzke from the Technical University of Berlin, is about 280 times more radioactive than the well-known bomb material Pu-239.

Major flaws in NASA's environmental impact statements were exposed by the Nuclear Safety Review Panel, appointed to study the safety of Cassini. Federal regulations require a separate evaluation whenever radioactive material is introduced into space.

The panel was made up of representatives from the US Environmental Protection Agency, Department of Energy, Department of Defense, Nuclear Regulatory Commission and NASA. In its July 1997 safety evaluation report, the panel noted at least three major discrepancies.

The most astounding error is that NASA claimed the plutonium containers were "designed to withstand re-entry" into our atmosphere. In fact, the report noted, these holders were not designed to withstand the heat of an accidental re-entry at 64,000 kilometres per hour.

Second, NASA claimed that almost none of the plutonium could become airborne in any accident. In contrast, the safety evaluation report noted that nine kilograms could become airborne in respirable form, the only hazardous state.

Third, NASA estimated that in the event of an accident, the plutonium could cause 120 fatal cancers. The report estimates that "tens of thousands" of such deaths could result from a major accident.

While NASA based its figures on the cancer-causing potential of plutonium in the dose from general ionising radiation, the report noted "the probability of a single inhaled particle inducing a cancer". NASA ignored this probability in all its environmental impact statements, although it was reported in the proceedings of the National Academy of Sciences (April 1997) from experiments financed in part by NASA.

Moreover, even the safety evaluation report's fatality estimate could fall far short of the truth. The report fails to mention that each kilogram of plutonium contains trillions of radioactive atoms; the number of fatal cancers might be many times greater than tens of thousands.

What are the chances of the Cassini space probe entering Earth's atmosphere? NASA claims the odds are one in a million, but according to Dr Michio Kaku, that figure is based solely on the chance of an impact with a meteor in outer space. Far greater risks are posed by mishaps such as lost radio contact or misfired rockets. Kaku calculates the chance of a Cassini Earth fly by error at about 10%.

NASA has taken frightening chances from the beginning of this mission. For example, the Titan IV rocket it used to launch Cassini now has a 12% failure rate on lift-off. On April 10, military officials admitted to another mishap; a US$250 million missile-warning satellite ended up in the wrong orbit following its launch aboard an air force Titan rocket. To date there have been nine documented space program accidents that released plutonium into our environment.

Cassini is expected to be travelling around 16 kilometres per second for 55 days from Venus toward Earth, beginning on June 24, during the height of solar flare activity. It is expected that a solar eruption, possibly the most severe in this century, will happen anytime between now and January 2001.

A solar eruption during its last highpoint cycle in 1989 knocked out power for 6 million Canadian households and businesses. Such an impact on Cassini would fry its communications systems.

We are reaching a point of no return, but it is still possible to redirect the probe away from Earth and towards the sun. A petition was drafted by the Cassini Redirect Coalition calling on heads of state and other national leaders to raise demands in the United Nations and International Court to stop Cassini's Earth fly by.

For more information, contact Jonathan Mark at <> or visit the Action Site to Stop Cassini Earth Flyby at <>.