Environmental and antinuclear activists have found a new enemy: the space program. The Cassini space probe to Saturn, scheduled for an October 6 launch from Cape Canaveral, is the target of an impassioned campaign of protests and grassroots lobbying -- a campaign marked by technological naivete and political paranoia. If the activists succeed, they will cripple not only the Cassini mission but space exploration in general.
Cassini is one of the most ambitious projects to date in planetary science, a $ 3.2 billion joint venture of NASA, the European Space Agency, and the Italian Space Agency. Reaching Saturn's orbit in 2004, Cassini will spend four years in close-up observation of the ringed planet, previously explored only by fly-by probes. A smaller probe will detach from the orbiting Cassini and descend toward Saturn's moon Titan, whose atmosphere, rich in organic molecules, may provide clues to the early evolution of life on Earth.
The controversy arises from the spacecraft's use of nuclear energy to power its scientific instruments. Similar to previous deep-space missions such as the Galileo probe to Jupiter, Cassini will carry a set of special generators that take the heat given off by the natural radioactive decay of plutonium- 238 and convert it to electricity. Such devices differ from nuclear reactors, which generate heat and electricity by initiating chain reactions. The spacecraft will also contain tiny heaters to protect its instruments in the cold of interplanetary space, and these, too, use the natural heat of decaying plutonium. Altogether, slightly more than 72 pounds of radioactive material will be on board.
Nuclear energy, it should be noted, is only being used as a glorified set of batteries, not as Cassini's means of propulsion. The spacecraft will be launched aboard an ordinary rocket using ordinary rocket fuel, and it will then proceed on a circuitous route through the solar system, using the gravitational "slingshot effect" as it passes Venus (twice), Earth, and Jupiter to speed it on its way to Saturn. (Without such "gravity assists," missions to the outer planets would take decades or more.)
According to Cassini's opponents, though, the mere presence of plutonium means the spacecraft could endanger the lives of millions -- perhaps even billions -- by spreading radioactive material in the event of an accident at launch or during the planned August 1999 fly-by of Earth. "What we are talking about here -- and I use this word advisedly -- is a holocaust in the making," said Karl Grossman, a State University of New York journalism professor, opening a recent presentation on Cassini at the Learning Alliance, a self-described "progressive education and organizing center" in New York's East Village.
Why would NASA do such a thing? Cassini's critics insist that the agency is ignoring viable solar-power alternatives. And that's because the nominally civilian, scientific mission to Saturn is actually a crucial step in the Pentagon's plans to develop "nuclear-powered battle stations in outer space," in the words of physicist and popular author Michio Kaku, Grossman's co- presenter at the lecture.
This bleak view is actually gaining currency beyond the leftist fever swamps of the East Village. Groups with names like Food Not Bombs and the Florida Coalition for Peace and Justice are planning "non-violent" sit-ins on the launch pad in October. Protest rallies are scheduled for September in New York and Washington, and a call-in campaign has begun that aims to periodically tie up the White House switchboard. Nor is such activity directed only at the government. At the Learning Alliance presentation, a sign-up sheet was passed around for a sit-in at the headquarters of the New York Times. Why? Because the establishment media have refused to cover the Cassini story. Indeed, Cassini was labeled this year's "most censored" story by a left-wing panel called Project Censored.
Thus it has been left to magazines such as the Nation and Covert Action Quarterly to spread the antiCassini message (not to mention the several Web sites devoted to fighting the spacecraft). Grossman, creator of a film documentary titled Nukes in Space: The Nuclearization and Weaponization of the Heavens, lectures widely on Cassini, sometimes accompanied by Kaku, a onetime Edward Teller protege who now campaigns against nuclear energy and space weapons. In Florida, demonstrations against the launch have already begun.
It is tempting to dismiss the anti-Cassini movement as a product of the political fringe. But at a time of widespread public aversion toward nuclear energy, and ambivalence about esoteric and expensive "rocket science," the demonization of the "plutonium probe" just might strike a chord with politicians and the public. And the well-publicized foul-ups and bureaucratic bumbling of NASA's recent history make it uncertain that the space agency can carry the day with public opinion, as it should be able to do with ease in this case.
Because despite the protest chants and "holocaust" rhetoric, the case against Cassini is exceedingly weak. Indeed, the case is unconvincing in all its major points -- ranging from the dangers of a plutonium release, to the availability of a solar-power alternative, to the military relevance of Cassini's nuclear devices. The anti-Cassini movement thrives on gross exaggerations of risk, bolstered by out-of-context quotes from NASA's and the European Space Agency's own publicly available documents.
One such document is a 1995 environmentalimpact statement for the mission. At the Learning Alliance, Grossman handed out copies of one page from this massive volume, with key phrases underlined; the gist is that "approximately 5 billion people" or "most of the world population" could experience " radiation exposure" in the event of an "inadvertent reentry" -- if Cassini were to collide with Earth or be burned up in the atmosphere -- during the 1999 fly-by. Sounds horrible. But consider:
Such a "reentry," first of all, is wildly unlikely; NASA places its probability at less than 1 in 1.2 million. For Cassini to return to Earth, the spacecraft would have to experience a precisely timed malfunction or collision with a passing micrometeoroid, throwing it off target by hundreds of miles in exactly the right direction and magnitude, and damaging Cassini so severely that neither its automated navigational systems nor its ground controllers could alter the probe's new course in the slightest.
Moreover, even if all this did happen, the consequences would be far from a doomsday scenario involving "most of the world population." True, the plutonium would likely vaporize and be scattered throughout the atmosphere, but it would be like the proverbial spit in the ocean. The casualties might total some 120 additional cancer fatalities worldwide over a 50-year period, according to an estimate by NASA and the Energy Department. Even this number may be an overstatement. It is unclear whether the expected extra dose of radiation would have any health effects whatsoever. At about 1 millirem per person over 50 years, it's a tiny fraction of the radiation already present from cosmic rays, radon, and other sources.
The Earth fly-by is only one of the "two key periods of extreme danger," in the words of the Florida Coalition for Peace and Justice. The anti-Cassini movement also focuses on the risks of an accident during or shortly after launch. Here, of course, the possibility of an accident is not absurd; rockets sometimes explode or otherwise malfunction, and NASA's own analysis puts the risk of a plutonium release during the mission's early phases at around 1 in 350. But the consequences would be extremely limited; the official estimates of casualties from such a release are decimal figures less than one, which is to say: nobody.
Multiple precautions reduce the risks involved in a launch accident. Cassini, for one thing, will be located near the nose cone of the Titan IV rocket that lifts it into space, far from its rocket boosters. Inside the probe, the plutonium will be shielded by highstrength graphite and heat- resistant iridium. The rocket will be over water during most of its ascent, isolating it from populated areas and reducing the danger of a hard landing. Furthermore, plutonium -- although sometimes described as the "most toxic substance known to science" -- in fact poses little danger to humans except in the form of tiny particles that can be inhaled; Cassini's plutonium dioxide will be in a ceramic form, unlikely to be smashed into such tiny pieces.
Of course, the safety analyses by NASA and other agencies could be wrong. If so, the mission's critics have done a remarkably poor job of documenting the errors and providing alternative analyses. Grossman frequently cites Dr. Ernest Sternglass, a longtime antinuclear activist and professor emeritus at the University of Pittsburgh School of Medicine, who claims that the death toll from a fly-by accident may be 30 to 40 million. But Sternglass has failed to respond to formal NASA requests that he substantiate this estimate. Far from discrediting the professor, this silence seems to have enhanced Sternglass's reputation among Cassini's opponents.
The notion that the spacecraft could use solar panels rather than nuclear energy is also unsubstantiated. Grossman hands audiences copies of an April 1994 European Space Agency press release announcing the development of "high- efficiency solar cells for use in future demanding deep-space missions," such as a planned comet probe called Rosetta. Not cited by Grossman is an August 1996 memo by the same agency, which concludes that even high-efficiency solar cells would be too weak for Cassini, operating nearly three times farther from the sun than the Rosetta spacecraft.
Indeed, Cassini would require solar arrays so large, heavy, and unwieldy that the spacecraft would be difficult to launch, let alone send to Saturn for scientific observations. But a blind faith in technology -- so long as it is solar technology -- pervades the anti-Cassini movement.
Could NASA's insistence on nuclear energy for Cassini be motivated by military considerations? Perhaps the space agency is secretly working toward the "nuclear-powered battle stations" of Kaku's warnings. According to the physicist: "What we are headed for is a nuclear-propelled rocket with nuclear- propelled lasers in outer space. That's what the military and that's what NASA would really like to do."
Besides the suspension of disbelief they require, such concerns are hard to reconcile with this fact: Cassini's nuclear generators will produce a mere 800 watts of electricity -- less than is used by a dozen common household light bulbs. The spacecraft's instruments are designed to require a remarkably modest power supply, but one that will operate reliably during a 12-year mission in deep space. Plutonium is ideal for this purpose. But Cassini will be a very poor trial run for any future military mission (unless the enemy is extraterrestrial).
In a different sense, however, the anti-Cassini forces are right: The probe is indeed part of a broader "nuclearization" of space. In fact, it is hard to see how the civilian space program could proceed if -- as the activists demand -- all use of nuclear power in space comes to an end. Nuclear energy is not only an excellent power source for deep-space scientific missions; it is also the key to a future human presence on Mars, the moon, and elsewhere in space.
Establishing a base on Mars, for example, would require compact, lightweight energy sources -- probably nuclear generators or reactors. (Massive solar arrays might eventually be built but would be impractical during the base's early phases.) In the longer run, a Mars colony might thrive on exports of deuterium, a substance useful to today's nuclear industry and essential for future nuclear-fusion reactors. As for nuclearpropelled rockets, they would rapidly accelerate transportation between Earth and Mars, as well as to more distant parts of the solar system.
Such visions, of course, are anathema to antinuclear activists. Yet space exploration holds vast potential for protecting Earth's environment. Mining and other polluting industries eventually might be relegated to the asteroid belt and other remote places, far removed from human populations. More mundanely, satellites and space probes provide valuable clues to climate change and other environmental processes on Earth.
The space program has long enjoyed broad public support, with controversy largely limited to questions of cost and practicality. With the Cassini mission, NASA now faces its first pitched battle with the antinuclear and environmental Left. It is not likely to be the last.
Kenneth Silber, a freelance journalist, has written about space technology for Commentary, Insight, Reason, and other publications.