Nuclear waste in space?
by Jonathan Coopersmith
|Where would this much new cargo come from? Fortunately, there is an answer. Unfortunately, it’s not intuitively attractive, at least at first glance: it’s high-level nuclear waste.|
Because of the obvious and real concern about moving such dangerous material anywhere, let alone into space, this proposal justly raises the question of safety. Can nuclear waste be safely launched into earth orbit? The answer is yes. By keeping the launch system on the ground instead of putting it on the vehicle, designing and building unbreakable containers, and arranging multiple layers of safety precautions, we can operate in a judicious and safe manner.
The problem of nuclear waste disposal is real, especially for future generations. Leaving radioactive wastes on earth creates permanent and tempting targets for terrorism as well as threatening the environment. We have a moral imperative to solve this problem now so we do not burden our children and their children.
For twenty years, the federal government’s preferred solution to the nuclear waste problem is underground disposal, specifically, over 11,000 30–80 ton canisters buried in 160 kilometers of tunnels hundreds of meters underneath Yucca Mountain in northern Nevada. Forty-nine states favor this plan. It’s not hard to guess which state does not.
To be fair to Nevada, any site would draw the same objections from anybody who lost this lottery, yet policymakers remain stuck on the idea of burial. Nevada’s fears are justified: researchers cannot guarantee complete environmental isolation for the thousands of years needed for these wastes to decay harmlessly. A recent report by the Government Accountability Office raised nearly 200 technical and managerial concerns about the site. Even the promise of construction and maintenance jobs has failed to sway a skeptical public.
Historically, garbage has been something to bury or recycle. Consequently, nuclear waste disposal has remained the province of the geologists, who are professionally inclined to look down, not up. That’s shortsighted. The permanent elimination of high-level radioactive waste demands a reconceptualization of the problem. We need to look up, not down. Let’s put high-level radioactive waste where it belongs, far out in space where it will not endanger anyone on earth.
Neither the space shuttle nor conventional rockets are up to this task. Not only are they expensive, but they lack the desired reliability and safety as insurance rates demonstrate. Instead, we need to develop a new generation of launch systems where the launcher remains on the ground so the spacecraft is almost all payload, not propellant. As well as being more efficient, ground-launched systems are inherently safer than rockets because the capsules will not carry liquid fuels, eliminating the in-flight danger of an explosion. Nor will the capsules have the pumps and other mechanical equipment of rockets, further reducing the chances of something going wrong.
|We need to develop a new generation of launch systems where the launcher remains on the ground so the spacecraft is almost all payload, not propellant.|
How would disposal of nuclear wastes in space actually work? In the simplest approach, a ground-based laser system will launch capsules directly out of the solar system. In a more complicated scheme, the laser system will place the capsules into a nuclear-safe orbit, at least 1,100 kilometers above the earth, so that they could not reenter for several hundred years at a minimum. Next, a space tug will attach the capsules to a solar sail for movement to their final destination orbiting around the sun, far, far from earth.
The underlying concept is simple: the launcher accelerates the capsule to escape velocity. Like a gun, only the bullet heads toward the target, not the entire gun. Unlike a shuttle or rocket, ground systems are designed for quick reuse. To continue the analogy, the gun is reloaded and fired again. These systems would send tens or hundreds of kilograms instead of tons into orbit per launch.
Of the three possible technologies—laser, microwave, and electromagnetic railguns—laser propulsion is the most promising for the next decade. In laser propulsion, a laser beam from the ground hits the bottom of the capsule. The resultant heat compresses and explodes the air or solid fuel there, providing lift and guidance. Although sounding like science fiction, the concept is more than just an elegant idea. In October 2000, a 10-kilowatt laser at White Sands Missile Range in New Mexico boosted a two-ounce (50 gram) lightcraft over 60 meters vertically. These numbers seem small, but prove the underlying feasibility of the concept.
American research, currently at Rensselaer Polytechnic Institute in New York with previous work at the Department of Energy’s Lawrence Livermore National Laboratory in California, has been funded at low levels by the United States Air Force, NASA, and FINDS, a space development group. The United States does not have a monopoly in the field. The four International Symposiums on Beamed Energy Propulsion have attracted researchers from Germany, France, Japan, Russia, South Korea, and other countries.
The long-term benefit of a ground-based system will be much greater if it can ultimately handle people as well as plutonium. Dartmouth physics professor Arthur R. Kantrowitz, who first proposed laser propulsion in 1972, considers the concept even more promising today due to more efficient lasers and adaptive optics, the technology used by astronomers to improve their viewing and the Air Force for its airborne anti-ballistic missile laser.
Where should the nuclear waste ultimately go? Sending the capsules out of the solar system is the simplest option because the laser can directly launch the capsule on its way. Both Ivan Bekey, the former director of NASA’s of Advanced Programs in the Office of Spaceflight, and Dr. Jordin T. Kare, the former technical director of the Strategic Defense Initiative Organization’s Laser Propulsion Program, which ran from 1987-90, emphasized solar escape is the most reliable choice because less could go wrong.
A second option, a solar orbit inside Venus, would retain the option of retrieving the capsules. Future generations might actually find our radioactive wastes valuable, just as old mine tailings are a useful source of precious metals today. After all, the spent fuel still contains over three-quarters of the original fuel and could be reprocessed. Terrorists or rogue states might be able to reach these capsules, but if they have that technical capability, stealing nuclear wastes will be among the least of our concerns. This approach is more complex, demanding a temporary earth orbit and a solar sail to move it into a solar orbit, thus increasing the possibility of something going wrong.