On the Defensive Regarding your November article on missile defense ["Shield of Dreams"]: If this idea is implausible, why did we sign an antiballistic missile treaty in 1972? Did ABMs work better 30 years ago? Why wouldn't an interceptor with a thermonuclear warhead knock out an incoming group of warheads or dummies? One day an American city will disappear along with 10 million people, and those who opposed defending against these things will be held in the same high esteem as the leaders of Western Europe in the late 1930s.
Winston Anderson—Campobello, South Carolina
Tim Folger responds: About 30 years ago the United States developed nuclear-armed interceptors to destroy enemy missiles. The system, called Safeguard, was abandoned when we realized that the nuclear explosion intended to knock out enemy missiles would generate an electromagnetic pulse that would blind our defense's communication and radar for several minutes, leaving us vulnerable to a second attacking wave. Building an improved version of Safeguard would have required redesigning radar, communications, and satellites to withstand a nuclear blast—a costly proposition with unthinkable consequences if the system proved unreliable. And by deploying nuclear-armed interceptors, we would probably start a more dangerous arms race than the one we left behind when the cold war ended.
Plug In, Turn On, Pay Up I think I understand why Amory Lovins believes building a hydrogen economy can be profitable at every stage ["Lovin' Hydrogen," November]. On one hand, he predicts private citizens plugging their vehicles into a hydrogen source and producing electricity for sale to the power grid, allowing the car to pay for itself by turning hydrogen into electricity. On the other hand, he claims that utilities could charge five to seven times more for hydrogen than they could for the electricity they used to make the hydrogen. Anyone can make any amount of money they wish by simply converting hydrogen to electricity and back again. Lovins has been awarded seven honorary doctorates; I doubt any were in economics. As a physicist, he should know better than to try to sell perpetual motion.
Ben Curtis—Pasadena, California
Amory Lovins responds: I've taught and published in economics, but that's not needed here. The five- to sevenfold increased value is in turning electricity into hydrogen to propel a car (versus $1.25 for a gallon of gas), not to make electricity for resale. Most hydrogen will be made not from electricity but from cheaper natural gas, at half the capital intensity of sustaining existing gasoline infrastructure. Yet electricity-to-hydrogen-to-electricity conversion can save fuel and money without perpetual motion: The generation used is three to four times more efficient than that displaced and often recaptures waste heat. Please see our April 1999 National Hydrogen Association paper "A Strategy for the Hydrogen Transition," at www.rmi.org/ images/other/HC-StrategyHCTrans.pdf.
A Place for Everything . . . It was interesting to see Terry Evans's photo of the plant Verbascum thapsus, a Eurasian weed, being "returned" to its original place on the Tallgrass Prairie Preserve in Oklahoma [Reviews, November], because its home is actually Europe and Asia. It may look photogenic in a meadow, but it is an ecological threat to North America's native perennial grasslands. When we reassess our relationship to nature, we need to have a deeper understanding of what makes up our natural surroundings in order for those assessments to have any meaning.
Craig C. Dremann—Redwood City, California
