An anonymous reader writes "The United States, since the 1980s, has been trying to make missile defense work. Billions of dollars spent, tons of political capital spent, and not a lot to show. The U.S. does have two viable options: the SM-2 and SM-3, although neither are perfect. The U.S., with European allies, has been deploying missile defense in Europe to block a possible strike from Iranian nuclear tipped missiles (even though they have not made nukes or the missiles to carry them). One problem: such defenses could, in theory, also block Russian and Chinese missiles. Russia is now planning to make more missiles to counter such defenses and could pull out of the New Start Treaty. They may also stop helping U.S. forces to supply themselves in Afghanistan. Is this all worth it for something that might not even work?"