From the earliest uses in 1959 of the intercontinental ballistic missile (ICBM), which is designed to deliver nuclear weapons, the U.S. has been working on methods that would protect people from such an attack. Yet decades later, the country still has only a flawed system that most experts believe would not reliably protect Americans against a nuclear attack, said Philip E. Coyle III, a senior science advisor with the Center for Arms Control and Non-Proliferation and the former director of operational tests and evaluation with the Pentagon, who has extensively evaluated missile defense systems.