I was surprised that in their otherwise excellent article “The Continuing Debate on National Missile Defenses” Lisbeth Gronlund, George N. Lewis, and David C. Wright (Physics Today, December 2000, page 36) did not mention one of the more serious problems associated with the NMD system as currently envisaged: The ground-based interceptor (GBI) rockets it will use are about the size of the proposed small intercontinental ballistic missile of the 1980s and will have similar launch signatures and flight characteristics. Since the NMD firing doctrine will require multiple (probably two to four) GBI launches per credible target—that is, disguised warheads and decoys—even a small rogue-country attack against the US could involve the salvo firing of dozens of GBIs. Add to this a possible attack from the Middle East that might necessitate firing the interceptors on a course toward western Russia (especially if the interceptors were based in North Dakota), and one begins to worry about the capability of Russia’s decaying missile warning system to make a timely and correct assessment of the situation.

If the US proceeds with NMD, it should consider measures to lessen the chances that Russia, detecting what could seem to be a US surprise attack, would launch its missiles in defense. Sharing early-warning data, as is now being discussed, would be a good start, but providing Russia with an ability to monitor NMD communications channels and the right to inspect GBIs should also be considered.