Jeffrey LewisPhysics 101: Boost Phase Missile Defense and the Shortfall Problem

Taylor Dinerman writing with a crayon over at The Space Review says:

“In the case of boost-phase weapons, the debris will fall back on the nation that launched the missile.”

Fall back? What kind of non-ballistic trajectory is that missile on? It’s called Newton’s first law of motion. Look into it.

Whatever debris remains will fall forward including the warhead, likely killing plenty of people where it lands. In some cases, according to Geoff Forden (see chart below), murdering more people than the terrorists on September 11, 2001.

Of course, many of those people are in Turkey, Europe and Canada for a missile traveling from Iran (Russia, China and Canada for one traveling from North Korea), so perhaps they don’t count for Mr. Dinerman. For detailed discussions of the “shortfall” problem—as in the warhead falling short, not Dinerman’s high school physics education—see:

  • Geoffrey Forden, “Laser defenses: What if they work?” Bulletin of Atomic Scientists, 58:5 (September/October 2002_: 48-53.
  • Report of the APS Study Group on Boost-Phase Intercept Systems for National Missile Defense (July 15, 2003): 96-99.


  1. Stephen Moore (History)

    I’ve just recently discovered this blog—great work.

    This shortfall problem certainly concerns me as a Canadian. Our government is trying to sell us on joining up with this missile scheme by telling us we need to be “at the table” when important decisions are made. They don’t tell us about the shortfall problem, that’s for sure.