64 Scientific American, June 2019The president was expressing extraordinary faith in the
Ground-based Midcourse Defense (GMD) system, currently the
country’s sole guard against intercontinental ballistic missiles
that carry nuclear warheads. But his faith was woefully misplaced,
and facts belie his claim. U.S. military testing data show there is
no basis to expect GMD interceptors to work more than about
50 percent of the time. Using multiple interceptors against each
target could in some cases improve these odds but will not funda-
mentally change the situation. The chances of a nuclear weapon
getting through in a real-world attack using multiple missiles is
still dangerously high. Our analysis of all 19 tests done—the most
recent one was in late March—as well as several government re-
views of the program, shows an alarmingly high failure rate.
The problems with these interceptors can be traced back de-
cades, to the beginnings of the program, because the Pentagon
rushed to develop it and abandoned tried-and-true oversight
and testing requirements that have been used for most major
weapons. Plus, the system is vulnerable to defense-penetrating
countermeasures that any country capable of building a long-
range missile could take. Yet the Pentagon is moving to expand
the troubled interceptor fleet despite already spending more
than $40 billion to produce these unreliable results.
THE ARMS RACE
thE world has been living under the threat of nuclear-armed in-
tercontinental ballistic missiles (ICBMs) since the late 1950s.
Two nuclear-armed nations, the former Soviet Union and the
U.S., were desperate to deter each other from using these weap-
ons. Both built more missiles, armed with multiple warheads, to
overwhelm any response the other country might be able to
mount. This cycle of action and reaction resulted in the rapidly
growing potential for mass destruction.
Eventually U.S. and Soviet leaders recognized the dangers of
this tit for tat, and in 1972 they signed the first Strategic Arms Lim-
itation Treaty (SALT I). They also agreed to the Anti-Ballistic Mis-
sile (ABM) Treaty, which strictly limited defenses against long-
range missiles and served to break the cycle of defensive advances
prompting the other side to improve its offense. These arms-con-
trol agreements and those that followed did the job. The break-
neck growth of the U.S. and Soviet nuclear arsenals peaked in 1986
at more than 60,000 weapons, and three decades of arms reduc-
tions have brought that number down to fewer than 10,000 today.
While the stockpiles were still high, in 1983, President Ronald
Reagan—driven by distrust of the Soviets and faith in new tech-
nologies—tried to revitalize missile defense and announced the
Strategic Defense Initiative, or “Star Wars.” His vision was based
on nonexistent and impractical innovations, such as space-based
lasers powered by nuclear explosions, and after a while plans for
the system were scrapped.
But research on strategic missile defense technology continued
as new threats emerged. North Korea’s pursuit of nuclear weapons
and ballistic missiles, which became apparent in the 1990s, pro-
vided a fresh argument for strategic defenses that took advantage
of improvements in missile tracking and interceptor guidance.
Still, limitations of the technology, skepticism about the magni-
tude of the threat, and concerns that deploying defenses would
threaten the successful and ongoing arms-reduction process led
the Clinton administration to respect the ABM Treaty limits.
Then, on September 11, 2001, everything changed. In the polit-
ical environment following the attacks on the World Trade Cen-
ter in New York City and the start of the “war on terror,” oppo-
nents of missile defense found it difficult to argue against any
military programs. Congress could muster only limited debate on
arms control. In late 2001, citing a potentially growing threat
from rogue nations and terrorism, the George W. Bush adminis-
tration announced that the U.S. would withdraw from the ABM
Treaty. Then the government said it would rush ahead with a
plan to build a missile defense system. The era of negotiated lim-
its on missile defenses was over.THE INCOMING THREAT
dEstroying an ICBM’s warhead is not easy. These missiles launch
thousands of kilometers from their targets, accelerated by pow-
erful engines in what is called their boost phase. Within minutes
they reach speeds of about 25,000 kilometers per hour and then
can release multiple warheads that arc through the vacuum of
space. After about half an hour of this midcourse flight, they re-IN BRIEFFor more than a decade the U.S. has been testing
a system to intercept incoming nuclear missiles.
It shows alarming unreliability and vulnerability.Problems stem from a rush to deploy the system,
called the Ground-based Midcourse Defense, and
abandonment of standard quality controls.These interceptor missiles have already been put
in the field and greatly add to global nuclear risks
while offering minimal protection.© 2019 Scientific American © 2019 Scientific American