within a few hundred kilometers of the
tionally feasible, it would probably cost at
defended target, which means that targets rel-
least $20 billion to acquire.
atively close to the coasts could be protected
But relying only on space-based sensors for
but targets in the middle of the country
sea-based NMD seems questionable when
would remain vulnerable. If a U.S. Navy ship
both space- and ground-based sensors are
in an overseas theater tried to destroy a missile
used for ground-based NMD. The ground-
in the ascent phase before it hit the United
based radar is presumed to be more precise
States, the ship would need to be within sev-
than the space-based sensor and can more
eral hundred kilometers of the launch point
accurately guide the interceptor to the pre-
or along the axis of flight, which means being
dicted intercept point. The space-based sen-
in the right place at the right time.
sor's "volume" of coverage for any intercept
If the SPY-1B radar is the limiting factor
will most likely be relatively large, and relying
for sea-based NMD, the obvious solution
solely on it could place undue stress on the
would be to replace the SPY-1B with a more
interceptor's on-board seeker to make the
powerful radar. The issue is whether a radar
final engagement.
with similar qualities and capabilities to the
In addition to technical and cost consider-
Army's proposed Ground Based Radar (GBR)
ations, sea-based NMD also raises some
for NMD can be packaged to fit on an Aegis
important operational questions. A certain
cruiser/destroyer, and the cost of doing so.
number of multimissile Aegis cruisers/de-
The estimated program cost for the Army's
stroyers would probably need to be dedicated
GBR is $9 billion to $10 billion.67 Although
exclusively to the NMD mission. The Navy at
no Navy program to develop and produce a
one time estimated that between 7 ships (2
shipborne GBR capability currently exists, it is
overseas) and 15 ships (5 overseas) would be
probably safe to assume that the costs would
required for sea-based NMD.70 Dedicating
be at least as much as the costs for the GBR.
those ships would reduce the number of Aegis
Building and integrating a shipborne GBR
ships available for other missions, including
into existing ships might be even more expen-
theater missile defense. Also, if sea-based
sive than simply building the GBR.
NMD required a constant forward deployment
Another possibility is to rely almost entire-
of ships to patrol all potential enemy launch
ly on space-based sensors for sea-based NMD.
areas and missile flight paths, it would be
According to CBO analyst David Mosher:
inconsistent with a more rational, restrained
military strategy that would reduce the U.S.
This system would require that Space
naval presence overseas.71 As noted in a previ-
In addition to
and Missile Tracking System (SMTS)
ous Cato Institute study on TMD:
infrared tracking satellites be de-
technical and cost
ployed to ensure that missiles were
With a more restrained military strat-
considerations,
intercepted shortly after they left the
egy, the United States would not need
atmosphere. Setting up such a system
forward-deployed forces or preposi-
sea-based NMD
would cost about $5 billion, and
tioned equipment in various theaters
raises some
deploying SMTS as part of it would
of operations. And we should expect
important opera-
cost another $5 billion.68
only a limited overseas naval presence in
any given region at any given time.72
tional questions.
Mosher further states: "Preliminary estimates
Conclusion
of the cost of this system, which as yet exists only
on paper, run to about $10 billion, not includ-
ing the use of SMTS and a few of the other
Table 3 summarizes a variety of options for
supporting systems that the Navy thinks it
NMD that have been discussed in this paper.
would need."69 Therefore, even if a sea-based
Obviously, the comparison in the table is not
strictly "apples to apples"--the cost estimates
NMD system were technically and opera-
18