Navy DDG-1000 (DD(X)), CG(X), and LCS Ship Acquisition Programs: Oversight Issues and Options for Congress Page: 28 of 53
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CRS-24
hull will be negated by its visibility to high-frequency (HF) surface
wave radars that are now for sale on the international market.
The article, which refers to the DDG-1000 by the previous designation DD(X), states:
In the case of the DD(X), the overriding requirement [in determining the hull
design] was to minimise radar cross section stealth. Much of the hull design
was dictated by the attempt to reflect radar pulses away from the radar emitting
them, so that radar returns would be minimised. By now the main technique is
well known: slope all flat surfaces and eliminate the corner reflector created by
the juncture of the hull and water....
If the ship could be stabilized sufficiently [against rolling from side to side], then
she would never (or almost never) present any vertical surfaces [to a radar]. In the
case of DD(X), stabilization is apparently achieved using ballast tanks. Such
tanks in turn demand internal volume deep in the ship. Overall, stealth demands
that as much as possible of the overall volume of the ship be buried in her hull,
where the shape of the ship can minimise radar returns. That is why,
paradoxically, a carefully-designed stealthy ship will be considerably larger for
more internal volume than a less stealthy and more conventional equivalent.
In the case of DD(X), there were also demands for improved survivability. The
demand for stealth implied that anti-ship missiles were the most important
envisaged threat. They hit above water, so an important survivability feature
would be to put as much of the ship's vitals as possible below water which
meant greater demands for underwater volume....
Once the tumblehome hull had been chosen, [the ship's designers] were
apparently also constrained to slope the bow back [creating a surface-piercing or
ram bow] instead of, as is usual, forward....
There were numerous reasons why [past] naval architects abandoned
tumblehome hulls and ram bows. Tumblehome reduces a ship's ability to deal
with underwater damage. When a conventional flared (outward-sloping) hull
sinks deeper in the water, its waterplane area [the cross-section of the ship where
it intersects the plane of the water] increases. It becomes somewhat more stable,
and it takes more water to sink it deeper into the water. Because the waterplane
area of a tumblehome ship decreases as it draws more water, such a ship is easier
to sink deeper. Tumblehome also apparently makes a ship less stable, and hence
less capable of resisting extreme weather conditions. The larger the ship, the
more extreme the weather has to be to make that critical. Critics of DD(X) haveconcentrated on the danger; defenders have concentrated on how extreme the
critical weather condition would be.
In the end, whether the DD(X) hull form is attractive depends on an
evaluation of anti-radar stealth as a design driver. About a decade ago, the DD(X)
design concept was sold on the basis of a lengthy (and, incidentally, unclassified)
analysis, the gist of which was that a heavily-armed surface combatant could play
a decisive role in a Korean scenario...
The key analytic point... was that it would be very important for the ship to
come reasonably close to enemy shores unobserved. That in turn meant anti-radar
stealth. However, it soon came to mean a particular kind of anti-radar
performance, against centimetric-wave radars [radars with wavelengths on the
order of centimeters] of the sort used by patrol aircraft (the ship would fire [its
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O'Rourke, Ronald. Navy DDG-1000 (DD(X)), CG(X), and LCS Ship Acquisition Programs: Oversight Issues and Options for Congress, report, August 29, 2006; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metacrs9354/m1/28/: accessed May 8, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.