The logistic support submarine — a dedicated cargo carrier would fit into the Rapid Deployment Force mission as a gap-filler. It would be a compromise between the C-5 cargo aircraft with its speedy delivery of miniscule quantities of supplies and the slow, surface cargo ship with its delivery of great quantities of overseas support “sometime next year.”
Cargo submarines are not new. The German DEUTCHLAND of WWI vintage was a successful
commercial “blockade runner”. The U.S. Navy’s first venture into the realm of cargo carrying
submarines was the conversion of Bass, Barracuda, and Bani ta during WWII. This program grew from
efforts at evacuation and re-supply of Philippine forces at the beginning of the war. While never
carrying any actual cargo, the “B” boats pointed the way to success as well as some of the pitfalls
which had to be “designed around”.
Until the advent of nuclear power, the attempts at development of submarines for logistic support
were based on their ability to remain undetected – so as to make surreptitious landings of personnel and material possible. With the advent of nuclear power, the picture changed. By designing a cargo carrier submarine with speed in mind while ignoring armament and detection devices, speeds in excess of 40 knots for displacements of 8,000 tons have been indicated by studies. The advantage of the extremely high speed submarine cargo carrier then lies in the rapid delivery of rather large amounts of resupply, rather than in its covertness — although the latter is also inherent to any submersible to some degree.
Consider for example a delivery time from Seattle to Diego Garcia at 40 knots. This would
be about one fourth the time required for an average cargo ship if weather was also taken into
account. Additionally, the 40 knot sub would alleviate somewhat costly inventories stockpiled
at a strategic point at the expense of other points by rapid delivery of large amounts of cargo
from central points. The high speed cargo submarine thus seems to be an ideal gap filler
and supplement to rapid deployment units.
So what are the problems facing this solution to rapid delivery? There are initially two large
ones — cargo density, and cargo access.
As an example of the first problem, let’s look at the cargo “hold” arrangement of the “B” boats.
To form cargo compartments, all torpedo gear and tubes were removed from the forward and after
compartments, and two of the four main engines were also removed. The three altered compartments were then made into cargo rooms by installing compartmented tanks the largest number being in the former engine room. The idea was that a mix of cargo in some tanks and water in others would allow maintenance of trim for the particular cargo density involved. This resulted in a “cargo efficiency” of 100~ if all cargo space was used for small arms ammunition. But if the cargo were hospital supplies the efficiency was less than 10%. The cargo submarine thus was designed with a large variable ballast capacity. Since such compartmented tanks would be partially filled under various conditions of loading, single hull construction seemed desirable.
As to the second problem, a member of the Bass cargo board once asked, “Why are all submarine
hatches round and all cargo packages square?” This summed up the situation rather succinctly.
A new cargo boat could have a form of clamshell door to take aboard large units like the Bradley
Fighting Vehicle. The “B” boat system of combination cargo/ballast tanks would be replaced
by a system of “reverse saddle tanks” inside the pressure hull and outboard of cargo spaces. This
arrangement would then enhance the “roll on-roll off” capability of a cargo submarine so designed.
Off-loading at sites unprepared for cargo handling requires that handling equipment be integral to the carrier submarine. Thanks to the U.S. space program, the state of the art in articulated arms allows “a” tightly packaged crane and davit type gear. Using a clamshell door, ramps can also be extended for discharge of rolling stock. Loading at a prepared site should then present little problem.
Other configurations would include the liquid “tanker” carrier which would differ from the bulk
cargo and heavy equipment types because of the ease in designing variable ballast systems for a
tanker. If the submarine carrier is faced with a single cargo density like oil more space can be
allotted to cargo at the expense of variable ballast. The increased effectiveness of a nonnuclear
carrier task group which could be fueled by a nuclear submarine tanker in any weather and
on any course should be extraordinary. An idea for further study would also be the “train”
concept with unpowered submersibles being towed by a nuclear tug or another nuclear powered cargo sub. For such a train of towed submersibles, a tonnage/speed tradeoff would be necessary to
define an economical design .
While the arguments between “nukes” and the diesel-electric aficionados frequently boils down
to the limits on “submarine money”, in the case of the submarine high speed cargo carrier there might
be additional funding for the mission of rapid deployment. This would, at least, be a step toward true rapid deployment as contrasted to forward strategic stockpiling of material and supplies.
CDR Rue O’Neill, USN (Ret)