As well as looking at submarines this blog looks at many related hardware and software issues. To that end unmanned underwater vehicles (UUVs) are an increasingly interesting topic. The Sea Stalker provides an example of a large-diameter UUV (LDUUV). For undersea cable tapping a more highly developed, specialised and deeper diving LDUUV is a possibility.

The current status of UUVs in the US Navy paints a confusing picture. Perhaps such confusion is  intentional for security and commercial competition reasons. There are small UUVs, medium size torpedo tube fitting UUVs (like the Bluefin-21 deployed by the US Navy in search of Malaysian Airlines MH370 off Western Australia). Then there are LDUUVs. The US Navy is learning what to ask for in LDUUV requirements by simultaneously testing LDUUVs like the Sea Stalker.

There may be widely varying degrees of remote control and autonomy of LDUUVs. LDUUVs might increasingly be used in littoral waters too shallow for full sized submarines or full sized high value warships. LDUUVs might also be used for missions too dangerous due to high possibilities of detection by anti-submarine or anti-shipping forces (eg. defending foreign submarines, ships, aircraft, anti-ship missiles etc).

The ability of a surface ship to deploy a LDUUV potentially permits that ship to have some of the intelligence gathering and weapons capabilities of a submarine. By weapons that might mean an LDUUV attaching small limpet mines to ships in harbour or an entire LDUUV exploding under a high value ship in harbour or other chokepoint.

LDUUVs as CABLE TAPPERS

The following is a logical outgrowth of the publication decades ago of undersea cable tapping under  Operation Ivy Bells http://en.wikipedia.org/wiki/Operation_Ivy_Bells  Also see the Wikipedia entry on modified Seawolf-class SSN USS Jimmy Carter"Past submarines outfitted this way were used to tap undersea cables, to intercept communications of foreign countries."  It is therefore assumed undersea cable tapping remains a reality.

For the delicate task of tapping undersea fibre-optic cables LDUUV's offer advantages over medium-large submarines (close to cables) or divers.

LDUUVs:

-  being without a crew are semi-deniable (unlike manned submarine crews and divers they cannot be questioned in front of the world media)
-  do not involve friendly deaths or risk of injury
-  may be capable of far deeper operation (1,000s meters?) than manned submarines and divers. LDUUVs could operate at or beyond estimated "crush depth" as there is no crew at risk
-  if the capture of a LDUUV is imminent remotely initiated or autonomous destruction could take place (of electronics, including hard-disc records and other high technology). The whole LDUUV could also self-destruct (preferably keeping would-be capturers at a safe distance)
-  are potentially of shallow water tapping in the littorals (too shallow)
-  can operate in areas too dangerous or too politically sensitive for manned submarines
-  would present a far lower sonic, visual and magnetic signature (and other emissions) than a manned submarine (thus reducing detectability)
-  can utilise their thrusters and specialised splicing technology for tapping or other work
-  are less likely to damage or break a cable, by mistake, than a much larger submarine attempting to work on a cable directly
-   not only submarines could operate, release and retrieve LDUUVs but mine-sweepers on up in a navy or more delicately large "trawlers" on up in commercial shipping terms
-   are not restricted to the US Navy or other agencies but LDUUVs may be possessed by foreign navies and agencies such as those of Russia (near Stockholm in late 2014?) and China.

SEA STALKER LDUUV DETAIL

The US Navy appears to be sponsoring the development of LDUUVs by private companies and academic institutions while it sets requirements for upgraded LDUUV technology. The Navy's approach is pragmatic. It is difficult to set requirement for a technology if one does not have some idea of its ever greater practical capabilities.

Since conducting a 2006 study, the US Navy has been developing requirements for submarine-deployable LDUUVs with payload capabilities much greater than the limitations posed by medium sized UUVs (that can fit in 533mm (21 inch) diameter torpedo tube). Examples of medium sized UUVs are the Bluefin-21 (hence 21 inch - which transmits data to the mother ship or sub) or upgraded Mark 48 torpedos (which carry sensors for data transmission). 

The Sea Stalker is a 38-inch (0.97m) diameter platform with a speed of nearly 5 knots. The US Navy has conducted some experimentation with the Sea Stalker UUV, a development of the Sea Horse UUV built by the Pennsylvania State University Applied Research Laboratory (ARL).



On November 25, 2014 US Naval Sea Systems Command (with Sea Stalker, other public LDUUVs and covert LDUUVs in mind) released a refined draft of top-level requirements. The requirements or instructions were: 

(Sea Stalker) AUV System Spec Sheet

[Base] Platform: Seahorse
Developer and Manufacturer: Pennsylvania State University Applied Research Laboratory

In what may be a future brand-name legal battle the Penn State ARL Sea Stalker LDUUV-UUV-AUV should not be confused with another Sea Stalker - the unmanned surface vehicle (USV).