Bremerton-Olympic Peninsula Council Navy League of the US

Submarines: Son Of Tomahawk Takes It Slow


ATLANTIC OCEAN (Sept. 11, 2013) A photo illustration created by combining several digital images, shows a Naval Research Laboratory-developed Sea Robin launch vehicle vertically deploy an unmanned aircraft from the submerged Los Angeles-class attack submarine USS Providence (SSN 719) during a test in early August 2013. The folding wing unmanned aerial system autonomously deploys its X-wing airfoil and, after achieving a marginal altitude, assumes horizontal flight configuration.

The U.S. Navy recently launched a UAV (unmanned aerial vehicle) from a submarine. This was done using much of the same tech used to launch Tomahawk cruise missiles from torpedo tubes, the XFC UAV deploys larger wings than a Tomahawk and is apparently more maneuverable and moves much more slowly (54-93 kilometers an hour versus 880 kilometers an hour for the Tomahawk). Thus while the Tomahawk only stays in the air for about two hours the XFC can remain in the air for over eight hours and uses propeller propulsion and not a jet engine. The XFC is powered by electricity, from a fuel cell rather than a battery. The XFC made its first flight in 2009 and may enter service in a few years is the navy perceives a real need.

All this began back in 2005 when everyone wanted in on the UAV action, including U.S. submarines. The U.S. Navy put up fifteen million dollars to determine the practicality of building a UAV (the Cormorant) that could be launched, and operated from a submerged submarine. At first this was not just any submarine, but specifically the two SSBN (ballistic missile subs) that have been converted to carry cruise missiles and commandoes. One of the sixteen ICBM launch tubes on these boats was to be converted to carry a UAV. The ICBM silo is over two meters (seven feet) in diameter, and the plan was to release the UAV while the sub was submerged. As the UAV floated on the surface, the wings, one presumes, would be extended, and two small rockets would be used to get the UAV into the air. There, the propeller would kick in, taking the UAV on a preplanned flight to collect information. Current subs are equipped to release a radio antenna buoy, via a cable, so the UAV can be guided from the sub. This is how the latest subs get their digital periscopes to the surface.

The original concept called for the submarine launched UAV, once it had completed its mission, to land near the sub, sink and be hauled into its launch silo. There it would be refueled, have new rocket motors installed, and get any needed repairs. The navy paid Lockheed Martin $4.2 million to get working on a working prototype.

Before that effort got too far someone realized that American submarines have been launching UAVs from underwater since the 1980s. These UAVs were called cruise missiles and, until recently, were the entirely robotic and not reusable Tomahawks. The navy finally accepted the fact that a reusable UAV would not be practical for a submarine, but one that was launched via the existing Tomahawk system and controlled via a radio connection on the periscope mast was doable.

While the passive (listen only) sensors aboard American subs make it possible to locate ships hundreds of kilometers away, there is little awareness of what is on nearby land or the air above. That’s where a torpedo tube launched UAV, even if it was only used once, would come in handy. The video and other data collected by the UAV would be streamed back to the sub for further analysis. When the sub has its radio connection active it can also receive updates of satellite or aircraft data but that is often a little dated while the sub launched UAV provides real time video.

Aircraft operating off submarines is nothing new. The Japanese did quite a lot of this sort of thing during World War II. This included a bombing mission on the U.S. west coast (Oregon in late 1942). The Japanese built 44 subs that could carry a small float plane for reconnaissance. This idea was fine in theory, but much less successful in practice. The U.S. Navy’s proposed Cormorant submersible UAV was to enter service by 2010. But that didn’t happen in part because someone remembered that the United States has plenty of other satellite and long range UAVs that could provide most air reconnaissance needs of U.S. subs. Then someone began tinkering with the Tomahawk concept and now we have the XFC.

Strategy Page, Dec 13