Ohio class ballistic missile submarines have tethered buoys allowing them to stay deeper and stealthier while receiving key transmissions.
The Trident Refit Facility (TRF) in Kings Bay, Georgia, posted the pictures of USS Tennessee undergoing a so-called “bouy fly” on its Facebook page.
A wider shot of the buoy being hoisted out of its compartment on the Ohio class ballistic missile submarine USS Tennessee during the recent post-repair test. The bay doors are also visible here. USN
“The ‘Buoy Fly’ is the final certification in a series of post repair testing for the AN/BRR-6/6B Communications Buoy Systems,” according to a post on Facebook accompanying the pictures. “The … testing protocol included a 3000-pound counter weight attached to a fly rig and crane that simulated water force pressure which allowed the system’s electronic and hydraulic components to respond as if the buoy was being deployed while underway.”
A picture of the recent “buoy fly” at the Trident Refit Facility. The counterweight mentioned in the TRF’s Facebook post is visible above to the right of the buoy itself. USN
The TRF is a central hub for major maintenance and upgrade work on the Navy’s 14 Ohio class ballistic missile submarines, or SSBNs, of which Tennessee is one. The facility also services the four additional Ohios that have been converted into guided missile submarines, or SSGNs, which have conventional-only strike capabilities and a host of other highly specialized features as The War Zone has explored in detail in this past feature.
An older picture of the USS Tennessee underway. USN
Tennessee notably received a major sonar upgrade at the TRF just a few years ago, as you can read more about here. Exactly what maintenance was performed on the boat’s buoy last month is unclear. At least as of 2017, the Navy upgrading these systems across the Ohio SSBN fleet, which are also known as boomers, to improve their performance and reliability, according to official budget documents.
“The AN/BRR-6/6B Towed Buoy Antenna system is installed on the OHIO-class Ballistic Missile Submarines (SSBN),” those same budget documents explain. “Each boat has two (2) towed communications buoys with the sole function of supporting Navy Nuclear Command, Control, and Communications (NC3) strategic requirements, connecting the President of the United States (POTUS) to Ballistic Missile Submarines (SSBN) communications reception for the strategic deterrent mission.”
On Ohio SSBNs, the buoys are stored in a compartment aft of the sail. When deployed, the buoy rises to a much shallower depth and is pulled along underwater behind the submarine below.
Since this specific system is solely related to the nuclear strike mission, it is not found on the four Ohio SSGNs. It’s not immediately clear if the SSGNs now have a different buoy communications system, a capability that is also found on a variety of other submarines around.
More specific details about the system, including the size and weight of the buoy and how long the tether is, are limited. The TRF’s “buoy fly” testing protocol does underscore the significant physical forces involved in dragging something like this along while deep underwater.
In addition, the buoy is designed to receive transmissions in the low-frequency (LF), very-low-frequency (VLF), and medium-frequency/high-frequency (MF/HF) bands, according to the Navy. This would point to the system being attached to a tether with substantial length given that typical VLF transmissions cannot penetrate down more than around 100 feet below the water under optimal conditions.
A US Navy chart showing various submarine communications options and their relative risk. The “bell” icon for VLF/ELF “stealth” transmissions reflect that these are one-way only “bell ringers” typically used to alert a submarine that it needs to find a safe place to get closer to the surface to receive additional information, even via buoy. USN
It’s also important to note that the AN/BRR-6/6B is a passive, receive-only system. This means that it cannot be used to send messages from the submarine, but has other important benefits.
“The buoy system provides significant operational flexibility by providing a means to passively receive communications while remaining at depth with minimal impact on [the] boat’s maneuverability or detectability,” according to the Navy.
Interestingly, the failure of the communications buoy system on an Ohio class submarine was a key plot point in the 1995 movie Crimson Tide, starring Denzel Washington and Gene Hackman. That film centers on dueling factions aboard the submarine, led by Washington and Hackman’s characters, who disagree vehemently about whether an earlier transmission is ordering them to launch a nuclear strike or not.
In real life, VLF transmissions have been the primary means of sending out what are known as Emergency Action Messages (EAM). EAMs are the mechanism through which orders to execute nuclear strikes, as well as abort them, would be dispatched to all of the U.S. military’s deterrent forces. Land-based VLF sites and E-6B Mercury strategic command post aircraft, also known as doomsday planes, are currently used to pass those messages along to Ohio SSBNs.
An E-6B Mercury aircraft. DOD
E-6Bs each have a five-mile-long VLF antenna they can deploy to reach submarines beneath the waves. The aircraft have to fly in very tight circles in order to get the antenna to point as straight down as possible for optimal performance. The Navy is now in the process of acquiring a new aircraft to perform this critical airborne strategic communications mission, referred to as Take Charge and Move Out (TACAMO), which will be based on the C-130J Hercules.
A rendering of what the Navy’s future C-130J-based TACAMO aircraft might look like. Howard Altman
In the past, the Navy had also used land-based extremely low frequency (ELF) communications arrays to reach its boomers, but it shut down the last of those sites in 2004. ELF signals can penetrate much deeper underwater than VLF ones, but also require massive amounts of infrastructure to transmit them. That being said, it is a well-established communications technology, especially for reaching submerged submarines, and China appeared to be establishing new ELF arrays for this purpose a few years ago, as you can read more about here.
A picture of the main building at the U.S. Navy’s Clam Lake ELF transmitter facility in 1982. USN
In the meantime, the Ohio SSBNs will continue to keep silent watch with their buoys and other communications systems at the ready to receive critical orders whenever they might come.
