Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Unmanned Underwater Vehicle (UUV)
deployment and retrieval considerations for
submarines
Tim Hardy, BEng(Hons), CEng
BMT Defence Services Ltd
Gavin Barlow, BSc(Hons)
BMT Defence Services Ltd
SYNOPSIS
Unmanned Underwater Vehicles (UUV) are increasingly being recognised as a potential force multiplier in
today’s battle-space. As UUV technologies evolve and their roles are defined, there is an increasing need to
develop tailored platform solutions to enable integrated and effective methods of UUV deployment and recovery
on vessels of all types. The maturity of such systems varies, ranging from reasonably mature surface vessel
UUV deployment and recovery systems to less mature submarine systems. The operational benefits of
submarine-based UUV operation could be enormous yet the integration challenges are significant, particularly
for smaller conventionally-powered submarines. The paper will briefly introduce some self-funded research that
BMT Defence Services continues to undertake in this area, focusing on the submarine platform as a base for
deploying and recovering UUVs.
The paper will report on issues relating to whether the UUV
deployment/recovery system should be maintained dry or wet, manned or unmanned, pressurised or not, integral
to the submarine or not, optimised for automation and the consequential effect on system complexity. The
overall feasibility of fitting such systems into a range of submarine types in various states of platform maturity
(i.e. concept and new build submarines to retro-fitting into in-service platforms) will also be considered. The
paper will also describe some potential UUV deployment/recovery concepts for further development. The paper
seeks to reveal some of the key design and technical areas which need to be addressed by both submarine and
UUV designers to enable such systems to be employed in the near and far term.
INTRODUCTION
The Military Need and the Opportunity
There are a number of technologies that will assist in delivering the aspiration for naval operations in the littoral
environment and the need to support and enable future network centric operations. One particular technology
family that could offer significant merit are Unmanned Underwater Vehicles (UUVs). To be clear the term UUVs
normally includes Remotely Operated Vehicles (ROVs), Autonomous Underwater Vehicles (AUVs), and Remotely
Operated Towed Vehicles (ROTVs), however the principal focus of this paper are AUVs.
Comparing the operation of AUVs from surface platforms, submarines have a clear advantage in that their
movements are far less likely to be detected. AUVs provide the opportunity for navies to operate in a covert way
within areas where normal manned submarines or other military assets may not be free to operate. Submarines are
not constrained by sea state and wave motions to the same degree as surface ships. Consequently, the submarine is
unique in its ability to deliver an AUV covertly to an area of interest, enabling it to perform its mission and be
retrieved if necessary, reducing the overall risk of submarine detection. Various nations’ navies have been
exploring the means and likely missions in which AUVs can assist them in their naval operations. The US Navy
updated their UUV Master Plan (Reference 1) in 2004, which identified nine high priority UUV missions which, in
decreasing order of importance, are listed at Table I.
Table I – Typical Missions
1.
Intelligence, Surveillance and Reconnaissance (ISR)
6.
Communication / Navigation Network Node
2.
Mine Countermeasures (MCM)
7.
Payload Delivery
3.
Anti-Submarine Warfare (ASW)
8.
Information Operations
4.
Inspection / Identification
9.
Time Critical Strike
5.
Oceanography
April 2008
Page 1 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
A recently published US Office of Naval Research (ONR) sponsored report (Reference 2) begins to define how
AUVs and UUVs are being considered in the context of the Networked Persistent Undersea Surveillance
(PLUSNet) programme of work. The report states that the recent SSBN (Ship Submersible Ballistic Missile
Nuclear Powered) to SSGN (Ship Submersible Guided Missile Nuclear Powered) conversion on the USS Ohio
provides an ideal platform for delivering payloads comprising multiple distributed autonomous sensor networks in
selected wide forward operating areas that will deny unmonitored movement of quiet SSKs (Ship Submersible
Hunter Killer Conventional Powered). Post conversion the SSGN USS Ohio will have a re-configurable payload
carrying margin approximately equivalent to twenty typical SSN (Ship Submersible Nuclear Powered) torpedo
rooms.
For other nations’ navies, the benefit that AUVs could bring to them in undertaking naval operations could be
significant. To illustrate, consider a typical SSK submerged patrol. The feasible patrol duration is largely a
function of the stored energy the SSK has onboard (i.e. main battery and/or adjunct Air Independent Propulsion
(AIP) system). The stored energy provides a means for the submarine to propel itself, maintain life support
demands and other essential hotel loads. The proportion of energy required to meet typical AIP demands is
significantly larger than the energy required to support the submarines other non-propulsive loads. With the
addition of AUV/s certain missions could be undertaken by the AUV in preference to the “mother-ship” SSK, thus
conserving the SSKs limited store of energy and increasing the SSKs submerged patrol duration as illustrated at
Figure 1. In addition, AUVs could also enhance the SSKs effective operational reach whilst it remains silent and
hidden.
Figure 1a - Non UUV Fitted SSK
Figure 1b - UUV Fitted SSK
Obviously, at the present time the maturity and capability within AUVs is far from matching that currently found
within SSKs but if the SSK can conserve a small amount of its energy and extend its submerged endurance by a
small margin by utilizing an AUV, then this could be considered to have significant operational benefit.
In addition to the “mother-ship” function described above, another scenario where the SSK could support AUV
operations is if it were to take on a “docking station” role to support a number of already deployed off-board AUVs.
Consider the scenario where a number of AUV hosting surface ships are in suitable stand-off positions some 50 –
100Nm from a hostile location. The Task Force Commanding Officer wants to undertake covert intelligence
gathering and MCM activities in the hostile area in preparation for future naval operations. The surface vessel
deploys a number of AUVs that transit to the hostile area and begin to carryout their missions. As each AUV uses
its limited energy store it can be instructed to transit to a friendly submarine that is already in the operational area.
On rendezvous with the submarine, each AUV could dock, recharge its onboard energy store and receive or
transmit any command and tactical data. Post recharge the AUV can disengage from the submarine and return to its
mission, should it be required or transit out of the hostile area, back to the host surface vessel for recovery.
The examples described above provide a small glimpse of the scenarios where operating AUVs from submarines
could offer tactical and strategic benefit. What is clear is that by hosting and operating AUVs from submarines the
effectiveness, potency, deniability and range of operations the submarine or combined expeditionary naval task
force can undertake could be significantly enhanced.
Commercial and Military AUV Development
With regard to the historical development of AUVs, a significant proportion of initial investment has been targeted
at meeting commercial offshore applications such as seabed survey and mapping, pipeline inspection and
environmental monitoring and research applications.
April 2008
Page 2 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Others
Inspection
Research
Military
Survey
Figure 2 - Existing AUV Applications
This has resulted in a plethora (i.e. >100 designs) of mature and reliable AUV and UUV technologies being
available in the commercial market place that are well suited to the particular mission they have been designed to
undertake. Recent research also suggests that alongside growth in offshore oil and gas AUV markets an increasing
proportion of future AUV research and development activity will be focused on meeting requirements that have
more of their basis on rapidly expanding military and homeland security markets (Reference 3).
Study Basis
Noting the evolving and expanding military need and the corresponding development of AUVs, BMT Defence
Services decided to explore the feasibility and impact of operating AUVs from submarines. The principal aim of
this work was to begin to understand some of the issues involved in such an endeavour for both the submarine and
the AUV, and in parallel begin to develop some initial concepts for AUV Launch and Recovery (L&R) systems.
Ultimately, we hoped that the outputs of our work would help in stimulating the debate, assisting both AUV and the
submarine community in understanding some of issues involved in delivering such a capability.
TYPICAL AUVS AND GENERATION OF A BASELINE SUBMARINE
Overview
To begin to reveal the challenges present in L&R of AUVs from submarines it was considered useful to gain an
understanding of some typical technical characteristics relating to a sample of AUVs that have merit for future
operation from submarines. This information was considered important as clearly it would have a fundamental
effect on the submarine L&R modifications that would be developed.
Some Typical AUVs
A large number of vehicles can be considered as being suitably mature and as having merit for future operations
from submarines. Table II illustrates a small sample of such vehicles with principal weight and form data.
Table II – Typical AUVs
Name
Manufacturer
Approximate Weight
(kg) (Note Dependant on speed
and payload/sensor
configuration)
Approximate
Length (m)
Approximate
Diameter/Width
(m)
Approximate Height
(m)
Remus 100
Hydroid LLC
37
1.60
0.19
N/A
Gavia
Hafmynd ehf
>44
>1.7m (modular)
0.2
N/A
SUBROV (Sea Owl
ROV)
Saab Underwater Systems
100
1.4
0.8
0.6
Remus 600
Hydroid LLC
240
3.25
0.32
N/A
Bluefin
Bluefin Robotics
Corporation
330
3.3
0.53
N/A
Remus 6000
Hydroid LLC
862
3.84
0.71
N/A
Hugin 1000
Kongsberg Maritime AS
650
5.00
0.75
N/A
Hugin 3000
Kongsberg Maritime AS
1400
5.35
1.00
N/A
Talisman
BAE SYSTEMS
1800
4.5
2.5
0.7
April 2008
Page 3 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Following scrutiny of Table II it can be seen that that there is a significant variation in weight and size between
different vehicle designs. Obviously, physical size and weight is a major contributing factor when considering the
most appropriate means of hosting such vehicles from submarines.
With regard to arrangement, most AUVs are modular designs with separate control and communications,
propulsion, energy storage and payload sections complimented by various sensors positioned on the nose and along
the length of the vehicle.
Almost all AUVs rely on primary and secondary batteries (i.e. of various compositions including but not limited to
NiCAD, NiMH, Li-ion) to provide energy for propulsion and hotel load demands. Battery capacity is the
fundamental limitation on AUV range and endurance and also plays a major part in determining the AUVs physical
volume and form (alongside payload considerations). Once hydrodynamic laws are considered (i.e. required
propulsive power is derived approximately by the cube of the AUVs required speed) a key AUV design and
selection driver is revealed. Consequently, a large limitation for AUVs will continue to be speed, extended range,
payload carrying capacity and endurance.
As a consequence of the challenges just discussed with respect to energy storage, almost all AUVs are limited to
ranges of the order of 200 km, or 24 hours, when travelling at optimum speed. Transit speeds tend to be in the
range of 3 – 5 knots. In terms of maximum operating depths these can range from hundreds to several thousands of
meters. This characteristic will become more important later in this paper as we begin to consider some of the
feasible means of hosting AUVs from different sized submarines.
Extended range underwater acoustic communications are limited to tens of miles and by transfer rates of several
tens of kilobits per second (kbit/s). Short range communications is significantly greater with recent advances in
underwater Radio Frequency (RF) communications potentially offering data rates of about 300kbit/s at two meter
range (Reference 4). This particular technology could be a significant enabler to future solutions.
Autonomous Control and Navigation is typically undertaken through the fusion of Inertial Sensing, Compass,
Doppler Log, GPS and DGPS systems and advanced software algorithms. Forward looking sonar can be employed
for obstacle and collision avoidance. In addition, Short Base Line (SBL), Ultra Short Base Line (USBL), other
transponder arrays are used to sense the relative position and relative heading of the AUV when in range.
Typically, most AUVs rely on a post mission recovery phase where they rendezvous with the host vessel between
missions to undertake routine maintenance activities (e.g. battery recharge) and to download and/or update mission
data ready for re-deployment.
Normally, AUVs are transported to dockside and transferred to the support vessel in a container which will usually
include any support equipment that is required. The container is typically secured on the aft working deck of the
surface vessel. Some AUVs are compact and light enough to be manual transferred to the vessel although most
require lifting equipment.
Figure 3 - AUV Deployment
Figure 4 - Containerised Transfer
For both commercial and military applications, at sea AUV deployment and recovery is in almost all cases
undertaken through the use of cranes and derricks fitted to purpose built or modified surface vessels. The principal
limiting factor in operating such vehicles being Sea State (SS) (i.e. generally limited to SS 5 or 6).
Some Initial Considerations
The initial AUV market survey revealed a number of factors that must be considered to begin to realise the
operation of such vehicles from submarines and understand the likely design drivers for any submarine based AUV
L&R systems. Key to this were aspects relating to the difference between operating AUVs from surface vessels
when compared to submarines.
April 2008
Page 4 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
The methods employed when deploying and recovering an AUV from a surface vessel (i.e. with relevant personnel
and equipment to assist) are likely to be considerably different in the underwater environment where human
assisted L&R requires complicated life and diving support equipment to be introduced into the submarine. More
automated L&R systems are likely to be required and if so, the simpler the better.
Whilst smaller AUVs still offer benefits, the ability to operate a larger AUV is in most cases believed to be more
appealing in most operational scenarios as the vehicle is likely to be able to carry a greater payload and/or offer an
improved range and endurance. Unfortunately, this begins to limit the feasible L&R options available beyond that
offered by the standard 21 inch torpedo tube.
If the AUV cannot be stored inboard then an alternative storage position may be the submarine casing in a “piggyback” fashion. The ability of the AUV to be located outside of the submarine in a wet environment for the duration
of the submarine patrol was considered. Whilst a significant change to current operation, AUV manufacturers
advised that this would almost certainly be possible. However, the feasibility of casing storage for the submarine
will be limited, as it is a function of surface stability, Reserve of Buoyancy (RoB) and available physical space on
the casing, without impacting on escape arrangements and other systems. For the AUV one consideration on casing
stowage will be its physical robustness (i.e. to resist surface and sub-surface hydrodynamic and corrosive effects)
along with the ability to deal with pressure effects associated with the deep diving depth of the submarine.
Almost all AUVs require regular intervention to charge and/or replace batteries and undertake maintenance and
data transfer. As stated previously, this is currently undertaken by recovering the vehicle and relying on human
intervention in a dry environment. Moving an AUV outside of this “safe” environment would invoke a step change
in its operation..
Finally, underwater navigation and communications to support docking of the AUV with the submarine would be
required to be developed. Interfaces with the host submarines command, control and combat system would be
necessary as would be a position onboard the submarine (e.g. in the command and control suite) to manage and
command AUV operations.
As some of the likely issues began to coalesce the study team began to explore the characteristics of a typical host
submarine in order to further expose some of the associated issues for both the L&R system and the submarine
platform itself.
Defining a Baseline Submarine
As already argued there is most likely significant benefit to be gained by operating AUVs from submarines of all
types and sizes. However, the feasibility of hosting some of the larger AUVs from smaller submarines is likely to
be more challenging. Submarines of SSK size formed the principal focus of the study with the initial argument
being that if it could be done on an SSK then it could almost certainly be done on a typically larger SSN.
There are approximately 178 SSKs in operation by 31 navies around the world and in-excess of 50 in the
procurement cycle. These submarines are dominated in number by the Howaldtswerke-Deutsche Werft AG
(HDW) developed 209, 212, and 214 Class submarines followed by the Russian Rubin Design Burea designed
Project 877 (Kilo Class). Basic dimensions of a selection of submarines are highlighted below at Table III.
Table III – Typical SSKs
Approximate Displacement (t)
Surfaced
Submerged
Approximate
Length (m)
Approximate
Beam (m)
209 (all types)
1,140
1,248
56
6.3
212
1,450
1,830
56
7
Germany
214
1,700
1,860
65
6.3
Greece, South Korea.
Victoria
2,200
2,400
70
7.2
Canada
877
2,325
3,076
73
9.9
Algeria, China, Iran, Poland,
Russian Federation
Collins
3,051
3,350
78
7.8
Australia
Class
Operating Navies
Argentina, Chile, Columbia,
Ecuador, Greece, India,
Indonesia, Portugal, South
Korea, Turkey, Venezuela.
When examining the 178 or so SSKs it can be observed that in terms of size, two groups of SSKs appear to emerge
(i.e. those with a submerged displacement greater than and less than 2,000t). A large proportion of submarines
being operated today fall between 1,400 and 2,000t submerged displacement, acknowledging a few significantly
April 2008
Page 5 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
larger vessels that peak at just over 4,000t. On inspection of Figure 5 an apparent convergence in SSK submerged
displacement is observed between the two groups from the 1960s up to the late 1990s with the 2000t or above
group of SSKs reducing in size and the group below 2000t increasing in size. However, when considering all SSKs
since the 1960s the overall trend has been a steady increase in SSK submerged displacement. For navies that
require higher than normal endurance, range and capability in their submarines, this trend of SSK growth is likely
to continue and it is most likely going to be at an increased rate.
4500
4000
Submerged Displacement (t)
3500
3000
Below 2000t
2500
Above 2000t
2000
Linear (All
Displacements)
1500
1000
500
0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
2015
Commision Date
Figure 5 - SSK Submerged Displacement Trends
Based on this information the study team decided to adopt a large baseline SSK concept design that would act as an
indicative platform to test the feasibility of some of the AUV L&R concepts. Figure 6 depicts the baseline
submarine general arrangement and Table IV outlines its principal characteristics.
Table IV – Indicative Study BMT SSK Characteristics
Characteristic
Value
Length Overall
80m
Diameter
8.5m
Displacement (Sub)
3,000t
Max Sub Speed
20 Knots
Max Surf Speed
10 Knots
Diving Depth
>180m
Figure 6 - Illustration of BMT SSK Concept
OVERALL INTERGRATION CONSIDERATIONS
Fitting a submarine with an AUV capability requires careful consideration of the host platform to provide a focus
on the wider issues of safety, military needs and capability trade offs. For existing in-service submarines the
integration of any new feature should always be recognised as an activity that is disturbing a very fine design
balance. For new build submarines the integration challenge can be considered marginally lesser, especially if the
hosting of the AUVs is considered during the submarine concept design stage where an element of flexibility and
adaptation is still available.
However, whatever state of maturity the submarine design is in, the decision to adapt it to suit AUV operations
should not be understated and limits of potential adaptations will quickly materialise. Integration considerations are
varied and many ranging throughout the entire submarine design (e.g. weight, buoyancy, trim, hydrostatic stability,
hydrodynamics, manoeuvring and control, combat system and navigation integration, platform and power systems,
signatures, watertight integrity, etc).
April 2008
Page 6 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
In order to begin to quantify the level of modification that could be required to be undertaken on the submarine and
the AUV, we need to ask a series of fundamental questions.
What are the overall mission aims and objectives? These will drive the selection of the particular AUV/s that will
be required to meet the mission requirement.
What role is the submarine going to take in supporting the AUV/s mission? This will define how the submarine
will interface with the AUV/s, how it is required to launch and/or recover and/or operate the AUV/s and what
design or operational changes it may have to accommodate.
Do we wish to fire and forget the AUV assuming it will be recovered by another surface vessel or undertake full
recovery also?
Do we wish to L&R the AUV whilst the submarine is in transit, hovering, on the sea bed, or in a stationary position
and do we wish to store and/or re-configure / re-charge the AUV/s within or external to the pressure vessel? This
will focus attention on the likely complexity of the candidate L&R system and the level of automation and/or diver
intervention required.
As an understanding is developed in terms of the mission aims and objectives then appropriate L&R options will
begin to emerge. As the study team considered these issues it quickly became clear that the range of feasible AUV
L&R options were likely to vary significantly but, generally, would always be a function of:
1.
AUV size (i.e. itself principally a function of endurance and payload carrying capacity);
2.
SSK margins (i.e. SSK volume and size, Reserve of Buoyancy, stability, casing area, existing torpedo tube
arrangements, etc).
For the purposes of this initial study it was considered that instead of focusing on a single mission or objective it
would be more beneficial to explore a broad range of L&R options tailored to a wide selection of potential AUVs.
Consequently, following some initial option generation sessions, a number of potentially AUV L&R concepts
began to emerge which are defined and explored further in the proceeding paragraphs.
AUV DEPLOYMENT / RECOVERY SYSTEM CONCEPT EXPLORATION
Option 1 - Deployment and Recovery via Conventional Torpedo Tubes
The first option that emerged was to deploy and recover AUVs via the submarines standard torpedo tube (i.e. 21
inch). The AUV/s could be housed prior to deployment in the submarines weapons stowage compartment and
deployed using the existing positive discharge system or utilizing AUV self propelled swim out. Recovery would
most likely require complex mechanical retrieval systems or an ROV assisted recovery systems.
Figure 7 - Launch and Recovery via Conventional Torpedo Tubes
This concept is not new and others have demonstrated it in some form already. For example, one solution being
developed by SAAB Underwater Systems, is the SUBROV system which is intended for deployment and recovery
from a submarine torpedo tube (Reference 5). The SUBROV system consists of an operator’s console, a power
supply, a winch and a Sea Owl ROV. The console is used for controlling the ROV and to display video and sonar
images to the operator. The system offers inspection, MCMV, Communications and Surveillance hub capabilities
but can also be used as an active docking tool to assist recovery of a separate AUV should it be required into the
host submarine.
In addition, recent US Navy sponsored work (Reference 6 and Reference 7) has demonstrated the first ever
complete end to end submerged operation of two UUVs from launch through to recovery at sea onboard an SSN
through the Long-Term Mine Reconnaissance System (LMRS) programme of work. The LMRS is a clandestine
mine reconnaissance system that employs UUVs and will provide an early, rapid, accurate means of surveying
potential mine fields (i.e. offering 35 - 50Nm2/day coverage) in support of proposed amphibious operations, other
battle group operations, and for safe ship transit around mined waters. The system comprises 2 UUVs and an 18m
recovery arm (i.e. weighing approximately 1,600kg) that is stowed in the upper submarines torpedo tube. A typical
April 2008
Page 7 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
mission would involve the AUV being deployed from a torpedo tube, undertaking its mission and then returning to
the submarine. Homing and docking sonar guides the AUV to the recovery arm which then guides the AUV back
into a separate torpedo tube.
This particular concept holds promise for a number of submarine types. It is relatively mature and beginning to be
proven. However, it significantly limits the size of the AUV that can be employed.
Figure 8 - Visualisation of Recovery via Conventional Torpedo Tubes
Key Advantages
Key Disadvantages
Permits multiple types of 21 inch torpedo type AUVs to be
deployed
Constrains AUV design to 21 inch torpedo design with
consequential endurance and payload capacity constraints
Assuming recovery can be undertaken then AUV maintenance,
recharging and payload reconfiguration activities are made easier
inside the submarine in a clean, dry environment. When not in
use the AUV is stored dry and safe
If recovery is required, recovery system will most likely take up
capacity of at least one torpedo tube (Unless modular recovery
system design is employed that can be retrieved into the weapons
stowage compartment)
Potentially minimal impact on the overall submarine design in
terms of arrangement and arguably easier to retrofit the system to
an existing submarine
Additional stowage’s required in the weapons stowage
compartment and/or loss of existing stowages
Potential to utilize existing torpedo discharge systems
Recovery is arguably more difficult when submarine is in transit
Allows covert AUV deployment. (e.g. no additional external
structures required such as hangars on the submarine so enemy
does not know if submarine is equipped with the AUV capability
Less risk of aborted AUV recovery fouling submarine propeller
Option 2 - Deployment and Recovery via Enlarged Torpedo Tubes
The second option to be considered was L&R via a new design enlarged submarine torpedo tube (e.g.
approximately 1m diameter) to allow the operation of larger AUVs. The L&R technology and evolution would be
similar to Option 1.
Figure 9 - Deployment and Recovery via Enlarged Torpedo Tube
Again, the design holds promise but the likely feasible maximum hull penetration size will be limited by the overall
submarine size so it is more suited to large submarines and almost exclusively to new build rather than retro-fit.
April 2008
Page 8 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Figure 10 - Visualisation of Recovery via Enlarged Torpedo Tube
Key Advantages
Key Disadvantages
Permits larger and greater range of AUVs to be deployed than
the 21 inch torpedo sized AUV
Very unlikely to be able to retrofit such a system to an existing
submarine
Assuming recovery can be undertaken then AUV maintenance,
recharging and payload reconfiguration activities are made easier
inside the submarine in a clean, dry environment. When not in
use the AUV is stored dry and safe
Still constrains AUV design and size to torpedo tube form with
consequential endurance and payload capacity constraints
Allows covert AUV deployment. (e.g. no additional external
structures required such as hangars on the submarine so enemy
does not know if submarine is equipped with the AUV capability
If recovery is required, recovery system may take up capacity of
at least one torpedo tube (Unless modular recovery system design
employed) and significant space in the weapons stowage
compartment
Less risk of aborted AUV recovery fouling submarine propeller
Additional stowage’s required in the weapons stowage
compartment
Recovery is arguably more difficult when submarine is in transit
Option 3 - Deployment and Recovery via Dry Casing Mounted Hangar
The third option to be considered was L&R via a dedicated AUV deployment and recovery system housed in a dry
Casing Mounted Hangar (CMH). A dry CMH is a removable module that can be attached to a submarine to allow
divers and vehicles to easily exit and entrance while the boat is submerged. The host submarine must be specially
modified to accommodate the CMH, with the appropriate mating hatch configuration, electrical connections, and
piping for ventilation, divers' air, and draining water.
Figure 11 - Deployment and Recovery via Dry Casing Mounted Hangar
The submarine-mounted Dry Deck Shelter (DDS) is an example of a dry CMH that has already been used by the
US Navy for diver operations from SSN platforms (Reference 8). At 11.6m long and 2.7m in diameter, the DDS is
a removable module that can be attached to a submarine to allow divers easy exit and entrance while the boat is
submerged. The host submarine must be specially modified to accommodate the DDS, with the appropriate mating
hatch configuration, electrical connections, and piping for ventilation, divers' air, and draining water.
April 2008
Page 9 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Figure 12 - US Navy Dry Deck Shelter
Figure 13 - US Navy Dry Deck Shelter
The AUV could be housed prior to L&R in the CMH and launched in a number of ways ranging from diver assisted
mechanical L&R to fully automated adaptations. With respect to the diver assisted AUV launch, divers would
transfer from the submarine into the CMH and prepare the AUV for deployment. The CMH would then be flooded
and a rear access door opened. The AUV would be positioned outside the CMH by the divers and winch equipment
and released to undertake its mission. The divers would transit back into the CMH where it would be drained and
made safe to enable the divers to transfer back into the main submarine until the AUV returns where the procedure
would be repeated.
Figure 14 - Dry CMH Concept
The dry CMH would be suited to retro fit and new build submarines but a limiting factor is CMH weight and its
effect on submarine stability. This tends to limit their appropriateness to large SSNs. For example, initial
calculations indicate that a dry CMH that could host a HUGIN 3000 and support diver/SF operations would have a
dry weight of around 30t. However, with further automation incorporated into the design and tailoring to just suit
AUV L&R rather than other operations, the size could be reduced accordingly.
Key Advantages
Key Disadvantages
Permits larger and greater range of AUVs to be deployed
Dry CMH weight will almost certainly preclude fitting of CMH
on smaller submarines
Assuming recovery can be undertaken then AUV maintenance,
recharging and payload reconfiguration activities made easier
inside the CMH. When not in use the AUV is stored dry and safe
Dry CMH is likely to require complex drain down and flood
systems, air and pressure management systems; etc
More potential to move capability around globe to and from
different submarines that are fitted for and not with
Safety justification is likely to be harder if divers are required to
work in and outside the CMH
Likely to be able to retrofit such a system to an existing
submarine of sufficient size
Recovery is arguably more difficult when submarine is in transit
Potential to build in most CMH and AUV support systems to
allow for fast fitting to submarine
Does not allow covert AUV deployment. (i.e. hangar on
submarine so enemy knows if submarine is likely to be equipped
with the AUV capability.
May allows other assets such as divers to be deployed
Impacts on submarine signature and manoeuvrability, etc
Could be designed to support transfer of human maintainers
between main pressure hull and CMH to undertaken maintenance
tasks, etc
Potential fin wake effects for L&R whilst in transit
AUV deployment and recovery system could be simpler (No need
for maximum automation, so less to go wrong) as divers could be
used to assist AUV operations
April 2008
Page 10 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Option 4 - Deployment and Recovery via a “Wet” Casing Mounted Hangar
The fourth option to be considered was deployment and recovery via a dedicated AUV L&R system housed in a
Casing Mounted Hangar (CMH) that would be wet (i.e. free flood). Positioned behind the fin, the hangar would
offer a level of protection to the AUV and provide a space for storage and fitting of associated deployment and
recovery support equipment.
Figure 15 - Deployment and Recovery via a “Wet” Casing Mounted Hangar
The AUV could be housed prior to submarine deployment in the CMH and launched and recovered in a similar
manner to Option 3. Although, if a Lock in Lock out (LiLo) chamber was available onboard the submarine, diver
transfer from submarine to casing could be undertaken to support AUV L&R. The CMH could be sized to suit
whatever AUV was to be operated and positioned accordingly so not necessarily behind the fin. Systems to support
AUV L&R could range from automated diver-less systems (i.e. ideal from safety perspective and if retrofitting in
submarines without existing LiLo capability) or simpler systems relying on diver intervention.
Figure 16 - Wet CMH
Figure 17 - Wet CMH with AUV Deployed
In consultation with AUV manufacturers we have concluded that navigating the AUV into a suitable position for
securing should be feasible as depicted in Figure 16 and 17. However, a drone assisted mechanism depicted in
Figure 18 and 19 could also be employed if required.
Figure 18 - AUV Secured in Wet CMH
Figure 19 - AUV Docking to Wet CMH
Key Advantages
Key Disadvantages
Permits larger and greater range of AUVs to be deployed
Does not allow human maintainers between main pressure hull
and CMH to undertaken maintenance tasks, etc
More potential to move capability around globe to and from
different submarines that are fitted for and not with
AUV deployment and recovery system is likely to be more
complex and require automation as divers are unlikely to be used
to assist AUV operations
Promotes a form of containerisation of AUV and most of its
support systems
Safety justification is likely to be harder if divers are required to
work in the CMH
April 2008
Page 11 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
Likely to be able to retrofit such a system to an existing
submarine as significantly reduced weight compared to dry CMH
Recovery is arguably more difficult when submarine is in transit
Potential to build in most CMH and AUV support systems to
allow for fast fitting of deployed capability to submarine
Impacts on submarine signature and manoeuvrability, etc
Does not allow covert AUV deployment. (i.e. hangar on
submarine so enemy knows if submarine is likely to be equipped
with the AUV capability
Potential fin wake effects for L&R whilst in transit
Option 5 - Deployment and Recovery Via AUV Bespoke Multiple Hangars
The fifth option to be considered involves a number of smaller wet CMHs positioned at suitable positions onboard
the submarine. The option envisages AUV bespoke sized hangars or enclosures positioned in suitable locations
around the submarine, not just limited to positions behind the fin.
Figure 20 - Deployment and Recovery via Multiple Hangars
A baseline hangar concept design is being conceived that would be arranged with openings at the front and rear and
would allow an AUV to swim out via the forward door and swim in via the rear door. The hangars would offer
limited protection to the AUVs whilst the submarine is in transit, but they would most likely be stored in a wet
condition, noting that they could be designed to be dry if relevant flood, drain and drying systems were to be
provided. Launch and recovery of the AUV is conceived to be undertaken by the AUV under its own propulsive
power. Various forms of fairing structure would be employed into the design dependant on the particular fit
location on the submarine (e.g. nose, behind the fin, on the side).
Figure 21 - Baseline Hangar Concept
Figure 22 - AUV Secured in Hangar
Figure 23 - Smaller AUV with Nose Mounted Hangar
Figure 24 - Small AUV Launched From Nose Mounted Hangar
Key Advantages
Key Disadvantages
Permits greater range and numbers of AUVs to be deployed in
various positions around the submarine in tailored hangars
Does not normally permit human maintainers to physically access
the AUV
When not in use the AUV is stored safely. Dependant on the
specific design the hangars could also be dry
Does not allow covert AUV deployment. (i.e. hangar on
submarine so enemy knows if submarine is likely to be equipped
with the AUV capability
April 2008
Page 12 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
More potential to move capability around the globe, to and from
different submarines that are fitted for and not with
Certain hangar positions may be challenging to integrate into
existing submarines (e.g. fin embedded hangars) so new build
would be preferred
Promotes a form of containerisation of AUV and most of its
support systems
Recovery is arguably more difficult when submarine is in transit
Likely to be able to retrofit such systems to an existing submarine
Reduced impact on submarine signature and manoeuvrability etc
compared to other large CMH designs
Interface with the Host Submarine Systems
The interface of the host platform systems with the AUV is an area of work in which the study team will be
exploring in the coming months. However, an indicative block diagram to illustrate likely interfaces is provided at
Figure 25.
INTERNAL
COMMUNICATIONS
SYSTEMS
RADAR SYSTEMS
VISUAL SYSTEM
UUV/S
NAVIGATION
SYSTEMS
Process
EXTERNAL
COMMUNICATIONS
SYSTEMS
UUV/S LAUNCH
& RECOVERY
SYSTEMS
COMMAND AND
CONTROL
SONAR SYSTEMS
DEPLOYED ASSETS INTERFACE SYSTEM
Figure 25 - Indicative Host Submarine Interfaces
Summary
Cleary, the suitability of the L&R options discussed depends on a number of factors to do with a submarines
margins and the need to retrofit to an existing submarine or if the opportunity presents itself, to incorporate into a
new build submarine during the preliminary design stage. Consequently, an attempt has been made to align a
number of the L&R concepts discussed with some indicative sized submarines. A summary of this work is
provided at Table V.
Table V – Feasibility Matrix of Likely AUV L&R System
Submerged Submarine Displacement (t) Groups and L&R Suitability
Likely AUV
Deployment/Recovery System
< or = 2,000t
(Submerged)
>2,000t and < or = to
3,000t (Submerged)
>3,000t and < or = to
4,500t (Submerged)
>4,500t and < or = to
17,000t (Submerged)
21 Inch Torpedo Tube
9
9
9
9
Enlarged Torpedo Tube (<1m
diameter)
8
8
8
9
Small Wet/Dry Hangar (<0.2m
diameter and 2.0m length
9
9
9
9
Medium Wet/Dry Hangar
(<0.8m diameter and 4.0m
length
8
9
9
9
Large Wet/Dry Hangar (<1.5m
diameter and 6.0m length
8
8
9
9
Dry Deck Hangar (>.3.0m
diameter and 10.0m length)
8
8
9
9
No hangar - Piggy Back AUV
9
9
9
9
April 2008
Page 13 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
CONCLUSIONS
Overview
This paper has summarized a number of initial concepts being explored by BMT Defence Services and has exposed
a number of the integration issues and challenges associated with launching and recovery AUVs from submarines.
The study team are continuing to undertake work in this area in consultation with AUV manufacturers and potential
operators over the coming months. Further definition of some of the concepts that are believed to hold most
promise will continue focused on exploring areas such as the extent of automation that could feasibly be introduced
during the L&R evolution and maintenance, re-programming and re-charge routines.
In terms of wider development of AUVs this is most likely going to be focused on four principal areas:
1.
Increases in vehicle energy storage provision to increase endurance and range of vessels and support more
power hungry sonar and communication;
2.
Reliable and standard command and control systems that will enable communication between the host
vessel, other vessels and other AUV/s;
3.
Increases in the adoption of open system architectures which will allow for easy and rapid re-configuration
of mission system software;
4.
Adaptations to the AUV design to enable militarization of the vehicle, allow for effective payload delivery
and those to suit the chosen L&R concept.
Summary
In whatever guise AUVs are to be adopted into submarines, an over-arching aim for designers and naval capability
definers is to enable a useful hybrid to be realized that maximizes the capabilities of both the host submarine and
the AUV, playing to each others strengths whilst mitigating wherever possible their respective weaknesses.
One of the first aspects that will require attention is to consider what is required from the AUV based on the
anticipated mission and then define how best the AUV may be employed. This will then help in identifying the
AUV design drivers and help determine the particular AUV that could be adopted, albeit a largely COTS based
AUV design or something more exotic and bespoke.
In the near future the aspiration to operate AUVs from submarines will require modifications to existing designs,
resulting in a capability that is arguably not fully optimised or balanced. As experience develops it is considered
entirely plausible that bespoke or hybrid submarine designs will emerge. As these designs evolve much more
attention in their design will be given to ensuring they are receptive to modular payloads, including those associated
with hosting AUVs.
Recent evidence is supporting the assumption that the some of the first experiences of conducting AUV operations
will be via a single mission focused AUV, deployed from a modified submarines that can accept and operate
AUVs. Once the benefit of such vehicles and the design and operational challenges are understood, then a
significant increase can be expected in the types of AUV that will be employed and the range of roles that they can
plausibly undertake.
However, it is essential for AUV designers, submarine integrators, and the military community to share and
develop their ideas, ensuring that conflicting requirements are managed and technology development is undertaken
in a planned and cohesive manner. These approaches will ensure delivery of the outputs that the operational
community demand and assist equipping submarines with the significantly capability enhancement that AUVs can
provide.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the image sources:
1.
Figures 3 & 4 - Image courtesy of Kongsberg Maritime Ltd.
2.
Figures 12 & 13 - Images courtesy of Mr. Paul Farley, U.S. Navy.
The authors wish to thank the following persons for their assistance in preparing this paper:
1.
Michael Topp, Tony Marshall and the team at Kongsberg Maritime Ltd.
April 2008
Page 14 of 15
© BMT Defence Services Ltd
Paper on UUV Deployment and Retrieval Options for Submarines presented at INEC 2008 in Hamburg, Germany.
2.
Simon Binns of BMT Defence Services for his assistance in the production of illustrations.
REFERENCES
1
US Department of the Navy, “The Navy Unmanned Undersea Vehicle (UUV) Master Plan”, 9th November
2004.
2
STEWART M.S, Applied Physics Laboratory, University of Washington, PAVLOS, J. General Dynamics
Electric Boat, “A Means to Networked Persistent Undersea Surveillance”, Submarine Technology
Symposium 2006.
3
NEWMAN.P, WESTWOOD R & WESTWOOD J, AUV Market Prospects, Results of a New
‘Gamechanger’ Study.
4
Engineering & Technology Magazine, The Institution of Engineering and Technology (IET), Page 14,
January 2007.
5
http://www.saabgroup.com/en/ProductsServices/products_az.htm.
6
http://www.defenseindustrydaily.com/boeings-blq-11-lmrs-a-sub-recoverable-uuv-04319/, Retrieved
December 2007.
7
http://www.boeing.com/defense-space/infoelect/lmrs/index.htm, Retrieved December 2007.
8
“To Come Unseen: Special Forces Delivery From Submarines”, Jane’s Navy International, 3rd November
2003.
April 2008
Page 15 of 15
© BMT Defence Services Ltd