The horizons of unmanned underwater technology stretch from meeting current operational requirements to future scenarios more akin to science fiction.
Julian Kerr | Sydney
In both instances, information on the roles to be played by unmanned underwater vehicles (UUVs) has been less comprehensive than that available on unmanned aerial vehicles (UAV) and unmanned ground vehicles (UGV), largely because UUVs remain less developed and have been less widely deployed.
So far as Australia is concerned, DST Group’s focus is very much on the development of UUVs to meet the RAN’s mine countermeasures (MCM) requirements in the littoral, albeit with a watching brief on the larger and more futuristic UUVs under development abroad for a range of blue water tasks.
Project Sea 1778 Phase 1 is intended to supply maritime units with the capability to detect, classify, avoid and where necessary, neutralise the mine threat.
According to the 2012 Defence Capability Plan, the project will furnish the initial means by which task groups implement self-protective MCM along intended routes, through choke points and within objective arenas; complemented by the current dedicated MCM force.
First Pass approval was announced in 2012 but since then the project has entered the cone of silence, with Defence telling ADM in mid-July that only high priority projects were being approved by government prior to publication later this year of the Defence White Paper and the associated Force Posture Review.
However, Dr David Battle, head of DST Group’s Unmanned Systems and Autonomy Group, expects the RAN will take delivery of its first autonomous underwater vehicles (AUV), equipped specifically for MCM work with sidescan or synthetic aperture sonar, soon after 2017.
Development work is proceeding on both manportable and midsized capabilities, using as test vehicles the commercially-available REMUS 100 and REMUS 600 AUVs developed by Kongsberg subsidiary Hydroid.
“There’s a lot of very good technology available off the shelf; you really have to build a lot of underwater vehicles to make them reliable and that stage has now been reached although the REMUS will not necessarily be the operational choice,” Dr Battle said to ADM.
“Our preferred solution is to incorporate intelligence to the vehicle; something we can do in an after-market way by adding or modifying software so we can make it a lot smarter.”
The untethered, battery-powered AUVs execute pre-determined search patterns in a harbour or other operational areas utilising their sonar and Automatic Target Recognition (ATR) software.
“Our preferred solution is to incorporate intelligence to the vehicle; something we can do in an after-market way by adding or modifying software so we can make it a lot smarter.”
ATR has two specific benefits – onboard data processing which accelerates post-mission analysis and thus the tempo of mine clearance operations; and the ability to program the vehicle’s autonomy system to perform in a certain way when it encounters an object on the sea bottom, “With acoustic imaging we find it’s always good to look at an object from different aspects to figure out what it is,” Dr Battle explained.
“The AUV can be programmed to automatically execute a reacquire/identify manoeuvre with a search pattern over the object at different angles, making it much easier for an operator to classify. But in both instances the data remains on the vehicle until its return to the host ship.
“All navies are trying to acquire this capability and we’re doing rather well. Last year we participated in an autonomy trial in the UK with other Five-Eyes nations and that was a bit of a coup because we had a US underwater vehicle with an Australian processor running Canadian software and it worked,” Dr Battle commented.
“We add an additional processor to the vehicle and then load what we call payload autonomy; various open-source software that is derived from the academic community in the UK and US and our focus is on the algorithms that execute the ATR.
“Down the track we’ll be doing much more with autonomy but the focus at the moment is ATR which the Navy has expressed a great desire to have.”
Dr Battle acknowledges the possibility of an AUV hitting a mine during a preprogrammed search pattern and being destroyed, but regards this as a fairly remote possibility.
“It could run into a tethered or moored mine but most mines are fairly insensitive to that sort of thing. Mines these days respond to a mixture of influences – acoustic, magnetic, even pressure – and they’re quietly processing information until they’re absolutely convinced there’s a large ship over them that they can take out.”
While the proposed manportable MCM capability could be deployed on a rigid-hulled inflatable boat, the mid-size would require access to a crane, and thus a host ship of reasonable size. Running at a speed of around three knots, the manportable capability would have an endurance of 10 to12 hours and cover 0.1 – 0.2 km² per hour.
A mid-size synthetic aperture capability would cover about five times that area and run for about 24 hours, depending on the amount of power drawn by the sensor.
Neither that nor sidescan sonar would detect a buried mine, meaning the RAN would probably rely on Dyad magnetic influence sweeps to trigger such threats where their presence was known or suspected.
US efforts
Inevitably the focus falls on the US when looking at deep sea unmanned underwater technology, given the number of developments being undertaken there, and the information that emerges.
Dramatic changes in undersea warfare and the role of UUVs were posited in a recent and widely-quoted report by the US Centre for Strategic and Budgetary Assessment (CSBA).
This suggested that improvements in anti-submarine warfare sensors would lead to large UUVs and other deployed systems being increasingly relied on as substitutes for manned submarines in conducting tactical operations such as coastal intelligence gathering, land attack, or anti-ship missions in hostile littorals.
The advent of undersea fire control networks facilitated by new long range sensors such as low frequency active sonar and wake detection could enable coordinated surveillance or attack operations, with swarms of UUVs operating autonomously or controlled from a manned submarine or other platforms, the report suggested.
Both possibilities are already being researched. The Large Displacement Unmanned Underseas Vehicle (LDUUV) project of the US Office of Naval Research (ONR) seeks to develop a pier or ship-launched unmanned submarine able to operate in the open ocean as well as in coastal waters and harbours on intelligence, surveillance and reconnaissance (ISR) missions lasting more than 70 days.
"Inevitably the focus falls on the US when looking at deep sea unmanned underwater technology, given the number of developments being undertaken there."
The ONR believes the LDUUV may also evolve into a large UUV mothership that launches and recovers smaller surveillance UUVs when it reaches its mission areas.
For its part, the US Defence Advanced Research Projects Agency’s (DARPA’s) Hydra program envisages unmanned motherships carrying multi-cell canisters of UUVs and Unmanned Aerial Vehicles capable of underwater launch, deploying to coastal areas and remaining there for weeks or months until called on to act as force multipliers.
DARPA’s separate Upward Falling Payload (UFP) project centres on pre-positioning deployable, unmanned, nonlethal distributed systems that would lie on the deep-ocean floor in special containers for years at a time. These deep-sea nodes would be remotely activated when needed and recalled to the surface. With nearly 50 per cent of the world’s oceans deeper than four kms, vast areas are available for concealment and storage.
Each node would comprised three main subsystems: a payload that executes waterborne or airborne applications after reaching the surface, a “riser” that encapsulates and launches the payload, and a communications system that would trigger the launch protocol. The UFP nodes would have to survive at a depth greater than six kms, last up to five years and be able to operate less than two hours after being commanded to launch from the bottom of the ocean.
Possible payloads could include waterborne and airborne cameras, decoys, networked nodes, beacons, jammers and obscurants, according to reports of the original 2013 DARPA outline.
Of more immediate interest to DST Group is the ZRay, developed as part of the US Navy's Persistent Littoral Undersea Surveillance
Network (PlusNet). The platform’s 6.1-metre wingspan makes it the world’s largest known autonomous blended wing underwater glider.
Evolved from the earlier XRay glider that was designed to track quiet diesel-electric submarines operating in the littoral, ZRay is primarily intended to track marine mammals in navy acoustic testing areas, but could easily be reconfigured to the type’s original military purpose.
“It so happens that the people behind the XRay vehicle are former colleagues of mine so we’re in regular communication anyway,” Dr Battle disclosed to ADM. “It sounds as if they’re open for collaboration, and that’s something we’re looking at now.”
Australian interest is particularly driven by the glider’s exceptional endurance – about one month with on-board energy supplies that would allow it to monitor more than 1,000 kms of ocean.
ZRay collects acoustic data via a 27-element hydrophone array installed in a sonar housing in the glider’s leading edge. Wide-band acoustic sensors are also located in the nose and tail.
“The ZRay/XRay model is essentially a sensor, you could think of it as a mobile sonobuoy on steroids with a lot of internal processing using only a small amount of power, though more processing could be switched on if you thought it had found something interesting,” Dr Battle said. “It would be completely autonomous; it would probably just come to the surface every few days to make contact via satellite.”