Designed for anti-tank warfare, possibly the last place you'd expect to see a Rafael Spike fire-and-forget guided missile would be at sea, let alone on a robotic boat, but they may offer a step towards revolutionising sea warfare. The US Navy has for the first time launched six Spike missiles from an unmanned surface vessel precision engagement module (USV PEM), successfully hitting a floating target as far away as 3.5km.
The demonstration was carried out by the Chief of Naval Operation's Expeditionary Warfare Division and the Naval Sea Systems Command's Naval Special Warfare Program Office as part of efforts to develop an arsenal that could successfully engage armed small boat swarms.
The USV PEM platform is an 11m-long inflatable hulled vessel armed with a 0.50 calibre gun alongside the missile launcher. Remotely operated by shore-based sailors at the US Navy's Patuxent River base, the PEM aims, fires and updates the missile in flight.
The Spike missile uses electro-optic and infrared sensors to identify and lock onto the target and send updated targeting information back to the operator through an ultra-thin fibre optic tether.
"The USV PEM project was developed in response to recent world events which have increased the concern over swarms of small attack craft, as well as threat assessments outlined in recent studies conducted by the Naval Warfare Development Command," said Naval Special Warfare Command assistant programme manager Mark Moses.
"The study punctuates the effectiveness of these swarm attacks against both military re-supply ships and naval vessels. Technology demonstrated in this project can provide a capability to combat terrorists who use small low-cost vehicles as weapons platforms."
Israel's pioneering Protector USV
Given its pioneering and market-leading approach to unmanned aerial vehicles (UAVs) it is perhaps little surprise that Israel is ahead of the game in armed USVs too.
Made by Rafael Defense Systems, the Protector Unmanned Naval Patrol Vehicle was deployed as far back as 2005 by the Republic of Singapore Navy, which is continuously plagued by pirates in the Strait of Malacca.
The rigid-hulled inflatable boat has since seen action supporting coalition forces in the Persian Gulf and protecting shipping from pirates in the Gulf of Aden.
Fitted with a remote-controlled, stabilised Mini Typhoon Weapon Station that can operate a range of small-calibre guns, its anti-terror mission payload includes a search radar and Toplite electro-optical pod to enable detection, identification and targeting.
UK to move from underwater to surface
Royal Navy's Type 26 Global Combat Ship
In August 2012 the UK Ministry of Defence (MoD) announced new plans for a fleet of armed maritime drones, including USVs, to reduce costs and carry out dangerous and repetitive tasks in support of Royal Navy operations.
Papers published by the Defence, Science and Technology Laboratory (Dstl) sought help from defence manufacturers to develop vessels which could provide greater support to maritime operations, such as mine countermeasures, anti-submarine warfare and missile defence.
The document identified that USV technology could be used to track ships and provide intelligence to maritime forces, particularly in combination with other types of drones and in support of covert operations.
"A range of unmanned systems including UUVs, unmanned surface vehicles (USVs) and unmanned air vehicles (UAVs) may be used to support these maritime tasks and could be expected to perform a number of roles, including, but not limited to, remote sensing, communications relay, delivery of effects such as the deployment of weapons or countermeasures," the report said.
Demonstrating the Royal Navy's support for robotic vessels, its future warship, the Type 26 Global Combat Ship, is specifically designed to launch and operate aerial, underwater and surface drones.
Canada considering USV technology
In June, Canada announced that the Royal Canadian Navy was also seeking a fleet of maritime drones, including USVs. Defence Minister Peter MacKay told The Canadian Press that while USV technology was in its infancy compared with aerial drones, they could have a role to play in the near future of the Canadian Navy.
"We're surrounded by water," he said. "Unmanned vessels, like unmanned aerial vehicles, give us reach and capability without the same risk. It allows you to keep harm at a distance, so there's a lot of interest."
In May, the Canadian Ministry of Defence awarded Rolls Royce Naval Marine Canada a C$3m contract as part of a project to automate the deployment of USVs, for everything from detonating mines to checking for oil spills.
Ecuador combating pirates with USVs
Not all armed USV development is in the hands of the big spenders, some is driven by necessity, such as the Ecuadorian Navy's bid to beat piracy in its waters. In February, it tested its prototype USV, B.A.E. Esgrum, on the Guayas River.
Developed for coastal patrol and jungle operations, the Esgrum is less than two metres-long, has a range of five kilometres and comes with an on-board sensor suite, CPU, camera and communication system.
Its weapons system consists of an electronically-ignited assault rifle with no moving parts and a rocket launcher operated by a fire control system.
Built using exclusively commercial off-the-shelf (COTS) materials without technical assistance from other countries, the USV can be remotely operated in remote mode or work in fully autonomous mode to carry out surveillance and reconnaissance missions.
Navy research director Eduardo Cadena said: "Under ideal conditions, the USV can detect installations occulted by high-density vegetation. Basically, you can't see the robot, but the robot can see you."
Advances in the field of remotely operated vehicles have meant that sailors aboard stricken submarines are no longer doomed.
Both the US and UK navies will soon be fielding new combat ships to fulfil a variety of operational capabilities.
Unmanned aerial vehicles (UAVs) are widely seen as a critical component of the defence strategies of the future.