Of all of the concept weapons, the railgun has arguably caused the biggest stir, and it is not hard to see why. An electromagnetic weapon that can fire a solid projectile towards a distant target at Mach 7 or more – three times faster than the typical 800m/s muzzle velocity of a conventional 5-inch naval gun – has clear appeal for tomorrow’s navy. But hypersonic speed is not the only lure.
Designed to provide an offensive power projection capability as a complement to conventional missiles and aircraft, it offers a sustained rate of fire of up to 12 rounds a minute.
With a 200 mile range and a flight-time of around six minutes, its notional 15kg projectile would dump a terminal 17MJ of kinetic energy – roughly twice the energy delivered by a traditional 5-incher’s warhead, weighing twice as much.
The weapon itself is effectively a high-tech slingshot, with the ‘bullet’ held in a conductive slide which bridges two parallel conductor rails.
A huge pulse of electricity applied to one of the rails travels along it, across the slide and back along the other, forming a current loop which induces a massive magnetic field, accelerating the slide along the rails and ultimately launching the projectile at 2,500m/s.
Operationally, it could be used both directly to engage surface targets, or indirectly against distant ones, where the short time-of-flight, over a largely out-of-atmosphere trajectory, makes enemy interference or interception highly unlikely.
Directed energy weapons
With the railgun representing the cutting edge of ballistic projectile research, work on directed energy weapons appears to have opened the way for ‘death-rays’ to leave their sci-fi image behind and finally become a practical military proposition.
In April, for example, scarcely 30 months after the contract to develop a ship-mounted, solid-state, high-energy laser had first been awarded, the US Office of Naval Research (ONR) and industry partner, Northrop Grumman, tested one at sea, successfully disabling a small target vessel.
Impressive though the demonstration was, conventional lasers are power-hungry, and onboard a warship in a maritime environment, that is a constraining factor and one which currently limits their potential use to a close defensive role.
One solution being investigated is the free electron laser (FEL) – a device with serious weapon potential, coupled with an energy demand that, according to Quentin Salter, ONR’s FEL programme manager "won’t slow down the ship."
Using an electron stream accelerated close to the speed of light to generate their beam, FELs have the widest frequency range of all laser types – and can be readily tuned by adjusting the energy of the electron beam, or the strength of the magnetic field, which guides the electrons’ path. It is this which gives the FEL its particular appeal, allowing it to be used for a variety of applications, by varying the power output in a way that other laser technologies cannot.
Both of these programmes have achieved significant milestones. In February, the ONR’s FEL generated a record-breaking 500kV blast, capable of slicing through steel at 20 feet/second – the culmination of six years of research – while in the previous December of 2010, their railgun produced a staggering 33MJ of muzzle energy, subsequently clocking up its 1,000th successful shot by the end of October.
It is a bitter irony for the US Navy that just as the efficacy of these technologies has begun to vindicate the historically high cost of their development, current budgetary constraints have called their future into question.
The Senate Armed Services Committee voted in April to cut the funding, but that may not be the last word on the matter – and others too are experimenting with railguns and lasers. While much of the speculation regarding the imminent deployment of such weapons by the Chinese is, of course, highly suspect, there is no doubt about their interest in developing them.
According to some estimates, military applications account for nearly half of all China’s laser R&D, while other ‘xin gainian wuqi’ (new concept weapons) projects include coil guns, high power microwaves and particle beam weapons.
Dwindling defence spending may have put some US exotic weapons research on hold, but the sharpened focus on cost effectiveness has, by contrast, incentivised programmes such as TacSat – the Pentagon’s experimental tactical microsatellite project – which offer low-outlay capability enhancement.
Cheaper to make and launch, typically utilising commercial-off-the-shelf components, these small satellites promise to set new standards in responsiveness and flexibility,and can be tasked with a range of missions that larger, more specialist conventional space vehicles cannot easily perform.
Launched in September, the US Navy’s TacSat-4 is the latest in the series, providing ten UHF channels which can be used for any combination of on-the-move communications, data ex-filtration or Blue Force tracking.
Placed into low, highly elliptical orbit, the 450kg spacecraft’s 3.5m diameter payload antennae provides high gain, thus obviating the need for ground antenna pointing, while its unique orbit augments geosynchronous communications, with a 4-hour periodicity that provides long dwell-time over theatres.
While versatile microsatellite reconnaissance watches surface vessels from space, future navies will inevitably need enhanced responsiveness underwater too.
Acoustic and non-acoustic sensors systems are now being explored to provide comprehensive tactical and strategic awareness in the submarine battle space, with emphasis on technologies to establish persistent undersea surveillance, improve mine detection and enhance undersea warfare.
Although much of the research is currently at the component level, system-level technology demonstrations are increasing and in the long term, next-generation systems could be carried on-board naval vessels, or deployed as fixed, autonomous installations to protect fleets or ports as required.
AUVs – the rise of the robots
Such a vision forms an ideal fit with the notable trend of many navies towards making greater use of submarine robotics and autonomous underwater vehicles (AUVs).
With many military analysts predicting that all kinds of unmanned underwater vehicles (UUVs) will become commonplace in naval operations of the future, the race is on to develop technologies which will allow multiple and heterogeneous UUVs to function effectively as an element in a hybrid force alongside manned vessels.
Ultimately, ongoing research into improved underwater awareness and enhanced autonomy should allow mixed AUV / UUV platforms to expand the operational envelope, while simultaneously reducing the exposure of high-value assets and personnel to threats, and adding another capability enhancement to the navy of the future.