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How electric propulsion will shape the next generation of military vehicles


Dr David Moore and Prof John Mackey

Until recently electric propulsion was being idly discussed as a promising technology for military vehicles. Now, the discussions are when, not if, it will happen.

Electric propulsion

Some are predicting electric fleets within a decade. QinetiQ’s announcement of a contract win with the US Office of Naval Research to research and develop our proprietary hub drive unit for its Armoured Reconnaissance Vehicles demonstrates the growing commitment and interest in this field.

Electric propulsion is not new. Trains have long used it, and many private sector companies, QinetiQ included, have been innovating in this area for years. But the global electric drives market is changing rapidly as new innovations make it more efficient and thus expand into new applications. Rapid growth in consumer electric vehicles has shown what is possible and has driven interest in applying similar technologies in the defence sector.

As a result, electrification, including electric propulsion now sits at the heart of a movement to reshape military vehicles, and how we use them. Some defence vehicles are approaching 30 years old. They were designed for a different era, using technology that is now outdated. Forces are turning their thoughts to the next generation of vehicles, and how they can take advantage of new technologies to improve, mobility, survivability and automation.

Innovative minds see a future where military vehicles are unrecognisable. Clunky mechanical systems will be replaced with fine-tuned, highly responsive electrical systems. New sensors will capture vast amounts of data on the environment, giving teams detailed information on their surroundings. AI will turn this data into insights and early warning systems, making operations safer and more efficient. This will all happen in a world slowly moving away from fossil fuels to clean energy.

Electric propulsion is just one part of this movement, but it underpins everything around it. Its significance in the bigger picture should not be understated. This breaks down into two key roles.

1.Efficiency and economy - Electric propulsion is more efficient and reliable than existing mechanical propulsion and allows a higher degree of control and startup speed (acceleration), bringing agility to vehicles, whilst reducing fuel demand. It can replace engines with electric power sources, and fixed mechanical parts with flexible cables, allowing vehicles to be designed around intended use rather than engineering necessity.

2. Enabling emerging technologies – Beyond the direct impact, electric propulsion supports the adoption of next generation autonomous/intelligent vehicles by providing precision control. Replacing engines and mechanical drive shafts with electrical power sources and motors allows a single system which combines propulsion with sensors, controls, on-board computers, communications and targeting systems. Electric propulsion is therefore a vital part of a broader move towards increased electrification and autonomous vehicles.

The future of the battlefield is hard to predict, but it will inevitably be disrupted by such technology. Armies are configuring themselves to cope with political and technological uncertainty, and this potentially includes greater roles for robots, drones and vehicles with some degree of autonomy. Both the US and UK are pursuing a highly flexible force that can operate in many different environments around the world. Updating armoured vehicles to support this new paradigm is a critical part of that strategy.

Armoured vehicles need an update

Current armoured vehicle designs face several problems. First, as weaponry becomes more destructive, heavier armour is needed but this increases vehicle weights beyond the design limits, which makes vehicles sluggish. Furthermore, they have an inherent weak point; the mechanical shaft that drives the wheels must run unimpeded along the base of the vehicle, limiting the level of protection provided by underbody armour. Explosions from below can turn the drivetrain into projectiles and blast it up through the vehicle. Roadside bombs and IEDs were responsible for 63% of coalition deaths in Iraq and 66% in Afghanistan.

Second, they are poorly-suited to the Fourth Industrial Revolution (4IR) technologies that militaries hope to deploy, and even less so to becoming autonomous. Increasing the number of sensors will mean adding new electrical power loads to an already cramped space, and necessitating communications protocols between mechanical and electrical platforms not designed to work together.

Third, the need for fossil fuels poses a problem that will exacerbate over the long term, since oil is subject to supply shocks and potentially long-term price increases due to geopolitical uncertainty and environmental costs, whilst clean energy is advancing rapidly. Transporting hydrocarbon fuels is expensive, increases the logistical burden and creates obvious attack points. The military - whose job it is to protect people from global threats - must do its bit to tackle the threat of global warming. There is a driver to reduce the amount of fuel transported to the battlefield and, longer-term, to switch to renewable fuels or electric charging.

The electric propulsion solution for armoured vehicles

These problems can be solved by a new generation of vehicles with electric propulsion at the heart of their design. There are four specific opportunities that can be realised from this change, which anyone researching or commissioning new vehicle designs must consider:

  • 1. Cost and fuel efficiency
    Electric propulsion can be powered by smaller, lighter and more energy efficient power sources, which deliver energy down cables to motors which could be housed in the wheels. As far back as 2003, QinetiQ took part in an MOD programme which demonstrated 10-15% fuel saving of an electrical propulsion system and 91% faster acceleration times compared to an equivalent mechanically propelled vehicle; significant advances have been made since.
  • 2. Survivability
    Replacing heavy mechanical systems with lighter electrical systems makes vehicles more agile and allow armour to be better distributed. The electric power source enables silent running, making vehicles stealthier. Significantly, electric propulsion removes the mechanical drive shaft on the underside of the wheeled fighting vehicle, allowing designs that offer greater protection against explosives.
  • 3. Mobility and manoeuvrability
    Electric propulsion can make military vehicles quicker and, for vehicles with in-wheel drives, more manoeuvrable, as each wheel can be controlled independently for both traction and direction of rotation.

In mechanical propulsion, fuel is burned to drive pistons which are connected to a crankshaft, producing torque and power. This  accelerates and propels the vehicle, taking a small amount of time. With a Hybrid electric drive system, once the demand to move is made, current flows through the motor to create torque almost instantaneously. This is why electric cars are quick off the starting blocks, and the same principle can be used for armoured vehicles. Armoured vehicles are of course heavier than cars, so military systems must be more powerful (QinetiQ’s electric drive systems, at 20 kilonewton metres, have around ten times greater available torque than some of the best consumer electric vehicles).

4. A step towards smarter vehicles
Current Combat Vehicles use an internal combustion engine to provide propulsion, and to generate power for electrical systems, such as increasingly complex networks of sensors and electronics. If we use an electric power source for propulsion, that same source can also power the electronic devices that represent the future of intelligent mobility. Since, computers naturally interface better with electrical than mechanical systems, this will assist the introduction of truly intelligent vehicles that can assess a situation and respond accordingly with precision movement.

Electric propulsion allows precision control of speed and direction, which computer systems deal with well. Whilst electric propulsion does not in itself make vehicles more intelligent, it makes the integration of intelligent technologies and systems much easier. This bodes well for the expectation that future combat vehicles will have the option to be unmanned, if not fully-autonomous.

The electric power generation needed for the propulsion system could also power off-board electrical systems, of which there are many in combat zones, such as Headquarters operations. Additionally, a tank could easily become an emergency power supply for a hospital, refugee camp, or small town.

Harnessing the opportunity

The opportunity is considerable, and the industries that will underpin this change are gearing up to support the shift. Visiongain suggests a $160Bn market for global armoured vehicles by 2027, many of which may use electric propulsion. And this is just military vehicles, the same kind of propulsion has applications in other heavy-duty vehicles, such as for mining, construction, and agriculture.

The UK is well placed to take the lead. It is investing heavily in electrical power storage and propulsion technologies, and it has world leading military electric drive technology in QinetiQ. The UK is also a leader is complementary technology such as sensors, AI, batteries and fuel cells. Armoured vehicle OEMs and government labs around the world should engage proactively with UK industry as a priority.

Electric propulsion, until recently a pipe dream for defence, has suddenly become a pressing need. The technology is rapidly advancing, and the benefits have been recognised. Private sector innovation is driving rapid advances in this field; and the global defence industry must actively engage to ensure they benefit from this innovation in a way that creates flexible, secure, intelligent next generation vehicles, fit for an uncertain future.

What is electric propulsion?

In an internal combustion engine, fuel creates mechanical energy that is transferred down a driveshaft to turn the wheels, or tracks in the case of a combat vehicle.

Electrical propulsion uses an electric motor to propel the vehicle, which can sit in or near the wheels. These motors are still powered by an energy source - which can be a diesel engine driving a generator, a battery or a fuel cell - but the source creates electrical energy which can be transferred to the motor through cables. This means the engine and generator can sit almost anywhere in the vehicle.

The immediate advantages are greater powertrain efficiency, enhanced mobility, reduced size and weight, faster launch speeds, and increased design flexibility, since the engine and cables can go wherever you like.

Longer term, this is part of a broader move towards electrification, which will play an important role in integrating intelligent systems and eventually creating autonomous vehicles.