By SYDNEY J. FREEDBERG JR.
WASHINGTON: Just outside Detroit, home of the muscle car, the Army's put together a powertrain as potent as three Trans Ams strapped together — with an electric stealth mode that sounds more like a lawnmower than a tank. The 1,000-horsepower Advanced Powertrain Demonstrator packs more diesel horsepower in less space than current engines, along with a 160-kilowatt generator that can power advanced electronics – like a drone-killing laser or anti-missile defenses – and even move an entire 50-ton vehicle for brief periods.
Now installed in an M2 Bradley hull for testing, the current version of the APD can move war machines up to 50 tons, but it's meant to be easily modified for larger or smaller vehicles.
“Each of the pieces can be scaled” up or down, said John Tasdemir, chief of the power & mobility branch of the Army's Ground Vehicle Systems Center (formerly TARDEC) in Warren, Mich. “It could not just fit a Bradley, it could fit a future vehicle, [or] it could fit a legacy vehicle as well.”
Compact enough to fit into the notoriously cramped Bradley, the 1,000-horsepower Advanced Powertrain Demonstrator produces 48 percent more horsepower than the most-upgraded Bradley variant and 67 percent more than the standard 600-hp model. The engine could also fit the turretless utility variant of the Bradley, the Armored Multi-Purpose Vehicle, or, with some rearrangement of the components, the M109A7 Paladin howitzer. And since the design is modular, the APD could be scaled down to 500 hp – potentially powering the more tank-like of the Robotic Combat Vehicles the Army's now developing – or up to 1,500 hp – enough to drive the 70-ton M1 Abrams main battle tank.
Another logical candidate for APD technology is the Optionally Manned Fighting Vehicle now in development to replace the Bradley. Fitting the new vehicle would require some redesign, said one of Tasdemir's engineers, Mike Claus, but if they could optimize the APD components for an all-new hull without the awkward compromises of the Bradley, the resulting design could be “way more compact.”
How It Works
Why is it important to be compact? Well, the heaviest part of a combat vehicle is its armor. The weight of the armor, in turn, is the product of its thickness and the surface area it has to protect. The bulkier you make your vehicle – the greater the “volume under armor,” in Army terms – the more tons of armor you need to get the same level of protection.
To make the APD more compact, it needs to be more efficient. To do that, the Army and its contractors went to work on every piece of the powertrain – for example:
- In the diesel engine itself, built by Cummins, the pistons go through a two-stroke cycle instead of the usual four, allowing them to generate more horsepower with less waste heat from the same amount of gas. Historically, two-stroke engines are also highly polluting, which is why they've not been widely adopted, but the APD uses cutting-edge emissions controls.
- The SAPA drive-by-wire transmission replaces traditional, inefficient mechanisms like pumps with precisely engineered electromagnetic controls called solenoids. The transmission is in fact so attractive to other Army programs that they're considering installing it even without the rest of the APD powertrain.
- The cooling system replaces traditional filters – which wear out in 20 hours in dusty areas like deserts – with a Donaldson pulse-jet air cleaner that lasts 500 hours and provides much more airflow. Cooling armored vehicles is always challenging, even when they're not fighting in the desert, because they're basically metal boxes in which you want to punch as few holes as possible.
- The L3-Harris Integrated Starter-Generator produces 160 kW – many times the current alternator on the Bradley – but doesn't require its own dedicated cooling system, unlike traditional electronics. That's because it uses heat-resistant silicon carbide components that can function at 105 centigrade (hot enough to boil water), the same as the engine block.
That electrical power is as important for modern combat vehicles as diesel horsepower. During the Iraq War, the Cold War-vintage Bradleys got upgraded with so many advanced sensors, communications networks, display screens, and radio jammers to deactivate roadside bombs that they couldn't power everything at once.
Now, worried about Russia's vast arsenal of RPGs and anti-tank missiles, the Army is pushing to install so-called Active Protection Systems on its armored vehicles, which use compact radars to track incoming projectiles – a big power drain – so miniature missile launchers can shoot them down. And for the near future, the Army is highly interested in high-powered laser and microwave weapons, albeit primarily against fast-moving, fragile targets like drones and rockets rather than heavily armored vehicles like tanks.
The Ground Vehicle Systems Center plans to test the APD powertrain on a stationary Bradley hull through this coming March, by which point they expect to have demonstrated what's called Technological Readiness Level (TRL) 6. Then they'll fully integrate the APD into a drivable Bradley, the Advanced Mobility Experimental Prototype (AMEP), which will be tested to TRL 7 or 8 – the highest level possible for a prototype – in 2022.
The next year, 2023, the Army will hold the final competition to build the Bradley replacement, the OMFV.
https://breakingdefense.com/2019/12/army-revs-high-tech-tank-engine
