The U.S. military's efforts to shrink its carbon bootprint have been well documented on GreenBiz. We've told you how the Defense Department is quietly leading the government's green efforts, about the Army's big push on renewable energy projects, the microgrid pilot on the largest Marine Corps base and the Navy's $500 million investment in biofuels and more.

Now defense contractor BAE Systems is in the running to deliver a design for a hybrid-electric, next-generation Ground Combat Vehicle (GCV) as part of the Army's effort to modernize its armored fighting vehicles.

Though any vehicle that's big, enclosed and has swiveling mounted guns tends to be called a tank by civilians, GCVs aren't tanks. They are expected to be among the vehicles that carry a squad of soldiers into combat in deployments that can include main battle tanks.

Just this summer, BAE Systems, in partnership with Northrup Grumman, landed a $450 million tech-development contract for the GCV program, and General Dynamics Land Systems, working with Lockheed Martin and Raytheon, won a $440 million contract, according to the Army Times.

Mark Signorelli, BAE's vice president and general manager of weapon systems, talked to me recently about why his firm is focusing on a hybrid electric drive system.

The design under development won't be the first hybrid BAE has offered to the Army.

"We've been pursuing this technology for a long time," Signorelli said. "We actually built 13 different electrical vehicle prototypes for the Army dating back to the early 1980s ... and we built five prototypes for the Army's Future Combat Systems program, which unfortunately was terminated [after running from 2003 to 2009]. So we're very hopeful this will be the first vehicle to make it all the way to production."

This time a confluence of several factors, not the least of which is the DoD's aggressive stance on energy efficiency and sustainability, could favor BAE.

There's a "unique combination of the technology reaching the appropriate level of maturity and the opportunities and timing being just right for those technologies to be widely accepted," said Signorelli.

Here are highlights from my discussion with Signorelli:

Leslie Guevarra: What is BAE is developing and how is it new and different?

Mark Signorelli: BAE Systems was one of two companies that were awarded a technology demonstration contract for the Army's new Ground Combat Vehicle. This is a vehicle that the Army is proposing to develop that would replace the Bradley Fighting Vehicles in its heavy force. GCV represents a whole next generation of combat vehicles.

Bradleys [manufactured by BAE subsidiary BAE Systems Land and Armaments] have been wonderful vehicles. But they are approaching the point at which the technology that was built into those platforms really is reaching the end of its lifecycle. So the Army is looking to develop a vehicle that integrates current mature technologies and provides a platform that, much like the Bradley has done for the last 40 years, can serve the Army for the next 40 years -- especially since we've seen new threats emerging and new expectations of our forces operating in a very rapidly changing battlefield environment.

Our offering for the ground combat vehicle is uniquely identified by its hybrid electric drive propulsion system.

LG: What do these new next-gen vehicles need to do and how do your designs accomplish that?

MS: The Army laid out four untradeable requirements for these vehicles:

The first is to carry a full squad of nine soldiers plus the vehicle crew.

The second is to provide force protection. These vehicles have to be designed to protect that infantry squad and vehicle crew in any environment that they might encounter. The one that probably is of most note today is improvised explosive devices or IEDs; they're seeing increasing use in Iraq and Afghanistan. But there is a broad spectrum of threats that these vehicles are expected to encounter -- everything from IEDS to direct-fire cannon systems.

The third is flexibility. They want this vehicle to be able to [accommodate] growth -- to be able to add technologies and capabilities over the expected lifetime of the vehicle. They want the vehicle to be modular [so it] can add or subtract armor or other protection systems.

And they want the vehicle to be able to be fielded in seven years. ... In terms of defense programs, that is lightning-fast.

Next Page: Don't call the BAE Ground Combat Vehicle a tank or a 'Battlefield Prius'