Wood-burning, robotic trucks could figure in the United States Army's future plans.

Ground vehicles that burn wood pulp for fuel are part of the Army's vision to have transportation that's self-sufficient, even when isolated from conventional fuel supplies for long periods.

Dr Jaret Riddick, from the US Army Research Laboratory's Vehicle Technology Directorate, says that the duration of foot patrol missions, isolated from bases and a ready supply of fuel, are often controlled "by power and energy."

So Riddick says, the directorate is working on developing engines that consume raw materials directly from the soldiers' environment, transforming any organic and combustible material into biofuel.

It's also looking to develop unmanned vehicles that can work with soldiers – it even has a name for it: Manned-unmanned teaming.

The aim is to provide future soldiers with an autonomous system that operates as a teammate – able to transport supplies "and enhance situational awareness by supporting the communication, surveillance and reconnaissance mission," says Riddick.

Advanced manned-unmanned teaming could see drones and autonomous ground vehicles act as the "tip of the spear," protecting soldiers from first contact with an enemy, he adds.