By Laura Smith-Spark
BBC News, Washington
Got a destination too dirty or dangerous for a person to want to go there? The day could soon come when a robot vehicle takes humans' place as a matter of course.
Unmanned vehicles can take military supplies into risky areas
Scientists are focused on developing unmanned machines that can operate in the air, on the ground and under water, doing jobs where deploying people is just too dangerous.
Some are already in use, such as the unmanned drones which fly over Iraq and Afghanistan carrying out reconnaissance for soldiers on the ground, or bomb disposal robots which disable deadly explosive devices.
Others, still in the development stage, are taking advantage of smaller, lighter components and advances in computer technology to do things never imagined a decade ago.
Some of the latest advances have been on show at the Association for Unmanned Vehicle Systems International (AUVSI) conference in Washington DC.
On the ground
So far the technology for unmanned ground vehicles has been the hardest to develop because of the amount of "clutter" they have to negotiate compared with those in the air or water.
The semi-autonomous vehicle can choose its own route and drive itself
But Dewar Donnithorne-Tait, of the Association for Unmanned Vehicle Systems International (AUVSI), predicted that by 2050 people will only drive themselves around if they choose to do so, because it will be safer, cheaper and easier to use automated machines.
One pioneering ground vehicle on display, developed by General Dynamics Robotic Systems, will be among the first semi-autonomous vehicles to be produced for the military.
Designed for use in sensitive areas such as a large ammunition compound, the MDARS machine can use data to choose its own routes, drive itself and even "talk" to the locks on bunkers to check they have not been tampered with.
Infrared sensors and cameras allow it to avoid obstacles, detect intruders, inventory equipment and see if anything has moved out of place.
It can share roads with other vehicles, run for 16 hours on one tank of petrol and, unlike a person, will not be bored by routine or become complacent. One human operator can monitor up to a dozen of the machines at a time.
Jay Rosenblum, of General Dynamics Robotic Systems, said the first customer would be the US Army, which has ordered six to start with. Other organisations would come on board once convinced of the "cost-effectiveness of replacing humans", he said.
The same semi-autonomous technology may in the future be transferred to a robust vehicle for use in combat situations, replacing current machines which must be remote controlled by human operators.
One such device was displayed by Robotic Systems JPO. The Packbot scout robot on their stand was partially mangled by an encounter with an improvised explosive device in Iraq. Having prevented the bomb blowing up a larger vehicle carrying people, it had done its job.
The military is also operating hundreds if not thousands of small unmanned planes in Iraq and Afghanistan.
They are often used by small units to patrol and assess the battlefield up to 10km ahead, said Captain James Lee, of the US Marine Corps.
The marines are due to switch from the Dragon Eye aircraft to the new Raven B model, which can fly for longer, has better night-time capability and weighs less, within the next six months.
A hidden explosive device in Iraq damaged this unmanned vehicle
"The good thing about this system is you don't have to send a marine out and risk that life," Capt Lee said.
"You can put this up in the air and it will give you that over-the-hill capability that you are looking for."
The machines cost over $100,000, he said, but they are designed to be easily fixed up using duct tape and other materials, giving them long lives.
"If you look at the fact they are helping save lives 'in country' right now, they are beyond priceless," Capt Lee said.
Technologies for small unmanned surveillance planes are developing fast. Lockheed Martin has developed one, the Stalker, which is silent, ideal for covert night-time operations.
The GoldenEye takes off and lands vertically and can hover for hours
The firm Aurora is producing the GoldenEye, which uses ducted fans for power, takes off and lands vertically and can fly for eight hours or hover for three.
On a larger scale, Mr Donnithorne-Tait said he believes the current generation of combat aircraft such as the Eurofighter could be the last to be flown by humans.
"It's already pretty clear that in the future if we are going to have combat aircraft, they will be unmanned, just because they will outperform manned aviation because of the limitations of the human frame," he said.
"And, because there's no human in there, they can be sent into hazardous places like fierce weather conditions where you could never put a person. And if the worse comes to the worse and it crashes, it doesn't kill the pilot."
While many unmanned vehicles are designed for military use, increasingly companies are also looking to tap into civilian commercial markets.
New sonar technology can be used to create images of the sea bed
Canadian firm MicroPilot has developed an autopilot that weighs only 28g and fits in a 6lb (2.7kg) radio-controlled model plane.
Using the Crop Cam system, the operator can programme the desired flight path using a laptop, launch the plane by hand and start receiving images in less than 20 minutes from the on-board camera.
Costing $7,000, it is already being used by universities to monitor wildlife such as eagles, by farmers to check on crops and by forestry managers to count trees in remote areas.
A design from the US Naval Research Laboratory, called the Sail-a-Plane, is still in the research phase but seeks to combine an unmanned water and airborne craft in one.
The idea is that it will fly to a location, then land on water and swivel its wings to act as sails if it needs to remain in one place for a longer time than an aircraft could circle or hover.
Meanwhile, unmanned vehicles are transforming exploration of the world's oceans.
Will robots one day make human beings redundant?
Surface water vehicles are ideal for monitoring coasts and harbours, while underwater devices can hunt for mines, pipelines and shipwrecks or map the ocean at great depths.
California-based firm Applied Signal Technology has developed a device which uses a process called synthetic aperture sonar to create detailed pictures of the sea bed using acoustic imaging.
Instead of having to store or send back digital images to be analysed, the sonar system can provide data in real time and is not hampered by murky water.
The US Department of Fisheries is using the technology to search for lobster traps that have come loose from their floats and now endanger marine life on the sea floor. It could also be used instead of divers to find debris from plane crashes.
With so many new machines on the drawing board or in production, people could for forgiven for fearing that human beings may become redundant.
But, Mr Donnithorne-Tait does not believe this will be the case.
"The general idea is that it's robotics to assist people, not to replace people."