The U.S. Department of Defense is developing a orbital refueling robot that could extend the life span of America's spy satellites many times over, New Scientist reported this week.

The robotic refueler, called an Autonomous Space Transporter and Robotic Orbiter (ASTRO), could shuttle between orbiting fuel dumps and satellites, the Defense Advance Research Projects Agency said.

As a result, the life of a satellite would no longer be limited to the amount of fuel with which it is launched.

Spy satellites carry a small amount of fuel, called hydrazine, which enable them to change position to scan a different part of the globe or to go into a higher orbit. Such maneuvering makes a satellite's position difficult for an enemy to predict.

But under the current system, when the fuel runs out, the satellite gradually falls out of orbit and goes crashing to Earth.

Aerospace contractors could start building prototypes of the refueler next year, New Scientist reported.

In the future, the refueler could also carry out repair work on faulty satellites, provided they have modular electronics systems that can be fixed by slot-in replacements, the article said.