"Prototype Satellites Demonstrate In-Orbit Refueling"

Great space stuff here.

Despite a rocky start, two unmanned spacecraft have succeeded in their first autonomous satellite refueling demonstration while orbiting high above Earth.

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"The first Orbital Express demonstration, Scenario 0-1, was very successful," a spokesperson Jan Walker for the U.S. Defense Advanced Research Projects Agency (DARPA), which is overseeing the mission, said in a written update Wednesday. "ASTRO transferred just under 32 pounds (14 kilograms) of hydrazine to the NextSat client, meeting the scenario objective."

Walker said the robotic arm-equipped ASTRO, short for Autonomous Space Transport Robotic Operations, first delivered the hydrazine during the early hours of April 1 via a fluid hookup, and then followed up by transferring an additional 19 pounds (8.6 kilograms) of propellant to NextSat a day later. NextSat was due to return propellant to ASTRO sometime today, she added.

In addition to refueling demonstrations, ASTRO is also designed to perform tasks such as autonomous undocking, proximity operations and re-docking, as well as use its robotic arm to install a battery on NextSat.

Robots in space. Satellites repairing and refueling each other. It don't get much cooler than that.