The Ariane rocket has used a commercial satellite launch to test the engine sequence needed to loft Europe's forthcoming space truck, the ATV.
The Ariane 5 GS moves away from the spaceport
The rocket flew as normal on Friday to orbit two communications satellites, but it then re-ignited its upperstage to check its performance.
A re-ignition sequence will be required on the launch that hurls the ATV on a path to the space station in January.
From 2008, the truck will become one of the station's main resupply vessels.
It will deliver air, water, fuel, scientific equipment, food, and clothing to the orbiting outpost's residents.
At almost 20 tonnes, the ATV (Automated Transfer Vehicle) will be the biggest spacecraft Europe has ever flown; and the European Space Agency (Esa) wants to be sure Ariane is up to the task.
A key feature of the flight will be a re-ignition of the upperstage some 50 minutes after the first burn, turning an initial elliptical orbit into a circular one from which the ATV can then travel under its own guidance systems to the International Space Station (ISS).
But this re-boost procedure is a novel one for Ariane and engineers wanted to use Friday's mission as a dress rehearsal.
"We've tested this on the ground for the last two years and that's worked perfectly," explained John Ellwood, Esa's ATV project manager, "but we want to demonstrate that this all works in orbit.
SPACE STATION CARGO TRUCKS
ATV (L) will re-supply the ISS with up to 7,500kg of cargo
Capacity is three times that of the Russian Progress craft (R)
Deliveries will include science equipment, food and clothing
Large tanks can transport vital air, water and fuel supplies
ATV project's estimated cost is about 1.3bn euros (£0.9bn)
At least four craft will follow the maiden ATV - Jules Verne
"As you go around the Earth, the temperatures evolve and we know that combustion processes are very dependent on temperature. We also have a lot of pipework which has fuel and gases that feed the engine from the tanks. We want to see how all this behaves," he told BBC News.
It would be at least a week before engineers could confirm all the systems worked as predicted during the re-ignition, said a spokesman for Arianespace, the company which operates the Ariane launcher.
The data would have to be examined in detail, he added.
Friday's mission, the fourth of the year for Ariane, orbited two spacecraft built by the US company Orbital Sciences Corporation.
The Intelsat 11 satellite will deliver TV pictures to the Americas, while the Optus D2 spacecraft will handle TV, data and telephone traffic for Australia and New Zealand.
The rocket left the Kourou spaceport in French Guiana at 1902 local time (2202 GMT).
The next Ariane flight is scheduled for 9 November. The mission will orbit the second of Britain's next-generation Skynet military satellites.