Inflatable shields look good

The shields were seen to deploy on radar

The Russians say they have successfully tested a new upper stage on their Soyuz rocket and have brought it back to Earth using a revolutionary re-entry device.

But the so-called "Fregat" accelerator block, which is crucial to a number of upcoming European space missions, has yet to be recovered. Helicopters are searching for the vehicle in the Orenburg region in the southern Ural mountains.

Much media interest in the mission has centred on the re-entry mechanism itself - an inflatable shield that looks much like a shuttlecock. This appears to have worked.

A demonstrator sent up with the Fregat also seems to have returned successfully using the inflatable device. This has been recovered.

Scientists are most concerned about the performance of the Fregat. The vehicle is important because it has the ability to stop and start its engines several times. The accelerator block is reported to have performed two successful test burns on the flight.

Cluster mission

This capability will be essential when Europe comes to launch its Cluster II spacecraft that will study Earth's near-space environment. A Soyuz-Fregat will be needed to put the satellites in their correct positions later this year. The European Space Agency hopes it will work well having watched the first Cluster mission blow up with the new Ariane 5 rocket in 1996.

A Soyuz-Fregat will also be called upon to launch Europe's Mars Express mission in 2003.

Russian engineers will now be keen to recover what remains of the Fregat, which can also be used with Proton, Zenit, and Dnepr boosters. If it is in a good condition, there will be much celebration at the German DaimlerChrysler aerospace company and the Russian Khrunichev company who have developed the new inflatable re-entry and descent technology (IRDT).

Their massive cone-shaped shield will decelerate craft coming back to Earth and promises to reduce greatly the cost of space technology by allowing space vehicles to be used several times.

Robin Zell from DaimlerChrysler Aerospace Space Infrastructure told BBC News Online: "The shields deployed because we saw them on the radar screen. So far it looks good. But we can't tell if it is a total success until we've had a look at the upper stage rocket and the demonstrator."