VERNON, France — Europe’s rocket-component manufacturers are confident they have secured political backing for a nine-year investment in a new Ariane 5 rocket upper stage to increase the vehicle’s payload-carrying capacity by 18 percent, to around 10,600 kilograms to geostationary transfer orbit, officials with one such company said here June 19.

The new upper stage, powered by the restartable, cryogenic Vinci engine that has been in design for eight years, would permit Ariane 5 to continue to launch two heavy telecommunications satellites at a time – a capacity that is under threat as commercial satellites continue to increase in weight by 125 kilograms per year, on average, officials with the propulsion firm Snecma said.

briefings at its motor production and test facility here were part of a broader effort to make the case for the Vinci stage to European Space Agency (ESA) government ministers, who are scheduled to meet in late November to set program and budget guidelines.

These governments’ space ministers meet every three years, on average. At the last meeting and the one that preceded it, an Ariane 5 launch failure that required a major review of the rocket’s design diverted attention from Ariane 5 enhancements. Government ministers subsequently invested in a five-year program called European Guaranteed Access to Space, valued at nearly 1 billion euros ($1.54 billion), to offset fixed costs associated with Ariane 5 production and operation. That program ends in 2009.

Led by France and Italy, ESA governments also poured investment into building a launch installation for Russia’s Soyuz rocket

at Europe’s Guiana Space Center in French Guiana, and in designing a new small-satellite launcher, called Vega. Both are scheduled to enter operation in 2009.

But even as they set aside investment in Ariane 5 enhancements, ESA governments agreed to continue work on Vinci as part of ESA’s Future Launcher Preparatory Program. Up to now, ESA governments have invested some 300 million euros in the new upper stage, most of it going to test the Vinci engine design at facilities in France and Germany.

With the launcher-support program now ending, and Ariane 5’s design now considered stable after 25 consecutive successful launches, Snecma and its partners hope to find a better reception for launch vehicle improvements.

joined Europe’s other principal rocket-hardware builders – including Astrium Space Transportation, Volvo Aero, Avio and Europropulsion – in presenting a launcher development proposal to ESA earlier this year.

Industry estimates that a new Ariane 5 upper stage would cost about 1.5 billion euros, including completion of design and testing of the Vinci engine. The industry proposal asks that the funding be spread out so that the first demonstration launch of the improved Ariane 5 could occur in 2016.

Jacques Serre, general manager of Snecma’s space engines division, said the current model of the standard Ariane 5 ECA rocket can lift two satellites weighing a combined 8,700 kilograms into geostationary transfer orbit.

Small but regular tinkering with the vehicle is expected to result in a performance increase, permitting the rocket to carry 9,000 kilograms of payload to the same orbit.

But that increase will not be enough to preserve Ariane 5’s trademark selling point: the ability to carry two large telecommunications satellites at a time.

According to Snecma, 21 commercial telecommunications satellites were ordered in 2007. Of these, 10 will weigh between 5,400 kilograms and 6,300 kilograms at launch. Another five will weigh more than 3,500 kilograms. With this launch weight spread among commercial satellites, Arianespace is having more and more difficulty in finding two spacecraft that will be ready at the same time and can share the same Ariane 5 rocket.

Serre conceded that the

Ariane 5 rocket is now in a comfortable position in the market relative to its competitors, in part because of recent failures of the Russian Proton-M rocket and the limited launch rate of Sea Launch Co. of Long Beach, Calif.

The U.S. Altas and Delta vehicles, while available for commercial use,

mainly are devoted to the U.S. government market. China’s Long March rocket has established a record of reliability in recent years

but is barred from most of the commercial market because of a U.S. government policy

prohibiting U.S. satellite parts from being exported to China.

Serre added: “It was only a few years ago that the situation was completely different, so we have seen how fast things can change. What we know today is that the Chinese have announced grand ambitions for the future capacity of their Long March vehicle. This must be considered a threat to us.”

In an argument that has not been used before, Snecma officials said the increasing use of electric propulsion on large telecommunications satellites will pressure Europe to develop a reignitable upper stage.

Under this reasoning, satellite owners employing electric propulsion instead of conventional chemical fuel on their satellites will increasingly ask launcher companies to place their satellites into orbits that are closer to final geostationary position than is the case today.

Both Proton and Sea Launch have reignitable upper stages and can adapt to this market change fairly easily, Serre said, while the current Ariane 5 vehicle cannot.