If all goes well, the Ariane 5-ESCA will blast off from the European Space Agency's launch base in Kourou, French Guiana, late Thursday (EDS: launch window is from 2221 to 2304 GMT Thursday).

It will take up two satellites, Hotbird TM7 for the European telecoms consortium Eutelsat, and Stentor, an experimental communications satellite for the French space research institute CNRS.

The scheduled launch comes on the heels of two US rivals, Boeing's Delta 4, which was launched on November 20, and Lockheed Martin's Atlas 5, which made its maiden flight on August 21.

The trio form the vanguard of the most powerful generation of rockets to go into space since the mighty Saturn V which blasted the Apollo astronauts to the Moon.

In their biggest planned design, these rockets will tower up to 70 metres (227.5 feet) above the launch pad and boast a capacity to place more than 13 tonnes of cargo into geostationary orbit.

Such awesome muscle power means that up to three satellites can be placed in orbit in one shot, thus slashing launch costs for satellite operators.

And -- more fancifully -- modules could be hauled into space and clipped together, to provide a spaceship for a long interplanetary manned mission.

The new Ariane, with the power to place 10 tonnes into geostationary orbit, is a beefed-up version of a 5.9-tonne-capacity launcher whose first operational flight, placing the XMM-Newton X-ray telescope into orbit, was in

It is scheduled to be followed in 2006 by the Ariane 5-ESCB, with a designed capacity of 12 tonnes.

Among the Americans, the Atlas-5, whose most powerful version will be able to take 8.6 tonnes aloft, although it will not be able to handle multiple launches.

The big mamma is the future Delta-4 Heavy, due for launch in 2006, which will be able to lift 13.1 tonnes, thanks to the world's largest liquid hydrogen engine -- a behemoth that according to its manufacturers produces 17 million horsepower and gobbles up one tonne of fuel per second.

New launchers take up to a decade to develop, and when the Ariane, Delta and Atlas giants were conceived, the market for satellite launches looked bright and its potential unlimited.

Today, though, the market has shrunk, partially as a result of the bursting of the telecoms bubble, which has left huge amounts of cheap capacity in fibre-optic cable, the alternative to satellites for transmitted big data streams.

And other competitors -- notably tie-ups such as Starsem and Sea Launch, which use tried-and-tested Russian launch technology -- have entered the fray, while China, India and Japan are also potential future competitors.

"There is at least double if not triple overcapacity" in the launcher market, John Karas, vice president of Lockheed Martin, said in August.

Arianespace, ESA's marketing arm, has a big problem because of its dependence on commercial launches.

Around 70 percent of its rivals' payloads are for the US government, but the government-backed figure for ESA is only 10 percent.

"The launch market is very difficult right now," Rachel Villain, chief consultant on satellite services at a Paris consultancy, Euroconsult, told AFP.

"It won't recover before 2006, which is when satellites launched in the boom in 1990s will start to need replacing. But the recovery could be quite strong, if applications for broadband and mobile phones take off."

SPACE.WIRE