Image caption Esa member states want Ariane 6 to be cheaper to manufacture and operate

The basic design for Europe's next generation rocket, the Ariane 6, has been selected.

It will be powered by two solid-fuelled lower stages and incorporate the liquid-fuelled upper-stage currently being developed as an upgrade for the existing Ariane 5 vehicle.

The concept was chosen following six months of trade-off studies.

European Space Agency member states approved Ariane 6 feasibility work at a ministerial council last November.

These nations expect the new launcher to enter service at the Kourou spaceport in French Guiana at the start of the next decade.

The 6 will have less lifting capacity than the 5 - some 3-6.5 tonnes to the high orbits occupied by telecoms satellites, versus the 11.5 tonnes the 5 will have after its upgrade.

But the 6 will launch just one spacecraft at a time, not the two routinely orbited by the 5 now.

Also, the primary driver for the new configuration is the quest to reduce costs of manufacture and operation.

Ariane 5, although remarkably reliable and successful, is priced above its competition.

Ministers fear the vehicle's current market dominance will be eroded over time unless a cheaper approach is adopted.

We don't reduce the costs via technologies; there are no breakthrough technologies that help us to make revolutionary launchers that can provide performance at low cost Antonio Fabrizi, Esa launchers director

"The desire is to simplify the design and to simplify the manufacturing, because these are the ways to reduce the costs," Antonio Fabrizi, Esa's director of launchers, said.

"We don't reduce the costs via technologies; there are no breakthrough technologies that help us to make revolutionary launchers that can provide performance at low cost."

Solid and liquid

The target is to try produce and launch Ariane 6 for no more than about 70m euros (£60m/$90m).

This would be a big challenge, conceded Alain Charmeau, the CEO of Astrium Space Transportation, which leads the Ariane industrial consortium.

"Astrium now has to capture the ball that has been sent to us today by the agency," he told BBC News.

"We will have to make Ariane 6 a very competitive launcher. It's really a complete change in Europe. It's the first time ever that we will try to develop a rocket thinking about production price and not just performance."

The 6 hopes to achieve economies by slimming down the production consortium, which is spread across the continent, and by including fewer, less complex components in the build itself.

The baseline configuration is what is termed "PPH", where the "P" stands for "poudre" (or "powder" in English) to indicate solid propulsion, and where "H" stands for "hydrogen", to indicate the use of super-chilled liquid propellants.

In the 6, the first stage will have a line of three motors, each loaded with 135 tonnes of solid propellant, to lift the vehicle and its payload off the pad.

Image caption The Vinci upper-stage will come out of orbit once deploying the satellite

The in-line trio of motors will burn for a few minutes before separating and falling away. A second solid stage will then ignite and lift what remains of the vehicle into space.

This too will separate once exhausted, to allow the liquid-fuelled Vinci upper-stage to complete the task of placing the satellite in its final intended orbit.

"The second stage will have a booster that is very similar to the ones on the first stage - not exactly, because the second stage will have to ignite out of the atmosphere and so will have to be adapted a little bit," explained Mr Charmeau.

"But there are advantages in having very similar configurations on the boosters of the first and second stage. And there is also the simplicity of operations in Kourou to prepare the launcher."

Unlike the current Ariane 5 upper-stage, Vinci will bring itself out of the sky after the mission to limit the amount of junk circling the Earth.

The clam-shell fairing which protects the payload during the early phases of the ascent will have a diameter of 5.4m - the same as Ariane 5.

Organisational costs

Esa says the Ariane 6 will build on the advances made by European industry in recent years, and will benefit from synergies with its newly introduced Vega rocket.

This is much smaller than Ariane but uses a lot of solids knowhow, and is manufactured with composite techniques that the 6 would hope to copy.

Image caption French science minister Geneviève Fioraso presented the basic design in Paris

Ariane 5 was introduced in 1996. After some early failures it has become the main means by which commercial telecoms satellites - the platforms that relay TV, phone and internet traffic - get into orbit.

The rocket also lifts the ATV space truck, the largest cargo vessel supplying the International Space Station. And in 2018, Ariane 5 is scheduled to launch the James Webb Space Telescope, the $10bn (£7bn/8bn euros) successor to the Hubble observatory.

A site at Kourou for the 6's new pad has already been identified. When it enters service, and once it has proved its performance, the new rocket will replace both the Ariane 5 and the Russian medium-class Soyuz launcher which also works out of French Guiana.

Operating just the Ariane 6 to fulfil a wide range of customers' needs is expected to bring substantial economies.

European industry will have a number of months to fill out the Ariane 6 design and likely workshare. The details will then be presented to the next Esa ministerial council in 2014.

"This will be the final green light," Mr Fabrizi told BBC News.

"It is when I hope to say to member states that we can develop a launcher that will allow you to launch your institutional missions and stay in the market without the support [payments] that are needed today to maintain Ariane 5."

The development cost to first launch is likely to be in the region of about 3bn euros.

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos