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.
Member states of the European Space Agency approved Ariane 6 development at a ministerial council last November.
Esa governments expect the new launcher to enter service at the start of the next decade.
The 6 will have less lifting capacity than the five - 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 to a new configuration is the desire 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.
The goal is to try produce and launch a rocket for no more than about 70m euros (?60m/?90m).
The 6 hopes to achieve this 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.
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.
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.
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 the 6 would hope to copy.
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.
Flying out of its Kourou base in French Guiana, 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.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos
Source: http://www.bbc.co.uk/news/science-environment-23241158#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa
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