The European Space Agency (ESA) has settled on the basic design of the Ariane 6, the first of many steps toward developing a next-generation launch vehicle to succeed the heavy-lift Ariane 5, to keep pace with new developments in China, Russia, India and the U.S.

A more cost-driven and less cumbersome rocket than the Ariane 5 of today, the Ariane 6 configuration is aimed at rapid, lower-cost development and a reduced launch price of €70 million ($90 million).

But despite a clear bias toward affordability, it remains to be seen whether the 20-nation ESA can build the Ariane 6 competitively while finding work for key financial backers, notably Germany, which funds 20% of Ariane 5.

“There is a lot of work now to be done on this configuration, to see who can produce what at what price,” says Antonio Fabrizi, head of ESA's launch vehicle directorate. “Only in the coming months, with data from industry, will we verify if it is in line with the target or not.”

The new design, known as “Multi P Linear,” comprises a first stage of three solid-fueled boosters, a second stage powered by a nearly identical booster and a restartable cryogenic third stage. This stage is based on the Vinci engine being developed at Safran's Snecma motors division as part of an Ariane 5 mid-life upgrade, the Ariane 5ME.

Although less capable than the Ariane 5, which can deliver two payloads weighing a combined 9,000 kg (20,000 lb.) to geostationary transfer orbit (GTO), the Ariane 6 will launch single payloads and is designed to be less reliant on the commercial market to break even.

French space agency CNES, which is expected to fund about half of Ariane 6 development, has spent several years studying designs that could be quickly developed for around €4 billion. In the past six months, project teams at ESA and CNES weighed concepts based on initial CNES designs calling for a modular rocket that could haul 2,000-6,500 kg to GTO, with the potential to grow lift capacity up to 8,000 kg.

Each of the designs was to incorporate a 34-ton cryogenic 4.4-meter-dia. (14.4-ft.) third stage based on an adapted version of the Vinci upper stage, as well as a common payload fairing similar to the Ariane 5 and a third-stage deorbiting kit included in the performance metrics.

By June, the teams had narrowed the focus to two: one with a main stage housing a large, single, solid-fueled booster; and a second design based on a cluster concept involving three solid-rocket boosters topped by a nearly identical fourth.

Fabrizi said last month that the latter option seems more affordable. “The cluster provides higher production rates for the motors, with a lower cost for each motor,” he said on the sidelines of the June 5 launch of Europe's Automated Transfer Vehicle (ATV-4) from Europe's Guiana Space Center in Kourou. “But there are integration complications with building the cluster, so we have to make the trade.”

ESA's final concept, unveiled July 9, is a non-modular, linear version of the cluster concept that would carry 3,000-6,500 kg to GTO, and is designed to maximize commonalities with the Ariane 5 ME and Italy's new Vega light launcher. In addition to the Vinci engine, the Ariane 6 will incorporate a 5.4-meter-dia. payload shroud to accommodate the same volume of satellites as the Ariane 5 and rely on P135 solid-fueled boosters that are in the range of what Vega has demonstrated with its P80 first-stage engine.

ESA says this “Multi P Linear” design could facilitate development of a more powerful P120 engine for future evolutions of Vega, lowering production costs, improving performance and making the rocket more competitive in the commercial smallsat market.

Unlike the single-booster concept, however, the Multi P Linear's P135 boosters will incorporate thrust vector control (TVC), a feature that is expected to increase costs.

“You have TVCs and all these stages, so it's inevitably a bit more expensive,” Christophe Bonnal, a technical specialist with CNES, said in Naples, Italy, last fall.

However, Fabrizi asserts that more development risk was associated with the single, larger booster, a factor that could prolong Ariane 6 development beyond the targeted service-entry date of 2021. “If something is more complex to develop, we take a risk in getting it to market,” he tells Aviation Week.

With the basic design settled, the next step is to solicit industry proposals this month based on the Multi P Linear concept in order to benchmark a competitive development cost that will be presented to ESA ministers next year.

“I shall organize a competition first,” says ESA Director General Jean-Jacques Dordain, a plan that bucks an agency rule guaranteeing 90% geographic return on investment via industry participation. “I have no chance to get the best product for cost because I am in the hands of a monopoly situation. I want serious industrial proposals first. If they are competitive, I am ready to make a launcher that is 60% German.”