After six months of back-and-forth, and with a key budget meeting fast approaching, France and Germany staked out a modest but crucial piece of common ground last month: In the debate over whether to start work on Europe's next-generation launch vehicle, the tab for building a successor to the Ariane 5 will run €3.8-5 billion ($5-6.5 billion) over a decade.

The agreement between the French and German space agencies, however, is just the beginning. Detailed in a report delivered to their respective governments in recent weeks, the cost estimate is only a point of departure from which the often polarized partners will move forward this fall, when European Space Agency (ESA) ministers meet in Caserta, Italy, to settle the organization's multi-year spending program.

At stake is France's continued support for key ESA programs, including the International Space Station (ISS), Europe's next-generation polar-orbiting weather satellite and an ambitious proposal to send robotic probes to Mars before the decade's end—all of which could be compromised if ESA presses ahead with development of the next-generation launch vehicle the French have tentatively dubbed Ariane 6. As the primary financial load-bearer for Europe's Ariane family of rockets, France is considering a proposal to scrap current Ariane 5 modernization efforts and go straight to development of the next-generation launcher. But as ESA's largest financial contributor, along with Germany, it is unclear whether France can pay the lion's share of Ariane 6 development without jeopardizing its contributions to other ESA programs.

“It should not be that we come out of the ministerial with only one program that is called the new launcher,” says Johann-Dietrich Woerner, chairman of the German Aerospace Center DLR. “We have to pay for Earth observation, the barter element for the ISS, and ExoMars, so my opinion is the ESA governments are not ready to pay the majority of their money just for a new launcher.”

Germany, which favors continued work on an upgrade to the current Ariane 5, known as the Ariane 5 Midlife Evolution (Ariane 5ME), argues that tandem development of both vehicles would only cost a bit more than continuing with Ariane 5ME alone. Woerner says synergies between the two rockets' industrial teams could cover as much as 25% of the cost to develop and produce the Ariane 6.

Woerner says going straight to Ariane 6 raises questions about industrial work share, and that it remains to be seen whether the new launcher will end roughly €120 million in annual ESA support payments to Arianespace, the commercial launch consortium that operates Ariane 5. Despite going almost a decade without a failure—Ariane 5 boasts 50 straight successes and claims approximately 50% of the commercial launch market—Arianespace is unable to break even without continued financial backing from the space agency's member states.

Even if it does, another decade could pass before the Ariane 6 is operational, leaving ESA to foot the bill for continued price supports to the tune of €1.2 billion during development.

Those support payments, plus the €3.8-5 billion cost estimate for development, means Ariane 6 will cost a minimum of €5 billion over 10 years. Continuing development of Ariane 5ME, in which Europe has already invested around €300 million, would cost €1.4 billion over five years, when an operational vehicle comes on line in 2018, putting the total cost at €2 billion.

Woerner says a recent letter to ESA from Ariane 5 prime contractor Astrium, the space division of EADS, suggests that once Ariane 5ME is operational, Arianespace will no longer need European price supports. Ariane 5ME is designed to offer a 20% boost in carrying capacity over Ariane 5. It is also more palatable in terms of environmental impacts, as its restartable upper stage is designed to be destroyed post-launch as it reenters Earth's atmosphere. Multiple conditions in the letter suggest industry participation is necessary for this to occur, but so long as the market remains nominal during the anticipated five-year development period, Astrium says it is doable.

But for Ariane 6, it is impossible to guarantee that ESA subsidies can be eliminated, Woerner argues.

Officials at the French space agency CNES declined to comment on the Franco-German launch vehicle report, but Michel Eymard, director of launchers at CNES, says France's interest in moving quickly ahead with Ariane 6 is driven by the need to end annual support payments to Arianespace while reducing the company's reliance on commercial business.

“In France, our objective is to keep a reliable system, an available system, but also a system which does not require any support from the public sector during the exploitation phase,” Eymard said at a May conference on space propulsion in Bordeaux. “The requirement for Ariane 6 is to have a balanced exploitation,” even if competition in the launch market escalates.

Woerner, however, says Germany's position is that Europe should be less concerned with building vehicles that will survive despite an uncertain commercial market and more with sustaining a consistent industrial policy that supports a highly skilled engineering workforce that can keep Europe on the leading edge of space.

“We are not producing launchers for the market, we are producing launchers for European access to space,” Woerner says. “The market is an interesting point but not the overall one governing the debate.”

With France's new government expected to unveil a new space policy by late summer, French Minister of Research and Higher Education Genevieve Fioraso says maintaining Europe's independent access to space is a key element of the forthcoming strategy.

“The space policy that we are backing must affirm independence as one of its major strategic objectives,” Fioraso said in June during the Toulouse Space Show, adding that “it is an absolute necessity for Europe to maintain its independent access to space.”