PARIS — The head of Airbus’ space division on July 1 said his company was forced to come up with an Ariane 6 rocket design that competed with the version approved by the European and French space agencies because the agency version ultimately would have decimated Europe’s rocket industry.

Testifying before the French Senate Committee on Foreign Affairs, Defense and Armed Forces, Francois Auque said the solid-fuel-dominated Ariane 6 design that the European Space Agency and the French space agency, CNES, approved in July 2013 would have attracted mainly European government customers — a market whose size would mean reducing Europe’s rocket design and production industry by two-thirds.

To avoid being decimated, he said, European rocket builders needed to be sure that the commercial market, which accounts for 90 percent of the launches of Europe’s current heavy-lift Ariane 5 vehicle, would support the new vehicle.

“We asked our customers and they said, ‘The Ariane 6 design you have will not be competitive — at all — on the commercial market,’” Auque said. “Since it’s human nature to resist being reduced by two-thirds, we reacted and came up with a solution that could attract the commercial market as well.”

Auque said it was a longstanding irony of Europe’s Ariane program that a rocket built to guarantee European governments’ autonomous access to space cannot survive without a substantial share of the commercial market. But that has been the case for decades and would remain so for Ariane 6, he said.

Airbus and rocket-motor builder Safran on July 18 presented their own version of Ariane 6 to the 20-nation ESA, the same day they met the agency’s deadline to present final cost information on the ESA-backed design.

The agency-proposed Ariane 6 was a vehicle that Auque said was “trapped, Ad vitam aeternam (for all time), in a single version when what we needed was a vehicle that could evolve with the market.”

Airbus and Safran are also urging ESA governments to give final approval to a proposed Ariane 5 upgrade that would increase its payload-carrying power and add a reignitable upper stage. This Ariane 5 ME version would be ready for launch starting in 2018 if it receives the requested 1.2 billion euros ($1.6 billion) in funding from ESA in December.

To those who urge an immediate move to Ariane 6 without the Ariane 5 ME program, Auque said Ariane’s history gives reason to be cautious when transitioning between vehicle generations.

“We were euphoric in abandoning Ariane 4 for Ariane 5,” Auque said. Ariane 5 failed in its first launch in June 1996 and took several years before establishing its reliability. But Ariane 4 production had been stopped by then.

“If we had been in the same government budget position then as we are today, that failure would have killed us,” Auque said. “We should all keep in mind the risks, and be careful in transitioning between launch vehicles.”

Stephane Israel, chief executive of the Arianespace launch consortium, which sells Europe’s rockets worldwide, said the 20 percent performance increase of Ariane 5 ME compared with the current Ariane 5 would make it easier for Arianespace to couple satellites for Ariane 5 launches.

Israel told the French Senate committee that Arianespace lost four satellite launch contracts in 2013 because it could not fit a midsize satellite in Ariane 5’s lower position. The company is likely to lose three more contracts in 2014 for the same reason, Israel said.

Auque said the Airbus-Safran rocket division merger would accomplish much of the cost savings necessary for Ariane 6, but that industry does not want to take risks with a vehicle that it cannot sell.

“Because we don’t want to die, we had to take our destiny in our own hands and act as quickly as the competitive threats are arriving in the market,” Auque said.

ESA and CNES were blindsided by the Airbus-Safran move and are now evaluating both Ariane 6 designs.

One industry official said the Airbus-Safran version of Ariane 6 will not cost much more to develop than the ESA-CNES design, even though it is two vehicles — one lighter version for government customers, one heavier for the commercial market — instead of one.

One industry official conceded that the new version’s commercial variant, to carry up to 8,500 kilograms into geostationary transfer orbit for telecommunications satellites, would cost around 100 million euros per launch instead of the 70 million euros that ESA and CNES had sought in their design.

Genevieve Fioraso, France’s state secretary for higher education and research, whose portfolio makes her the French space minister, added her weight to the Airbus-Safran design June 30 in an address to the Toulouse Space Show in Toulouse, France.

Fioraso said that in addition to its other merits, the Airbus-Safran proposal is much more acceptable to Germany than the previous version. French-German cohesion is indispensable for a viable European space sector, she said.

Follow Peter on Twitter: @pbdes

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Peter B. de Selding was the Paris Bureau Chief for SpaceNews.