LE BOURGET, France — Designers of Europe’s Ariane 5 rocket are crafting a defense against U.S. startup rocket builder Space Exploration Technologies Corp. (SpaceX) even before the next-generation Ariane 6 rocket — itself spurred in part by SpaceX — has been approved for production.

The first line of defense is the Ariane 5 Midlife Evolution (ME) vehicle, whose new upper stage is halfway completed and awaits final approval, in late 2014, of European governments.

Ariane 5 ME will increase the current Ariane 5 ECA’s payload-carrying power by about 20 percent, meaning it will carry two satellites weighing a combined 11,000 kilograms.

Alain Charmeau, president of Ariane 5 prime contractor Astrium Space Transportation, outlined Ariane 5 ME’s two-pronged defense —­ one aimed at Russia’s heavy-lift Proton rocket, Ariane 5’s biggest competitor, and the second aimed at SpaceX’s Falcon 9 vehicle — during a June 18 briefing here at the Paris Air Show.

The upper position under the Ariane 5 ME fairing is occupied by a satellite weighing around 6,500 kilograms, which is what the current Proton vehicle carries solo into orbit on its commercial flights. Because most commercial satellite fleet operators tailor their satellites to be compatible with at least two launch vehicles, there is little incentive for rocket builders to get too far ahead of the competition in terms of satellite mass.

With the upper position in the Ariane 5 ME competing with Proton, marketed by International Launch Services of Reston, Va., it is up to the lower position to compete with Hawthorne, Calif.-based SpaceX and the upgraded Falcon 9 v1.1 rocket scheduled to make its debut this year.

The upgraded Falcon 9 is capable of carrying a 4,500-kilogram satellite into geostationary transfer orbit.

One of the Falcon 9’s most potent arguments is that it is capable of carrying two all-electric-propulsion satellites at a time into geostationary transfer orbit. But according to the first customer of Boeing Space and Intelligence Systems’ all-electric 702SP platform, Satmex of Mexico, it will take the Satmex satellite about eight months to reach its final orbital position and begin generating revenue.

Charmeau said Ariane 5 ME will use its re-ignitable upper stage to place an all-electric satellite into a higher transfer orbit than what is offered by the Falcon 9, reducing the time to arrival by around two months.

Jacques Breton, commercial director of the Arianespace launch consortium of Evry, France, which operates the Ariane 5, said it is too soon to say how much closer to its final operating slot Ariane 5 ME can place a satellite compared with Falcon 9. But the idea, he said, is to make maximum use of Ariane 5 ME’s extra power to minimize the amount of time needed for operators to start earning a return on their investment.

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