Lacking the ability to finance costly manned space missions on its own, Europe has long had ambitions to serve as a junior partner in a collaborative campaign that would send astronauts beyond low-Earth orbit.

In January, the European Space Agency (ESA) found the right partner in NASA when the U.S. space agency announced plans to put Europe on the critical path for early development of its Orion/Multi-Purpose Crew Vehicle, a vessel designed for mission to cislunar space, near-Earth asteroids and perhaps Mars.

Under the agreement announced Jan. 16, ESA will leverage its International Space Station experience with the Automated Transfer Vehicle (ATV) into a critical-path responsibility: an ATV-derived service module for one and possibly two test flights of the Orion atop the new Space Launch System (SLS) that NASA is developing for manned exploration of the moon and beyond.

Top officials at both agencies credit their long-standing partnership in the 15-nation International Space Station (ISS) as the basis of a budding alliance that could place European astronauts aboard future U.S.-led deep-space missions. Specifically, ESA's pledge to provide five ATV cargo resupply missions to the six-person orbiting space lab between 2008-14, a barter agreement that covers Europe's share of the ISS common operating costs through 2017.

Instead of continuing ATV production, elements of the EADS-Astrium ATV will be adapted for NASA's Exploration Space Mission-1, an unpiloted 2017 test flight of the Orion capsule and an initial version of the SLS on a flight to the lunar environs, says William Gerstenmaier, NASA associate administrator for human exploration and operations. Spare service module components developed under the new agreement, if available, could be rededicated to the service module portion of Exploration Space Mission-2, a 2021 piloted test of the Orion and SLS on a similar trajectory.

The preliminaries, including hardware responsibilities and contractor roles, have been in the works for months. ESA ministers pledged a 60% commitment of their cost—about €455 million ($600 million) in late 2012. The balance could come in mid-2014 if ESA's 20 member states commit the remaining money in a new multi-year spending plan, says Thomas Reiter, a former astronaut who heads ESA's human spaceflight and operations division.

“This is the normal process,” Reiter says. “There is a clear path forward and a clear commitment on a basic programmatic ground for the time until the end of this decade.”

The service module contribution has strong backing from Germany, which has shouldered 40% of Europe's spending on the space station to date. Others, notably Italy, reduced their contribution to the program through 2014, while France—ESA's second-largest contributor—is cautioning only provisional support for ISS through the end of the decade.

“France is ready to pursue ISS to 2020 provided we are able to master the costs,” Joel Barre, head of operations for French space agency CNES, said Jan. 15 in Paris. “We also believe there should be better balance between Europe and the U.S., and hope [Orion] could redirect our operation to a more balanced relationship in the decision-making process.”

Still, the two agencies expressed cautious optimism about the future course of the partnership, the first international involvement in NASA's deep-space ambitions, which are focused on a human mission to a near-Earth asteroid in 2025.

“When we talk about international cooperation, it is not talked about lightly here,” Gerstenmaier says. “We probably would not have done this without the experience we had on the space station. We have learned the real meaning of cooperation is not actually counting on your partner to be there. It's actually giving up a piece of the spacecraft. That was not done lightly.”

Reiter agrees: “We are looking for synergies in technical and programmatic ways. ESA has proven to be a reliable partner in the context of the ISS. Based on that, especially the ATV, this is a good choice to make for exploration—synergies that have been developed in the past that can be beneficial for reaching a common objective.”

Under the terms of the agreement, NASA will furnish the Orion capsule, launch-abort system and adapters that protect the capsule's heat shield. NASA will also merge the service module to the SLS as well as jettisonable fairings.

ESA—most likely through ATV industrial prime contractor Astrium Space Transportation—will provide the actual service module structure, holding propulsion and solar-power components as well as the life-support needs of the Orion crews. The first service module will integrate spare NASA shuttle Orbital Maneuvering System components. The Europeans will also provide sustaining engineering for their hardware, which could be used for the second Orion flight in 2021. Beyond that, however, Gerstenmaier says Europe's continued participation in Orion is unknown.

“We have made sure we have kept the right intellectual property that's available to us on the NASA/U.S.-government side so that we can manufacture the follow-on service modules if we need to on our side, or if we decide it is advantageous to us to continue on those future flights with the Europeans, we can work with the Europeans to do that,” Gerstenmaier says. “We've really made no decisions about those future flights.”

In the meantime, Bernardo Patti, ESA director of operations for the ISS, says industry will operate under a tight schedule to develop and integrate the service module hardware in time for NASA's planned 2017 test flight. Although industry contracts have not been awarded, he expects the project to achieve preliminary design review (PDR) in 2013.

“We are placing industrial contracts and we are facing the very challenging schedule that will bring us to PDR by the second part of the year,” Patti says. “The team is extremely excited and enthusiastic [and] looks forward to the PDR to confirm that all the expectations we are building will materialize further.”

NASA has no plans to alter its $6.6 billion agreement with Lockheed Martin, Orion/MPCV prime contractor, says Mark Geyer, NASA's Orion project manager. Plans for a late-2014 unpiloted test flight of the Orion atop a Delta IV heavy will not be affected by the ESA agreement. That test will feature a high-speed reentry of the capsule to test the heating shielding and verify other systems prior to the capsule's planned critical design review.

ESA decided a sixth ATV would cost more than the €455 million the agency's member states owe to cover Europe's share of ISS common operating costs through 2020. Instead, NASA accepted the ATV-derived service module proposal, leaving ATV's supply role to new U.S. commercial resuppliers, SpaceX and Orbital Sciences Corp. The propellant that the ATV furnished will not be needed, as past operations show the station's propulsion needs can be handled by future Russian Progress flights, said Mike Suffredini, NASA's ISS program manager.