NASA has forged its first international partner in plans to develop a future human deep space exploration capability.

The European Space Agency will furnish the U. S. Orion/Multipurpose Crew Vehicle with the service module for its first unpiloted test flight atop the new NASA Space Launch System in 2017 and potentially for the  first crewed mission of the capsule and heavy lift rocket in 2021.

In this artist's illustration, the European Space Agency's service module with solar arrays sits behind NASA's Orion capsule. Image credit/NASA

The two test flights may take the four people Orion spacecraft around the moon, though the specific mission details are likely to be worked out over time.

The deal, which was announced at NASA’s Johnson Space Center in Houston on Jan. 16, places the Europeans in the “critical path” of future U.S. human space exploration. The agreement has roots in the longstanding International Space Station partnership between the U. S., Russia,  ESA, the Canadian Space Agency and the National Space Development Agency of Japan. It releases ESA from an obligation to provide the space station with a sixth Automated Transfer Vehicle for the delivery of supplies and fuel.

Instead, ESA will convert that ATV hardware into the Orion service module for the 2017 mission. Spare components could be fashioned into a second service module for the 2021 flight. ESA’s ATV based service module will fit behind Orion and carry the propulsion and solar power components as well as the life support resources needed by Orion crews.

Orion, center, on deep space mission in this illustration. Image credit/NASA

“To make a commitment this big there needs to be a lot of engineering done behind the scenes to make sure this is really the right thing to do,” said Bill Gerstenmaier, NASA’s associate administrator for human exploration and operations. “Can we really integrate these two vehicles together? The teams have done a tremendous job in the last several months figuring out those technical interfaces.”

Further negotiations could open a seat on the 2021 mission for an ESA astronaut. A longer running agreement could assure Europe of  long standing opportunities for its astronauts to join U. S.led deep space missions. Three years ago, President Obama directed NASA to develop the hardware to explore an asteroid with humans by 2025 and reach towards the Martian environs a decade of so later. In recent weeks, U. S. policy makers have begun to contemplate a lunar orbital base among alternate destinations as well.

The U. S. deep space architecture includes Orion, which is under development at Johnson; the Space Launch System, a multi-stage heavy lift rocket  in development at the Marshall Space Flight Center; and the launch complex at the Kennedy Space Center.

“NASA’s decision to cooperate with ESA on their exploration program with ESA delivering a critical element for the mission is a strong sign of trust and confidence in ESA’s capabilities,” said Thomas Reiter, ESA director of Human Spaceflight and Operations. “For ESA it is an important contribution to human exploration.”

ESA’s fourth ATV is scheduled to lift off for the space station in April, the fifth in 2014.