The head of the European Space Agency says he has promised NASA the service module for the Orion crew exploration capsule will be delivered in time for an unmanned test flight by the end of 2017 despite problems with mass and development delays.

Artist's concept of the Orion multipurpose crew vehicle with the European-built service module. Photo credit: NASA
 
The service module's preliminary design review, a major developmental milestone in which engineers assess the maturity of the spacecraft's design, was delayed late last year from November to the spring.

Jean-Jacques Dordain, ESA's director general, told reporters Friday the design review will kick off at the beginning of April and run until May 15.

"The delay is linked to a number of technical problems, including mass-related issues," Dordain said.

But Dordain said he has assured NASA the six-month delay will not affect the service module's delivery schedule.

"I have undertaken to NASA that the delay in the PDR will not lead to any delay of the delivery of the service module," Dordain said Friday.

The service module is the Orion crew capsule's propulsion and power element and is based on Europe's Automated Transfer Vehicle, a robotic resupply freighter for the International Space Station.

Technicians will assemble the service module at Airbus Defence and Space's facility in Bremen, Germany, the site of ATV integration. Airbus will ship the service module to the Kennedy Space Center in Florida for attachment to the Orion crew vehicle built by Lockheed Martin Corp.

The European-built propulsion section has a height and diameter of about four meters, or 13 feet.

ESA director general Jean-Jacques Dordain, at center, says the Orion spacecraft's European-built service module will be ready to fly by the end of 2017. Photo credit: ESA/S. Corvaja
 
The schedule calls for the service module's arrival in Florida by the first quarter of 2017, but Dordain and Thomas Reiter, ESA's human spaceflight division chief, said the plan will be reassessed in June following the completion of the preliminary design review.

In a Jan. 10 interview, Reiter said engineers have made good progress on the service module's design documentation in the last few weeks.

Despite the delay of the PDR, Reiter said ESA will authorize Airbus Defence and Space to start procurement of "long-lead items which are more or less independent of the outcome of the PDR."

"We are trying to be as flexible and creative as possible," Reiter said.

ESA is ordering service module work to Airbus in slices and is waiting to award the next big contract, known as the Phase C/D contract, after the preliminary design review.

The PDR delay "cuts down the time we have to prepare our C/D contract with industry, but it's achievable," Reiter said.

The flight at the end of 2017 will be the first full-up space mission for the Orion multipurpose crew vehicle, but it will not carry astronauts. The spacecraft will blast off on NASA's heavy-lift Space Launch System, a mega-rocket under development using recycled and redesigned space shuttle technologies.

Diagram of the key components of the Orion spacecraft. Photo credit: NASA
 
The 2017 flight, known as Exploration Mission 1, is planned to conduct a lunar fly and enter a so-called "distant retrograde orbit" about 43,000 miles from the moon.

The 2017 test flight, planned to last more than three weeks, will be a pathfinder for NASA's asteroid redirect mission, an effort to send a robotic spacecraft into deep space and guide a 500-ton rock to a stable location near the moon for visits by human crews aboard the Orion spacecraft. The first crewed flight to an asteroid is expected no sooner than 2021.

A partially-functional Orion crew module will launch on an unmanned test flight in Earth orbit in September on-board a United Launch Alliance Delta 4-Heavy rocket. This year's test flight will not include a European service module.

European industry is designing and building the service module's primary structure, power-generating solar arrays, and hardware for the craft's main propulsion system. NASA is providing an orbital maneuvering system engine from the space shuttle program.

ESA and NASA agreed on the service module contribution in a barter agreement for Europe to pay for its share of the space station's operating costs. ESA pays for its part of the space station by providing in-kind services, such as cargo transportation with the Automated Transfer Vehicle.

The service module initiative is valued at 450 million euros, or more than $600 million, and pays for ESA's share of the station's costs from 2017 to 2020.

ESA's member states signed off more than half of service module's 450 million euro budget at a meeting in November 2012. Member states will meet again in December to approve the rest of the funding.

Follow Stephen Clark on Twitter: @StephenClark1.