European Cargo Ship Switches to Backup Propulsion System

Liftoff of Europe's ATV cargo ship Jules Verne on March, 8, 2008. CREDIT: ESA/Stephane Corvaja.

PARIS -- Managers of Europe's large cargo vessel launched Sunday to the International Space Station said they likely will modify their planned in-orbit test schedule as they investigate why one of the vehicle's four propulsion systems was shut down by an on-board computer shortly after launch.

They said that even if the affected system remains shut down, the Automated Transfer Vehicle (ATV) can continue its mission and dock as planned with the space station. The ATV Jules Verne lifted off Sunday at 3:03 a.m. GMT (11:03 p.m. March 8 GMT) atop an Ariane 5 rocket that launched from European spaceport in Kourou, French Guiana.

In a March 9 press briefing, officials from the European Space Agency (ESA) and from the ATV's prime contractor, Astrium, said the vehicle's on-board computer did its job correctly in shutting down one of the four propulsion systems after finding an unexpected difference in pressure between the system's fuel lines and its oxidizer lines.

The propulsion function was automatically transferred to a second system, which reported no similar problems.

John Ellwood, ESA's ATV mission manager, said in an interview that all other ATV systems appear to be in good health, with the craft in a stable, 161-mile (260-km) circular orbit. While the ATV had been scheduled to climb closer to the station's 214-miles (345-km) orbit in the next couple of days, Ellwood said there is "absolutely no rush for us to do this. We have plenty of time and we are going to be looking carefully at this anomaly."

Nicolas Chamussy, Astrium's ATV program manager, said the vehicle -- often described as the most complex machine ever launched into space by Europe -- is designed to function with only three of the four propulsion systems operating.

"What we have had so far is the nominal operation of the ATV failure detection, isolation and recovery system," Chamussy said during the press briefing, held at Europe's Guiana Space Center spaceport in French Guiana several hours after the launch aboard a specially designed Ariane 5 rocket. "We had detection of an anomaly, and its isolation, with the [propulsion] chain being put aside. Now we are in recovery mode, and we can reintegrate this chain if it is demonstrated that it is safe and will not endanger anything."

The ATV had been scheduled to climb into its operational orbit and then begin a series of maneuvers to demonstrate to the station's partners -- the United States, Russia, Japan and Canada in addition to Europe -- that the 41,887-pound (19,000-kg) vehicle can safely dock with the station. The ATV is about three times the size of Russia's unmanned Progress cargo vessel.

A collision-avoidance maneuver demonstration had been planned for March 12, but Ellwood said that could be postponed if ATV controllers want to spend more time examining the propulsion issue.

Docking with the station still is tentatively scheduled for April 3.

Ellwood said the ATV's Propulsion Drive Electronics (PDE) element controlling the affected propulsion system shut itself off after transferring propulsion responsibility, as it is designed to do.

"The PDE detected some difference in pressure between the [oxidizer and the fuel lines]," Ellwood said. "As planned, the software took over, put control over to the other [propulsion] chain, and then it turned itself off, just in case the anomaly is in the [PDE] itself.

Ellwood said ATV managers have a large amount of telemetry data on the vehicle's different systems, including the propulsion system, that they will need to analyze before deciding how to proceed.

“We have a 10-day margin before we need to start going into demo days at the end of the month," Ellwood said. "We are obviously not going to take any risks."

Ellwood said the only other notable glitch during the launch was a short-lived issue with NASA over the use of the U.S. space agency's Tracking and Data Relay Satellite System (TDRSS), which the ATV needs during launch to communicate with the ground.

ATV managers during the launch realized they were not getting the planned level of use of TDRSS as the ATV climbed into orbit. "You know, a lot of satellites are using" TDRSS, Ellwood said. "We were in touch with NASA and they realized the priorities weren't quite right. They actually got rid of another payload, which wasn't a high-priority payload. That was 30 seconds after the second boost [of the ATV by the Ariane 5's specially designed upper stage]. That could have been horrific, but we had a good procedure [with NASA] to do that."

• VIDEO: Part 1: Europe's First ISS Cargo Ship
• VIDEO: Part 2: Jules Verne, Europe's First ISS Cargo Tug
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