Jules Verne propulsion system glitch resolved
BY STEPHEN CLARK
Posted: March 11, 2008
Two days after an electronics box cut off a quarter of a European space station resupply ship's propulsion system, controllers successfully revived the suspect command chain and tested its ability to work properly during a series of engine firings Tuesday.
Moments after arriving in orbit early Sunday, propulsion system electronics on Europe's Jules Verne cargo spacecraft detected trouble within one of four command chains governing the ship's four main engines and 28 smaller thrusters.
The computers noticed an unacceptable pressure difference between Jules Verne's hydrazine and nitrogen tetroxide propellants, according to the European Space Agency.
The problematic circuit, responsible for one of Jules Verne's main engines and seven maneuvering jets, was automatically removed from the propulsion system and replaced by another chain.
Jules Verne is the first of at least five European-built Automated Transfer Vehicles to transport supplies, water and fuel to the international space station.
Engineers traced the problem to an issue within the chain's helium gas system, which is used to pressurize the craft's propellants, according to ESA officials.
The team at the ATV mission control center reintegrated the downed chain in the propulsion system Monday.
"In a complex operation, commands to reintegrate an electronics box which drives that part of the propulsion system were up-linked to the spacecraft from within the ATV control center in Toulouse, France," ESA said in a written statement. "After the entire propulsion system was disabled, all four propulsion chains were progressively enabled, thereby restoring full failure tolerance."
Jules Verne completed its first two major orbit-raising maneuvers using all four chains Tuesday, kicking off a series of more than a dozen burns to move the ship from its current 162-mile-high orbit to a point 1,200 miles in front of the station by next week.
The spacecraft will park there until March 27 to wait out the shuttle Endeavour's mission to the station, which began Tuesday morning with a nighttime blastoff from Florida.
Officials plan a critical burn on Friday, two days later than originally planned, to demonstrate the ship's ability to rapidly depart the station's vicinity in case of a serious malfunction during the docking sequence.
The collision avoidance maneuver would push Jules Verne away from the station at a relative velocity of about 11 miles per hour.
The two-day pause in Jules Verne's mission to recover from the propulsion command system setback will have no impact on the ATV's planned arrival date at the space station, according to Alan Thirkettle, ESA space station program manager.
Thirkettle said the schedule has enough room to make up for the delays early in the mission because Jules Verne must wait for Endeavour to end its visit to the station on March 24.
Two demonstration days are still planned for March 29 and March 31 to test Jules Verne's myriad of rendezvous sensors before officials give a "go" for docking, currently scheduled for April 3.