Launch of European-made station cargo freighter slips
BY STEPHEN CLARK
Posted: March 25, 2007
A European craft designed to ferry science experiments, fuel and other supplies to the international space station will launch this fall, several months later than originally planned, officials said last week.
The ATV was previously scheduled for launch this summer.
The postponement is due to several factors, including a problem with the Russian Global Positioning System, issues developing test procedures last year, and the compatibility of this year's space station manifest, ESA astronaut Jean-Francois Clervoy, a senior advisor to the $1.3 billion ATV program, told Spaceflight Now.
"The exact impact of the latter remains to be evaluated," Clervoy said in an interview.
The uncertainty stems from last month's hail storm in Florida, which damaged foam on the external fuel tank attached to space shuttle Atlantis. The dented foam forced NASA managers to opt to roll the shuttle back from the launch pad for repairs.
The storm has pushed back Atlantis's upcoming station construction mission until at least May. Further delays of subsequent missions by a few weeks are also expected.
The shuttle delays will force the station's international partners to overhaul the schedule for visiting spacecraft, including Russia's Progress cargo vehicle. The Progress often occupies the Russian Zvezda service module's aft docking port, where the ATV must dock during its mission.
Depending on how the space shuttle and Progress manifests are reshuffled, the flight of Jules Verne could be booted to November. International discussions are underway between space agency leaders in Europe, Russia and the United States, according to Clervoy.
"(The) two launch windows are compatible with the vehicle and control center readiness, but the final choice will take into account the availability of the aft docking port of the Russian segment and the resolution of potential conflicts with other space vehicle traffic," he said.
Another factor in the delay involved a critical test at a simulator facility outside Moscow to check the interface between the Russian segment of the station and the ATV that faced challenges from problems with the Russian Global Positioning System, which is required for the craft to successfully rendezvous and dock with the orbiting outpost.
Engineers had to create a software upgrade to fix the GPS problem, and the test proceeded as planned to verify the spacecraft's Russian-built rendezvous system and docking mechanism. Other software tests in Russia validated the ATV propulsion system, which will transfer spare propellant to the space station, in addition to conducting attitude control activities and reboosts.
Software development issues have resulted in delays for the ATV in the past. Flight software tests had to be pushed back due to difficulties with the ground test bed facility designed to check the software, Clervoy said.
But the ATV's flight software is now ready for its big debut later this year.
"Both the main software and backup safety software have completed software dedicated testing and are now in (a) regular maintenance status, meaning that they are mature and used for functional testing," Clervoy said.
Hardware tests using a ground replica of Russia's Zvezda module are planned for later this spring to make sure the ATV can successfully feed maneuvering propellant into Zvezda's fuel tanks. The ATV is designed to refuel the station with up to 1,900 pounds of propellant, according to ESA.
Officials are also running extensive mission simulations including the ATV control center in Toulouse, France, and space station mission control centers in Houston and Moscow.
Expedition 16 crew members Peggy Whitson and Yuri Malenchenko are also undergoing training for ATV docking operations. The crew will monitor the automatic rendezvous sequence and can issue an abort command if necessary.
While software engineers and flight controllers have been continuing mission simulations, the first ATV spacecraft has been sitting in a clean room at ESA's technical center in the Netherlands, Clervoy said.
The flight model of the ATV underwent two key environmental tests last year. An acoustic test to simulate the violent sound and vibrations of launch was successfully completed last July. In December, engineers finished the thermal vacuum test, which exposed Jules Verne to the extreme temperatures and vacuum of space.
Clervoy said the thermal vacuum test was postponed from last summer due to problems developing the test procedures for flight hardware.
The resupply ship should be transported to its launch site in Kourou, French Guiana, later this spring, Clervoy said.
The ATV's cargo and resource modules were recently disassembled for the two-week trek to South America. The craft and its nearly one million pounds of support equipment will be shipped to Kourou by sea.
Once it arrives at the launch site, technicians will spend nearly four months readying the craft for its maiden launch. Work in Kourou will include the loading of the ATV's cargo and fuel.
After launch aboard an Ariane 5 rocket, the 45,000-pound craft will unfurl its four solar panels spanning 73 feet to produce electricity as it begins its journey to each the station. Once the 32-foot-long spacecraft is docked, the space station crew will open hatches between Jules Verne and Zvezda to begin offloading supplies. The craft will likely remain attached to the station for up to six months, according to ESA.
The ATV can carry almost 17,000 pounds of supplies to the space station, including scientific payload racks for the station's science laboratories, food, clothing, and water. Pressurized tanks aboard the ATV can also hold oxygen, nitrogen and propellant to be transferred to the station.
About 14,000 pounds of trash and other unnecessary materials can be stored on the ATV until it is undocked. The spacecraft is designed to burn up during a guided reentry into Earth's atmosphere over the Pacific Ocean, providing an economical way to get rid of discarded supplies.
The ATV's cargo capacity to the space station is more than three times that of the venerable Russian Progress resupply vessel. The European craft can also hold almost four times more trash than the Progress for the trip back into the atmosphere.
At least five ATV's are officially planned by ESA, and parts for the second flight vehicle are built and awaiting assembly, Clervoy said.
Clervoy said most of those components come from spares constructed for Jules Verne.
ESA hopes to launch about one ATV mission per year in the future. Cargo delivery duties will be shared between NASA's space shuttle fleet, the Russian Progress capsule, the ATV, and Japan's H-2 Transfer Vehicle, which is projected to fly in late 2008.