Aerospace Daily January 8, 2003
Arianespace hopes to relaunch Ariane 5 ECA in six months
By Nick Jonson (nick_jonson@AviationNow.com)
Senior Arianespace officials said Jan. 7 that another heavier-lift Ariane 5 ECA, similar to one that had to be destroyed shortly after launch on Dec. 11, could fly in six months.
The Ariane 5 ECA is an enhanced version of the company's baseline Ariane 5 launcher and features a new cryogenic upper stage and Vulcain 2 main engine.
A report released Jan. 6 by an inquiry board investigating the Dec. 11 launch failure said the Vulcain 2's cooling circuit nozzle overheated after cracks developed in the nozzle's cooling tubes. The nozzle's deterioration during flight caused a major imbalance in the Vulcain 2 engine's thrust, which resulted in a loss of control over the rocket's trajectory, the report concluded.
The Vulcain 2 engine, built by the Snecma Group, has a larger nozzle than the baseline Ariane 5's Vulcain 1 engine and was designed to withstand greater flight loads during launch.
Wolfgang Koschel, chairman of the inquiry board, said during a Jan. 7 news conference in Paris that the increased thermal and dynamic flight loads caused cracks to develop in the engine nozzle's tubes. Those loads cannot easily be simulated in ground test firings, he said.
The rocket was carrying the Hot Bird 7, a $ 250 million communications satellite built by Astrium for Eutelsat, and the $ 500 million Stentor satellite, an experimental communications satellite built by Alcatel Space and Astrium for the French space agency CNES (DAILY, Dec. 13, 2002).
The board recommended that Arianespace modify the nozzle on the Vulcain 2 engine, taking into account the lessons learned from the 12 previous successful launches using the Vulcain 1 engine.
The board also recommended that Arianespace explore further the possibility of simulating in ground tests the flight loads that appeared during the failed launch.
Arianespace CEO Jean-Yves Le Gall said during the news conference that Arianespace plans to move forward with its scheduled launches.
The final flight of the Ariane 4, which will carry the Intelsat 907 satellite built by Space Systems/Loral, is scheduled for launch Feb. 12. A launch involving a baseline Ariane 5 is scheduled for Feb. 24.
"We are extremely confident about the flight worthiness of the Ariane 5 baseline launcher with its Vulcain 1 engine, and our confidence is being borne out by reverifications of the nozzle behavior that currently are underway," Le Gall said. "For the Ariane 5 ECA, we currently are working on a recovery plan that should be ready for presentation on Jan. 20." He said company's plan to conduct another launch of an Ariane 5 ECA in about six months is "very ambitious, but extremely realistic."
Space and defense analyst John Pike, director of GlobalSecurity.org, said determining the root cause of the fissures and redesigning the engine nozzle will not be easy. "It typically takes weeks to identify the problem and some number of months to fix the problem," Pike said.
The larger nozzle used on the Vulcain 2 appears to have been under-designed, given the increased vibrations, shock and temperatures that occurred during flight, he said.
Arianespace has not decided on the launch date for another baseline Ariane 5 carrying the European Space Agency's Rosetta scientific satellite, Le Gall said
The launch, which was scheduled for Jan. 12, is special because of the unusual trajectory involving a planned delayed ignition of the upper stage, he said. Rosetta's mission will involve intercepting and studying the comet Wirtanen. "Because of the particular nature of this mission, we are taking a thorough look at the flight," Le Gall said. "We should be ready to make a launch decision by Jan. 14."
Copyright © 2003 The McGraw-Hill Companies
