IT LOOKS like third time lucky for the European Space Agency鈥檚 Ariane 5
rocket. Following the disastrous pyro-technics of the first launch and the
misguided wanderings of the second test flight, ESA officials are proclaiming
last week鈥檚 mission a complete success.
This time the rocket propelled a dummy satellite into the correct orbit. ESA
also tested an atmospheric re-entry vehicle. 鈥淭he splashdown was extremely
accurate, five kilometres from the expected point,鈥� says Stefano Bianchi, who is
responsible for technical aspects of Ariane 5 at ESA鈥檚 headquarters in
Paris.
ESA engineers corrected the fault that caused the second test flight to veer
off course (This Week, 8 November 1997, p 14). The problem was traced to a
channel carrying coolant in the nozzle of the rocket鈥檚 main stage. This produced
a torque that made the rocket spin faster than expected. By redirecting the
exhausts of two turbopumps that supply the nozzle with fuel, engineers created
an opposite torque to cancel out the problem.
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The only minor glitch in last week鈥檚 proceedings was the loss of one of the
two booster rockets. ESA had planned to recover both to check that the launch
had not damaged their casings. On this occasion, preliminary data suggest that
one of the boosters broke up before the start of the recovery sequence that
fires the chutes. But ESA officials still have one intact booster for
inspection.