Newest -5 Design Iteration Affected; Base Design OK

There may have been cracks in the cooling circuits of the hot-rodded Ariane-5 that blew up last month; and those cracks, while critical, aren't something that's likely to really foul up the entire European launch system.

The formal Inquiry Board, set up after the failed December launch attempt, concluded that, "...the most probable cause of the failure of Flight 157 was the simultaneous occurrence of two aggravating factors:

• The degraded thermal condition of the nozzle due to fissures in the cooling tubes, and
• Non-exhaustive definition of the loads to which the Vulcain 2 engine is subjected during flight

The board also noted that it would be difficult to simulate these additional loads during ground tests.

The newest-version Ariane-5 certainly needs attention, though.

On Wednesday, Arianespace boss Jean-Yves LeGall told the AP, "I consider that the generic Ariane-5 has been cleared by the commission’s work. We have no worries about the basic Ariane-5 launcher." Apparently, not all the rocket's engines failed; the asymmetric thrust, as well as the overall loss of power, doomed December's launch.

That kind of good news/bad news statement needs to be put into perspective. The Vulcain-2 engine is what makes the latest -5 such a workhorse: it can send 10 tons of expensive stuff into orbit, as opposed to the Vulcain-1's 7-ton limit.

The Vulcain-2 is slated to launch three times in 2003; repairs and modifications are expected to take six months. LeGall says the Vulcain-1-powered rockets will handle this year's launches, if necessary -- the heavier payloads aren't scheduled for at least a year.

The smaller Ariane-4 rockets continue to be launched and might shoulder some of the short-term launch load, even though their production has already stopped. The next Ariane-4 launch is set for February 11.

FMI: report