ARIANESPACE, the company responsible for the commercial operation of
the Ariane launcher, established a board of inquiry this week to investigate
last Friday’s explosion of an Ariane 4 rocket. The explosion took place
shortly after takeoff from the European Space Agency’s launch pad in Kourou,
French Guyana. The company estimates that it will be at least three months
before the board has any answers to what went wrong.
Mission control first noticed a problem 6.2 seconds after ignition.
Engineering data showed a drop in pressure of 28 bars in one of the four
engines of the first stage of the rocket. The pressure drop meant a large
decrease in the engine’s thrust.
For just over a minute, two other engines struggled to compensate for
the drop in thrust. Some 101 seconds after ignition, the engines could do
no more. The rocket was at the wrong pitch angle to its trajectory, and
dynamic pressure shook it apart. The first stage exploded, and the flight
safety officers destroyed the remaining two stages, together with their
cargo of two Japanese communication satellites.
David Baker, an aerospace and defence consultant, says that since combustion
continued, though at a lower pressure, the fuel flow must have been reduced.
‘That could mean a failure to a turbopump or a fuel line,’ says Baker.
Each Ariane rocket uses several engines of the type that failed. The
company has successfully used 250 of them on its 36 launches to date. Of
these, only one other failed, during the second launch. For this reason,
Suna Abrahamson, a project manager for the company who liaises with US customers,
believes that the fault is unlikely to be a generic design failure.
Baker, however, believes that the failure highlights a fault in the
design thinking. He says that random failures of engines are bound to occur,
and that it should be possible to attain orbit with one engine out.
Despite the failure, John Logsdon, a space analyst from George Washington
University, believes that the long-term trends in commercial launches will
not change and that Arianespace will not lose custom.
But the accident could affect insurance rates. The insurance premiums
for launching satellites have decreased steadily from a high in 1987. That
high was a result of failures that grounded the entire Western fleet of
launchers. Jean Grenier, director-general of Eutelsate, told journalists
at the weekend that he expects the downward trend to level off, but not
to reverse upward.
The ill-fated rocket was carrying two Japanese communications satellites.
One was BS-2X, which was owned by the state broadcasting authority NHK.
The other was a private spacecraft, Superbird-B. The loss of the BS-2X satellite
in the Ariane explosion could damage Japan’s efforts to promote its technology
for the next generation of television.
BS-2X, built by General Electric of the US, was to back up the BS-2B
satellite, which relays daily broadcasts of high-definition television to
special television sets at exhibition halls around Japan. The project has
already suffered one mishap in space, when the first satellite used for
broadcasts, BS-2A, failed. NHK has recently admitted that transponders on
BS-2B are malfunctioning.
To add to Arianespace’s embarrassment, Japan’s main space agency NASDA
announced on Monday that it was ready to resume firing tests on the main
engine for its new rocket, the H-II.