Picked up the thread again

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Picked up the thread again
Picked up the thread again

Picked up the thread

When the stakes are high, the tension builds. An editor from Spektrum der Wissenschaft was able to experience this live during the maiden flight of the new Ariane 5. And promptly there was a glitch - but this time it only deprived the invited guests of the visual enjoyment of the start.

Tensions eased in the control room at Kourou as Ariane 502 gained altitude yesterday, October 30th after a picture-perfect launch. The disaster last year cost no less than 600 million marks. Because data from the inertial system had been incorrectly converted, the onboard computer diagnosed a deviation from the specified trajectory during the first qualification flight of the new carrier rocket and tried to counteract it. Now that it was actually off course, the rocket burst under the aerodynamic forces after just 37 seconds of flight time.

The team at the European space center in Kourou (French Guiana) could see the strain on the team when the countdown was interrupted less than a minute before the start. In the start-up procedure, a voltage value of a ground system should have been read out, which was not done. After about 20 minutes, the countdown started again at minus seven minutes.

But now everything went like clockwork. The only exception: the satellite connection between Kourou and the ESA control center in Darmstadt broke down. Several hundred guests from science, business, politics and the media enjoyed the start like in the good old days of steam radio, listening to the voices of the mission leader and commentators. "Dix, neuf, …" The outside microphones transmitted the chirping of exotic birds, then at "zero" the roar of the main engine ignited. Its function was checked for another seven seconds; the launch could have been aborted, then the two solid-fuel rockets also ignited.

These boosters are the most striking new feature of Ariane 5 compared to its predecessors. Each is designed to generate thrust for 130 seconds, a maximum of 6254 kilonewtons. Together with the main engine, the carrier rocket can then bring up to 6.3 tons of payload - the equivalent of about two heavy satellites - into a geostationary orbit. Because various financial costs remain constant regardless of projectile size, transportation costs decrease and the system provides market advantages.

Two minutes and 20 seconds after liftoff, these solid rocket boosters were ejected. A critical moment, because each booster still weighs almost 40 tons, so it exerts considerable forces on the comparatively fragile main stage. But this phase also went according to plan, as did the next: disconnect the main stage and fire the upper stage engine, eject the upper envelope, release the payload.

The consisted of two satellite dummies, Maqsat B and H, equipped with numerous sensors to log the applied forces during flight. The upper dummy also carried the Teamsat research platform with five experiments that young engineers and students built within a few months; they were looked after by the Dutch ESA headquarters ESTEC. It got exciting at the end when the ground station in Australia only discovered the Teamsat signal after going through several search routines. There was one unforeseen event, however: the premature launch put Ariane in an orbit 524 kilometers above Earth, 57 kilometers lower than planned. "Even if the orbit is slightly different than planned, it will be able to fulfill its mission," said Daniel Mugnier, director of space at CNES, France's space agency.

The launch vehicle's third and final qualification flight will probably follow within a few months. Then Ariane 5, like its predecessor, should have a reliability of 98.5 percent, a best value worldwide. By the way: the satellite connection to Darmstadt could be re-established and the guests saw in the replay what they had vividly imagined live.

The Heidelberger Verlag Spektrum der Wissenschaft is the operator of this portal. Its online and print magazines, including "Spektrum der Wissenschaft", "Gehirn&Geist" and "Spektrum – Die Woche", report on current research findings.

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