Europe’s Workhorse Sounding Rocket Grounded until Fall

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KOUROU, French Guiana — Europe’s principal sounding-rocket program, Texus, has been grounded following suspected defects in the launch tower guide rails that help aim the rudderless vehicle to assure its payload lands in a specified area, Swedish and German program managers said.

Operated from northern Sweden’s Esrange Space Center and supported by the Swedish Space Center and the German Aerospace Center, DLR, Texus was unable to perform its 51st flight as scheduled in mid-April following the 50th flight on April 12. That mission’s payload landed within the permitted landing zone but more than 20 kilometers from its planned drop point.

Mikael Toyra, sounding rocket and balloon program manager at Esrange, said initial suspicion has centered on the launch tower guide rails but that an investigation has not yet reached any final conclusions.

In a May 6 interview, Toyra said the investigation and any required repairs will delay the Texus 51 flight until the vehicle’s next launch season, in the fall.

“It will take us several weeks, and perhaps a few months, to determine a final cause and then complete any repairs,” Toyra said. “For now it does look like the fixed guide rails are the major cause, but the investigation will tell us.”

Otfried Joop, Texus project manager at DLR, said one possible conclusion is that the guide rails somehow became misaligned, causing a much wider than expected dispersion in the landing areas.

“The deviation we had in the past has been plus or minus 10 kilometers or so,” Joop said in a May 3 interview. “But in the most recent flight it was 20-30 kilometers. It was still within the safety area, but fear of safety concerns are nonetheless raised, so Texus 51 was suspended. We hope to have everything settled and the remedial action completed for a launch in November.”

The 12.6-meter-long Texus rocket is sent on a ballistic trajectory at launch and does not have thrust-vector control or other on-board guidance. The guide rails serve to assure that the 2,570-kilogram vehicle, which carries up to 400 kilograms of experiment payloads to an altitude of around 260 kilometers, is properly oriented when it leaves the launch tower.

Texus, which has conducted 50 missions since 1977, carries experiments for its most frequent customer, DLR, and also for the 20-nation European Space Agency. The launches offer a bit more than six minutes of microgravity conditions to experiments that one day may be flown to the European laboratory on the international space station.

In addition to Texus and the smaller Rexus rocket, European suborbital facilities include a drop tower in Bremen, Germany, and a specially designed Airbus jet that performs parabolic maneuvers to offer 20 seconds of microgravity during its descents.