spacetoday.net: Frozen hydrazine lines blamed for Soyuz Galileo launch anomaly

Posted: Fri, Oct 10, 2014, 7:57 AM ET (1157 GMT)
Soyuz launch of Galileo satellites, August 2014 (ESA)

An investigation into a problem that stranded two Galileo satellites in the wrong orbits in August concluded that hydrazine fuel lines in the Soyuz rocket's upper stage froze during the launch. The August 22 launch of the two Galileo satellites on a Soyuz rocket from Kourou, French Guiana, was initially declared a success, but hours later officials said the satellites had been deployed in the wrong orbit. The orbital error, investigators concluded this week, was linked to an orientation error in the Fregat upper stage caused by the failure of the stage's attitude control thrusters. Those thrusters failed because their hydrazine fuel lines had frozen by being in close contact with cold helium feed lines. Investigators said poor design, and not manufacturing error, caused the lines to be close enough to freeze the hydrazine. Vehicle engineers can correct the problem with relatively simple design changes, investigators concluded. Arianespace, which operates the Soyuz out of French Guiana, said launches of the vehicle could resume as soon as December.