Interruption of Hydrazine Propellant Supply to Thrusters Caused Galileo Satellites’ Insertion Into Wrong Orbits

Back in August, two of the EU’s highly ambitious GNSS satellites were dropped into wrong orbits, though the space agency said at the time they were still under its control. Arianespace, the company responsible for the launch of those satellites, set up an Independent Inquiry Board in the aftermath to identify and analyze the anomaly that caused the insertion of the satellites into wrong orbits. The initial findings of the Board talked about an anomaly which they thought to have occurred during the flight phase involving the Fregat upper stage, causing the satellites to be injected into a non-compliant orbit.

The Board has now announced its definitive conclusions which blame the failure of two of Fregat’s attitude control thrusters during the preceding ballistic phase due to a temporary interruption of the joint hydrazine propellant supply for the Gallileo satellites insertion into wrong orbits.

But what the hell is Fregat?

GalileoSatellitesWrongOrbit2Fregat is an upper stage (see this image to understand what a ‘stage’ is) used by some of the Soyuz rockets. An upper stage like Fregat is the main component which places a satellite into its designated orbit.

How did Fregat get screwed up?

Hydrazine is used as a rocket fuel via a joint propellant supply to Fregat’s attitude control thrusters, and it froze after liftoff which resulted from the proximity of hydrazine and cold helium feed lines. These feed lines were connected by the same support structure, which acted as a thermal bridge and froze Hydrazine.

Some ‘trustworthy’ media outlets at the time were rounding up on Soyuz, but the Board’s conclusions confirm that the first part of the mission proceeded correctly, which means that the three-stage Soyuz launcher was not at fault. Too bad NASA has decided to call it quits with the Soyuz, right?

European Union’s ambitious project is supposed to provide GPS like functionality for the European countries. A total of thirty satellites are to be launched to complete the Galileo Global Navigation System, with six satellites (including the ones in the wrong orbit) having been launched as of now.

Head over here to read the latest findings of the Board setup by Arianespace, and over here to read more about the entire episode. Here‘s a link to the initial findings of the Board for those of you interested.

As stated on Arianespace’s website, the Board was created on August 25, 2014 by the company, in conjunction with the European Space Agency and the European Commission. It is chaired by Peter Dubock, former inspector-general of ESA. Its conclusions draw on data supplied by the company’s Russian partners in the program, and are consistent with the final conclusions of the inquiry board appointed by the Russian space agency Roscosmos.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s