Looking behind the scences of the ArianeGroup in Les Mureaux (part 2)

Link to German version/Deutschsprachige Version

After having the great pleasure of visiting the main assembly hall for the central stage of the ESA launcher Ariane 5 in Les Mureaux another highlight of the visit was following. We were permitted to see how the cool double launch systems for the Ariane 5 – called SYLDA – are assembled.



We were able to have a look at three SYLDA structures in different assembly stages. As you can see these are available in different sizes. This allows to optimize the SYLDAs for the real sizes of the satellites.


The name SYLDA is a great one for sure. It also has a meaning: it is the acronym for „SYstème de Lancement Double Ariane„. That is French for „double launch system for Ariane“. This system is very important for the commercial success of the Ariane 5 launchers as it enables to launch two communication satellites with a single Ariane 5 launch. Thus, launch costs can be shared between the owners of the two satellites.



Model of  an Ariane 5 launcher. The black SYLDA structure can be spotted inside the cutted payload fairing.


During the launch of two satellites one is encapsuled inside the SYLDA and the second sits on top of it. The satellite at the top is the first one to be released after the Ariane 5 upper stage has reach the desired orbit. The next step is to separate the entire cylindrical part of the SYLDA. The mechanical separation is done via small explosives. Then several springs are pushing the entire cylindrical part of the SYLDA away. For this all the springs have to be pre-loaded very carefully to avoid that the SYLDA cylinder contacts the satellite inside during the push. Often there are only 10 centimeters space between the inner SYLDA wall and the encapsuled satellite. Nevertheless, there was never a problem with the SYLDA system so far. And the engineers continue to work hard to keep it that way. Fingers crossed!



Here we have the smallest SYLDA unit (shown to us).


The SYLDA units are available in different sizes. This allows to adopt the SYLDAs to the actual sizes of the satellites to be launched.



These are segments for the conical part of SYLDA. They made of light-weight carbon composite material.



Here we have a carbon fiber based segment for the cylindrical part of a SYLDA structure.


When the SYLDA was designed it was important that the structure is stiff enough to survive the loads during launch and has low weight at the same time as the mass of the SYLDA is directly reducing the available payload mass. Therefore the SYLDA is mainly made of carbon fiber composite material. Segments of this material are glewed together to form the SYLDA structure.



Oops, we have a hole in this SYLDA. It is made by purpose and is called „man hole“. This hole allows that technicians can have access to the satellite encapsuled inside. It can be closed by a cap.


As already stated SYLDA allows to launch two relatively big communication satellites by a single Ariane 5 launch. But there are smaller satellites for constellations where it makes sense to launch more than two satellites at the same time. One of these constellations is the European Galileo navigation satellite network.   Thus, last year in November four Galileo satellites were launched with a single Ariane 5 ES. A system different from the SYLDA one is needed for that kind of launch. A dispenser system was developed for that – also build by ArianeGroup in Les Mureaux. We had the pleasure to see such a dispenser system for four Galileo satellites (these satellites are build by the German company OHB in Bremen).



This is a Galileo dispenser. Four European Galileo navigation satellites will be connected to it for a launch with an Ariane 5 next summer. Two satellites at one time will be released after reaching the desired orbit.


The Galileo dispenser seen is planned to be used for a launch during the summer of 2018. Now after this meeting we are really looking forward to see this launch. This launch may even be more exciting as it might be the 100th Ariane 5 launch based on the current planning. Yeah!

And that is all for today! Many thanks.

Yours truly,



Part I: Visiting the assembly hall for the Ariane 5 main stage




Part III: News about my favourite ESA launcher Ariane 6 



3 Gedanken zu “Looking behind the scences of the ArianeGroup in Les Mureaux (part 2)

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