Synthesis and casting

The process begins in the Guiana Propellant Plant (UPG), which is operated by Regulus, a French/Italian company. The two main segments of the solid propellant motor (MPS), S2 and S3, are filled with propellant here. The top segment, S1, is filled in Colleferro, Italy and sent by sea to the UPG at the same time as the stage igniter. To describe this process chronologically, Regulus first takes delivery of the segment casings, or structures. These are manufactured in Germany by MT Aerospace (formerly MAN Spatial Technologies), then sent to Avio in Italy where the internal thermal protection is applied, before finally being sent to French Guiana. Regulus is then responsible for cleaning ('burnishing') the structures before filling them in a three stage operation: mixing, casting and non-destructive testing.

Mixing

The process of loading the segments begins with combining several ingredients to form a mixture which is 'kneaded' as uniformly as possible before being cast in a mould, baked, then removed from the mould.

In buildings 301 and 302 of the UPG, the raw materials (mainly ammonium perchlorate and aluminium, together with a resin used as a binder) are placed in two enormous mixing vats, each with a capacity of 1,800 gallons. The shape and distribution of the mixing paddles is critical to obtaining the required consistency: just 7 mm separates them from each other and from the wall of the vat.

Casting

First the segment casing is positioned in the propellant casting pit. Then what is known as the 'core' is put in place. This slightly conical metal cylinder is used to shape the propellant – the conical shape is designed to ease removal by reducing friction between the metal and the propellant. The propellant mixture is then poured in at three different points, in a vacuum at a temperature of 50°C. The entire casting process is remotely controlled using a video system, as the pyrotechnic constraints prohibit any person from being in the building during this phase, which lasts several hours. Once casting has been completed, the mixture is baked at 50°C for ten days.

The cover of the pit is then removed and the core taken out, then the segment is extracted using a travelling crane. The propellant has by this stage become solid. After the segment is removed from its pit, it is weighed in order to establish how much propellant mixture has actually been cast.

A few figures

1 cast = 10 batches of 1,800 gallons
(1 gallon = 3,785 litres)
Capacity of one mixing vat = 1,800 gallons
S1 Segment capacity = 24 tonnes of propellant
S2 Segment capacity = 107 tonnes
S3 Segment capacity = 106 tonnes
Propellant baking temperature = around 50° C
Duration of EAP combustion = 135 seconds
The UPG represents 1/5th og the ariane 5 ground infrastructures in French Guiana
41 buildings spread over 300 hectares
18 km of roads, including 3 km of heavy-duty roads
150 segments produced as of 1 October 2005, representing around :
15,000 tonnes of propellant manufactured.
1 cast = 70 people working round the clock for two weeks

Next:
Testing and integration

Chapters :

Synthesis and casting

Testing and integration

Assembly and equipment

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