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The objective of this project is to define the characteristics and requirements for a 745 litres propellant tank "EUROSTAR 3000" containing the necessary tasks concerning the delta development tasks, the manufacturing and the delta qualification of the enlarged tank. The propellant tank originally has been developed by ASTRIUM SAS, adapted to 651 litres and qualified by ASTRIUM Space Transportation (ST).
For the delta qualification of the 745 litres tank it will be made use of the qualification data of the 651 litres tank to the extent possible, the PMD is therefore considered as a qualified item.
The envisaged 745 L version will be the biggest version which belongs to the EUROSTAR 3000 tank family. For the qualification of this tank the benefit of the 651 L tank qualification is used (qualification per similarity), when feasible. A QM tank is foreseen to perform necessary delta qualification tests.
The enlarged volume has been obtained by an additional cylinder, which leads to the specified mass increase.
A total propellant mass of 3300 kg corresponds to a maximum load of 1056 kg of MON 3 (and approximately 642 kg of MMH), for a ~ 98 % fill level at 16 deg C. This has led to the 745 litres maximum volume.
The 745 L version will become compatible with the horizontal transportation for various mission scenarios that is anticipated today requirement, which comes from SEA LAUNCH and PROTON launchers. The requirement has been put on the tank functional performance to be able to withstand a minimum fill ratio of 80% in case of horizontal transportation. Due to the increased tank length this requirement has to be analysed in the course of the delta qualification.
The increased tank mass, which is due to the higher mass of the propellant load and an increased tank mass leads to lower resonance frequencies. The tank design has been maintained in principle except the insertion of an additional cylinder. Applying the same acceleration loads, additional mass provides higher loads into the tank bosses.
The European satellite manufacturers have currently problems to compete in the segment of large GEOs, since the available sizes of European propellant tanks are limiting the propellant capacities of European GEOs remarkably below that of the US GEOs. Therefore the development of large tanks is ongoing in Europe, supported by National and by ESA funding. Therefore ESA has initiated the development of 1900 Liter tanks for the new European GEO bus Alphabus on basis of a technology which later can also be applied on future tank derivates for the spacebus family of Thales-Alenia. The second European GEO bus family “Eurostar” requires an analogue increase of its propellant tank size to remain competitive in the future market.
The Eurostar satellite configuration is clearly different from that of Spacebus and Alphabus, especially in view of propellant tank arrangement, tank size and tank accommodation and thus also the tanks themselves are very different to that of the above spacecraft. The Eurostar 3000 tanks have currently a volume of some 600 Liters each and need to be enlarged to 745 Liters. With this new tank size Eurostar 3000 will have a propellant capacity of 3,300 kg (4 tanks per satellite) which will finally allow the European industry to maintain its strong position in the world-wide GEO market.
The 745 litre propellant tank design and proposed qualification sequence is based on the fully qualified 651 litre ‘LX’ tank.
The additional 95 litres of volume will be achieved by including an additional cylinder component to the upper compartment of the tank. The geometric configurations of the two tanks are illustrated below.
The resulting architecture of the 745 litres propellant tank is shown hereafter.
The delivery scheme for the flight tanks of the EUROSTAR 3000 745 Litres tanks is dominated by the lead times of the titanium half shells and tank rings. For this reason for the Qualification unit shell elements from the current EURSTAR 3000 LX program will be used, which must be replaced later by re-ordered items. Parts to be used will be identified and reserved. The only forging currently not in house is the new, additional intermediate ring. To comply with the need dates for the flight units an early procurement of half shells and rings is necessary.
The PDR will be performed within a few months after K/O. In case of a successful PDR the delta qualification is planned to become approved. In case of non-compliances within the design verification status, these deviations will be highlighted and recovered. In case of non-compliances within the qualification status of the PTA, it will be checked whether this non-compliances can be covered by the considered delta qualification.
This approach has been chosen for two major reasons:
The CDR is planned to be performed a few months after successful PDR in order to finally release the design of start with the QM integration and prepare for the PTA delta qualification test campaign. In order to avoid programmatic risks as a result of failures during delta qualification testing it is foreseen to start assembly of flight items not before successfully passed QM test verification. The delta qualification will be closed with successful completion of the QTRB/FR.