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ATV “Jules Verne” ready for launch
By Matthias Gründer
The tension is rising among all the participants. Europe's first Europe-developed launch vehicle has been waiting at the launch site in Kourou, French Guyana since the middle of July 2007. As well as the space transporter itself, which has an empty weight of about eleven tonnes, some 400 tonnes of additional material have been assembled at the launch site on the Equator. The two main assemblies, the propulsion section with the tanks, engines and electronics, and the pressurised cargo section are connected up and are undergoing a series of thorough tests. Nothing, absolutely nothing must be allowed to go wrong on the maiden flight of this product, which represents the pinnacle of European engineering craft.
Design and construction of the space vehicle have taken eleven years. Testing and checks alone have consumed three years. Including the launch costs, the “Jules Verne” will have cost around Euro1.3 billion. After all, the European Space Agency (ESA) is investing about €300 million in construction and launch costs for every other of the five ATVs currently planned, none of which have yet borne its name.
The launch vehicle for the first flight into orbit, the Ariane 5 Evolution Storable upper stage Automated Transfer Vehicle (5ES-ATV), is already ready. It has the same lower stage combination as the AR-5ECA, with no change in the solid rocket boosters or cryogenic main stage (EPC) with performance-enhanced Vulcain 2 engine. But the upper stage has been adapted to the enormous takeoff weight of the ATV and has a new, reinforced vehicle equipment bay (VEB) plus the re-ignitable storable propellant upper stage (EPS). The EPS will be ignited for the first time immediately after separation of the EPC, following which the upper stage will fly on a ballistic trajectory for about 45 minutes. Only then will a second, brief ignition take place, to be followed by separation of the ATV. When the Ariane 5 ignites for the third and last time it will be to enable the VEB-EPS combination to de-orbit into the atmosphere, the density of which will cause it to burn up. The construction contracts for the next ATVs have already been placed with European industry.
The ATV will be released at an altitude of about 260 km above the earth's surface on a path angle inclined 51.6 degrees above the Equator. From there, it will fly to the ISS automatically under its own propulsion and then dock at the back of the Russian service module. For this reason the European cargo ship is also equipped with the extremely reliable docking system used for the Russian Soyuz and Progress capsules. This will not only ensure that the ATV is reliably attached for the entire duration of the time in orbit, but also enable automatic connection of all the necessary fuel and energy lines. Moreover, its ingenious design will make it possible to move straight from the station to the cargo bay of the ATV to unload the supplies and then to reload the ATV with waste products no longer required.
ESA's decision by to buy this system instead of developing and building a system of its own from scratch was sensible and reduced costs. Nevertheless, for safety reasons the docking unit was combined with a specially developed laser-based collision avoidance system, as the ATV may have zero gravity in orbit but is not without mass. Even at an approach speed of only one metre per second, a malfunction could cause it to crash into the back of the station like a bomb. For this reason, the programming allows a number of opportunities to terminate the mission, to transition to a temporary parking orbit and make another approach later, and the fuel reserves for the onboard propulsion system have been calculated accordingly. Extensive tests of these assemblies were carried out in a French Navy research facility which is normally used to measure flow resistances to different buoyancy devices over a long water tunnel.
While the last tasks, including the loading and fuelling of the space shuttle, were being carried out in Kourou in the autumn of 2007, launch, mission, docking, decoupling and re-entry simulations involving the ATV Control Centre in Toulouse, NASA's Johnson Space Centre in Houston, Texas and the Russian ZUP Control Centre in Moscow were being performed. Ten such cycles were enacted at extreme precision in order to exclude every possible imponderable.
The preparations also included expanding the existing network of telemetry and tracking equipment for Ariane 5 specially for these missions, as there was a need to be able to track the separation of the spacecraft, its entry into the target trajectory and the third ignition of the booster upper stage above southern Oceania. Finally, under an agreement to this effect with New Zealand, €200,000 was invested in the Awarua area of Invercargill, on erecting a mobile telemetry station.
The Europeans are thus well prepared for the first mission of their space shuttle, the date of which depends only on the ISS timetable. After all, due account has to be taken of the Progress transporter schedule, as these use the same docking unit as the ATV.
Meanwhile there is even the possibility that more than the six supply spaceships planned up to now could be built and launched. After all, NASA will face a supply gap in the period after the original Space Shuttle is retired from service in 2010. In anticipation of possible future business, Boeing has already announced that the ATVs are also compatible with the Delta IV.
From FLUG REVUE 11/2007
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