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Mission concept and the role of ATV
The International Space Station depends on regular deliveries of experiment equipment and spare parts, as well as food, air and water for its permanent crew.
Since its first voyage in April 2008, the Automated Transfer Vehicle (ATV) has been an indispensable supply ship to the Space Station.
Approximately every 17 months, ATV carries 6.6 tonnes of cargo to the Station 400 km above Earth. An onboard high-precision navigation system automatically guides ATV on a rendezvous trajectory towards the orbital outpost, where it docks with the Station's Russian service module Zvezda.
ATV then remains attached as a pressurised and integral part of the Station for up to six months. After that it detaches and reenters Earth's atmosphere, where it breaks up and burns, together with up to 6.4 tonnes of waste from the Station.
Intelligent and powerful
To dock safely ATV is a highly intelligent and powerful spacecraft.
ATV is equipped with its own propulsion and navigation systems and is a multi-functional spacecraft, which combines both the full automatic capabilities of an unmanned vehicle, with human spacecraft safety requirements. ATV's mission in space is almost a combination of tug boat and river barge.
The exterior is a white cylinder 10.3 metres long and up to 4.5 metres in diameter. The ATV structure is covered with an insulating foil layer on top of meteorite-protection panels. Extending from the main body of the spacecraft are its characteristic X-shaped metallic blue solar arrays.
Inside, ATV consists of two modules, the Service Module and the pressurised Integrated Cargo Carrier. The forward part of the Cargo Carrier docks with the ISS. Although no crew travels in an ATV, once attached to the Station, astronauts dressed in normal clothing can enter the pressurised environment to load and unload cargo.
The Cargo Carrier is very much like the European-built Multi-Purpose Logistics Module (MPLM), from which it is derived. The MPLM has already flown as a space barge transporting equipment to and from the Station using the Space Shuttle.
Racks and tanks
The 48 m³ pressurised section has room for up to eight standard racks which are loaded with modular storage elements used for cargo. The Integrated Cargo Carrier also holds several tanks, containing up to 840 kg of drinking water, 860 kg of refuelling propellant for the Station's own propulsion system and 100 kg of air (oxygen and nitrogen). The 'nose' of the cargo section contains the Russian-made docking equipment with rendezvous sensors and antennas.
ATV's Service Module navigates with four main engines (490 N thrust) plus 28 smaller thrusters (220 N) for attitude control. After docking, the ATV can perform attitude control and debris avoidance manoeuvres for the whole Station.
ISS altitude boost
At regular intervals ATV also boosts the Space Station into a higher orbit to overcome the effects of the drag of the remaining atomic oxygen molecules above Earth's atmosphere. The Station loses up to several hundred metres altitude a day. To perform these manoeuvres ATV has up to 4 tonnes of propellant.
Depending on the operational lifetime of the International Space Station, ESA plans to build five ATVs. Thirty companies from ten European countries, as well as eight other companies from Russia and the United States share the work, with EADS Space Transportation based in France as the prime contractor.
Last update: 19 October 2012
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