|  | Approximately every 17 months, ATV carries 7.7 tonnes of cargo to the Station 400 km above the Earth | |
Mission concept and the role of ATV
The International Space Station (ISS) depends on regular deliveries of experiment equipment and spare parts, as well as food, air and water for its permanent crew.
Since the arrival of the first vehicle in April 2008, the Automated Transfer Vehicle (ATV) is one of the indispensable ISS supply spaceships. It is developed under ESA contract by a European industrial consortium lead by EADS Space Transportation, in France.
Approximately every 17 months, ATV carries 7.7 tonnes of cargo to the Station 400 km above the Earth. An onboard high precision navigation system automatically guides ATV on a rendezvous trajectory towards ISS, where it docks with the Station's Russian service module Zvezda.
The ATV remains attached as a pressurised and integral part of the Station for up to six months. After that it starts its final mission: a so-called destructive re-entry into the Earth's atmosphere during which it breaks up and burns, together with up to 6.4 tonnes of material that is no longer used on the Station.
| | | The Automated Transfer Vehicle |
Intelligent and powerful
To succeed in docking safely with a huge manned station, ATV has to be a highly intelligent and powerful spacecraft.
The exterior is a white coloured 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, the 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 will ever be launched in an ATV, once attached to the Station, astronauts dressed in regular clothing will enter inside 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.
The ATV, which is equipped with its own propulsion and navigation systems, 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 resembles the combination of a tug boat and a river barge.
| | There is room for eight standard racks inside ATV | |
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.
The 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 configuration after the addition of ESA's Columbus laboratory in February 2008 |
ISS altitude boost
At regular intervals the ATV also boosts the ISS into a higher orbit to overcome the effects of the drag of the remaining atomic oxygen molecules above the Earth's atmosphere. The Station's natural altitude loss can reach up to several hundreds of metres a day. To perform these manoeuvres the ATV uses up to 4.7 tonnes of propellant.
Since the first operational flight in March 2008, Europe's most challenging spacecraft has a vital role to play in Station servicing. It is also a way for Europe to pay its share in ISS running costs by spending money within the European industry rather than by cash transfers to its International Partners.
Depending on the operational lifetime of the ISS, 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 (France) as the Prime Contractor.
Last update: 22 July 2008 | 
