Since its first voyage in April 2008, the Automated Transfer Vehicle (ATV) has been an indispensable ISS supply ship.
 
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 the ATV on a rendezvous trajectory towards the ISS, where it docks with the Station's Russian service module Zvezda.

The 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, during which it breaks up and burns, together with up to 6.4 tonnes of waste from the Station.  
 

The Automated Transfer Vehicle

Intelligent and powerful

To succeed in docking safely with the ISS ATV has to be a highly intelligent and powerful spacecraft.

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 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, 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 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 Mod-ule (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.
 
 

There is room for eight standard racks

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 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 has up to 4 tonnes of propellant.

Depending on the operational lifetime of the ISS, ESA plans to build seven 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: 9 March 2010