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Last Updated: Friday, 14 March 2008, 17:11 GMT
Space truck does emergency drill
By Jonathan Amos
Science reporter, BBC News

ATV artist's impression (Astrium)
Total cargo: 4,860kg
1,340kg - 'dry' supplies
20kg - air (oxygen/nitrogen)
280kg - drinking water
860kg - propellant for ISS
2,360kg - re-boost propellant
The ship itself has 3,490kg of propellant for rendezvous, re-boost and de-orbit manoeuvres

Europe's space freighter, the ATV, has demonstrated its last-gasp emergency stop and retreat ability.

This Collision Avoidance Manoeuvre is what the truck will initiate if it suffers a major failure just as it is about to dock with the space station.

The practice manoeuvre was demanded by Europe's partners before they would let ATV approach the platform on 3 April.

The freighter is carrying just under five tonnes of supplies for the station's astronauts.

It is currently shadowing the International Space Station, awaiting the opportunity to dock once the current shuttle Endeavour mission is completed in two weeks' time.

Friday's test is just one of several demonstrations planned for the truck in the meantime - but by far the most important.

The freighter weighs some 20 tonnes and could do immense damage if it gets out of control.

Although, the ATV will be moving at a relative speed that is less than walking pace when it docks with the ISS; in reality, the freighter and the station will be travelling across the surface of the Earth at 27,000km/h.

Mission managers want to be absolutely sure the truck will behave as predicted.

ATV control room (Esa)
Mission control in Toulouse watched over the demonstration
The ATV's systems have been designed with multiple layers of redundancy. It has three main flight-control computers that run in parallel. These in turn are overseen by a totally independent computer.

If the latter recognises an anomaly in the primary system during the final approach, it will intervene and command the ATV to remove itself rapidly - at a relative speed of 5m/s - to a safe distance.

Both the controllers on the ground in Toulouse, France, and the astronauts on the station can also initiate the Collision Avoidance Manoeuvre. The astronauts do it by hitting a big red button on a panel positioned in the Russian Zvezda module.

The Automated Transfer Vehicle - dubbed Jules Verne for this mission - is the biggest, most complex spacecraft ever flown by the European Space Agency (Esa).

The freighter is the way Europe will pay for its membership of the International Space Station (ISS) project. Four vehicles will follow this initial flight.

Jules Verne was launched by an Ariane 5 rocket from the Kourou spaceport in French Guiana on Sunday 9 March.

ATV at the ISS (Astrium)

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