A brief history of Europe's ISS cargo programme

The European Space Agency's Albert Einstein cargo craft, set for launch on Wednesday, is the fourth and penultimate in a series of hi-tech lifeline vessels bringing supplies and critical altitude boosts to the International Space Station.

Europe's Automated Transfer Vehicles (ATVs), blasted into space by ESA's Ariane rocket, are the biggest cargo carriers to the ISS since the retirement of the US space shuttle in 2011.

ESA sends an ATV to the orbiting outpost about once every 17 months with around six tonnes of cargo -- much of it fuel needed to boost the ISS, which is constantly falling towards Earth due to atmospheric resistance.

Named in honour of the father of relativity theory, the Albert Einstein follows the hi-tech trail of three others since 2008 that also carried the names of science gurus -- the Jules Verne, the Johannes Kepler and the Edoardo Amaldi.

It will be followed next year by the last in the ATV series -- the George Lamaitre named for the father of the Big Bang theory of the Universe's creation.

At 20.2 tonnes, the ATV-4 is the heaviest yet launched and will bring a record 2.5 tonnes of dry cargo to the six-member space station crew.

ATV-1: Jules Verne (2008)

The first in the series carried a total load of 4.5 tonnes consisting of 3.4 tonnes of fluid and 1.1 tonnes of dry supplies.

The payload heavily favoured propulsion fuel, including enough reserves in case of unforeseen problems with this first-ever ATV docking to the ISS.

The Jules Verne had no late load -- that part of the cargo nowadays reserved for last-minute requests and perishables whose packing poses great technical difficulties once the capsule is perched vertically on top of the Ariane rocket that will propel it into space. The loading hatch is right on the vessel's nose -- about 10 storeys high.

ATV-2: Johannes Keppler (2011)

This vessel holds the record for the largest boost given to the ISS by an ATV -- 40 kilometres in a single push.

It also holds the record for the heaviest cargo ever delivered to the outpost -- over seven tonnes, though the ATV-4 will have more dry cargo.

The Johannes Keppler took 1.6 tonnes of dry supplies and 5.4 tonnes of fluid cargo, and a big supply of fuel that was used for the special orbital boost.

This was the last ATV not to bring water to the ISS -- a task until this point performed by the US space shuttles which had also been responsible for boosting the space station's altitude.

ATV-3: Edoardo Amaldi (2012)

The third ATV carried 4.3 tonnes of fluid cargo and 2.2 tonnes of dry supplies.

As the technology and confidence grew with each successive mission, the ATVs started favouring a balance of more cargo and less backup fuel.

ATV-4: Albert Einstein (2013)

Will carry 4.1 tones of fluid and 2.5 tonnes of dry cargo -- 6.6 tonnes in total.

It boasts the most complex flight software ever developed by ESA -- a million lines of code.

It has the biggest-ever late cargo load, exceeding its nearest rival by more than 218 kg thanks to a new device that can lower an operator deep into the hull to load the holding racks, aided by a mechanical arm that can hold bags weighing as much as 75 kg each.

The Albert Einstein has the largest-ever assortment of goods taken into space, some 1,400 individual items.

The launch of ATV-5, the George Lemaitre, next year, will not mean the end of ESA's ATV programme.

The European agency will supply ATV-derived hardware for NASA's Orion spacecraft being designed to take humans to the Moon and beyond, and scheduled for a test flight in 2017.

This will be the first collaboration between ESA and NASA on a crew transport vehicle.

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