A European rocket blasted off from French Guiana on Wednesday carrying a record 6.6 tonnes of cargo for the International Space Station (ISS) and its orbiting crew.

A space freighter with food, water, oxygen, science experiments and special treats for the astronauts was launched on an Ariane 5 rocket from Europe's spaceport in Kourou as planned at 6:52:11 pm (21:52:11 GMT).

The robot craft dubbed Albert Einstein is scheduled to separate from its launcher an hour after liftoff, somewhere over New Zealand, and enter orbit at an altitude of 260 kilometres (160 miles).

The Automated Transfer Vehicle (ATV) will then deploy four energy-generating solar panels and start its autonomous navigation, guided by starlight, to the space station.

It is set to dock with the ISS on June 15 at an altitude of about 400 kilometres (250 miles) above the planet -- at a speed of some 28,000 kilometres (18,000 miles) per hour.

At nearly 20.2 tonnes, the fourth and penultimate cargo delivery of the European Space Agency (ESA) to the ISS is the heaviest spacecraft ever launched by an Ariane rocket.

The robot space freighter is the size of a double-decker bus -- 10 metres (33 feet) long and 4.5 metres (15 feet) in diameter.

The Albert Einstein boasts the largest assortment of goods yet for the ISS -- a total of 1,400 individual items that include clothes, tools and enough food for several months.

Its dry cargo is the heaviest ever at nearly 2.5 tonnes, packed into 209 bags fixed to the vessel's internal shelves.

It is also loaded with some 4.8 tonnes of fuel needed to dock with the ISS and give it a boost into higher orbit with the ATV's onboard engines.

The ISS is in a low Earth orbit and encounters atmospheric resistance which causes it to fall towards our planet at a rate of about 100 m (300 feet) per day.

The ATV can also push the ISS out of the way of oncoming space debris.

The Albert Einstein carries 860 kg (1,760 pounds) of propellant to be pumped into the ISS itself, more than 500 kilos (1,100 pounds) of water and 100 kilos of oxygen and air, according to the Astrium space company which built the lifeline craft.

It's pressurised cabin will provide welcome extra space for the ISS crew -- Americans Chris Cassidy and Karen Nyberg, Russians Fyodor Yurchikhin, Pavel Vinogradov and Alexander Misurkin, and Italian Luca Parmitano.

After completing its mission, the ATV-4 is set to undock from the ISS in October filled with about six tonnes of garbage and human waste, and burn up over the Pacific.

ESA is contracted to provide five ATVs as its contribution to the ISS, a US-led international collaboration.

The previous three missions had performed flawlessly, muting criticism of the billion-euro ($1.3 billion) development cost.

Europe's ATVs are the largest cargo carriers to the ISS since the retirement of the US space shuttle in 2011.

But increasing competition in the space launch sector has prompted ESA to opt for a different route in future -- supplying ATV-derived hardware for NASA's Orion spacecraft which is being designed to take humans to the Moon and beyond, and is scheduled for a test flight in 2017.

The fifth and final ATV, named Georges Lemaitre after the father of the Big Bang theory of the Universe's creation, is scheduled for blastoff next year.