Automated Transfer Vehicle (ATV)-4, also called ATV-4 and "Albert Einstein," weighs in at 20 tonnes and has a maximum net cargo capacity of up to seven tonnes. The composition of this payload can vary depending on the mission:
· between 1.5 and 5.5 tonnes of freight and supplies (food, research instruments, tools, etc.),
· up to 840 kilograms of drinking water,
· up to 100 kilograms of gases (air, oxygen and nitrogen),
· up to four tonnes of fuel for orbit correction,
· up to 860 kilograms of propellant to refuel the space station.
On August 1, the “Albert Einstein” had filled the “Zarya” ISS Functional Cargo Block with 860 kg of fuel. Refuelling took around an hour and a half to complete. Moreover, by the end of August, the supply vehicle had transferred a total of 33 kilograms (kg) of oxygen and 66 kg of synthetic air to the space station.
On top of all the functions described above, the supply vehicle also serves as a fully inhabitable ISS module, offering the crew 45 square-meters of additional space in which to live and work. Previous astronauts have spoken of the ATVs as their preferred place to sleep, because the ATVs are much quieter than the rest of the ISS.
In addition to delivering supplies, ATV also carries out reboost manoeuvres to counteract the effects of atmospheric drag, which causes the ISS to lose altitude by as much as 100 metres a day. And if space debris threatens the ISS, ATV can carry out the requisite avoidance manoeuvres. It also carries out attitude control manoeuvres when other spacecraft approach the ISS. During its mission, “Albert Einstein”’s engines powered a total of six reboost manoeuvres that each keeps the ISS back up to its operational orbit.
Loaded with the liquid and dry waste, as well as redundant equipment, the European ATV burned up as planned during controlled re-entry into Earth’s atmosphere over the South Pacific. Throughout the course of its mission, ATV-4 managed to clock up some four million kilometres.
At the same time that “Albert Einstein” finished its mission, “Georges Lemaître”, the fifth and final European ATV built by Astrium arrived at the European spaceport in Kourou, French Guiana, demonstrating the ability of Astrium to manage the production of the ATV on a regular basis and on schedule. Astrium was commissioned by the European Space Agency (ESA) as systems leader within a European consortium to design and manufacture the ATVs.