A graphic ATV docked to the International Space Station

ESA pulls its weight with heavy-haul space freighter

Mark Williamson reports from French Guiana on the launch of ESA’s space cargo vehicle.

Just after sunset on 5 June 2013, against the backdrop of a reddening sky, the latest incarnation of Europe’s Ariane 5 rocket cleared the jungle canopy of French Guiana and powered its way towards low Earth orbit. This 213th Ariane mission was different. Rather than delivering its usual fare of geostationary communications satellites, the launcher was carrying a cargo vessel destined for the International Space Station.

A further departure from the norm was the need for a precisely-timed launch (6:52:13pm local time) to enable synchronisation with the orbital parameters of the ISS. Without the luxury of an extended launch window, the blinding light and staccato crackle of the Ariane’s solid rocket boosters came as a relief to watching dignitaries and journalists alike.

Having clocked up 55 consecutive launch successes over the past decade, the Ariane 5 heavy lifter has become the ‘launch vehicle of choice’ for many commercial and government customers. As one of the latter, and as leading financial backer of Europe’s launch systems, the European Space Agency has a vested interest in Ariane’s performance. The fact that the VA213 mission carried ESA’s Automated Transfer Vehicle (ATV) cargo carrier, a key part of the ISS infrastructure, only served to heighten the agency’s interest.

The importance of ATV to ESA lies with its role in the so-called ‘barter agreement’ with Nasa, which is ESA’s way of paying for European astronaut time on the station. Rather than simply funding rides on the Soyuz ‘astronaut ferry’ and booking ISS facilities as one might rent a hotel room, the barter agreement allows ESA to support European industry in its development of advanced space systems and technologies. Thus EADS Astrium, as industrial prime contractor, is responsible for the detailed design and manufacture of the ATV and management of more than 30 subcontractors in 10 European countries.

Speaking before the launch, ESA director general Jean-Jacques Dordain was clear on the significance of the ATV for the ISS partnership. It ultimately comes down to mass. “Kilos on the ATV are money,” Dordain explained. “We have to pay our share of ISS costs and we are paying in kilos”.

Some 2.6 tonnes of freight in 209 bags were loaded onto the vehicle, along with oxygen and water for the crew and 4.8 tonnes of propellant to dock with the ISS and later boost its altitude.

In describing the ATV as a “multi-functional spaceship”, ESA director of human spaceflight and operations Thomas Reiter pointed out that it has “the largest upload capability of all visiting cargo vehicles”, specifically comparing it with the Russian Progress which can deliver “only two or three tonnes”. In fact, with an all-up mass of some 20.2 tonnes, the current ATV - named Albert Einstein - is the heaviest Ariane 5 payload to date.

Albert Einstein is the fourth version of the ATV to be launched to the station, following Jules Verne in March 2008, Johannes Kepler in February 2011 and Edoardo Amaldi in March 2012. Despite his experience of ATV and other Ariane launches, Dordain admitted to being as nervous as he was for the first ATV launch. Indeed, the difference in demeanour of many key officials present was palpable once the vehicle’s solar arrays and communications antennas had deployed in orbit.

Mission

As an indication of Europe’s continuing contributions to manned spaceflight in general and ISS operations in particular, the ATV-4 launch closely followed the delivery of ESA astronaut Luca Parmitano to the station on 28 May.

Dordain said he had told Parmitano that his first mission was “to take care of ATV-4”, which would include monitoring the automated docking (using its integrated German-built lidar and French infrared detector system) and physically unloading cargo. By way of compensation, the vehicle would deliver some “lasagne, parmesan and tiramisu”, said Dordain, as well as some clothes; “clothes are very important for a young Italian”, he added mischievously.

In addition to such everyday items, ATV-4 carries a new experiment for the station’s Fluid Science Lab developed by Astrium: FASES, the Fundamental and Applied Studies in Emulsion Stability experiment, is designed to explore the behaviour of emulsions - which have important roles in food production, cosmetics and pharmaceuticals - in microgravity conditions.

Space tug

Once unloaded, the ATV switches from cargo vehicle to space tug, using its onboard propellant to increase the height of the station’s orbit. Although the density of the atmosphere is low at the station’s operating altitude of about 350km, it is sufficient to cause a drag on the football-field sized structure. Indeed, it can lose up to 100m a day. According to Reiter, the highest reboost performed by an ATV was some 40km in the case of ATV-2, which clearly illustrates its capabilities.

In addition, the ATV can control the attitude (orientation) of the entire ISS complex when other spacecraft are approaching and, if necessary, can even provide debris avoidance manoeuvres (typically required several times a year).

Finally, as its five-month mission draws to a close in October, ATV-4 will assume the role of refuse vehicle and incinerator when it is filled with up to seven tonnes of waste and unwanted hardware and deorbited over the southern Pacific Ocean to burn up in the atmosphere.

Less obviously, Dordain revealed, “the ATV is also a place of rest, because it is quiet compared with the ISS itself”. Apparently, astronauts like to go there to ‘chill out’ when the combined racket of air conditioners, disk drives and other paraphernalia gets too much.

Future Rendezvous

As the Albert Einstein manoeuvred its way to the ISS, the fifth ATV, George Lemaître, was being readied for shipping to French Guiana, from where it will be launched in 2014. Since ATV production was terminated in 2011 it will be the last. But if the vehicle is so useful, flexible and appreciated by the crew, why not build more? Dordain was ready with the answers.

The first reason, he explained, is the rise of commercial cargo services to the ISS in the guise of the SpaceX Dragon capsule and Orbital’s Cygnus. “ATV is no longer unique,” he said. Indeed, Luca Parmitano will see four deliveries during his 166-day stay on the ISS: the ATV, Japan’s HTV, a Dragon and a Cygnus. “We almost need traffic lights around the station,” Dordain quipped.

His second reason for retiring ATV is “to prepare for the future and the development of new vehicles using ATV heritage”. The first (and so far only) example of this development is the recently announced adaptation of ATV technology to the role of service module for Nasa’s Orion manned spacecraft, currently expected to rendezvous with a small asteroid ‘relocated’ to lunar orbit.

“That is a fantastic demonstration that Nasa trusts ESA enough to place it in the critical path for technology development,” said Dordain, adding that this was just the “first part of a discussion with Nasa” on joint space exploration.

The morning after the launch celebration party, Europe’s spaceport was back to its usual routine, preparing for the forthcoming missions of its Ariane 5, Soyuz and Vega launch vehicles. In fact, an initial objective of Arianespace’s new CEO, Stephane Israel, is “to reduce the time between launches from three weeks to two”. If his vision takes shape, the South American jungle will be vibrating to a rocket’s roar even more often in future.

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