Tim Furniss/LONDON
The Columbus Orbital Facility (COF), a pressurised science laboratory, was until recently the European Space Agency's (ESA) only major contribution to the International Space Station (ISS).
Now, development of a fleet of Automated Transfer Vehicles (ATVs) to support ISS operations has begun with the award of a $470 million contract to a pan-European industrial team managed by Aerospatiale.
The COF is one of the last components scheduled to be docked to the Space Station, probably in about 2003-4. The ATV will not only be launched earlier, but is also considered more technically challenging, giving Europe its first rendezvous and docking experience, albeit with help from Russia.
The ATV was given the political go-ahead in October 1995, with the services that the vehicle will provide making up part of ESA's contribution to the operating costs of the ISS.
The vehicle will be built by an industrial team managed by Aerospatiale and including subcontractors Alenia Spazio, DaimlerChrysler Aerospace (Dasa) and Matra Marconi Space. It will include rendezvous and docking system components supplied by the Russian Space Agency and RSC Energia. Dasa will be the production prime contractor and will head the project until about 2000, when a transition of overall management to Aerospatiale will take place.
The logistics vehicles will be launched on uprated Ariane 5 boosters starting in about 2003, with up to 13 flights expected by 2013. ESA's official remit is to provide eight missions up to 2012.
The ATV will be 10m (33ft) long, 4.5m wide, weigh about 16,000kg (35,000lb) fully loaded and have an 18.32m-span solar array. It will dock with the Russian Service Module (to be launched in July) and will supply cargo, such as compressed air and water, and payloads requiring pressurisation such as food, clothing and experiments.
The vehicle will also refuel the ISS and provide orbital reboosting and attitude control for the Station. At the end of its six-month stay at the ISS, the ATV will be loaded with waste, which will be destroyed along with the vehicle during re-entry.
The ATV can be likened to an advanced version of the Russian Progress unmanned tanker, which has provided similar resupply services to Russian space stations, starting with Salyut 6 in 1978. A larger Russian Star module was used occasionally, but also provided additional pressurised working space.
ATV COMPONENTS
The ATV will consist of a systems bus and integrated cargo carrier. The bus will contain the propulsion and avionics bays and will be inaccessible to the ISS crew. It will incorporate the propulsion system used to provide initial separation from the Ariane 5 and subsequent major orbital manoeuvres, plus the solar arrays. The four arrays can provide 3.8kW of power, but the ATV will be able to draw 300W from the ISS when attached. The electrical system will be augmented by batteries for night orbital passes.
The carrier will consist of a pressurised module and the Russian docking system, based on that used on Progress and Soyuz vehicles. It will have external bays for the fluid and gas cargoes, plus avionics such as rendezvous sensors, video cameras and antennas. A meteorite and debris protection system will surround the vehicle's primary structure.
Europe sees the ATV as the first of a new generation of vehicles which may enable the automatic assembly of structures in orbit, such as elements of a space telescope, or be used as a free-flying experiment base for the ISS, providing interference-free microgravity conditions for processing experiments.
The ATV will be injected by the Ariane 5 into an orbital plane compatible with the ISS and, shortly after, the solar panels will be deployed. For the next 100h the ATV will perform phasing manoeuvres, starting with a perigee-raising manoeuvre at the first orbital high point, or apogee, after separation from the booster's final stage. The operation will be controlled by ESA's centre in Darmstadt, Germany, and will use NASA's Tracking and Data Relay Satellites for S-band communications.
A second series of manoeuvres will bring the ATV to ISS altitude, and integrated operations will begin about 90min before the vehicle enters its final approach to the Space Station, with mission authority passing to NASA's new ISS control centre in Houston, Texas.
The ATV will begin its final approach and docking manoeuvres automatically and, after the first telemetry contact between the vehicle and its target cone on the Russian Service Module, will make a final thrust forward for docking, contact triggering the automatic capture sequence.
During its six-month stay, the ATV's internal hatch-in the docking system - will remain open to allow the ISS crew to unload cargo through a pressurised tunnel, while the vehicle is in a dormant mode. Up to 850kg of water can be carried, as well as 100kg of oxygen and nitrogen, while there will be 5,500kg of "dry" cargo carried in the pressurised area of the ATV.
ISS refuelling will be controlled by the Space Station, the crew performing tightness checks, line venting, fluid transfer and line purging. Propellants tanks will be in the exterior module of the ATV cargo carrier and will carry 305kg of fuel and 555kg of oxidiser. Refuelling may be done in increments, one propellant at a time. The ATV will be reactivated during the attitude and reboost operations, which use the four 110lb (490N) thrusters of the main propulsion system or the twenty 220N thrusters of the attitude control system.
Source: Flight International
