| | Expanding frontiers
Thanks to ESA’s development of the Ariane series of launchers, and to science missions carrying the flags of Europe to Mars, Venus, Mercury, Titan and far-flung comets, the scope of Europe’s space activities is growing rapidly. Pushing back the frontiers during the 21st Century, whether in science, applications or human spaceflight, calls for better ways of launching spacecraft and accelerating them in flight. Solar-electric propulsion is already in use. When the time and the technology are ripe, Europe will devise unmanned reusable launchers. Existing launch facilities are second to none, and ESA’s skill in controlling complex space operations is evident every day.
|  | Ariane-1 rocket, with Giotto on board, blasts off | |
The Ariane tradition
Christmas Eve 1979 saw the initial flight of the first space launcher developed by ESA. Called Ariane 1, it could lift a 1.8 tonne satellite to a geostationary transfer orbit (GTO) – a standard manoeuvre used for comparing weightlifting capacity. Ariane 4, introduced in 1988 with a payload of 2 to 4.8 tonnes, became the world’s favourite launcher for commercial satellites. By the time Ariane 4 retired in 2003, Ariane 5, able to place a payload of 6.5 tonnes into GTO, had already been in commercial service for 4 years.
Soon an upgraded Ariane 5 called ECA, with a new cryogenic upper stage, will be able to lift up to 10 tonnes into geostationary orbit. To complement such weightlifters, a small launcher called Vega is also under development as a result of an Italian initiative, and work is also well in progress to provide a launch base for Soyuz at Europe’s Spaceport in Kourou, French Guiana.
| | | Integral launch |
The Russian connection
ESA now uses Russian launchers when appropriate. In 2000, the four satellites of the Cluster solar-terrestrial mission went into orbit in two Soyuz launches and a Proton rocket launched ESA’s astronomy satellite Integral in 2002.
Since the end of the Cold War, the West has courted the rocket engineers who gave the Soviet Union its competence in missiles and launchers. Thus the French-Russian company Starsem markets launches by the Soyuz rocket, while Proton is cultivated by a US-Russian collaboration. Eurockot, a German-Russian company, offers the smaller Rockot launch vehicle, which has been selected for ESA’s Earth Explorer mission GOCE.
| | Future Launchers Preparatory Programme artist view | |
Future launchers
Ideas for cheaper ways of putting satellites into space are under review by ESA and Europe’s aerospace industry. One possibility being examined is that of reusable launchers as these could offer major cost reductions compared to current expendable launchers.
At present, the US Space Shuttle is the only partly reusable launch vehicle. ESA’s Future Launcher Technology Programme is busy assessing which of several launcher concept schemes is most likely to be viable, timely and profitable. Making the right choices will be crucial to safeguarding Europe’s leading role in space launches.
| | | Saturn orbit insertion manoeuvre |
Swinging by the planets
On a long interplanetary voyage, a spacecraft can steal power from the planets. Instead of burning rocket fuel, it approaches a planet on a trajectory that will allow the the planet’s gravity to change its course and speed it up or slow it down, as required.
After visiting Halley’s Comet, ESA’s Giotto spacecraft swung by the Earth in 1990 to re-aim itself at a second comet. With gravitational assistance from Jupiter, in 1992 Ulysses became the first spacecraft ever to route itself over the poles of the Sun. Multiple swingbys have taken the NASA-ESA Cassini-Huygens spacecraft to Saturn and on its 10-year journey to rendezvous with the Comet Churyumov-Gerasimenko, ESA’s Rosetta uses the same technique.
| | SMART-1 is travelling to the Moon using a new solar-electric propulsion system | |
Solar-electric drive
Electric power from solar cells can accelerate a high-speed jet of heavy atoms - xenon ions, for example. Weight for weight, these can propel a spacecraft far more efficiently than chemical fuels, though at a rate limited by the power from solar panels of manageable size.
ESA’s first major application was unexpected, when ground controllers used solar-electric thrusters on the telecommunications satellite Artemis (2001) to rescue the mission after it went into the wrong orbit in 2001. SMART-1 (2003) employed this technique for its journey to the Moon. Early in the next decade, a solar-electric drive will enable BepiColombo to reach the planet Mercury more quickly than it could with chemical rockets alone.
| | | Panoramic view |
Europe's Spaceport
Europe's Spaceport is near Kourou in French Guiana, on the northern coast of South America. This provides an ideal location suitable for safe launches over the Atlantic Ocean. It benefits from the Earth’s rotation near the Equator, which gives a free boost of 463 metres per second to eastward-launched rockets.
Originally selected by the French space agency CNES, which still runs the centre, the Kourou site has been vastly developed with funding by ESA for its Ariane launcher programmes. The Ariane-5 facilities alone, called ELA-3, cover 21 square kilometres in a total of 750 square kilometres that make up the Guiana Space Centre. New launch pads are now being prepared for ESA’s Vega and Russia’s Soyuz launchers.
| | Main Control Room at ESOC, Darmstadt, Germany | |
Mission control
Spaceflights begin in the computers of the European Space Operations Centre (ESOC) in Darmstadt, Germany, which visualise the best orbits, whether for low-flying Earth-observation satellites or for a clever route to the planet Mercury. Ground links are organised via worldwide tracking stations. By the time a spacecraft is launched, well-rehearsed teams of engineers are ready to take control of it, often executing complex manoeuvres and sometimes coping with crises.
Last update: 24 October 2006 | |
