Mention the words “space exploration” and people will immediately think of the Apollo missions, or a space rocket, or the International Space Station. A lesser-known part of the story is how these pioneering journeys were powered. At Saft, we know just how important energy supply has been in making space travel happen, and we’ve been working on it since the earliest days of exploration.
Saft started supplying batteries for satellites back in 1966. The first to be equipped – with nickel-cadmium (Ni-Cd) batteries – was Diapason, the first French satellite, designed by the Centre national d’études spatiales (CNES). It was meant to perform a two-year scientific mission, but remained in operation for six years.
On satellites, batteries are used to provide power at "night", when the satellite passes behind the Earth and is no longer illuminated by the Sun. In the "day" phase, energy is produced by solar panels, which recharge the batteries. Using the power of the Sun in this way is very important because it gives the batteries a long operating life. Batteries designed for space must meet a unique set of demands: they must be reliable, have an operating life of more than 20 years and be able to withstand extreme temperatures and radiation. They must also be strong enough to survive launch vibrations, landing impact and other physical shocks.
Since the success of Diapason, Saft has supplied more than 800 Ni-Cd batteries for satellites in low orbits – military observation satellites such as Helios - and geostationary satellites for telecommunications, meteorological data and television, as well as the 10 largest GPS satellites. We have become so used to these communication tools that it is hard to imagine life without them, yet they are less than 50 years old.
Saft has also played a role in exploration programs such as the Solar Heliospheric Observatory (SOHO) and Hipparcos missions. Launched in 1995, the SOHO satellite came within a short distance of the Sun, enabling hundreds of astronomers to study incredible photos of solar eruptions. Then in June 1998, contact was lost for unknown reasons. The satellite's position in relation to the Sun could no longer be tracked and a month went by before the American and European space agencies were able to locate and reactivate the satellite. The battery managed to withstand enormous temperature fluctuations (-150°C in the Earth's shadow, +200°C in the Sun) and, even more remarkably, it is still in operation today. The mission, initially planned for two years, was extended until December 2018.
Hipparcos – the European Space Agency (ESA) scientific satellite – was launched in 1989 and remained active until 1993. Its purpose was to precisely measure the position of celestial bodies in space. The Hipparcos catalog, published in 1997, gives the precise coordinates of 118,200 stars.
Starting in 1979, Saft also equipped all of Arianespace’s satellite launchers, providing each rocket with 15 to 20 Ni-Cd batteries for guidance, telemetry and firing purposes. There have now been more than 240 launches. From 1986 to 1990, Saft developed highly reliable and resistant nickel-hydrogen batteries. More than 60 satellites were equipped with these batteries, at least 20 of which are still operating today.
In the early 2000s, lithium-ion (Li-ion) technology – which significantly reduces the weight of the equipment and therefore its cost – took over. Li-ion was developed and qualified with Stentor, a French communications satellite. It was due to be launched in 2002 as part of the first flight of the Ariane 5 rocket, but unfortunately the rocket failed minutes into the maiden flight. Despite this setback, Li-ion batteries were used again in Smart-1 in 2003. This technology demonstrator was placed in orbit around the Moon by the ESA to test the use of electrical energy for propulsion, in preparation for future interstellar missions using plasma propulsion.
The most resounding success for Saft’s Li-ion batteries came with the launch of Airbus's first Eurostar geostationary telecommunications satellite, the W3A. After 13 years in orbit, its Li-ion battery is still going strong, with only 2 percent power loss since the start of the mission.
Since then, some 265 satellites have used Saft's Li-ion battery technology. They have been designed in co-operation with the major players in the space industry: Airbus Defence and Space, Thales Alenia Space, OBH (Germany), SSTL (UK), NASA, the Russian space agency Roscosmos, Boeing, Lockheed Martin, Orbital Sciences Corporation (US), and smaller companies in Russia, China, India and Argentina.
The most advanced US weather satellites the GOES-R and S built by Lockheed Martin have been placed in geostationary orbit respectively in November 2016 and March 2018. The most recent success is the launch of 10 satellites of Iridium Next program, which will comprise 81 satellites. Built by Thales Alenia Space, this project will provide a telecommunications service through its network of satellites around the planet.
Space research, which had slowed down somewhat in the 1990s, has once again become an important issue, with successful entrepreneurs such as Richard Branson of Virgin and Elon Musk of SpaceX investing seriously in space travel.
In 2020, the ESA will launch Euclid, a six-year mission to study dark energy and dark matter. The same year, the ExoMars Rover will be launched to search for signs of life on the red planet. Once again, Saft will be on board.