No gravity and plenty of solar energy: These are ideal conditions for ion engines. Using solar power and rare gas propellants, they ensure that satellites stay on course. Messer offers these gases with a high level of purity and specifications tailored to this application.
North-South drift changes orbit
To launch a satellite into space, one needs a rocket with a large “internal combustion engine”, plus fuel and oxygen tanks. However, once the satellite reaches its orbit, the massive rocket has already served its purpose. Yet the satellite is subject to north-south drift caused by the gravitational pull of the Sun and the Moon. This shifts its orbit, and this deviation must be corrected regularly.
Lightweight electric motor for short pulses
At zero gravity, a small impulse from a delicate ion engine is sufficient for this. For example, on a one-metric-ton satellite, this mini-engine weighs just 1.5 kilograms. It draws its energy from the solar array, which also supplies the satellite with power for other purposes. It is used to ionize a small amount of propellant.
For instance, Xenon ions are accelerated to a speed of up to 100,000 kilometers per hour by applying an electric field and directed into space through an exhaust. The thrust generated this way applies the desired change in position within a few minutes.
Rare gases are ideal working masses
The gaseous propellant should have a high specific mass. The heavy rare gas xenon is therefore particularly well-suited and is used in most satellite applications. It offers remarkably high efficiency: the specific impulse is more than six times greater than that of a thermal rocket engine.
Although krypton produces less thrust than xenon at the same tank volume, this difference becomes less significant as the efficiency of the state-of-the-art engines increases. At around 1 ppm, krypton constitutes more than ten times the abundance of Earth’s atmosphere than xenon, which is 0.09 ppm, and is less expensive to extract. Both gases are environmentally neutral and easy to handle.
Gas quality ensures efficiency
To generate the electrons needed for ionization, a filament is used that is sensitive to various molecules, particularly oxygen and water. The propellant should therefore contain as little of these as possible so that the engine can operate efficiently over long term. The propellant gas must therefore meet high quality standards.
In addition to the degree of purity, the composition of the remaining residual molecules plays an important role. The extent to which the performance of an ion engine is impaired depends heavily on the type and quantity of these molecules.
Standard or tailored
Messer offers two gases in which the level of impurity of residual molecules is controlled carefully: Xenon 5.0 and Krypton 5.0 for ion engines. They were developed specifically for this application and ensure consistently high thrust efficiency. The extraction and quality control processes are meticulously tailored to the specific requirements of this application and are fully documented. They exceed the standard specification for the already high purity grade of 5.0.
The quality process covers not only the gas itself but also the containers, fittings, and filling process. The gas quality is then verified using gas chromatography and thermal conductivity detectors. In addition to standard products, Messer also offers customized solutions tailored to the specific requirements of each application.
For more than 125 years, Messer, the today’s world's largest privately owned company for industrial gases, medical gases, specialty gases, and gases for electronics, committed to its guiding principles of safety, focus on customers and employees, responsibility for our society, sustainability, trust, and respect. Messer's Gases for Life and patented gas applications are essential for environmental protection, climate protection, decarbonization, and innovation.