2024-02-16 06:36:54
Silicon Austria Labs’ ignition system is smaller and lighter than those used in conventional rocket and satellite engines.
Around 20 years ago, researchers at the forerunner of what is now Silicon Austria Labs (SAL) began developing a laser ignition system that was intended to replace conventional spark plugs in the automotive and aviation industries. The system, which offers advantages especially in terms of weight and size, has now been adapted for space travel and could take off into space for the first time in the next few years, said project manager Gerhard Kroupa to the APA.
High-energy light pulses
“The ignition laser is based on extremely short and high-energy light pulses, which are focused into the combustion chamber of an engine and generate plasma in the fuel and thus an ignition spark,” said SAL researcher Kroupa. The first idea at the research institution or its Carinthian predecessor company Carinthian Tech Research (CTR) was to develop a small, compact laser that could be screwed directly onto combustion engines. “The advantage of this system is that the plasma that the laser generates can be arranged relatively freely in the combustion chamber,” says Kroupa. In conventional electric spark plugs, the plasma is limited to the electrodes and can therefore only be generated near the edge.
A second advantage is that the laser creates the plasma in nanoseconds. This then has a lifespan of 10 to 20 microseconds (i.e. millionths of a second) – the timing of the laser spark plug is therefore significantly better than that of electrical sparks. “Third, the energy density of the laser is much higher because it creates the plasma in a smaller spot,” Kroupa said. Accordingly, leaner mixtures can be ignited and the process in combustion engines can therefore be carried out with fewer pollutants. “These positive aspects were offset by the costs of the laser ignition systems, which were simply too high for mass production in the automotive sector,” explained the researcher.
Size of the lasers has been drastically reduced
In further cooperation with aviation companies, the size of the lasers was then drastically reduced. Associated publications attracted the attention of the space industry: In cooperation with the German Aerospace Center (DLR) and the ArianeGroup (then: Airbus Defense and Space), laser ignitions began around 15 years ago on small rocket combustion chambers – “Das worked surprisingly well,” Kroupa recalled.
The advantages of laser ignition in space travel lie mainly in the size and weight of the systems: Currently, many engines are still ignited with small explosive capsules, so-called pyrocapsules. These cannot be tested and represent a safety risk before launch. For these reasons and because of their high weight, most rocket manufacturers want to use other systems in the future. The common alternative to pyrocapsules are gas torch igniters, i.e. small combustion chambers with electric spark plugs that create a kind of flare and thus ignite the main chamber. But they need an additional fuel supply; the entire system weighs a few dozen kilograms. “In comparison, the laser weighs around three to four kilos – that means a significant saving,” said Kroupa. In addition, it only requires an electrical supply, i.e. no additional fuel, and can be tested and used for ignition as often as required.
Despite all the plus points, the biggest challenge in adaptation is the environmental conditions when used in rocket or satellite engines: “Due to the liquid fuel, the temperature of the laser drops to as low as minus 180 degrees Celsius during a flight. After ignition, it has The combustion chamber is up to 3,000 degrees, and there are also very strong vibrations, temperature shocks and possibly pressure shocks that affect the system,” says the researcher. With the construction and testing of a technology demonstrator of the laser igniter for the upper stage engine “Vinci” of the Ariane rocket in 2016, a significant step towards a system that can be used under real operating conditions was achieved. Together with ArianeGroup and Airbus, the materials and structure of the systems were then adapted to the strict criteria in the space sector.
“We have now reached a stage where we can hand over the fifth generation of the laser ignition system to further space development. A license agreement has been concluded with ArianeGroup to bring the laser into series production,” says Kroupa. What is still missing, however, is certification of the suitability for space travel of all components. While the system will be ready to fly in around two years, the researcher estimates the time horizon for a first flight to be three to five years after the rigorous tests and further bureaucratic hurdles.
“In the future, all major rocket manufacturers will move towards cluster engines for cost and reliability reasons,” said Kroupa. The most extreme example of this is the booster of the “Starship” concept from the American space company SpaceX – here, 33 engines are used in the lower stage of the rocket. ArianeGroup is also working with the Prometheus engine on a propulsion system that uses multiple thrust chambers in the lower stage of a reusable carrier. That’s why the project team is currently researching, among other things, how to distribute the laser beam via fiber optics – so several engines could be ignited with just one laser beam.
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