CNES (French Space Agency), which is already working on the post-Ariane 6 launchers, with a dual evolutionary possibility (Ariane Next) foreseen in 2025, is also looking to a more distant horizon with Ariane Ultimate, a forward-looking concept hardly envisaged before 2040, but which will mark a real technological breakthrough in propulsion, and also on the launcher’s architecture. Ariane Next can either be an advanced version of Ariane 6 to improve its competitiveness, by adding new boosters to increase its performance, for example, or a more radical solution involving the development of a new, partially reusable launcher. CNES is preparing for this through several precursor programs, including Prometheus, Callisto and Frog. Prometheus is a new European engine that is ten times cheaper than the Vulcain and also, is potentially reusable. Callisto is a reusable first-stage demonstrator, produced in cooperation between the CNES and the German (DLR) and Japanese (JAXA) space agencies, which will fly at the Guyana Space Centre in 2020 or 2021. As for Frog, it is a small-scale flight demonstrator designed to test vertical landing algorithms for future reusable launchers. Beyond Ariane Next In the longer term, i.e. beyond Ariane Next, many space transportation solutions that could succeed the current Ariane 6 family are being studied within ArianeWorks Lab. This multidisciplinary team is exploring and testing, with great freedom, promising technologies and solutions that could radically improve the performance, costs and services of today's launch vehicles. Among these breakthrough technologies under consideration, such as polyazotated propellants or new materials based on carbon nanotubes, CNES is also working on new propulsion technologies, some of which seem promising, such as laser propulsion, which is based on the principle of mass ejection of a thin layer of material generated by pulsed laser on to a solid surface. Laser propulsion Cnes' idea is to use a pulsed laser with very short periods of time, of the order of 100 picoseconds every 20 ms, in order to vaporize the surface of a material, which creates high-speed degassing and therefore thrust similar to a launcher engine. The relevant criterion on the subject is the coupling coefficient, i.e. the number of newtons per watt. Standard values range from 40 to 100 newtons per megawatt. CNES, in cooperation with colleagues from the 'Ecole Polytechnique' and the 'Mines Paris-Tech', has identified a revolutionary material called POM (polyoxymethylene), which seems to be the most promising due to a coupling coefficient of the quantity of movement and the specific impulse, which makes it possible to judge the efficiency of the propulsion, the highest. With a value of 700 N/MW, this POM breaks the world record for coupling. With this polymer, the thrust generated by mass ejection means that it is possible to levitate a payload like a 30 kg sphere covered with polyoxymethylene and then accelerate it and send up to 20 kg of payload into orbit, out of the 30 kg of the sphere!! . A demonstration is planned. It would consist of sending, with the help of a laser, a football ball at an altitude of 1 Km at a speed of 1Km/Sec. This technology shows that it is possible to launch small satellites into low earth orbits or into interplanetary space using repetitive pulse lasers with costs in the order of a few hundred dollars per kilogram in orbit compared to several thousand today.
