Both the aeronautics and space industries are currently subject to considerable technological changes resulting from increasing ecological awareness. Further reductions of greenhouse gases, pollutant emissions and noise and the renunciation of conventional fuels are planned as part of minimising the ecological footprint. ‘Green Aerospace’ is the watchword for this trend manifesting in the areas of propulsion, energy, structures, manufacturing, operations and systems. The aviation industry in particular has set ambitious targets for itself: From 2020 onward the industry intends to achieve carbon-neutral growth despite a considerable increase in air traffic volume, which will mean reducing emissions to 50% of the 2005 level by the year 2050. To achieve this ambitious target, developing alternative fuel and energy sources is a necessity in addition to improving propulsion engines technologically and developing a new air traffic concept – for instance by choosing climate-optimised flight paths. The space travel industry still relies on the highly toxic propulsion fuel hydrazine but recent EU legislation has led to an increase in the production of alternative fuels and propulsion systems. Besides the positive ecological effects, these developments will eventually lead to independence from limited fossil commodities.