Fig. 1.
![Relative specific fuel consumption for aircraft engines, plotted against certification year [8].](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/6869a05be88a4c302353f78c/j_tar-2025-0006_fig_001.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKBB6FQMPH%2F20260318%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260318T185450Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjED4aDGV1LWNlbnRyYWwtMSJHMEUCIQDHvADvXmqYTWfoDAKGUCwg%2BBPAIYGj%2FRm7%2FL%2FLjAoDLQIgB8VLaEPQjjleWgOrdlUOHaw3kWD%2BGYTZec6Y8t%2FrP5cqvQUIBxACGgw5NjMxMzQyODk5NDAiDIxaO7J4%2BbV8bwX4OCqaBQMyrn%2BzKNsxUgSW%2FmMgzv7vFasUUrVFZ57wvcKKg%2F92yqerJ%2Fa%2BLAicsBfrqkzMmnaK480spPVvpy7If257%2B59Do68fOXp%2FfyD5iFZGmjBSeZFHV6F0g%2FscPfrnlkTg9w6lnms%2FgMRlZu%2FvRwBFRsDTv6zSgSao%2BLsP0V8a99w0TB0NmjK8as2fSduEq1aAGBi0MjAsjnCiI7BX6C0U5qrjEVD2ug5Zv%2F9odcSFYUpNiE4twE4zSCZ4C%2F9UNPRGCHkw7qSusSgH6T1CRLGta01jbuf9cP0euHpm7PjD1R8k4fRvyrbzpaIqoNIrF3fty6OCfMaPcNEPKY%2FbdzcdWpa6uNiCVkg3D80YlscqL1R7RrWjkqKG9lsp3x7i9Unu7qVCz2psX4OGNHlFlxT85x9dOLQGhR4oty2Ip5iCYSKFNHlq8zWA8Qmju6pf5u0aAmELF51bnOmaTxjMQDFX0yKq5AKLUDfepKJXMm1W3KEu0KGI661%2B%2FiUwO6bx%2FEXodiN3UhoDhSlaWsxjNeooN05q5yPYhbiwplH9d4mXYgy4CcLt%2FHLTkAYIgYrcoMp0PQqg5Qv27duP53GQ7HhxtrqDoWX5rmktOr7zeVTqEDK8qV09fSfKFbzdUDpuuvBZU1H8f0Q6Aj9itgFa7BcKCkermDiyBeF8YYwNDTPfHQiByQy4qxlfZwf36cGcjmwCdVIe1UCvj8qvHesRU%2F9TfKvM3WVQhCTD59bEXhRncjdnQfSrL%2Fqse8Naj9saSKzxtQop%2B1bMXjMJytZY4SPf%2FPOGrJLxkQweVROV8ypA%2F2TQlfYzphwguyJMz9KzR3vUYoG%2F73%2Bwkiuq8cdrl8woh9%2FzxYBPpBiiU1KUVzyCnS3o7FLky04KKfS89zDD4urNBjqxAV6XsBlUSaXk1jU1mvFzZSTCkBQaRWV2%2F071ql6gl2b8T23WnJaTJAO4iQrWwCbK8YbvH%2Byh7WDmjWeU8WpzhsLL6Z0wcn%2FgYerjnwrpA2G6dvOW%2BYWlsEe7Q9ZmyJHGIhGIPw%2BduJ37DwdNynaZ74rH646tIApaz5Rv1AAjZpmr5uWfHPrgonXXShNnwv3Gve9yyh8cvNltmUHwFRTR%2FVmgPb%2FTQSLM8uNBH7hW68phAQ%3D%3D&X-Amz-Signature=8e1c16a2761913075da26abad48a62cc407c3aa311f84be5369e6cc4d9927348&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Fig. 2.

Energy density comparison of different fuels_
| Fuel | Energy Density [MJ/kg] | Energy Volumetric Density [MJ/liter] |
|---|---|---|
| Hydrogen (Gas at 1 bar) | 120 | 0.1 |
| Hydrogen (Gas at 300 bar) | 120 | 3.03 |
| Hydrogen (Gas at 600 bar) | 120 | 6.06 |
| Hydrogen (Liquid) | 120 | 8.49 |
| Jet-A Fuel | 45 | 34 |
| Gasoline | 44 | 31.5 |
| Diesel | 46 | 35 |
| Ethanol | 28.8 | 20 |