> I doubt there’s a reasonable way to capture jet exhaust, and even if it did it would increase the weight of the aircraft.
Just taking it with you is a non-starter.
If your fuel is mostly carbon by weight, then the CO2 will weigh 2-3x as much. At that point batteries are starting to look appealing by comparison. There are battery techs with around 400Wh/kg and various almost-working ideas in the 500-600 region. Once you run 11000Wh/kg hydrocarbons through a turbine at 30% and carry the 2 Oxygen atoms for every C you might only be getting 1000Wh per kg of exhaust you carry.
Just taking it with you is a non-starter.
If your fuel is mostly carbon by weight, then the CO2 will weigh 2-3x as much. At that point batteries are starting to look appealing by comparison. There are battery techs with around 400Wh/kg and various almost-working ideas in the 500-600 region. Once you run 11000Wh/kg hydrocarbons through a turbine at 30% and carry the 2 Oxygen atoms for every C you might only be getting 1000Wh per kg of exhaust you carry.