Don't try to weasel your way out of this. Just be honest and say you like working on cool plane tech stuff and admit it's not great for the environment when more people will fly. No shame in that. Or maybe there is shame, but that's up to you.
If your company is successful enough for you to invest significant resources into "greener propulsion technology", what is going to happen to all the planes you already sold to get there? Are you going to send an email blast out to all your customers telling them to stop flying now because it's time to pivot to hydrogen planes?
The existence of the a fossil fuel based car market provided an impetus for electric car and battery technology to develop. Similarly, practical alternative energy flight will likely develop faster if there is a market for small, innovative aircrafts.
> to fix it requires capital and public demand.
In my engineering career, one thing I've learned is that if you fix problems B, C, and D, often it becomes a lot easier to fix orthogonal problem A, because the other fixes have made new things possible.
I see what you are doing as fixing a lot of problems with flying, so then more attention can go into making planes quieter and more energy efficient.
Perhaps yours is one of the steps to making planes as peaceful in the environment as birds[0].
To someone not surrounded by the same aerospace/defence/pentagon welfare state people that you are surrounded by, you come across as very genuine, caring, and hard-working but completely missing the point. Your statements in this thread indicate that you think there maaaaay be an environmental issue but you don’t care because it could never affect you personally. You demonstrate no sense of urgency, which is what the people questioning you are looking for, because that’s what the science shows.
Sounds like some wicked variation of Jevon's paradox.