I noticed Anton Petrov explained it recently: https://www.youtube.com/watch?v=_abdV-HtEJQ https://www.youtube.com/watch?v=_abdV-HtEJQ It's named the Oberth eff

I noticed Anton Petrov explained it recently: https://www.youtube.com/watch?v=_abdV-HtEJQ https://www.youtube.com/watch?v=_abdV-HtEJQ It's named the Oberth effect - something like a powered slingshot.