The ramjet in the novel "Tau Zero" required a separate decelerator which, spoilers, breaks, and causes the ship to career endlessly through the universe. Is this accurate from a real-world engineering standpoint? Could they not simply have adjusted the collector to reduce the efficiency and tip the balance between thrust and drag?
This makes me sad because I grew up reading Niven's novels about ramscoops, but as early as 1978 T. A. Heppenheimer showed that the power required to compress protons enough to fuse exceeds the power that can be produced. Other reactions have been proposed but they have problems as well. There is a good writeup here: https://www.centauri-dreams.org/?p=22274