Most notional implementations of the Bussard Ramjet depend upon some sort of heretofore undiscovered force field rather than a physical structure to collect hyd

Most notional implementations of the Bussard Ramjet depend upon some sort of heretofore undiscovered force field rather than a physical structure to collect hydrogen, because size matters. Naturally, a very large force field ramjet will deplete interstellar hydrogen along the main routes between stars, leading to a situation known as "peak hydrogen", and possibly prompting the invasion of developing hydrogen-rich planets on some sort of flimsy pretext. Most scientists working on imaginary spacecraft projects therefore eschew the Bussard, correctly anticipating the moment when, shortly after the leader gives a speech on the deck of a starship in front of a huge "Hydrogen Accomplished" banner, the price of hydrogen rises to over $5 a gallon and starships are all left to rust in the front yard.