The Fishback ramjet revisited

In 1969, John Ford Fishback proposed a solution for the interstellar ramjet with magnetic scooping. With the exception of two papers published in the early 1970s, this model has not been revisited up to now for viability. Here, we analyze Fishback’s axial scoop field configuration. Computer simulations prove its functionality, albeit with absurdly long magnetic coils when reasonable thrust is to be achieved. Based on the Maxwell stress tensor we obtain a much lower upper bound for the cut-off speed at a given acceleration of the ramjet than published before. Our results indicate that there are severe engineering problems with the magnetic collection process. It is very unlikely that even Kardashev Civilizations of type II might build magnetic ramjets with axial solenoids.