One of the more ambitious proposals for an improved Black Knight involved substantially increasing the diameter of the tank from 36 inches to 54 inches, which had the effect of nearly doubling the rocket's fuel capacity, along with the adoption of a more powerful solid fuel second stage, named "Kestrel". This envisioned more powerful Black Knight rocket was to have been used as part of a further set of planned experiments, which had been codenamed 'Crusade'. Upon review, HM Treasury refused provide any funding for further Black Knight projects, and work on an enlarged Black Knight was abandoned in favour of the larger Black Arrow satellite launcher.