there are two main ways to increase the veocity of a rocket
one increase the Isp of propellants.
two or increase the effective mass ratio . traditionally this is done by staging in sequence or in side by side. But I have been kicking around another form of staging. where the tankage of the rocket is also the fuel, in a hybrid motor system. picture a long plexiglass thin walled tube ( banded with narrow carbon fiber reenforcments. The tube contains a solid plug-spike motor pulled forward by a steel-kevlar cable attached to pressure driven wench anhored to the nose. When in operation the Tube is pressurizes with liquid n2o. the oxidizer sprays against the plexglass in the combustion region of the spike and is ingnited as the fuel walls are burned the motor is pulled forward in the end all that remains is the motor and the nose of the rocket. this is a oversimplifation but it seem one could have mass ratio of 20 to 1 or better, any thoughts .