Amateur rocketry has access to a wide variety of similar and well understood components for the quick assembly of solid rockets from the scale of the smallest model rocket to that of sounding rockets, but this wide catalogue does not extend to liquid bipropellant rockets. Instead of designing a single rocket from start to finish to achieve a specific mission profile, a Modular Launch Vehicle Architecture (MLVA) was created to provide a great deal of flexibility to vehicle design and integration as well as a wider range of performance parameters for the ever-evolving Reusable Launch Vehicle (RLV) market. With many complex components in liquid rocketry, the MLVA approaches rocket design from the perspective of manufacturability and in performance by simplicity, rather than the traditional approach of optimized mass fractions. In doing so, rockets produced with the MLVA process are generally cheaper and easier to create than its custom-built counterparts while the vehicles and subsystems themselves are easier to test and scale using subscale vehicles. The MLVA design process is applied to the design of two launch vehicles with two vastly different mission profiles, one for affordable moderate altitude flight and the other with the goal of breaking past the Karmen line of 100 km.