Launch vehicle subsystem preliminary design tools that are fast, accurate, and seamlessly integrated into an electronic design and optimization environment have become an essential part of the preliminary design process. A Phase I study is proposed to significantly enhance the capabilities of the existing Aerospike Design and Performance Tool (ADAPT) computer code for use in the design and analysis of launch vehicle concepts employing altitude-compensating nozzles. Proposed Phase I enhancements include: 1) provisions to enable the analysis of user defined nozzle geometry, 2) consideration of base pressure with and without base bleed in the performance calculations, 3) methods to accommodate user defined combustion devise and nozzle efficiencies, and 4) methods to estimate potential side (control) forces resulting from asymmetric throttling of individual thrusters on an aerospike, plug, or plug-cluster engine. The proposed Phase I enhancements fit within a broader and more comprehensive Phase I-II plan. Future (Phase II) enhancements will include: 1) extension of the design and analysis methodology to other altitude compensating nozzle types, 2) modification of ADAPT allowing it to be used as an analysis module within a broader multidisciplinary optimization (MDO) framework, and 3) a web-based user interface.