The continuous growth of the small launcher market and the emergence of many new concepts in the past years, combined with the growing need for sustainability in the space sector, raises the question of their environmental impact. The sustainability of space activities is becoming a significant constraint on future space applications. There is a need to integrate sustainability into the framework of micro launchers design at the preliminary phase. This work presents a novel methodology that considers the environmental impact of a launcher in its design phase, using Life Cycle Assessment (LCA) and Multidisciplinary optimization tools (MDAO). Life cycle analysis studies the environmental impact throughout the launcher life cycle, from conception to disposal. This includes operations, but also development, manufacturing, testing of the launcher, logistics, construction and maintenance of ground facilities, as well as the recovery, refurbishment, and recycling if applicable. This paper focuses on greenhouse gas emissions and their influence on global warming. Multidisciplinary analysis and optimization (MDAO) has been successfully applied to the design and optimization of space systems, including launcher vehicles. Launchers are usually optimized to fulfill a specific mission while minimizing the overall mass at takeoff. The idea developed in the present work is to integrate outputs from the LCA of the launcher in the optimization process. First, the parameters needed to perform the LCA for a generic micro-launcher are identified, based on the dominant design from the many small launchers that are either operational or in development. Then the LCA is then integrated into the multidisciplinary framework to include ecodesign constraints in the optimization loop, using OpenMDAO. Finally, the results of the optimization of the launcher design using global greenhouse gas emissions as the main objectives are discussed, highlighting the current limitation of the model and possible developments of this methodology.