This is a one-year effort to answer key questions on a deployable nozzle extension (DNE). The DNE is an innovative approach to increasing upper stage engine Isp. The objective of this task is to obtain sufficient understanding of DNE capabilities such that a subsequent development investment can be made with high confidence. DNEs add no volume, no length and comparatively little weight to the upper stage engine while enabling large nozzle area ratios for increased payload delivery. The three key questions concerning DNEs to be answered by this effort are: (1) What is the delivered Isp? (2) Will the DNE survive the thermal loads? and (3) What are the loads on a base nozzle-to-DNE joint? This task proposes to assess these questions on a DNE designed with the translating nozzle extension of the RL-10B-2 as a reference for comparison. MSFC's Thermal Analysis and Structural and Dynamics Analysis Branches will be participating in this effort, as will ATK. The work plan below is based on a conceptual DNE design using the translating NE of the RL-10B-2 as reference. However, the fixed nozzle portion of the RL-10B-2 is also very similar to the RL-10A nozzle. The RL-10A is baselined for the SLS Exploration Upper Stage. The work here will be directly applicable to SLS expressed (but not quantified) desire to develop higher performing nozzle for the RL-10. The CIF work can be changed develop a conceptual design for the SLS EUS RL-10s for reference if that should be deemed a higher priority. Task 1 of this project will be to optimize the DNE contour for RL-10. This effort, using Two-Dimensional Kinetics (TDK), would extend the limited nozzle design trades previously performed by ATK. The optimization would be done for two configurations: first, the baseline RL-10 fixed nozzle contour, and second, an RL-10 fixed nozzle recontoured to maximize the benefit provided by a DNE. The team will then decide, after consultation with the RL-10 vendor and potential RL-10 users, which of these two configurations should be analyzed further. Task 2 begins with a conceptual design for the fixed nozzle-to-DNE joint. ATK will develop a mechanical design of sufficient detail for thermal and structural analysis of the joint. The mechanical design part files will enable all analysts to work on a consistent geometry. The optimized DNE contours will be used to develop a solid model of the nozzle wall. Secondly, ATK will lay out create multiple solid model representations of different DNE designs. These part files will be used in the CFD, thermal and structural analyses of the NE in different nozzle shapes as it progresses toward fully open. The third part of the ATK task is preliminary assessment of the DNE manufacturability (availability of material, approaches for handling, etc.) After completing the DNE contour optimization, MSFC will conduct the CFD analysis (task 3). The first step will be to analyze the existing RL-10A and RL-10B-2 to anchor the CFD methodology to relevant, well-established nozzle performance. The next step will be to analyze the DNE in its initial state to fully capture the effects of the local wall features. Both cases provide boundary conditions (BC) for subsequent thermal and stress analyses. The prediction of delivered Isp will be derived from the CFD analysis. Task 4 includes the thermal analysis of the joint and the DNE using BCs derived from the CFD analyses. Lastly, task 5 includes the structural analyses of the joint and DNE. The BCs for these analyses will be taken from the CFD and Thermal analyses. The structural analysis of the DNE will assess primary strength margin of the NE wall at thermal equilibrium conditions to determine if the required safety factors are maintained. First-order assessments of both low and high cycle fatigue will also be made.