Electrical Pressurization Concept for the Orion MPCV European Service Module Propulsion System

The paper presents the design of the pressurization system of the European Service Module (ESM) of the Orion Multi-Purpose Crew Vehicle (MPCV). Being part of the propulsion subsystem, an electrical pressurization concept is implemented to condition propellants according to the engine needs via a bang-bang regulation system. Separate pressurization for the oxidizer and the fuel tank permits mixture ratio adjustments and prevents vapor mixing of the two hypergolic propellants during nominal operation. In case of loss of pressurization capability of a single side, the system can be converted into a common pressurization system. The regulation concept is based on evaluation of a set of tank pressure sensors and according activation of regulation valves, based on a single-failure tolerant weighting of three pressure signals. While regulation is performed on ESM level, commanding of regulation parameters as well as failure detection, isolation and recovery is performed from within the Crew Module, developed by Lockheed Martin Space System Company. The overall design and development maturity presented is post Preliminary Design Review (PDR) and reflects the current status of the MPCV ESM pressurization system

Evolution of MPCV Service Module Propulsion and GNC Interface Requirements

The Orion Multi-Purpose Crew Vehicle Service Module Propulsion Subsystem provides propulsion for the integrated Crew and Service Module. Updates in the exploration architecture between Constellation and MPCV as well as NASA's partnership with the European Space Agency have resulted in design changes to the SM Propulsion Subsystem and updates to the Propulsion interface requirements with Guidance Navigation and Control. This paper focuses on the Propulsion and GNC interface requirement updates between the Constellation Service Module and the European Service Module and how the requirement updates were driven or supported by architecture updates and the desired use of hardware with heritage to United States and European spacecraft for the Exploration Missions, EM-1 and EM-2

HEM modeling for subcritical flows in liquid rocket engine cooling systems

During off-design operations of liquid rocket engines, the coolant operating conditions can easily extend from the subcritical to the supercritical regime. As a matter of fact, it is very useful to have a single software able to study the flow in this range of operating conditions, providing reliable simulations able to correctly estimate and assess the coolant temperature increase along the channel, as well as the wall temperature field. This objective is pursued by the extension of a 3D CFD software, which is available to the research team for the study of supercritical flows, to the case of subcritical heating (i.e. two-phase flow) with an approach based on the so-called Homogeneous Equilibrium Model (HEM), which has shown to be rather predictive and accurate in one-dimensional models. In this work, the selected approach is presented and described in detail. Some preliminary results concerning test cases like variable cross section ducts and heated pipes are shown

Analysis and Reconstruction of Zefiro 40 Solid Rocket Motor Static Firing Tests and Extrapolation to Flight

An independent assessment of the steady-state and tail-off ballistic performance of the two static firing tests of Zefiro 40 solid rocket motor has been performed. The analysis is carried out with a post-firing 0D quasi-steady performance reconstruction model, developed for the purpose and already used for the analysis of VEGA SRM SFTs. The study has been focused on two different aspects: i) the SFTs ballistic performance analysis with the reconstruction of the non-ideal parameters and the performance extrapolation to flight configuration; ii) the motor performance extrapolation to flight unit based on the reconstructed non-ideal parameters and exploiting the SFT to flight expertise of Zefiro 23 SRM. The final goal is to increase the understanding of VEGA's solid rocket motors behavior in terms of non-ideal parameters and to consolidate the methodology used for the performance reconstruction and extrapolation to flight unit. Previous Chapte