Issues of Long-Term Cryogenic Propellant Storage in Microgravity

Modern multi-layer insulation (MLI) allows to sharply reduce the heat leak into cryogenic propellant storage tanks through the tank surface and, as a consequence, significantly extend the storage duration. In this situation the MLI penetrations, such as support struts, feed lines, etc., become one of the most significant challenges of the tanks heat management. This problem is especially acute for liquid hydrogen (LH2) storage, since currently no efficient cryocoolers exist that operate at very low LH2 temperatures (20K). Even small heat leaks under microgravity conditions and over the period of many months give rise to a complex slowly-developing, large-scale spatiotemporal physical phenomena in a multi-phase liquid-vapor mixture. These phenomena are not well-understood nor can be easily controlled. They can be of a potentially hazardous nature for long-term on-orbital cryogenic torage, propellant loading, tank chilldown, engine restart, and other in-space cryogenic fluid management operations. To support the engineering design solutions that would mitigate these effects a detailed physics-based analysis of heat transfer, vapor bubble formation, growth, motion, coalescence and collapse is required in the presence of stirring jets of different configurations and passive cooling devices such as MLI, thermodynamic vent system, and vapor-cooled shield. To develop physics-based models and correlations reliable for microgravity conditions and long-time scales there is a need for new fundamental data to be collected from on-orbit cryogenic storage experiments. Our report discusses some of these physical phenomena and the design requirements and future studies necessary for their mitigation. Special attention is payed to the phenomena occurring near MLI penetrations

Risk Assessment and scaling for the SLS LOx ET

In this report we analyze the transpiration cooling by He bubble injection of the long LOx tank feedline heated by the environment heat. We consider possible hazards that can arise in the proposed design of the SLS core stage where the feedline length is much longer than that used in the Space Shuttle

Risk Assessment and Scaling for the SLS LH2 ET

In this report the main physics processes in LH2 tank during prepress and rocket flight are studied. The goal of this investigation is to analyze possible hazards and to make risk assessment in proposed LH2 tank designs for SLS with 5 engines (the situation with 4 engines is less critical). For analysis we use the multinode model (MNM) developed by us and presented in a separate report and also 3D ANSYS simulations. We carry out simulation and theoretical analysis the physics processes such as (i) accumulation of bubbles in LH2 during replenish stage and their collapsing in the liquid during the prepress; (ii) condensation-evaporation at the liquid-vapor interface and tank wall, (iv) heating the liquid near the interface and wall due to condensation and environment heat, (v) injection of hot He during prepress and of hot GH2 during flight, (vi) mixing and cooling of the injected gases due to heat transfer between the gases, liquid and the tank wall. We analyze the effects of these physical processes on the thermo- and fluid gas dynamics in the ullage and on the stratification of temperature in the liquid and assess the associated hazards. A special emphasize is put on the scaling predictions for the larger SLS LH2 tank

Physics-Based Methods of Failure Analysis and Diagnostics in Human Space Flight

The Integrated Health Management (IHM) for the future aerospace systems requires to interface models of multiple subsystems in an efficient and accurate information environment at the earlier stages of system design. The complexity of modern aeronautic and aircraft systems (including e.g. the power distribution, flight control, solid and liquid motors) dictates employment of hybrid models and high-level reasoners for analysing mixed continuous and discrete information flow involving multiple modes of operation in uncertain environments, unknown state variables, heterogeneous software and hardware components. To provide the information link between key design/performance parameters and high-level reasoners we rely on development of multi-physics performance models, distributed sensors networks, and fault diagnostic and prognostic (FD&P) technologies in close collaboration with system designers. The main challenges of our research are related to the in-flight assessment of the structural stability, engine performance, and trajectory control. The main goal is to develop an intelligent IHM that not only enhances components and system reliability, but also provides a post-flight feedback helping to optimize design of the next generation of aerospace systems. Our efforts are concentrated on several directions of the research. One of the key components of our strategy is an innovative approach to the diagnostics/prognostics based on the real time dynamical inference (DI) technologies extended to encompass hybrid systems with hidden state trajectories. The major investments are into the multiphysics performance modelling that provides an access of the FD&P technologies to the main performance parameters of e.g. solid and liquid rocket motors and composite materials of the nozzle and case. Some of the recent results of our research are discussed in this chapter. We begin by introducing the problem of dynamical inference of stochastic nonlinear models and reviewing earlier results. Next, we present our analytical approach to the solution of this problem based on the path integral formulation. The resulting algorithm does not require an extensive global search for the model parameters, provides optimal compensation for the effects of dynamical noise, and is robust for a broad range of dynamical models. In the following Section the strengths of the algorithm are illustrated illustrated by inferring the parameters of the stochastic Lorenz system and comparing the results with those of earlier research. Next, we discuss a number of recent results in application to the development of the IHM for aerospace system. Firstly, we apply dynamical inference approach to a solution of classical three tank problems with mixed unknown continuous and binary parameters. The problem is considered in the context of ground support system for filling fuel tanks of liquid rocket motors. It is shown that the DI algorithm is well suited for successful solution of a hybrid version of this benchmark problem even in the presence of additional periodic and stochastic perturbation of unknown strength. Secondly, we illustrate our approach by its application to an analysis of the nozzle fault in a solid rocket motor (SRM). The internal ballistics of the SRM is modelled as a set of one-dimensional partial differential equations coupled to the dynamics of the propellant regression. In this example we are specifically focussed on the inference of discrete and continuous parameters of the nozzle blocking fault and on the possibility of an application of the DI algorithm to reducing the probability of "misses" of an on-board FD&P for SRM. In the next section re-contact problem caused by first stage/upper stage separation failure is discussed. The reaction forces imposed on the nozzle of the upper stage during the re-contact and their connection to the nozzle damage and to the thrust vector control (TVC) signal are obtained. It is shown that transient impact induced torquean be modelled as a response of an effective damped oscillator. A possible application of the DI algorithm to the inference of damage parameters and predicting fault dynamics ahead of time using the actuator signal is discussed. Finally, we formulate Bayesian inferential framework for development of the IHM system for in-flight structural health monitoring (SHM) of composite materials. We consider the signal generated by piezoelectric actuator mounted on composite structure generating elastic waves in it. The signal received by the sensor is than compared with the baseline signal. The possibility of damage inference is discussed in the context of development of the SHM

Case breach fault model and diagnostic for the solid rocket

A model of the case breach fault for solid rocket boosters (SRBs) that takes into account burning-through hole in propellant, insulator and metal layers of a rocket case is developed. Melting of the metal layer and an ablation of the insulator layer in the presence of hot gas flow through the hole are analyzed in detail. Dynamics of the lateral (side) thrust produced by the growing hole is calculated for typical parameters of the SRB. A problem of inference of the fault parameters from the measurements of the nominal values of stagnation pressure and thrust is formulated and solved in quasi-steady approximation. An application of the recently developed Bayesian framework for diagnostics and prognostics of the case breach fault that can cause loss of flight control is discussed

Dynamical Model of Rocket Propellant Loading with Liquid Hydrogen

A dynamical model describing the multistage process of rocket propellant loading has been developed. It accounts for both the nominal and faulty regimes of cryogenic fuel loading when liquid hydrogen is moved from a storage tank to an external tank via a transfer line. By employing basic conservation laws, the reduced lumped-parameter model takes into consideration the major multiphase mass and energy exchange processes involved, such as highly nonequilibrium condensation evaporation of hydrogen, pressurization of the tanks, and liquid hydrogen and hydrogen vapor flows in the presence of pressurizing helium gas. A self-consistent theory of dynamical condensation evaporation has been developed that incorporates heat flow by both conduction and convection through the liquid/vapor interface inside the tanks. A simulation has been developed in MATLAB for a generic refueling system that involves the solution of a system of ordinary integro-differential equations. The results of these simulations are in good agreement with space shuttle refueling data

Model-based diagnostics and prognostics for solid rocket motors

Progress in development of the physics model based diagnostic and prognostic system for solid rocket motors (SRMs) of the new generation of the crew exploration vehicles is reported. The performance model (PM) of the internal ballistics of large segmented SRMs in the regime of steady burning in the presence of the case breach fault is presented. This model takes into account propellant regression, erosive burning, surface friction, nozzle ablation, and also processes describing specific faults. The performance of the model is verified by comparison with the results of 2D high-fidelity simulations. Importantly, the PM allows for the simulation of a number of faults observed earlier in large segmented SRMs including nozzle blocking, bore choking, propellant debonding, and case breach fault. The developed model of the case breach allows calculations of the side thrust at a given location along the rocket axis. The model takes into account the effect of mass addition along the rocket axis, erosive burning, and surface friction. In this paper we illustrate to use the developed PM for analysis of the case breach fault. The model of the internal ballistics is combined with the model of dynamics of burning-through case at a given location along the motor axis. The case breach fault diagnostic is developed via inference of the case breach area in a quasi-steady approximation. Prognosis of the case breach fault is achieved using a scaling algorithm. The diagnostic and prognostic algorithms were verified using the results of a ground firing test of a sub-scale motor