Reaction Control System Jets Research Articles

Improved fault detection and control allocation for hypersonic re‐entry vehicle subject to intermittent fault and disturbance

AbstractThis study investigates the nonlinear fault detection and control allocation of a hypersonic re‐entry vehicle with intermittent faults and disturbances. The uncertain external disturbances in the inner loop system are processed on the basis of the studied intermittent fault mode. A set of residuals is generated by sliding time windows, and two hypothesis tests based on the residual mean are proposed to detect the appearance and disappearance of faults. An augmented observer is used to estimate the faults subject to the ‐gain disturbance rejection constraint. A nonlinear backstepping fault‐tolerant control is designed to generate the desired control torque and make the output attitude track the given signal. An optimization control allocation algorithm distributes the desired torque to aerodynamic surfaces and reaction control system jets. The stability of the schemes is analyzed by Lyapunov and linear matrix inequality theories. Numerical simulation and rapid prototyping results are presented to demonstrate the validity of the proposed methods.

Fault estimation and compensation for hypersonic flight vehicle via type-2 fuzzy technique and cuckoo search algorithm

This study proposes a fault estimation and compensation scheme for hypersonic flight vehicle (HFV) attitude system with body flap fault. To achieve the fault compensation capability, an interval type-2 fuzzy estimator is designed to approximate the unknown nonlinear function caused by modeling uncertainties and the fault. The fault-tolerant controller via the terminal sliding mode and dynamic surface techniques is developed to ensure the tracking accuracy of attitude angles for HFV and the desired control torque can be achieved. Then, a novel control allocation scheme with a cuckoo search algorithm and linear programming method is proposed to distribute the desired torque to aerodynamic surfaces and reaction control system jets. The stability of the proposed scheme is analyzed using the Lyapunov stability theory. The validity of the method is verified by a series of comparisons on numerical simulation results.

Effectiveness of a Reaction Control System Jet in a Supersonic Crossflow

A transverse side jet in a supersonic crossflow causes a significant region of separated flow in its vicinity. This separation alters the effectiveness of the jet in producing control forces and moments. In this study, numerical simulations are carried out in order to estimate this change in effectiveness. The effect of a number of parameters such as the angle of attack, angle of yaw, jet pressure ratio, injection Mach number, and presence or absence of a flare aft of the injection are studied. For the geometry considered, it is seen that the effectiveness is enhanced significantly as the angle of attack, angle of yaw, or the jet pressure ratio are increased. The jet injection Mach number does not have a significant effect as long as the jet pressure ratio and jet mass flow rate are unchanged.

Fluorescence Imaging of Reaction Control Jets and Backshell Aeroheating of Orion Capsule

Planar laser-induced fluorescence of nitric oxide was used to visualize the interaction of reaction control system jet flows on the afterbody of a hypersonic capsule reentry vehicle at the Calspan-University at Buffalo Research Center’s Large Energy National Shock Tunnel I reflected shock tunnel facility. The interaction of pitch and roll jets with the flowfield was investigated. Additionally, thin-film sensors were used to monitor heat transfer on the surface of the model to detect localized heating resulting from the firing of the reaction control system jets. Visualizations of the capsule shear layer using both planar laser-induced fluorescence and schlieren imaging compared favorably. The structure of the roll jet was found to be significantly altered due to interactions with the flowfield. Additionally, the presence of the roll jet appeared to change the nature of the shear layer from steady laminar to unsteady. The pitch jet structure was only disturbed in the far field. Comparison of the planar laser-induced fluorescence jet-fluid visualizations and the surface heat flux distributions indicate that the regions of enhanced aeroheating are not caused by the jet fluid itself impinging on the surface, but rather by the presence of jet-induced horseshoe vortices and shock wave/boundary-layer interactions.

Planar Laser-Induced Fluorescence of Mars Science Laboratory Reaction Control System Jets

Nitric-oxide planar laser-induced fluorescence was used to visualize the flow in the wake of a Mars Science Laboratory entry capsule with activated reaction control system jets in NASA Langley Research Center’s 31 in. Mach 10 air tunnel facility. Images were processed using the virtual diagnostics interface method, which brings out the three-dimensional nature of the flow visualization data while showing the relative location of the data with respect to the model. Comparison of wind-on and wind-off results illustrates the effect that the hypersonic crossflow has on the trajectory and structure of individual reaction control system jets. The visualization and comparison of both single and multiple activated jets indicate low levels of jet–jet interaction. Quantitative streamwise velocity was also obtained via molecular tagging velocimetry.

Crew exploration vehicle (CEV) attitude control using a neural–immunology/memory network

This paper addresses the problem of the crew exploration vehicle (CEV) attitude control. CEVs are NASA's next-generation human spaceflight vehicles, and they use reaction control system (RCS) jet engines for attitude adjustment, which calls for control algorithms for firing the small propulsion engines mounted on vehicles. In this work, the resultant CEV dynamics combines both actuation and attitude dynamics. Therefore, it is highly nonlinear and even coupled with significant uncertainties. To cope with this situation, a neural–immunology/memory network is proposed. It is inspired by the human memory and immune systems. The control network does not rely on precise system dynamics information. Furthermore, the overall control scheme has a simple structure and demands much less computation as compared with most existing methods, making it attractive for real-time implementation. The effectiveness of this approach is also verified via simulation.

Velocity Profile Measurements in Hypersonic Flows Using Sequentially Imaged Fluorescence-Based Molecular Tagging

Nitric-oxide planar laser-induced fluorescence was used to perform velocity measurements in hypersonic flows by generatingmultiple tagged lines thatfluoresce as they convect downstream.Determination of axial velocitywasmade by application of a cross-correlation analysis of the horizontal shift of individual tagged lines. A single interline, progressive scan-intensified charge-coupled device camera was used to obtain two sequential images of the nitricoxide molecules that had been tagged by the laser. The charge-coupled device allowed for submicrosecond acquisition of both images, resulting in submicrosecond temporal resolution as well as submillimeter spatial resolution (0.5 mm horizontal, 0.7 mm vertical). Quantification of systematic errors, the contribution of gating/ exposure duration errors, and the influence of collision rate on temporal uncertainty were made. This velocity measurement technique has been demonstrated for two hypersonic flow experiments: 1) a reaction control system jet on an Orion crew exploration vehicle wind-tunnel model and 2) a 10 deg half-angle wedge with a 2-mm-tall 4-mmwide cylindrical boundary-layer trip. Mean-velocity uncertainties below 30 m=s (2.7% of the measured average velocity) and single-shot uncertainties below 100 m=s (9.7%of themeasured average velocity) have been obtained in regions with optimal signal intensities using this technique.

Integrated Design-Stage Failure Analysis of Software-Driven Hardware Systems

Software-driven hardware configurations account for the majority of modern safety-critical complex systems. The often costly failures of such systems can be attributed to software specific, hardware specific, or software/hardware interaction failures. The understanding of how failures propagate in such complex systems might provide critical information to designers, because, while a software component may not fail in terms of loss of function, a software operational state can cause an associated hardware failure. The least expensive phase of the product life cycle to address failures is during the design stage. This research presents a means to evaluate how a combined software/hardware system behaves and how such failures propagate to result in potential failures downstream, during the conceptual design stage. In particular, this paper proposes the use of high-level system modeling and model-based reasoning approaches to model failure propagation in combined software-hardware systems, introducing the Function-Failure Identification and Propagation (FFIP) analysis framework to help formalize the design of safety-critical systems. The fact that the hardware and software designers do not share the same background, knowledge, methods, or language contributes significantly to software/hardware interaction failures. A high-level systems analysis method, such as FFIP, is geared toward the unification of language and modeling concepts and may help to more seamlessly bridge such a gap. The technique is applied to the design of the Reaction Control System Jet Selection of the NASA space shuttle to evaluate failure propagation within the Reaction Control System Jet selection, specifically for the redundancy management system. The paper concludes with the extensions and mappings to the software domain that are required for a truly integrated methodology.

History of Space Shuttle Rendezvous and Proximity Operations

Space Shuttle rendezvous missions present unique challenges that were not fully recognized when the Shuttle was designed. Rendezvous targets could be passive (i.e., no lights or transponders), and not designed to facilitate Shuttle rendezvous, proximity operations, and retrieval. Shuttle reaction control system jet plume impingement on target spacecraft presented induced dynamics, structural loading, and contamination concerns. These issues, along with limited reaction control system propellant in the Shuttle nose, drove a change from the legacy Gemini/Apollo coelliptic profile to a stable orbit profile, and the development of new proximity operations techniques. Multiple scientific and on-orbit servicing missions, and crew exchange, assembly and replenishment flights to Mir and to the International Space Station drove further profile and piloting technique changes. These changes included new proximity operations, relative navigation sensors, and new computer generated piloting cues. However, the Shuttle's baseline rendezvous navigation system has not required modification to place the Shuttle at the proximity operations initiation point for all rendezvous missions flown.

Direct simulation Monte Carlo calculation of a jet interaction experiment

This study deals with the development of a methodology for numerically simulating the interaction of a reaction control system (RCS) jet with a low-density external flow. A European Space Agency experiment was chosen as a test case, since it provided experimental data that could validate some of the numerical results. The initial approach was to focus on several subproblems having direct relevance to the full interaction problem. This enabled different numerical methods to be investigated separately and validated for each part of the interaction problem. In this manner, the best methodology for solving the full interaction problem was developed. The subproblems considered in this study included typical RCS nozzle and plume flows, a flat plate at zero incidence, and the flow past the experimental test model without the control jet firing. Once these calculations were completed, a simulation was performed of the test model with the control jet operating at the experimental density. The results from this final simulation were compared with experimental measurements. Nomenclature = reference diameter, m = Knudsen number at nozzle throat = Knudsen number at nozzle lip = Mach number = number density, molecules/m3 = freestream number density, molecules/m3 = pressure, Pa = Reynolds number T^ef = reference temperature, K 7waii = temperature of nozzle wall T^ = freestream temperature, K X, Y, Z = Cartesian body coordinates p , - density, kg/m3 Poo = freestream density, kg/m3 Kn\ip M