SEARCH · Search NASA

Results for “Reaction Control System Design”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22

All sources NASA NTRS DOE OSTI

NASA NTRS2019

Testing of the Lunar Reconnaissance Orbiter Attitude Control System Re-Design Without a Gyro

The Lunar Reconnaissance Orbiter (LRO) was launched in 2009 and, with itsseven science instruments, has made numerous contributions to our understandingof the moon. LRO is in an elliptical, polar lunar orbit and nominally maintainsa nadir orientation. There are frequent slews off nadir to observe various sciencetargets. LRO attitude control system (ACS) has two star trackers and a gyro forattitude estimation in an extended Kalman filter (EKF) and four reaction wheelsused in a proportional-integral-derivative (PID) controller. LRO is equipped withthrusters for orbit adjustments and momentum management. In early 2018, thegyro was powered off following a fairly rapid decline in the laser intensity on theX axis. Without the gyro, the EKF has been disabled. Attitude is provided by asingle star tracker and a coarse rate estimate is computed by a back differencingof the star tracker quaternions. Slews have also been disabled. A new rate estimationapproach makes use of a complementary filter, combining the quaterniondifferentiated rates and the integrated PID limited control torque (with reactionwheel drag and feedforward torque removed). The filtered rate estimate replacesthe MIMU rate in the EKF, resulting in minimal flight software changes. The paperwill cover the preparation and testing of the new gyroless algorithm, both inground simulations and inflight.

Halverson, Julie↗

NASA NTRS1975

Evaluation and characterization of the methane-carbon dioxide decomposition reaction

A program was conducted to evaluate and characterize the carbon dioxide-methane (CO2-CH4) decomposition reaction, i.e., CO2 + CH4 = 2C + 2H2O. The primary objective was to determine the feasibility of applying this reaction at low temperatures as a technique for recovering the oxygen (O2) remaining in the CO2 which exits mixed with CH4 from a Sabatier CO2 reduction subsystem (as part of an air revitalization system of a manned spacecraft). A test unit was designed, fabricated, and assembled for characterizing the performance of various catalysts for the reaction and ultraviolet activation of the CH4 and CO2. The reactor included in the test unit was designed to have sufficient capacity to evaluate catalyst charges of up to 76 g (0.17 lb). The test stand contained the necessary instrumentation and controls to obtain the data required to characterize the performance of the catalysts and sensitizers tested: flow control and measurement, temperature control and measurement, product and inlet gas analysis, and pressure measurement. A product assurance program was performed implementing the concepts of quality control and safety into the program effort.

Davenport, R. J.↗

NASA NTRS1984

Reaction wheels for kinetic energy storage

In contrast to all existing reaction wheel implementations, an order of magnitude increase in speed can be obtained efficiently if power to the actuators can be recovered. This allows a combined attitude control-energy storage system to be developed with structure mounted reaction wheels. The feasibility of combining reaction wheels with energy storage wwheels is demonstrated. The power required for control torques is a function of wheel speed but this energy is not dissipated; it is stored in the wheel. The I(2)R loss resulting from a given torque is shown to be constant, independent of the design speed of the motor. What remains, in order to efficiently use high speed wheels (essential for energy storage) for control purposes, is to reduce rotational losses to acceptable levels. Progress was made in permanent magnet motor design for high speed operation. Variable field motors offer more control flexibility and efficiency over a broader speed range.

Studer, P. A.↗

NASA NTRS2008

The Characterization of the Selected Materials for Space Shuttle

The harsh conditions to which the Space Shuttles are exposed during flight required the development and use of many unique materials. These materials were specially designed to withstand extreme temperatures, in some cases over 1600 C, while other material must withstand the cryogenic conditions of -253 C, and others must operate while under extreme loads. All of these materials must not only operate in the harsh condition but they must be light weight as well. The Space Shuttle is composed of three major components when configured for launch, Figure 1; the Shuttle, solid rocket boosters, and external tank (ET). The different heat shields of the Shuttle make up the thermal protection system (TPS); this system consists of many different types of components designed to operate on various parts of the vehicle. The body of the Shuttle and ET are composed mainly of aluminum alloy and graphite epoxy. The TPS consists of reinforced carbon-carbon (RCC) used on the wing leading edges and nose cap areas while the upper forward fuselage areas, the entire underside of the Shuttle, the Orbiter maneuvering system, and reaction control system utilize blacc high temperature reusable surface insulation (HRSI) tiles, Figure 2. Other areas of the Orbiter are protected by fibrous refractory composite insulation (FRCI) tiles. Areas where the temperature stays below 649 C, such as the forward fuselage, mid-fuselage, aft fuselage, vertical tail, and upper wing, are protected by other material such as, white low temperature reusable surface insulation (LRSI) tiles, advanced flexible reusable surface insulation (AFRSI) blankets, and felt reusable surface insulation (FRSI) white blankets. The RCC is a pyrolized laminated carbon with the outer surface converted to silicon carbide to prevent oxidation. The FiRST tiles are made of a low-density, high purity silica 99.8-percent amorphous fiber insulation that is made rigid by ceramic bonding resulting in 90-percent void and 10-percent materials. The RCC and HRSI are used in areas where the temperature rises above 1260 T. The FRCI tiles are high strength tiles derived by adding alumina-bososilicate fiber to the pure silica tile slurry that welds the micron-sizes fibers of pure silica into a rigid structure during sintering. The FRCI is composed of 20-percent alumina-borosilicate fibers and 80-percent silica fibers, and provided improved strength, durability and resistance to coating cracking and weight reduction than HRSI.

Kim, Hae-Soo↗

NASA NTRS2024

Nonlinear Dynamic Analyses of STS-1 Forward RCS Oxidizer Tank Structural Failure

At liftoff of the first Space Shuttle mission, a strong ignition overpressure pulse excited the stack. The frequency of the experienced pressure wave exceeded pre-launch predictions, and resulted in high, alternating normal accelerations along the length of the vehicle. As result of this unexpected loading, an oxidizer tank support strut in the orbiter’s forward reaction control system module failed in buckling under axial compression, which could have led to loss of the mission, crew, and vehicle. This incident is investigated in more detail using linear and nonlinear finite element analyses, complementing previous analyses with classical structural mechanics. The results of these analyses are examined to provide additional insight into the accident and to better inform future design decisions for modern space vehicle systems and structures.

Space Shuttle↗

NASA NTRS2024

Nonlinear Dynamic Analyses of STS-1 Forward RCS Oxidizer Tank Structural Failure

Space Shuttle↗

DOE OSTI2020

Fault diagnosis and fault tolerant control for T-S fuzzy stochastic distribution systems subject to sensor and actuator faults

The problem of fault diagnosis (FD) and fault tolerant control (FTC) for a class of Takagi-Sugeno (T-S) fuzzy stochastic distribution control (SDC) systems subject to sensor and actuator faults is discussed in this paper. First, fuzzy logic models are used to approximate the output probability density function (PDF). Next, an adaptive augmented state/fault diagnosis observer is proposed to estimate the system state, sensor and the actuator faults simultaneously. New expected weights based on the sensor fault estimation information and a PI-type fuzzy feedback fault tolerant (FT) controller are designed to compensate the effect of sensor fault and actuator fault simultaneously. When the sensor fault occurs, the expected objective is redesigned to compensate the sensor fault. Meanwhile, the PI controller can compensate the effect of actuator fault, and the output PDF of the system can still track the desired PDF after the fault occurs. Finally, an example of quality distribution control in chemical reaction process is given to confirm the effectiveness of the algorithm.

42 ENGINEERING↗

DOE OSTI2022

Characterizing Sustained Solar-to-Hydrogen Electrocatalysis at Low Cell Potentials Enabled by Crude Glycerol Oxidation

Unassisted solar-driven water electrolysis as a sustainable source for H 2 is limited by the high overpotential necessary to drive the oxygen evolution reaction (OER). Crude glycerol is an extremely alkaline byproduct of biodiesel synthesis that can be valorized or refined to produce more desirable chemicals. Glycerol can also be directly oxidized on an anode, replacing water oxidation, to reduce the applied cell potential requirements of electrolytic H 2 production or CO 2 reduction. An advantage of oxidizing glycerol in its crude form is the opportunity to valorize it without initial refinement. We describe an approach to replace the OER half-reaction with the sacrificial crude glycerol electrooxidation on a layered Au–Pt–Bi electrocatalyst on a Ni substrate. Compared to compositions with fewer components, the AuPtBi–Ni electrocatalyst improved the duration of performance and reduced the overall cell potential for glycerol electrooxidation in the extreme alkaline solutions representative of crude glycerol. These enhancements facilitated extended, unassisted hydrogen evolution from crude glycerol electrolysis, even under the power of a single-junction silicon solar cell at less than 1 sun illumination. We characterized the oxidation products of crude glycerol electrolysis and the subsequent products formed spontaneously in the electrolyte in the highly alkaline solution. This analysis helps to both identify the stoichiometric limits of glycerol oxidation at the low cell potentials of interest here and to understand the chemical control imparted by electrocatalysis on the ultimate compounds formed in the crude solution. Furthermore, the results for the AuPtBi electrocatalyst show that incorporating crude glycerol oxidation into integrated electrochemical systems can simultaneously simplify their design and significantly improve solar-to-hydrogen rates.

08 HYDROGEN↗

DOE OSTI2023

Understanding the Control of Speciation of Molybdenum Oxides in MFI-Type Zeolites

Metal oxide-impregnated zeolites are employed in a wide variety of catalytic reactions, including methane dehydroaromatization (MDA). The most studied catalysts for MDA are Mo carbides supported on H-ZSM-5, formed through the carburization of Mo-oxide-loaded H-ZSM-5. A complete structural understanding of these materials has not yet been achieved, limiting the potential for rational catalyst design for improved performance. We hereby pursue experimental and theoretical investigations of these catalyst precursors to uncover rational design principles. We employ temperature-programmed oxidation and extended X-ray absorption fine-structure experiments, density functional theory calculations, and QuantEXAFS analysis to unveil Mo-oxide speciation in H-ZSM-5. Finally, we demonstrate that Mo-oxides exist within these systems as a combination of various motifs, and the relative abundance of these species is controlled through tailored preparation methods. The synergies exploited in this work may be leveraged in other related catalysts. The conclusions drawn are applicable to other relevant applications of zeolite-supported metal oxides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2017

Narrowband Rejection of Reaction Wheel and Environmental Disturbances for the WFIRST OMC Testbed

The Wide Field Infrared Survey Telescope (WFIRST) is a NASA observatory with two scientific instruments. The first is the Wide Field Instrument (WFI) designed to perform wide field imaging and surveys of the near infrared (NIR) sky. The second is a coronagraph (CGI) that will enable astronomers to detect and measure properties of planets in other solar systems. The coronagraph requires 0.5 milli-arcsecond (mas) RMS pointing per axis of the line of sight (LOS) to achieve a contrast of 1x10-9. This paper discusses the approach used for achieving this level of pointing performance on the occulting mask coronagraph (OMC) testbed at JPL. This testbed uses a low-order wavefront sensing (LOWFS) camera and fast steering mirror (FSM) to suppress injected LOS jitter and environmental LOS jitter. The injected jitter includes representative broadband spacecraft attitude control system (ACS) LOS motion and tonal LOS jitter caused by the reaction wheel assemblies (RWA). The environmental jitter includes thermal LOS variations and harmonics of the line noise. The LOWFS camera uses high flux from the obscured science target to achieve high rate measurements of the LOS. These measurements are augmented with fictitious RWA tachometer information and an estimate of the line noise frequency. A LOS servo using a combination of feedback and feedforward control is used in the testbed to compensate for all of the disturbance sources and to mitigate jitter caused by in-band camera noise. The feedforward uses a novel robust least mean squares (RLMS) filter algorithm to reject the RWA and line frequency tones. High fidelity models of the sensors, disturbances and actuator are presented in this paper. These models were developed as part of a simulation of the LOS control system. Performance results from the hardware testbed at the Jet Propulsion Laboratory (JPL) are discussed in this paper.

Shields, Joel↗

NASA NTRS1982

Longitudinal control effectiveness and entry dynamics of a single-stage-to-orbit vehicle

The classical theory of flight dynamics for airplane longitudinal stability and control analysis was extended to the case of a hypervelocity reentry vehicle. This includes the elements inherent in supersonic and hypersonic flight such as the influence of the Mach number on aerodynamic characteristics, and the effect of the reaction control system and aerodynamic controls on the trim condition through a wide range of speed. Phugoid motion and angle of attack oscillation for typical cases of cruising flight, ballistic entry, and glide entry are investigated. In each case, closed form solutions for the variations in altitude, flight path angle, speed and angle of attack are obtained. The solutions explicitly display the influence of different regions design parameters and trajectory variables on the stability of the motion.

Vinh, N. X.↗

NASA NTRS2011

The Effects of Propellant Slosh Dynamics on the Solar Dynamics Observatory

The Solar Dynamics Observatory (SDO) mission, which is part of the Living With a Star program, was successfully launched and deployed from its Atlas V launch vehicle on February 11, 2010. SDO is an Explorer-class mission now operating in a geosynchronous orbit (GEO). The basic mission is to observe the Sun for a very high percentage of the 5-year mission (10-year goal) with long stretches of uninterrupted observations and with constant, high-data-rate transmission to a dedicated ground station located in White Sands, New Mexico. A significant portion of SDO's launch mass was propellant, contained in two large tanks. To ensure performance with this level of propellant, a slosh analysis was performed. This paper provides an overview of the SDO slosh analysis, the on-orbit experience, and the lessons learned. SDO is a three-axis controlled, single fault tolerant spacecraft. The attitude sensor complement includes sixteen coarse Sun sensors, a digital Sun sensor, three two-axis inertial reference units, two star trackers, and four guide telescopes. Attitude actuation is performed either using four reaction wheels or eight thrusters, depending on the control mode, along with single main engine which nominally provides velocity-change thrust. The attitude control software has five nominal control modes: three wheel-based modes and two thruster-based modes. A wheel-based Safehold running in the Attitude Control Electronics (ACE) box improves the robustness of the system as a whole. All six modes are designed on the same basic proportional-integral-derivative attitude error structure, with more robust modes setting their integral gains to zero. To achieve and maintain a geosynchronous orbit for a 2974-kilogram spacecraft in a cost effective manner, the SDO team designed a high-efficiency propulsive system. This bi-propellant design includes a 100-pound-force main engine and eight 5-pound-force attitude control thrusters. The main engine provides high specific impulse for the maneuvers to attain GEO, while the smaller Attitude Control System (ACS) thrusters manage the disturbance torques of the larger main engine and provide the capability for much smaller orbit adjustment burns. SDO's large solar profile produces a large solar torque disturbance and momentum buildup. This buildup drives the frequency of momentum unloads via ACS thrusters. SDO requires 1409 kilograms (which is approximately half the launch mass) of propellant to achieve and maintain the GEO orbit while performing the momentum unloads for 10 years.

Mason, Paul↗

DOE OSTI2021

Resonant amplification of enzymatic chemical oscillations by oscillating flow

Using theory and simulation, we analyzed the resonant amplification of chemical oscillations that occur due to externally imposed oscillatory fluid flows. The chemical reactions are promoted by two enzyme-coated patches located sequentially on the inner surface of a pipe that transports the enclosed chemical solution. In the case of diffusion-limited systems, the period of oscillations in chemical reaction networks is determined by the rate of the chemical transport, which is diffusive in nature and, therefore, can be effectively accelerated by the imposed fluid flows. In this work, we first identify the natural frequencies of the chemical oscillations in the unperturbed reaction–diffusion system and, then, use the frequencies as a forcing input to drive the system to resonance. We demonstrate that flow-induced resonance can be used to amplify the amplitude of the chemical oscillations and to synchronize their frequency to the external forcing. In particular, we show that even 10% perturbations in the flow velocities can double the amplitude of the resulting chemical oscillations. Particularly, effective control can be achieved for the two-step chemical reactions where during the first half-period, the fluid flow accelerates the chemical flux toward the second catalytic patch, while during the second half-period, the flow amplifies the flux to the first patch. The results can provide design rules for regulating the dynamics of coupled reaction–diffusion processes and can facilitate the development of chemical reaction networks that act as chemical clocks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2003

System Identification of X-33 Neural Network

Modern flight control research has improved spacecraft survivability as its goal. To this end we need to have a failure detection system on board. In case the spacecraft is performing imperfectly, reconfiguration of control is needed. For that purpose we need to have parameter identification of spacecraft dynamics. Parameter identification of a system is called system identification. We treat the system as a black box which receives some inputs that lead to some outputs. The question is: what kind of parameters for a particular black box can correlate the observed inputs and outputs? Can these parameters help us to predict the outputs for a new given set of inputs? This is the basic problem of system identification. The X33 was supposed to have the onboard capability of evaluating the current performance and if needed to take the corrective measures to adapt to desired performance. The X33 is comprised of both rocket and aircraft vehicle design characteristics and requires, in general, analytical methods for evaluating its flight performance. Its flight consists of four phases: ascent, transition, entry and TAEM (Terminal Area Energy Management). It spends about 200 seconds in ascent phase, reaching an altitude of about 180,000 feet and a speed of about 10 to 15 Mach. During the transition phase which lasts only about 30 seconds, its altitude may increase to about 190,000 feet but its speed is reduced to about 9 Mach. At the beginning of this phase, the Main Engine is Cut Off (MECO) and the control is reconfigured with the help of aerosurfaces (four elevons, two flaps and two rudders) and reaction control system (RCS). The entry phase brings down the altitude of X33 to about 90,000 feet and its speed to about Mach 3. It spends about 250 seconds in this phase. Main engine is still cut off and the vehicle is controlled by complex maneuvers of aerosurfaces. The last phase TAEM lasts for about 450 seconds and the altitude and speed, both are reduced to zero. The present attempt, as a start, focuses only on the entry phase. Since the main engine remains cut off in this phase, there is no thrust acting on the system. This considerably simplifies the equations of motion. We introduce another simplification by assuming the system to be linear after some non-linearities are removed analytically from our consideration. Under these assumptions, the problem could be solved by Classical Statistics by employing the least sum of squares approach. Instead we chose to use the Neural Network method. This method has many advantages. It is modern, more efficient, can be adapted to work even when the assumptions are diluted. In fact, Neural Networks try to model the human brain and are capable of pattern recognition.

Aggarwal, Shiv↗

DOE OSTI2026

Multilevel Analysis of Electrochemically Mediated Methanolysis of Poly(ethylene terephthalate) (PET)

Here, this study presents a multilevel analysis of electrochemically mediated methanolysis as a promising method for reducing the environmental impacts of plastic recycling, with a focus on depolymerizing poly(ethylene terephthalate) (PET) into dimethyl terephthalate (DMT). Instead of conventional chemical PET depolymerization, this electrochemical approach provides distinct technical advantages in process control and efficiency. At the process level, key operational parameters, including applied current and reaction time, were systematically investigated to optimize PET conversion and DMT selectivity. The electrochemical approach was directly compared to equivalent chemical methanolysis systems and demonstrated superior performance in terms of PET conversion and DMT selectivity. Building on these findings, a technoeconomic assessment identified the current economic bottlenecks and revealed that improvements in process design, DMT selectivity, PET conversion, and energy efficiency are key to reducing the overall process cost and enabling future implementation. While further optimization is required for market competitiveness, these results establish a performance baseline for the electrochemically mediated PET methanolysis process and underscore the importance of combining process-level innovation with systems-level evaluation in the development of sustainable recycling technologies.

chemical recycling↗

NASA NTRS1977

Spacecraft flight control with the new phase space control law and optimal linear jet select

An autopilot designed for rotation and translation control of a rigid spacecraft is described. The autopilot uses reaction control jets as control effectors and incorporates a six-dimensional phase space control law as well as a linear programming algorithm for jet selection. The interaction of the control law and jet selection was investigated and a recommended configuration proposed. By means of a simulation procedure the new autopilot was compared with an existing system and was found to be superior in terms of core memory, central processing unit time, firings, and propellant consumption. But it is thought that the cycle time required to perform the jet selection computations might render the new autopilot unsuitable for existing flight computer applications, without modifications. The new autopilot is capable of maintaining attitude control in the presence of a large number of jet failures.

Bergmann, E. V.↗

NASA NTRS1984

Detailed fuel spray analysis techniques

Fuel spray analyses which are a necessary input to the analytical modeling of the complex mixing and combustion processes which occur in advanced combustor systems are discussed. It is anticipated that by controlling fuel air reaction conditions, combustor temperatures can be better controlled, leading to improved combustion system durability. The capability to measure liquid droplet size, velocity, and number density throughout a fuel spray and to utilize this measurement technique in laboratory benchmark experiments was demonstrated. The experiment to characterize fuel sprays is described. The experiments and data are useful for application to and validation of turbulent flow modeling to improve the design systems of future advanced technology engines.

Mularz, E. J.↗

NASA NTRS1999

Advanced Design and Implementation of a Control Architecture for Long Range Autonomous Planetary Rovers

An advanced design and implementation of a Control Architecture for Long Range Autonomous Planetary Rovers is presented using a hierarchical top-down task decomposition, and the common structure of each design is presented based on feedback control theory. Graphical programming is presented as a common intuitive language for the design when a large design team is composed of managers, architecture designers, engineers, programmers, and maintenance personnel. The whole design of the control architecture consists in the classic control concepts of cyclic data processing and event-driven reaction to achieve all the reasoning and behaviors needed. For this purpose, a commercial graphical tool is presented that includes the mentioned control capabilities. Messages queues are used for inter-communication among control functions, allowing Artificial Intelligence (AI) reasoning techniques based on queue manipulation. Experimental results show a highly autonomous control system running in real time on top the JPL micro-rover Rocky 7 controlling simultaneously several robotic devices. This paper validates the sinergy between Artificial Intelligence and classic control concepts in having in advanced Control Architecture for Long Range Autonomous Planetary Rovers.

Martin-Alvarez, A.↗