Real-time detection and control of the isolator shock-train leading edge (STLE) is important to the performance of high-speed air-breathing engines, such as dual-mode scramjets. Typically, the STLE location is determined using wall static-pressure measurements, but there are often restrictions on the placement and overall number of the pressure transducers, reducing the viability and accuracy of such

Two types of combustion instabilities were observed in a multi-injector research combustor with liquid oxygen and liquefied natural gas (LOX/LNG) propellants operating at conditions similar to an upper stage rocket engine. The first was identified as an excited tangential acoustic mode of the combustion chamber and can be explained by coupling with the LOX injectors, similar to the mechanism previously

Two-fluid atomization of highly viscous and shear thinning non-Newtonian fluids must overcome the viscous resistance. Conventional air-blast atomizers address this requirement by operating at higher gas–liquid mass ratios (GLRs) at the cost of deteriorated efficiency. In this investigation, the atomization efficiency ηatom of a two-fluid atomizer is characterized. Fluidic design of the atomizer reduces

Low-thrust long-burn-time solid rocket motors may be useful as propulsion for small, fast, uncrewed aerial vehicles. These motors require a slow-burning propellant that can operate at unusually low chamber pressures (0.3–2 MPa). Slow-burn propellants were developed using ammonium perchlorate oxidizer and the burn rate suppressant oxamide. By varying the amount of oxamide (from 0 to 20%), burn rates

Electric aircraft propulsion is a growing research area that looks into achieving propulsion through fully electric or hybrid electric systems while achieving low CO2 emissions. The system-level benefit gained by different electric and hybrid-electric propulsion schemes depends heavily on the performance of system-level components in the electric drive-train, including the electric motor, gear box

An electrospray thruster designed for nanosatellites is introduced in this paper. The thruster has a compact size featuring a passive propellant transport method through the use of porous materials. Porous electrospray emitters with 1, 25, and 100 emission tips were fabricated using conventional machining techniques. The geometrical features of the emission tips were measured using a high-precision

A generalized flat plate cascade model is used in this study to predict the unsteady aerodynamics of a vibrating blade row with nonuniform blade spacing in subsonic compressible flow. The blade row is assumed to vibrate in an isolated family of blade-dominated modes. The effect of nonuniform blade spacing on compressor rotor flutter stability is demonstrated by case studies based on the geometric and

Journal of Propulsion and Power, Ahead of Print.

The overall propulsion efficiency for ion-mode electrospray thrusters has been predicted to be as high as 90%; however, experimental measurements currently fall far short of these predictions. Further complicating this is that for passively fed electrospray thrusters, the mass flow rate, which is required to obtain the propulsion efficiency and specific impulse, is not directly controlled or measured

The present research work introduces a novel combustion model formulation based on the flamelet concept suitable to investigate characteristic flow conditions in rocket engine thrust chambers. The new approach extends the validity domain of existing flamelet models to fully cover the observed flow conditions by incorporating kinetic rate effects into a state-of-the-art nonadiabatic flamelet manifold

This study provides an experimental analysis of the throttling methods implemented using a throttleable injector that generates a thrust in the range 24–64% on a 50 N monopropellant thruster using 90 wt.% hydrogen peroxide and MnO2/PbO/Al2O3. The injector proposed in this study is a dual-plate injector. It is capable of controlling the mass flow rate using radial slotted and showerhead-type plates

A computational and experimental study was conducted on nozzle geometries for rocket application rotating detonation engines (RDEs). Three geometries, including a nozzleless blunt body typically employed in RDE combustor hot-fire testing and two aerospike nozzles, were investigated. Simulations of the exhaust flow of a rotating high-frequency, high-pressure ratio wave based on rocket RDE test results

Typically, the burning surface of a composite solid propellant is controlled through grain geometry and formulation. However, combustion studies of grains constructed from different propellant formulations at fine scales (nominally 1 mm) are not readily accessible in open literature. With additive manufacturing, such configurations can be investigated easily. Propellants with a faster burning inner

The combustion of pyrotechnic delay composition based on metallic fuel and perchlorate oxidizer involves complex reaction mechanisms and condensed phase heat release. Studies on the effect of aging on ignition/burning properties, and understanding of such multicomponent pyrotechnic delay mixtures are quite limited. The present work focuses on investigating the reaction kinetics, ignition, and combustion

To further characterize the roles of aluminum and ammonium perchlorate (AP) characteristics in ammonium perchlorate/R45-M hydroxyl-terminated polybutadiene (AP/HTPB)–composite propellants, aluminized and nonaluminized formulations were tested at very high pressures, up to 68.9 MPa (10,000 psi). A total of nine formulations were examined: seven nonaluminized with varying AP distributions, concentrations

Spark discharges were parametrically examined for a cylindrical air-gap electrode configuration. The aim of this study was to elucidate spark discharge characteristics, arc penetration, and exhaust plume development to guide designers of relevant ignition devices. Spark gaps ranged from 0.5 to 2.3 mm, nominal pressures ranged from 150 to 2200 kPa, and two exciter types (bipolar and unipolar) were tested

Carbonaceous deposits can reduce heat flux in fuel-film-cooled kerosene rocket engines, but the deposition process at rocket conditions is poorly understood. Heat flux was measured in a 4.8 MPa (700 psia) fuel-film-cooled kerosene–hydrogen peroxide axisymmetric rocket combustor using 50 null point calorimeters and the Gauss–Newton algorithm with a constant Jacobian matrix. Carbon deposition caused

Experiments have been carried out to investigate the effect of cowl length variation on performance characteristics of a single expansion ramp nozzle. The performance parameters were estimated for cowl lengths of 0, 25, 50, 75, and 100% with respect to the horizontal length of the ramp. Experiments were conducted for different nozzle pressure ratios ranging between 1.5 and 9. The wall static pressure

In this study, a 1.35 kW HEP-100X Hall thruster is used to explore effective methods for improving the global efficiency of a Hall thruster across a wide range of flow rates, from the perspective of optimizing the channel configuration. Experimental and simulation results indicate that an appropriate increase in the length of the straight segment in the variable cross section channel can increase the

An experimental investigation has been conducted on a subscale dual-bell nozzle to study the effect of throttle settings on sneak-transition side loads. The results are from a cold-gas test campaign conducted in a high-altitude simulation chamber for three throttle settings of 1, 2, and 3 bar/s. An analysis is carried out by correlating the simultaneously acquired side-load measurements and real-time

Fuel-film cooling is necessary to mitigate heat transfer in high-pressure oxygen-rich staged combustion engines. A 4.8 MPa (700 psia) axisymmetric kerosene–H2O2 combustor used fuel-film cooling to deposit carbonaceous material on removable metal samples. Posttest inspection of the samples revealed a two-layer structure, with a tenacious dense lower layer and a soot-like upper layer. Total deposit depth

The impact on range and endurance of increasing electrical loads on aircraft and burgeoning interest in all-electric aircraft are driving a need for more efficient replacements for engine-driven mechanical generators. This Paper presents a model of a synergistic gas turbine/solid oxide fuel cell system for combined propulsion and electrical power on aircraft. It is developed using Numerical Propulsion

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

The Paper involves experimental and numerical heat transfer analyses of four pin-fin cooling configurations in a rectangular channel. Two design concepts were studied with two separate pin-fin (cylindrical and triangular) geometries. The first design includes a single-wall pin-fin configuration where the coolant flows through an array of full-length cylindrical (PF) and triangular pin fins (TF). The

A torsional thrust stand, calibrated for impulse bits in the range of 0.1–0.5 mN⋅s, was used to measure impulse bits from a metal plasma thruster. Impulse data were obtained on roughly 1400 shots, with metal plasma thruster targets of molybdenum, niobium, palladium, aluminum, and carbon. Model predictions (based on a simple circuit model and published plasma parameters) were validated by data from

Lifetime assessment of hollow cathode (HC) sources is an experimentally demanding process, due to the large amount of hours space qualification requires. In this Paper, we present a one-dimensional orifice model coupled to a global-averaged insert model, developed for lifetime prediction of a HC neutralizer in terms of orifice erosion; a modified sputtering yield curve is derived, similar to a previous

This Paper discusses the results of an experimental study to investigate the performance of a converging nozzle with fluidic thrust vectoring, using secondary-jet injection, through the measurements of various parameters such as thrust, flow rates, and pressures over a range of operating conditions. The thrust coefficient is found to be dependent on the nozzle pressure ratio (NPR) of the primary nozzle

A group of liquid simulants was developed in order to ease the process of cold-flow testing by lowering associated costs and hazards while providing accurate analysis of desired liquid behavior through an injector. Simulants were made with the intention of modeling certain physical properties of the liquid such as density, viscosity, and surface tension. These simulant solutions are capable of modeling

This study investigated the impact of fuel injection distribution on flame stabilization and heat release in a cavity-stabilized scramjet. Experiments were conducted using a hydrogen air heater that provided vitiated air at an average stagnation temperature of 1570 K and stagnation pressure of 12.7 atm, accelerated to a Mach number of 2.2 at the combustor entrance. Ethylene was injected using two fuel

Because of its excellent insulation capability, the usage of a silica-phenolic charring ablator as a nozzle liner is a common practice in the solid rocket motor industry. During the design of a solid rocket motor employing a silica-phenolic nozzle liner, it is desired to conduct an accurate analysis yielding in-depth thermal response and recession characteristics. As the interior ballistics and nozzle

The performance (specific impulse, Isp) of a modular, 150-lbf-class rotating detonation rocket engine (RDRE) was measured with three gaseous fuels (methane, ethane, and ethylene) and gaseous oxygen over a wide range of flow rates and equivalence ratios. All tests exhausted to sea level backpressure and were conducted using a calibrated thrust stand and Coriolis mass flow meters. Configurations tested

Computational fluid dynamics was used to study the flow through a scaled, mixed-compression, high-speed inlet with a rotating cowl at Mach 4.0 conditions. First, steady Reynolds-averaged Navier–Stokes computations were undertaken with a range of popular turbulence models including the Spalart–Allmaras model, the realizable k–ε model, the cubic k–ε model, and the Menter shear stress transport (SST)

The detrended fluctuation analysis, a technique for detecting long-range correlations in fractal time series, is used to characterize thermoacoustic oscillations of impending combustion instabilities. The slope of the linear regime of the structure function with respect to the time scale in a logarithmic plot, referred to as the Hurst exponent, takes a different value across a critical time scale corresponding

Because of their potential reductions of fuel consumption, disruptive propulsion concepts such as boundary layer ingestion have lately earned the attention of the aerospace community. Because of the increased level of interactions brought by the tight airframe–propulsor integration, an accurate assessment of this benefit requires a detailed study of the engine behavior from both an aerodynamics and

This study directly measures the performance of a thruster nozzle using water vapor as propellant in the Reynolds number below 1000. Because of its properties, water is suitable as a propellant for small satellites, often with a low-Reynolds-number flow using a micronozzle. The low Reynolds number of the flow and the phase changes in supersonic vapor flow should affect nozzle performance. It is essential

This paper describes the analysis of the flowfield in a four-stage low-speed axial compressor at the design point investigated both numerically and experimentally, with particular emphasis on the impact of stator hub flow leakage in a section of the machine featuring a change of stator configuration. The goal of the work is to give insight into the effect of the stator hub configuration on the aerodynamic

Flow visualization experiments, pressure and particle image velocimetry (PIV) measurements were conducted in supersonic internal compression inlet models in a Mach 2 flow. In the first phase of the study, the inlet model having a single sharp-edged shock generator on the upper lip of the inlet was investigated. In the second phase, another ramp was added to the floor of the single-ramp inlet model

The response behavior of capillary tube attenuated pressure sensor arrangements is studied using a rotating detonation engine as a nonlinear pressure wave source. The resulting measured pressures are examined as a function of the magnitude of the nonlinear pressure fluctuations, the mean pressure, and the forcing frequency applied to the pressure input port of the sensor. In addition, length and inner

Conventional expressions and definitions describing performance of plasma thrusters, including the thrust, specific impulse, and the thruster efficiency, assume a steady-state plasma flow with a constant flow velocity. However, it is very common for these thrusters that the plasma exhibits unstable behavior resulting in time variations of the thrust and the exhaust velocity. For example, in Hall thrusters

Journal of Propulsion and Power, Volume 37, Issue 1, Page 1-2, January 2021.

A rocket–ramjet combined cycle engine model, embedding twin rocket chambers driven with gaseous hydrogen and oxygen on the top wall side of a scramjet flowpath, was tested in its ejector-mode operation under sea-level static conditions. Gaseous hydrogen was also injected through secondary injector orifices to pressurize a ramjet combustor located downstream of the rocket chambers. Mixing between the

Experimental investigations on the self-pulsation dynamics in a gas-centered swirl coaxial atomizer are conducted using water and air. Experiments are performed in the pulsation regime by precisely varying the momentum flux ratio for different values of swirl number, recess length, and lip thickness. High-speed imaging is used to understand the underlying mechanism of the onset of pulsation. While

The T6 ion thruster is providing in-space propulsion for the BepiColombo mission, currently en route to Mercury. Simulations of the accelerator grid erosion during flight operation were carried out using the CEX2D and CEX3D codes in order to verify that the grid lifetime will be sufficient to impart the 5.75 MN⋅s total impulse per thruster required for the mission. Before calculating in-space erosion

The present paper numerically investigates the rotating stall mechanism in the NASA CC3 transonic centrifugal compressor with wedge-type vaned diffuser. The three-dimensional compressible, unsteady Navier–Stokes equations have been applied to a full-annulus high-speed centrifugal compressor comprising an inlet duct, impeller, and vaned diffuser. The scale-adaptive simulation model is selected as the

This paper discusses the aerodynamic analysis and design of a novel, hubless, contra-rotating, rim-driven fan (RDF) device. Rim-driven thruster technology has been used for marine propulsion for decades, yet RDF technology has not been comparably developed for aerospace applications. This paper demonstrates that an innovative two-stage contra-rotating RDF configuration provides the potential for a

The Photonic Laser Thruster (PLT) efficiently uses photons as propellant and thus promises to enable innovative space endeavors beyond the reach of propellant-based conventional thrusters. Previously, the proof-of-principle demonstration of PLT used a neodymium-doped yttrium aluminum garnet (Nd:YAG) rod gain medium and resulted in the maximum thrust of 35 μN. This Paper reports 100 times scaling up

In recent years, there has been significantly increased interest in using nitrous oxide as an oxidizer in hybrid rocket motor systems. The attraction of nitrous oxide is its low relative toxicity and high vapor pressure, potentially enabling self-pressurizing systems. Its decomposition is highly exothermic with a large energy barrier, typically requiring high temperature (700°C) to achieve appreciable

The paper presents an efficient method for analyzing complex periodic unsteady flows within turbomachinery. The method transforms the original initial value problem of unsteady flows to a boundary value problem by taking advantage of temporal periodicity known a priori. This transform allows a pseudotime marching at all physical time instants to be performed simultaneously, for which the method is

Aging induced changes in the mechanical properties of solid propellant can lead to defects, such as cracks and grain–liner separations, which limit the service lifetime of solid rocket motors. This Paper presents an active sensing in situ identification method based on the electromechanical impedance technique, which is particularly suited for monitoring aging of solid propellants. This Paper first

The lean blow-off (LBO) limits and structure of turbulent premixed flames were investigated with vaporized liquid fuels stabilized by a bluff-body burner. Ethanol, heptane, and two kerosenes were used. To facilitate comparisons to gaseous-fueled flames, results were also obtained from methane flames. The measured LBO limits indicate that, for this burner, the ethanol and heptane flames are more resilient

This Paper presents the results of a rotating detonation engine rocket sled test demonstration on a 127 mm gauge rail at 100 m long high-speed running track test equipment to evaluate the thrust performance of a stand-alone rotating detonation engine propulsion system. The developed sled test demonstrator contained all onboard subsystems, including engine, gas cylinders, valves, controller, and a data

Gaseous hydrogen/liquid oxygen turbulent shear coaxial flames were subjected experimentally to both pressure antinode (PAN) and pressure node (PN) transverse acoustic forcing as a function of the gas-to-liquid momentum flux ratio. The response of the flow was recorded using simultaneous high-speed imaging of backlit shadowgraphs and OH* chemiluminescence emission. It was observed that a wave amplification

An experimental investigation into small pressure-swirl spill-return atomizers was made to determine the effect of the entry port number, swirl-chamber shape, spill-line design, and the manufacturing precision on the spray quality and stability. The atomizers were studied using phase-Doppler anemometry, high-speed visualization, and mechanical patternation. Jet A-1 fuel was sprayed at inlet pressures

In this study, the effects of fuel port geometry and fuel additives on the performance characteristics of additively manufactured solid fuels in a hybrid rocket are explored. Static rocket motor firings were used to examine the performance characteristics, such as fuel regression rate and C* efficiency. Using a baseline fuel of poly(methyl methacrylate) (PMMA), a traditional center-perforated fuel

Slip in centrifugal compressors arises from imperfect guidance of the flow by the impeller blades and reduces the work input delivered by the impeller. Slip models are used to predict slip in preliminary design. However, slip models are typically calibrated with data that are not representative of modern aerospace compressors (i.e., pumps, turbochargers, or industrial compressors) and do not account

The gasification process of a low-melting fuel (polypropylene) in a high-temperature flow of inert gas (nitrogen) has been studied experimentally, implying the application to solid-fuel ramjets. The mass flow rate of gasification products attained the value of 8 g/s, and the ratio of the mass flow rates of the working gas and gasification products was 4.5. A semiempirical model for calculating the

Journal of Propulsion and Power, Ahead of Print.

A variety of methods have been developed to enhance solid propellant burning rates, including adjusting oxidizer particle size, changing the formulation, modifying the propellant core geometry, and adding catalysts or wires. Fully consumable reactive wires embedded in propellant have been demonstrated to increase the burning rate by increasing the surface area; however, the observation of this effect