An experimental study was performed on an ethylene/oxygen/air pulse detonation engine to examine the effect of frequency and spark delay time on the thrust output and efficiency. Reactants were mixed in a stainless-steel combustion chamber at frequencies ranging from 1 to 40 Hz. Dynamic pressure measurements were recorded throughout the system over the testing interval to determine exhaust velocities

There has been a recent need for rapid response power generation device on aircraft. Current power generators consume a large portion of the aircraft’s usable volume, and they are also extremely heavy relative to their power output; therefore, the need for compact, power-dense auxiliary power units or bleed air turbine (BAT) arose. A solution comes in the form of coupling rotating detonation engines

This Paper investigates the role of microcracks in Hall thruster wall erosion. The formation and growth of microcracks on the surface of M26 grade boron nitride composite due to repeated thermal shock was quantified, and the subsequent impact of microcracks on plasma erosion was assessed. Thermal shock cycles (20 → 800 → 20°C) were provided by a radiation oven to induce thermal stresses similar to

Journal of Propulsion and Power, Ahead of Print.

Oxidizer feed-system coupled instabilities have been observed in several liquid and hybrid propellant rocket engines, although they are not likely to be catastrophic for the latter. However, severe pressure oscillation in hybrid rocket may result in a significant reduction in the performance of the propulsion system restricting the application of the technology. In this research, feed-system coupled

A predictive numerical approach, based on Reynolds-averaged Navier–Stokes simulations including the effects of turbulence, chemistry, fluid/surface interaction, and radiation, has been developed for paraffin-wax/oxygen hybrid rocket engines. A recently fired single-port paraffin-based hybrid rocket engine, with chamber pressures up to 19.1 bar, is taken as reference for the discussion of the results

It has been recognized in recent years that high-altitude atmospheric ice crystals pose a threat to aircraft engines in flight. It is believed that ice can accrete inside the core compressor, although the mechanism by which this occurs remains poorly understood. To model ice crystal accretion, an estimate of the proportion of the impinging ice and water that sticks to a surface (the sticking efficiency)

This paper presents the use of a conventional computational-fluid-dynamics-based throughflow method to model the effects of a bypass fan in a propulsion system (for example, nacelle) under the restriction that information about the fan blade geometry is unavailable. Instead, the fan body-force model requires fan-performance data at different operating points as input. A simple implementation strategy

The effect of Tandem-Hole configuration on penetration and combustion in supersonic crossflow was studied using three injectors having two tandem holes of 0.7 mm diameter with a spacing of 5, 10, and 14 mm. A Single-Hole injector with the same injection area was studied for comparison. Shadowgraph results in Mach 1.9, Po=2.0 bar, To=305 K flow condition with kerosene as injectant indicated that higher

Aeroelastic instability in turbomachinery is one of the severe problems limiting its performance. Of particular interest is the phenomenon of stall flutter in compressors, which occurs when blades encounter large incidence flows. With the objective to understand the aerodynamics associated with stall flutter, the present experimental study is conducted on a subsonic annular compressor cascade. Five

Boron-containing coatings are actively used to improve the surface properties of mechanical parts of various devices and cutting tools. In this Paper, we demonstrate that deposition of boron-containing coatings by direct electron-beam evaporation of a boron target with a fore-vacuum plasma-cathode electron source can be used to substantially (by a factor of approximately 6–17) improve the lifetime

Journal of Propulsion and Power, Ahead of Print.

The combustion enhancement by ozone has been studied for single-component fuels in many different settings; however, the impact of ozone addition on a multicomponent fuel has been experimentally underexplored. This paper investigates the ozone-assisted flame propagation of a mixture of alkenes and alkanes in a low-pressure Hencken burner over a range of equivalence ratios, ozone concentrations, and

A liquid bipropellant rotating detonation rocket engine was successfully test fired. The 6.5-in.-diam engine operates on a mixture of rocket-grade hydrogen peroxide and triglyme. Ignition is accomplished hypergolically, with the addition of a promoter to the fuel. Eight cases of spontaneously initiated, single-wave, rotating detonations were observed. Detonation wave speeds were near or exceeding Chapman–Jouguet

A high-power nested Hall thruster was operated with cathode flow fractions from 7 to 3% of the total anode flow rate in a two-channel operating configuration at 27 kW total discharge power. The thruster was operated with a state-of-the-art high-current cathode featuring novel external propellant injectors. In stand-alone testing, the cathode has been shown to operate stably up to 300 A with a total

A numerical investigation of the performance of a supersonic combustor designed for a flight Mach 8 is presented. Numerical simulations are used to assess the characteristics and operational limits of the combustor at design and off-design conditions. The combustor design point corresponds to the cruise condition at a Mach number of 8 and an altitude of 30 km. Off-design conditions correspond to a

Three different heat exchangers (copper metal foam, copper disks, and stainless-steel disks) with lower effective surface areas than nominal catalysts used in thrusters were tested for nitrous oxide decomposition. These heat exchangers were preheated to thermal decomposition temperatures using an inductive heating system and placed in a vacuum bell jar to mitigate heat loss to the environment. Testing

Room-temperature ionic liquids offer a potential technological approach for propellant production on Mars using in situ resources. These unique salts can be employed to preferentially capture carbon dioxide (CO2) from the atmosphere of the planet for subsequent processing. To explore this application, CO2 and argon solubility experiments were performed with 1-butyl-3-methylimidazolium trifluoromethanesulfonate

Paraffin-based fuels incorporating solid amine boranes are investigated to identify formulations suitable for use as hypergolic hybrid rocket propellants. Their ignition delays are measured following contact with 90% white fuming nitric acid droplets. The mechanical properties of the paraffin binder and of the melt layer it produces are modified using an alpha-olefin polymer. The tests are carried

Hybrid rockets have several advantages with respect to current propulsion systems like simplicity, safety, reliability, environmental friendliness, and lower cost. To size the combustion chamber, it is fundamental to understand how the length, the external diameter, the volume loading, and the length-to-diameter ratio vary with the design parameters like scale, burning time, average mixture ratio,

Hypergolic hybrid motors are advantageous for rocket propulsion due to their simplicity, reliability, low weight, and safety. Many hypergolic hybrid fuels with promising theoretical performance are not practical due to their sensitivity to temperature or moisture. Ammonia borane (AB) has been proposed and studied as a potential hypergolic hybrid fuel that provides both excellent performance and storability

During their operation, solid rocket boosters experience axial stresses caused among other things also by fluid mechanical loads from the internal flow. The accurate prediction of the flowfield is mandatory for an accurate prediction of axial stresses and strains during the mission. In the present Paper, a very efficient but still accurate approach is presented to simulate the internal flow featuring

Flame behavior at conditions approaching boundary layer flashback was studied in fuel-lean premixed swirl flames with a central bluff-body flame holder. High-speed OH* chemiluminescence images were collected at over 450 different combinations of fuel composition (hydrogen/methane blends), equivalence ratio, flow rate, and reactant temperature. A selected group of conditions was further examined using

A pulsed electric thruster named Pulsed Electrogasdynamic (PEG) thruster was investigated. In this thruster, the propellant gas is accelerated gasdynamically to high exhaust velocities (10–15 km/s) by pulsed electric discharge. Laboratory models of the PEG thruster were developed and successfully operated for evaluation of performance potentials. The PEG thruster is intended for in-space propulsion

In recent years, phosphor thermography has received increased attention as an alternative to other common temperature measurement techniques (e.g., thermocouples, pyrometry). This technique has been successfully used for surface temperature measurements on coated surfaces (e.g., turbine blades, furnace walls) and, in some cases, mixed with a reacting material. However, this technique has yet to be

This work presents the modeling, control design, and simulation of a Cirrus SR20 with a hybrid electric propulsion (HEP) system composed of a combustion engine and battery-supplied electric drive that operates in one of two modes: 1) battery discharging and electric drive propelling, and 2) battery charging and electric drive generating. Given a supervisory-level system model, two optimization control

A novel diode laser-based ignition technique for hybrid propulsion systems has been developed. In an effort to determine the physical ignition mechanism, a test series was conducted in an optically accessible, slab-burning combustion chamber. High-speed imaging of the ignition event has revealed that high-temperature carbon particles created during laser-induced flash pyrolysis of the solid fuel grain

Journal of Propulsion and Power, Volume 36, Issue 4, Page 639-641, July 2020.

Rotating detonation engines (RDEs) are gaining significant interest as a practical approach to increasing the operating efficiency of propulsion systems through pressure gain combustion. To use RDEs in practical gas turbines, their stability and performance with regard to hydrocarbon fuels need to be tested. Prior experimental work has shown that ethylene/air systems exhibit suppressed wave propagation

The performance of a diode laser igniter as a restart-capable device has been assessed for single-port, poly(methyl methacrylate) (PMMA)/gaseous oxygen (GOX) hybrid motors. For this testing a prototype version of the igniter has been designed and implemented as a substitute to a traditional methane/GOX torch ignition system. Ignition tests have been conducted at atmospheric ambient conditions using

Iron oxide is the most common catalyst in solid rocket propellant. Increased performance of propellant by encapsulating iron oxide particles within ammonium perchlorate (AP) has been previously demonstrated, but only nanoscale particles were used, and encapsulation was only accomplished in fine AP (∼20 microns in diameter). In this study, the size of the particle inclusions were extended to micron

Reactive hydrocode calculations of shock-to-detonation transition in heterogeneous energetic (HE) materials need to be closed with burn models. One requirement of burn models is to supply a macroscale control volume with an energy release rate due to chemical reactions that reflects the subgrid physics of hotspot ignition and growth. Energy localization at hotspots delivers chemical energy at a rate

A generalized flat plate cascade model is developed in this study to predict the unsteady aerodynamics of a blade row with circumferentially nonuniform spacing in subsonic compressible flow. With no constraints on symmetry, this model can be applied to a blade row with any user-specified nonuniform blade spacing pattern. The effect of nonuniform blade spacing on compressor rotor forced response and

Journal of Propulsion and Power, Volume 36, Issue 4, Page 632-638, July 2020.

The performance of many Hall thrusters has been shown to exhibit sensitivity to background pressure in ground-based test facilities, and this property can have an impact on the prediction of in-space performance. The SPT-140 Hall thruster, similar in design to the SPT-100 thruster, which shows such sensitivity, was subjected to a series of tests to characterize the effects of background pressure on

A novel fuel regression measurement technique was developed using a single-port, clear polymethylmethacrylate (PMMA) grain and a high-resolution camera, providing temporally and spatially resolved data in a small-scale hybrid motor. By visualizing the fully illuminated port through a flat PMMA surface, the fuel grain diameter can be measured along the axial dimension. This paper provides the details

Subnanosecond laser ablation of asteroid simulants has been studied, and direct force measurements were made. A 0.7 ns pulsed laser was used, with a 40 kHz pulse repetition frequency, 1064 nm wavelength, and 33 W average power. High-fidelity simulants for carbonaceous chondrite meteorites of types CM, CR, and CI, as well as pyroxene rock and 6061 aluminum were ablated. The force response over 500 ms

A new direct-connect supersonic combustor has been designed and tested for the study of plasma-assisted combustion in the ACT-II supersonic combustion tunnel. Laser-induced plasma ignition was investigated in an ethylene-fueled cavity flame holder at Mach 3. Combustor design, geometry, and flow characteristics are discussed in the first part of the paper. The supersonic combustor includes a cavity

Iodine has the potential to be a mission-enabling propellant for electric propulsion; however, iodine as the working gas in a hollow cathode presents many challenges. Iodine propellant was compared with a typical propellant, xenon, in both cathode operation and plume properties. In this work, a low-current (<5 A) barium oxide hollow cathode was operated on xenon and iodine propellants. Its discharge

The pulse firing mode of bipropellant thrusters is crucial for the precise attitude control of spacecraft. This research explains how to simultaneously measure the chamber pressure and observe the combustion dynamics in the consecutive pulse firing of the monomethylhydrazine and the mixture of nitrogen tetroxide with approximately 3% nitric oxide bipropellant thruster. This study investigated transient

Wake ingestion has been studied in order to develop a physics-based understanding of its effect on engine power and propulsive efficiency. A combination of analysis and testing has been employed. A control volume analysis of the one-dimensional flow through an actuator disk has been used to derive a set of equations for the power and propulsive efficiency of a propeller ingesting a wake. This analysis

Reported is a three-step procedure (also referred to as the observer) for fast and unbiased determination of the dominant frequencies and amplitude of thermoacoustic oscillations. The first step is to determine the rang of the dominant frequency by computing the amplitude at frequency bins uniformly distributed from the lowest possible frequency to the Nyquist frequency (i.e., one-half of the sampling

This paper presents the initial development and characterization of a novel micropropulsion system for nanosatellite applications: a liquid-fed pulsed plasma thruster (LF-PPT) comprising a Lorentz-force pulsed plasma accelerator (PPA) and a low-energy surface flashover (LESF) igniter. In this work, LESF was demonstrated as a sufficient means of igniting the primary discharge in a 3 μF/2 kV PPA operating

Computational fluid dynamic (CFD) simulations of hydrogen injection through a multi-porthole injector array into a Mach 10 enthalpy supersonic crossflow are presented and compared to experimental data. Reynolds-averaged Navier–Stokes simulations using a Menter shear-stress transport turbulence model are performed with the CFD code CFD++. The experimental results showed transient flow behavior in the

This paper describes a metal plasma thruster (MPT) that is suited to nano- and microsatellites. The MPT uses solid metal propellant (hence requires no liquids, gases, flow valves, or flow controls), has no moving parts, generates approximately 5000 N·s/U, and may be packaged into ½-U, 1-U, and multiple-U increments. A vacuum arc generates a metal plasma plume that accelerates into space at 6.8 km/s

Pressure gain combustion (PGC) has gained significant attention in airbreathing gas turbine applications due to its increased thermodynamic efficiency over a constant-pressure Brayton cycle. Rotating detonation engine (RDE) is a form of PGC, and in most RDEs, fuel and oxidizer are injected into the combustion chamber from separate plenums (for safety reasons), leading to an inhomogeneous mixture in

This paper studies the effect of internozzle spacing on the lean blow-off of a linear combustor array. The combustor’s lean operability limit did not have a monotonic relationship with internozzle spacing; the configuration with the intermediate nozzle spacing was the most stable. Simultaneous multi-kHz repetition-rate OH planar laser–induced fluorescence (OH-PLIF) and stereoscopic particle image velocimetry

A natural-gas-fueled rotating detonation engine was operated at flow conditions typical of gas turbine engines. High-speed broadband chemiluminescence images, particle image velocimetry (PIV), and dynamic pressure measurements were used to characterize the combustion process. A parametric survey was performed with variations of reactant mass flux (50–500 kg/(m2⋅s), inlet air temperature (520–710 K)

This paper focuses on investigating “combustion instability,” a phenomenon that mainly involves the interaction of the propellant flames with the acoustic oscillations prevalent in full-scale rocket motors. The effect of excited acoustic pressure oscillations on the mean burning rate of solid propellants was estimated over the pressure ranges from 1 to 7 MPa using a window bomb facility coupled with

A low-cost and reliable propellant flow controller is necessary to offer competitive electric propulsion systems. This paper first reviews xenon flow control methods for Hall thrusters and ion engines. Through a trade study, a simple and low-cost xenon flow controller applying a heated capillary is proposed. The test article is fabricated based on a developed theory and tested with xenon. The estimation

Staging of space propulsion systems would allow lifetime limitations inherent to small propulsion systems to be bypassed in order to enable high-ΔV capabilities for small spacecraft, in particular mass and volume constrained CubeSats. In addition, staging can be used to provide redundancy in the propulsion system, counteract thruster degradation, or open up new avenues of mission optimization. Analytical

This work provides the design methodology of a radioisotope thermophotovoltaic system (RTPV) using spectral control for space missions. The focus is on the feasibility of a practical system by using two-dimensional micropatterned photonic crystal emitters, selecting the proper thermophotovoltaic cell and insulation material to exclude material incompatibilities, to optimize the system efficiency by

Journal of Propulsion and Power, Ahead of Print.

This study is focused on the morphology of a quasi-DC discharge generated concurrently with a jet of fuel injected normally into Mach 2 crossflow. It was observed that the filamentary plasma follows the local flowfield and localizes in the shear layer between the core flow and fuel jet. The details of behavior were explored by means of stereoscopic two-dimensional imaging with subsequent image processing

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.

Journal of Propulsion and Power, Ahead of Print.