Localized arc filament plasma actuators are used to control an axisymmetric Mach 1.3 ideally expanded jet of 2.54 cm exit diameter and a Reynolds number based on the nozzle exit diameter of about 1.1×106. Measurements of growth and decay of perturbations seeded in the flow by the actuators, laser-based planar flow visualizations, and particle imaging velocimetry measurements are used to evaluate the effects of control. Eight actuators distributed azimuthally inside the nozzle, approximately 1 mm upstream of the nozzle exit, are used to force various azimuthal modes over a large frequency range (StDF of 0.13 to 1.3). The jet responded to the forcing over the entire range of frequencies, but the response was optimum (in terms of the development of large coherent structures and mixing enhancement) around the jet preferred Strouhal number of 0.33 (f = 5 kHz), in good agreement with the results in the literature for low-speed and low-Reynolds-number jets. The jet (with a thin boundary layer, D/θ ∼ 250) also responded to forcing with various azimuthal modes (m = 0 to 3 and m = ±1, ±2, ±4), again in agreement with instability analysis and experimental results in the literature for low-speed and low-Reynolds-number jets. Forcing the jet with the azimuthal mode m = ±1 at the jet preferred-mode frequency provided the maximum mixing enhancement, with a significant reduction in the jet potential core length and a significant increase in the jet centreline velocity decay rate beyond the end of the potential core.

Active control of high-speed and high-Reynolds-number jets using plasma actuators

Bending analysis of FGM plates under hygro-thermo-mechanical loading using a four variable refined plate theory

LASER ablation propulsion (LAP) is a major new electric propulsion concept with a 35-year history. In LAP, an intense
laser beam [pulsed or continuous wave (CW)] strikes a condensedmatter surface (solid or liquid) and produces a jet of vapor or plasma.
Just as in a chemical rocket, thrust is produced by the resulting reaction force on the surface. Spacecraft and other objects can be propelled in this way. In some circumstances, there are advantages for this technique compared with other chemical and electric propulsion schemes. It is difficult to make a performance metric for LAP, because only a few of its applications are beyond the research phase and because it can be applied in widely different circumstances that would require entirely different metrics. These applications range from milliwatt-average-power satellite attitude-correction
thrusters through kilowatt-average-power systems for reentering near-Earth space debris and megawatt-to-gigawatt systems for direct launch to lowEarth orbit (LEO). 
We assume an electric laser rather than a gas-dynamic or
chemical laser driving the ablation, to emphasize the performance as an electric thruster. How is it possible for moderate laser electrical efficiency to givevery high electrical efficiency? Because laser energy can be used to drive an exothermic reaction in the target material controlled by the laser input, and electrical efficiency only measures the ratio of exhaust power to electrical power. This distinction may
seem artificial, but electrical efficiency is a key parameter for space applications, in which electrical power is at a premium.
The laser system involved in LAP may be remote from the
propelled object (on another spacecraft or planet-based), for
example, in laser-induced space-debris reentry or payload launch to low planetary orbit. In other applications (e.g., the laser–plasma microthruster that we will describe), a lightweight laser is part of the propulsion engine onboard the spacecraft.

Review: Laser-Ablation Propulsion

http://absimage.aps.org/image/DFD05/MWS_DFD05-2005-000785.pdf

Active Control of High Speed and High Reynolds Number Jets via Plasma Actuators$^{\ast }$

Active control of high Reynolds number and high-speed jets has been hampered due to the lack of suitable actuators. Some of the attributes that would make an actuator suitable for such flows are: high amplitude and bandwidth; small size for distribution around the jet; phase-locking ability for jet azimuthal mode forcing; and sufficient ruggedness for hot jets. We have been developing a class of actuators termed ‘localized arc filament plasma actuators,’ which possess such characteristics. In this paper, we present the development and characterization of these actuators as well as preliminary results on their applications in high Reynolds number Mach 0.9 and ideally expanded Mach 1.3 jets.

Development and characterization of plasma actuators for high-speed jet control

: A laser propelled Lightcraft vehicle has been successfully flown in a series of experiments conducted at the High Energy Laser Systems Test Facility (HELSTF), White Sands Missile Range (WSMR), NM. The flight tests, conducted under a joint USAF/NASA flight demonstration program, used a single optimized geometry scaled over a range of sizes designed to fly on the 10 kW Pulsed Laser Vulnerability Test System (PLVTS) pulsed carbon dioxide laser. The axisymmetric Lightcraft vehicles were propelled by airbreathing, pulsed-detonation engines with an infinite fuel specific impulse. Schlieren and shadowgraph pictures were taken as a function of time, and laser beam propagation studies were conducted with different focal length telescopes. Spin-stabilized free-flight launches outside the laboratory have been accomplished to altitudes approaching 30 m (100 ft).

Ground and Flight Tests of a Laser Propelled Vehicle

Laser-induced air spike for advanced transatmospheric vehicles

On 2 October 2000, a 12.2-cm diameter, 50.6-gram laser-boosted rocket Lightcraft flew to a new altitude record of 71-meters (233-ft) at White Sands Missile Range (WSMR) in New Mexico. The PLVTS 10-kW pulsed carbon dioxide laser, located on the High Energy Laser Systems Test Facility (HELSTF) powered the record flight, as well as six others two of which reached 48.4-m (159-ft) and 56-m (184-ft). These were the first outdoor vertical, spinstabilized flights of laser Lightcraft to be performed with assigned launch windows secured from NORAD, with the cooperation of WSMR range control to avoid illuminating LEO satellites and/or low flying aircraft. Besides nearly doubling the previous altitude record of 39 meters (128-ft) set on 9 July '99, the Model #200 Lightcraft simultaneously demonstrated the longest laser-powered free-flight, and the greatest 'air time' (i.e., launch-to-landing/recovery). With a modest investment of under a million dollars, a string of ever-increasing Lightcraft altitude records have been set over the past four years since the first flight on 23 April 1997. This embryonic, propulsion concept embodies "disruptive technology" that promises to radically transform our ideas about global flight transportation and space launch systems, over the next 15 to 25 years.

World record flights of beam-riding rocket lightcraft : Demonstration of 'disruptive' propulsion technology

A computational plasma aerodynamics model is developed to study the performance of a laser-propelled lightcraft. The computational methodology is based on a time-accurate, multi-dimensional, finite volume, chemically reacting, unstructured grid pressure-based formulation. The underlying physics are modeled using a building-block approach. The physics modeled include nonequilibrium thermodynamics, nonequilibrium air-plasma finite rate kinetics, specular ray tracing, laser beam energy absorption and refraction by plasma, nonequilibrium plasma radiation, and plasma resonance. A series of transient computations are performed at several laser pulse energy levels and the simulated physics are discussed and compared with those of tests and literatures. The computed impulses and coupling coefficients for the lightcraft compared reasonably well with those of tests conducted on a pendulum apparatus.

Advanced Performance Modeling of Experimental Laser Lightcraft

Provided is a laser propelled craft having a) a forebody or nose, b) a tapering parabolic afterbody optic or mirror, c) a shroud mounted therebetween and extending aft to define an annular space around a portion of the afterbody near its base and d) means to transmit a pulsed laser beam toward the laser craft and afterbody optic and thence to focus into the annular shroud. The laser beam is pulsed to heat and pressurize the air in the annular space to expand same and propel such craft, the afterbody and shroud being so shaped as to self center or remain in the laser beam as the craft is propelled thereby. Such craft, which is spin-stablized, can also carry a fuel insert ring mounted in the shroud around the afterbody, to be ablated by the laser beam at a desired altitude, so as to transition from an air breathing craft to a rocket craft, when the atmospheric density becomes too low, e.g., at 30 km altitude so that the lasercraft can thereafter be propelled into, e.g., low earth orbit.

Leik N. Myrabo

Papers

Ground and Flight Tests of a Laser Propelled Vehicle

Laser-induced air spike for advanced transatmospheric vehicles

World record flights of beam-riding rocket lightcraft : Demonstration of 'disruptive' propulsion technology

Advanced Performance Modeling of Experimental Laser Lightcraft

Laser propelled vehicle