Laser Propulsion Research Articles

Effect of nozzle geometry on the performance of laser ablative propulsion thruster

The performance of “ablation mode” laser propulsion thrusters can be improved obviously by nozzle constraint. The nozzle geometry of “ablation mode” laser propulsion thrusters has been studied experimentally with CO2 lasers. Experimental results indicate that the propulsion performance of cylindrical nozzle thrusters is better than expansionary nozzle thrusters at the same lengths. The cylindrical nozzle thrusters were optimized by different laser energies. The results show that two important factors, the length-to-diameter ratio α and the thruster diameter to laser-spot diameter ratio β, affect the propulsion performance of the thruster obviously. The momentum coupling coefficient Cm increases with the increase of α, while Cm increases at first and then decreases with the increase of β.

Characteristics of droplets ejected from liquid glycerol doped with carbon in laser ablation propulsion**Project supported by the National Natural Science Foundation of China (Grant No. 10905049) and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 53200859165 and 2562010050).

The characteristics of droplets ejected from liquid glycerol doped with carbon are investigated in laser ablation propulsion. Results show that carbon content has an effect on both the coupling coefficient and the specific impulse. The doped-carbon moves the laser focal position from the glycerol interior to the surface. This results in a less consumed glycerol and a high specific impulse. An optimal propulsion can be realized by varying carbon content in glycerol.

Numerical investigation on shielding properties of the laser ablation plume of polymer doped metal

For laser ablation propulsion, the shielding effect of ablation plume on the incident laser is an essential factor affecting the propulsion performance. When the polymer doped metal is utilized as the propellant, the shielding effect would be more significant because the metal dopant is easily ionized. In order to study the shielding effect of ablation plume on the incident laser energy, a laser ablation model with taking into account the plume expansion, ionization and the shielding effect is built in the present work. For the polyoxymethylene doped aluminum particles irradiated by a laser with a fluence of 3-40 J/cm2, the specific impulse of laser ablation is calculated, and the consistency of the numerical results with the experimental data demonstrates the availability of the model. Furthermore, the effects of both the incompletely decomposed polymer chains and the plasma induced by laser ablation on the incident laser are considered. The time variations of electron number density distribution under different laser fluences are calculated based on the laser induced ionization model. Subsequently, the absorption coefficient distributions and the time variations of shielding coefficient under different laser fluences are obtained. The results show that at a low laser fluence (5 J/cm2), the electron number density is small, so the plume shielding effect is dominated by the laser energy absorption of the small polymer chains which are not completely decomposed. While at a high laser fluence (20 J/cm2), small polymer chains are almost completely decomposed into atoms even plasma, hence the shielding effect is dominated by the plasma since the electron number density in the plume increases up to 1020 m-3, and the complicated characteristic in the time variation of shielding coefficient appears. The quantitative analysis results obtained in the present work can be helpful for optimizing the performances of laser ablation propulsion.

Femtosecond laser ablation of an aluminum target in air

The dynamics of laser ablation of solid target with ultrashort intense laser pulses is not only fundamentally interesting, but also relevant to a few important applications such as microfabrication, laser propulsion, laser induced breakdown spectroscopy, etc. By use of time-resolved pump-probe shadowgraphic imaging technology, we study the dynamic process of laser ablation of a planar aluminum target in air. The incident laser pulses are from a Ti: sapphire femtosecond laser amplifier system with a duration of 50 fs, central wavelength of 800 nm, pulse energy varying between 4 mJ and 7 mJ. Time-resolved shadowgraphs of material ejection from the aluminum target are recorded at the time delay up to a few nanoseconds after laser irradiation. By changing the distance between the target and the focal point of the incident laser, we obtain the shadowgraphs of the target ejection under different laser spot sizes. When the laser spot size is relatively large say, over 1 mm, the irradiated target surface is ablated in the form of a planar shock. However, when the laser spot size is relatively small, the ejection appears in the form of a hemispherical blast wave. It is found that the hemispherical blast wave well conforms to the Sedov's blast wave theory. When the laser energy is relatively large, it is found that ionization of air has a great effect on laser ablation. Additional small ejections appear as columnar and hemispherical structures near the laser axis, which are superimposed on the large planar shock. These can be attributed to the following processes. Firstly, as the ionization of air occurs near the laser axis, effective heat transfer from air plasma to the aluminium target leads to enhanced target temperature. This leads to the formation of a columnar structure on a picosecond time scale. Secondly, the columnar ejection and air plasma expansion near the laser axis result in the decrease of air density and pressure, which leads to the formation of the hemispherical structure on a nanosecond time scale.

The Process of a Laser-Supported Combustion Wave Induced by Millisecond Pulsed Laser on Aluminum Alloy

We study the process of a laser-supported combustion wave (LSCW) when an aluminum alloy is irradiated by a millisecond pulse laser based on the method of laser shadowgraphy. Under the condition of different laser parameters, the obtained results include the velocity, ignition threshold of LSCW and the variation law. The speed of LSCW increases with the laser energy under the same irradiation laser pulse width, and the speed of LSCW reduces with the increase of the laser pulse width under the same irradiation laser energy. Moreover, the ignition time of LSCW becomes shorter by increasing the laser number of the pulse and is not effected by changing the frequencies, when keeping the laser pulse width and energy unchanged. The results of the study can be applied in the laser propulsion technology and metal surface laser heat treatment, etc.

Laser propulsion of nanobullets by adiabatic compression of surface plasmon polaritons.

Laser propulsion and guide of nanosized objects is fundamental for a wide number of applications. These applications are often limited by the fact that the optical forces acting on nanoparticles are almost negligible even in the favorable case of metallic particles and hence large laser powers are needed to accelerate and guide nanosize devices in practical applications. Furthermore, metallic nanoparticles exhibit strong absorption bands and scattering and this makes more difficult controlling nanopropulsion. Thus, finding some mechanism enhancing the optomechanical interaction at the nanoscale controlled by laser is specifically challenging and pivotal. Here, we demonstrate a novel physical effect where the well-known adiabatic localization of the enhanced plasmonic surface field on the apex of metallic nanocones produces a significant optical pressure employable as a propulsive mechanism. The proposed method gives the possibility to develop new photonics devices to accelerate metallic nanobullets over long distances for a variety of applications.

GHz laser-free time-resolved transmission electron microscopy: A stroboscopic high-duty-cycle method

A device and a method for producing ultrashort electron pulses with GHz repetition rates via pulsing an input direct current (dc) electron beam are provided. The device and the method are based on an electromagnetic-mechanical pulser (EMMP) that consists of a series of transverse deflecting cavities and magnetic quadrupoles. The EMMP modulates and chops the incoming dc electron beam and converts it into pico- and sub-pico-second electron pulse sequences (pulse trains) at >1GHz repetition rates, as well as controllably manipulates the resulting pulses. Ultimately, it leads to negligible electron pulse phase-space degradation compared to the incoming dc beam parameters. The temporal pulse length and repetition rate for the EMMP can be continuously tunable over wide ranges.Applying the EMMP to a transmission electron microscope (TEM) with any dc electron source (e.g. thermionic, Schottky, or field-emission source), a GHz stroboscopic high-duty-cycle TEM can be realized. Unlike in many recent developments in time-resolved TEM that rely on a sample pumping laser paired with a laser launching electrons from a photocathode to probe the sample, there is no laser in the presented experimental set-up. This is expected to be a significant relief for electron microscopists who are not familiar with laser systems. The EMMP and the sample are externally driven by a radiofrequency (RF) source synchronized through a delay line. With no laser pumping the sample, the problem of the pump laser induced residual heating/damaging the sample is eliminated. As many RF-driven processes can be cycled indefinitely, sampling rates of 1–50GHz become accessible. Such a GHz stroboscopic TEM would open up a new paradigm for in situ and in operando experiments to study samples externally driven electromagnetically. Complementary to the lower (MHz) repetition rates experiments enabled by laser photocathode TEM, new experiments in the multi-GHz regime will be enabled by the proposed RF design. Because TEM is also a platform for various analytical methods, there are infinite application opportunities in energy and electronics to resolve charge (electronic and ionic) transport, and magnetic, plasmonic and excitonic dynamics in advanced functional materials. In addition, because the beam duty-cycle can be as high as ~10−1 (or 10%), detection can be accomplished by commercially available detectors.In this article, we report an optimal design of the EMMP. The optimal design was found using an analytical generalized matrix approach in the thin lens approximation along with detailed beam dynamics taking actual realistic dc beam parameters in a TEM operating at 200keV.

Refined model of the optical system for space mini-vehicles with laser propulsion

Simulation results for on-board optical system of a space mini-vehicle with laser propulsion are presented. This system gives the possibility for receiving theremote laser radiation power independently of a system telescope mutual orientation to the vehicle orbiting direction. The on-board optical system is designed with the use of such optical elements as optical hinges and turrets. The system incorporates the optical switch that is a special optical system adapting optically both receiving telescope and laser propulsion engines. Modeling and numerical simulation of the system have been performed with the use of ZEMAX software (Radiant Ltd). The object matter of calculations lied in size definition of system optical elements, requirements to accuracy of their manufacturing and reciprocal adjusting to achieve an efficient radiation energy delivery to УТОЧНЕННАЯ МОДЕЛЬ ОПТИЧЕСКОЙ СИСТЕМЫ КОСМИЧЕСКИХ... Научно-технический вестник информационных технологий, механики и оптики, 2015, том 15, No 5 826 laser propulsion engine. Calculations have been performed with account to the limitations on the mini-vehicle mass, its overall dimensions, and radiation threshold density of the optical elements utilized. The requirements to the laser beam quality at the entrance aperture of laser propulsion engine have been considered too. State-of-the-art optical technologies make it possible to manufacture space reflectors made of CO-115M glassceramics with weight-reducing coefficient of 0.72 and the radiation threshold of 5 J/cm for the radiation with a 1.064 microns wavelength at 10-20 ns pulse duration. The optimal diameter of a receiving telescope primary mirror has been 0.5 m when a coordinated transmitting telescope diameter is equal to 1 m. This provides the reception of at least 84% of laser energy. The main losses of radiation energy are caused by improper installation of receiving telescope mirrors and by in-process errors arising at manufacturing the telescope mirrors with a parabolic surface. It is shown that requirements to the in-process admissible errors for the on-board optical system elements and to their mutual adjustment accuracy are enhanced, but they are feasible at the same time. The proposed onboard optical system are usable both for space mini-vehicle with laser propulsion and for wireless technology of energy delivery through space with the use of lasers.

Beam-Riding Flight of a Laser Propulsion Vehicle Using Actively Controlled Pulse

This paper discusses active laser control using a genetic algorithm and a mirror-actuating system to achieve kilometer-order in-air flight using a laser propulsion vehicle while riding a beam. A 10 kg vehicle reaction driven by a strong shock wave is examined using our flight simulator to analyze interaction with unsteady blast wave propagation based on coupling calculation between hydrodynamic simulation of the shock wave propagation and orbital simulation of the vehicle flight motion, and the generated impulses are characterized by the spherically symmetric Sedov solution. Beam-riding flight with an initial offset of 5 mm is successfully sustained by controlling angular offset, while vehicle acceleration is kept low for safe launch to the target altitude. A system delay of laser control is introduced into the flight simulator, and beam-riding flight is maintained for a 20 ms system delay using delay correction following prediction by six-degree-of-freedom equations of motion. This study also examines robustness of the flying technique for wind perturbation, and an active control scheme that can ensure stable flight with a wind of up to . The stability of flight control is assessed when there is a positioning error of laser incident light, and flight is stably sustained by keeping the angular offset small for the positioning error with a standard deviation 1 cm. This paper examines the lower limit of repetition frequency of multiple pulses for stable flight, and found that a repetition frequency exceeding 15 Hz should be selected in order to maintain posture stability. Stable flight is not maintained for the combination of larger system delay and positioning error because translational velocity and angular offset simultaneously increase. However, the vehicle can fly to kilometer-order altitude while maintaining posture stability if the translational and angular impulses are adjusted. Flight performance can be improved by adjusting impulse direction and size using our flight simulator as an impulse design tool.

Impacts of Commutation Voltage Drop on Self-Exciting Air-Core Pulsed Alternator

As a novel pulsed-power supply, the air-core pulsed alternator is outstanding in providing repetitive pulse with high energy density, and preferred in a variety of fields including laser and electromagnetic launch, etc. To achieve a superior field excitation power supply, the air-core pulsed alternator usually adopts a self-excitation module, putting some emphasis on the design of the excitation conditions. In previous studies, the commutation voltage drop is neglected in excitation condition analysis. However, the voltage drop may have some significant impacts on the excitation conditions, and the neglect would cause a deviation between analysis and practices. This paper focuses on the analysis of excitation condition, taking the commutation voltage drop into account.

A new perspective of ablative pulsed laser propulsion: study on different morphologies of nano-structured ZnO

We report for the first time a new application of four different morphologies including nano-noodles of zinc oxide as a laser ablation micro-thruster. Nano-noodles represent a unique class of materials in which the electrons are confined near the surface owing to the majority of the near surface atoms. The synthesized samples of ZnO were of single phase, having a wurtzite hexagonal structure. Three different morphologies, viz. initial (nanoparticles), intermediate (nano-noodles) and final (complete nano-noodles) of zinc oxide were ablated using a Nd : YAG laser operating at 1064 nm for the measurement of propulsion parameters. The momentum coupling coefficient (Cm) and the specific impulse (Isp) were evaluated using the non-contact optical triangulation method. It has been observed that the morphology of the material affects the laser ablation propulsion (LAP) parameters. For each sample, the laser fluence for the optimum coupling coefficient owing to the plasma shielding effect has also been found. The synthesized nanostructured zinc oxide samples have been found useful as efficient laser propellants that can be used in a variety of applications due to diversity in their momentum coupling coefficient and specific impulse values.

Refinement in the structural and magnetic properties of Co0.5Ni0.5Fe2O4 and its application as laser micro-propellant using ablation confinement

The transition metal-substituted cobalt ferrite nanoparticles Co0.5X0.5Fe2O4 (with X=Cu, Zn, Mn and Ni) exhibit a wide range of properties that result in their application in low loss magnetic core materials, vertical recording heads, antenna rods, memory elements, ferrofluids, biomedical applications, sensors and laser propulsion. Keeping in view its importance we investigated for the first time the structural and magnetic properties of the Co0.5Ni0.5Fe2O4 samples that were subsequently subjected to thermal treatments for different time durations. The average crystallite sizes of the synthesized samples were found in the range of 24–46nm. The values of the saturation magnetization and coercivity varied from 25.7 to 31.2emu/g and 523.59 to 927.62Oe, respectively. The XRD patterns showed that increase in thermal treatment time resulted in the refinement of the structure whereas the SEM micrographs depicted a uniform particle size distribution of the synthesized material. We also explored the application of the synthesized material as a micro-thruster. It was found that the confinement of the laser induced plasma of Co0.5×0.5Fe2O4 led to an increase in the value of coupling coefficient from the range of 5.747×10−5–7.0644×10−5N-s/J for unconfined to that of 1.41×10−4–2.68×10−4N-s/J for confined plasma corresponding to the Nd:YAG laser fluencies of 4×109J/m2–6×109J/m2.

Mass Transportation to Space by Laser Propulsion

Mass Transportation to Space by Laser Propulsion

ICOPE-15-C048 The ideal power cycle model for Laser propulsion with gas-liquid two phase propellant

ICOPE-15-C048 The ideal power cycle model for Laser propulsion with gas-liquid two phase propellant

Theoretical and Numerical Studies of Dynamic Scaling of a Six-Degree-of-Freedom Laser Propulsion Vehicle

To estimate the flight reactions of a full-scale vehicle from reduced-scale tests, we constructed a scaling theory for the vehicle size, input energy, moment of inertia, and pulse frequency needed to maintain dynamic equivalence between a laboratory-scale and full-scale launch of a laser propulsion vehicle. The dynamic scaling law for a single pulse was constructed using translational and angular equations of motion. The analytical scaling was confirmed for a single-pulse incident using a fluid-orbit coupling simulator for the interaction between the blast wave and the vehicle. Motion equivalence was maintained for multiple pulses by adjusting the repetition frequency of the pulse incident to correct for the effect of aerodynamic drag during the free flight of the pulse-to-pulse interval. The flight of a full-scale vehicle can be estimated for single- and multiple-pulse operations from the flight data for a small-scale vehicle using the proposed scaling theory, which provides correlations between the characteristics of small-scale and large-scale flight systems. Small-scale tests were shown to be useful in estimating the flight of a full-scale vehicle using dynamic scaling theory.

Supersonic laser propulsion.

To produce supersonic laser propulsion, a new technique based on the interaction of a laser-ablated jet with supersonic gas flow in a nozzle is proposed. It is shown that such parameters of the jet, such as gas-plasma pressure and temperature in the ablation region as well as the mass consumption rate of the ablated solid propellant, are characteristic in this respect. The results of numerical simulations of the supersonic laser propulsion are presented for two types of nozzle configuration. The feasibility to achieve the momentum coupling coefficient of C(m)∼10(-3) N/W is shown.

Application of Study on Liquid Ablation in Laser Propulsion

It was found that evaporation and thermal elastic stress wave and cavity were dominant phenomenon in laser-induced ablation propulsion with liquid propellant according to our perceptual knowledge established in relative experiment and by analysis of physical mechanism of laser-induced ablation of liquid. The research result of the above phenomenon was introduced in this paper in order to give some elicitations to the researchers who were interested in the mechanism of laser propulsion with liquid ablation.

Study of underwater laser propulsion using different target materials.

In order to investigate the influence of target materials, including aluminum (Al), titanium (Ti) and copper (Cu), on underwater laser propulsion, the analytical formula of the target momentum IT is deduced from the enhanced coupling theory of laser propulsion in atmosphere with transparent overlay metal target. The high-speed photography method and numerical simulation are employed to verify the IT model. It is shown that the enhanced coupling theory, which was developed originally for laser propulsion in atmosphere, is also applicable to underwater laser propulsion with metal targets.

Design and characterization of nozzles and solid propellants for IR laser propulsion

In this article, we present an experimental study of the effect of conical section nozzles coupled to solid targets on laser ablation propulsion. The impulse produced on the target by laser ablation was measured in terms of the coupling coefficient C m using a piezoelectric (PZT) sensor. The standard deviation of the PZT signal was used as an estimator of the transferred impulse. The ablation was performed with a TEA CO2 laser at room temperature and atmospheric pressure. The targets were pellets of 90/10 % w/w Zn/CaCO3 concentration ratio. Aluminum nozzles with conical section were coupled to these propellant pellets. A comparative study of the variation of C m using nozzles of different inlet and outlet diameters of the ejected material as well as of different heights was made. The results demonstrate that for the pellet composition analyzed, as the nozzle’s height increases and its diameter decreases improvements up to 250 % respect to the target without nozzle are obtained. These are promising results for the potential development of laser ablation microthrusters.

Research on detection system of optical sights triaxial parallelism

A method for testing triaxial parallelism of optical sights, the triaxial which involve optical sights targeting axis of white & infrared and laser launching axis, is put forward in this paper on the basis of analyzing conventional measuring technique. At first, measuring optical path is improved, and some equipments such as aspherical mirror, high precision CCD camera are employed to eliminate the subjective error; with the analysis of the optical path, the mathematical model of triaxial parallelism is built, and the error factors are analyzed and calculated. Finally the system is calibrated by autocollimation theodolite whose accuracy is 0.5″ and the experimental results show that measurement error is <3″. In a word, the method has great significant engineering value.