Ablative Propulsion Research Articles

Nanoparticles enhanced laser ablation propulsion (NE-LAP) of Cu: A response surface regression approach

The nanoparticles (NPs) present on the surface of the sample interact with the electromagnetic field of the incident laser pulse and provide better ablation efficiency. The large surface area of NPs and the mechanism of surface plasmon resonance (SPR) positively affect the Laser Matter Interaction. In this work, we report for the first time to the best of our knowledge the use of silver (Ag) NPs for the enhancement of Laser Ablation Propulsion (LAP) parameters of the metallic targets. An Nd:YAG laser (Quantel Brilliant) having pulse duration 5 ns operating at 1064 nm was used to ablate the copper samples with and without Ag NPs coatings. The Ag Nanoparticles layer was deposited using a spin coating technique. The spatial distribution of the deposited nanoparticles layer on the copper substrate was confirmed using the Atomic Force Microscopy (AFM). The LAP parameters, namely the momentum coupling coefficient Cm, the exhaust velocity VE, the specific impulse Isp and the ablation efficiency ηAB, were calculated. We have also studied the effects of various parameters like laser fluenece, coating of nanoparticles, as well as the interaction effect (fluence × coating) on the ablation efficiency using the Response Surface Regression approach. The analysis has revealed that the Ag nanoparticles coating over the surface of the propellant significantly enhances the LAP parameters. This opens a new avenue for the application of nanoparticles in the field of laser propulsion.

Imperative of adopting a new access-to-space paradigm and the role of the laser ablation propulsion launch system (LAPLaS)

In the not so distant future, the laser ablation propulsion rockets powered by ground-based high average power laser will challenge the existing techniques of accessing space based on chemical propulsion. Chemical rocket propulsion, which made access to space possible to begin with and continues to be the only technology in use to that end, cannot, however, adequately serve the emerged and quickly growing launch-to-orbit needs of the pico-nano-micro-satellites niche markets. No further technological improvements in chemical rocket propulsion can change its well-known inherent limitations and disadvantages. The ongoing and imminent developments in the satellites’ markets as well as the timeless fundamental need in robust low-cost ground-to-orbit logistics urgently call for adopting a new game-changing technological paradigm for accessing space. By elaborating and expanding on the potentially key role of the laser ablation propulsion launch system in enabling the affordable and safe access to space, this paper logically continues the author’s previous work “Optimizing access to space: ground-to-orbit logistics framework (GOLF)” published in 2017 in the New Space journal.

Launching swarms of microsatellites using a 100 kW average power pulsed laser

Transferring small payloads from Earth to low Earth orbit (LEO) and to interplanetary space using laser ablation propulsion is a new application of pulsed laser ablation propulsion, which offers parameters not available with chemical propulsion. In earlier work, we showed how to use a 1 MW average power pulsed laser to launch a 25 kg satellite from LEO to a Mars Hohmann transfer orbit in 18 minutes. Here, we discuss a lower-power application that can achieve the same result, and also cheaply and rapidly launch swarms of microsatellites into geosynchronous orbit (GEO) for communication, Earth observation, and observation of assets in GEO. The result will be a network of satellites with different functions that is robust to failures. Laser propulsion offers orbit/launch mass ratio m/M impossible with chemical rockets as well as low launch cost/kg. The main purpose in this paper is to illustrate satellite launch with repetitive pulse lasers at realistic laser average power levels. The benchmark laser has 80 ps pulsewidth, 5 kJ pulse energy, 355 nm wavelength (third Nd harmonic), and 20 Hz pulse repetition rate, using the “L’ADROIT” laser station design. To minimize laser power, we employ eight loops of steadily increasing apogee, propelled at perigee by a L’ADROIT laser in LEO, followed by a circularization “burn” at apogee using a second L’ADROIT in GEO with similar laser power. We estimate the final mf/M ratio for these maneuvers to be 43%–53%, delivering 10.8 kg into a Mars Hofmann transfer orbit and 13.2 kg to GEO. The ablated mass is contained in a spherical shell surrounding the satellite payload composed of a mixture of metal powder and polyoxymethylene. The mixture is tailored to the mission to give a matched specific impulse Isp and momentum coupling coefficient Cm. For the GEO insertion, the ablation shell splits and is re-entered after one orbit by a final “burn” from the GEO laser.

Contactless laser fabrication and propulsion of freely moving structures

Origami-inspired folding is a well-established method for creating 3D shapes from two dimensional sheets. Here we demonstrate for the first time using a laser to fold, assemble and propel the resulting free-moving part, all without any need for handling. Being able to remotely assemble and move complex parts is an important manufacturing innovation, with potential for controlling doors and latches as well as launching parts off of the build platform without direct assistance. Beginning with only a blank sheet of metal, the parts are first cut and folded using laser forming, where a laser is used to create localized plastic stresses to bend the workpiece. After dropping into place with a final cut, the resulting rotor is actuated with laser ablation propulsion, using a jet of ablated material to apply thrust.

Optimization exploration of laser ablation propulsion performance of infrared dye doped glycidyl azide polymer

The energetic polymer glycidyl azide polymer (GAP) is selected as the propellant of laser ablation micro thruster, and the effect of infrared dye doping on the propelling performance of laser ablative GAP is analyzed. By comparing the propulsion performance data with the plumes of infrared dyes doped GAP under different laser intensities, doping concentrations, target thickness and laser ablation modes, the optimization of the propulsion performance of infrared dye doped GAP is explored preliminarily. The experimental results show that the exponential attenuation characteristics of laser energy and the strong viscosity of GAP doped with infrared dye in the transmission mode lead to the existence of incomplete ablative GAP in the plume. The propulsion performances of GAP are influenced by the doping concentration of infrared dye and the thickness of propellant. Only when the target thickness is close to the laser absorption depth, can the mass of incomplete ablation along the direction of laser propagation be the least and can the laser energy be fully absorbed by the propellant to make the central ablation region reach the temperature threshold of the release of chemical energy. At the same time the optimum value of propulsion performance can be achieved. The GAP doped with infrared dyes in which laser ablation process follows the rule of absorbing laser energy first and spraying first is decomposed adequately under the reflection mode and the propelling performance is better than that in the transmission mode.

Laser impulse coupling measurements at 400 fs and 80 ps using the LULI facility at 1057 nm wavelength

At the École Polytechnique « LULI » facility, we have measured the impulse coupling coefficient Cm (target momentum per joule of incident laser light) with several target materials in vacuum, at 1057 nm and 400 fs and 80 ps pulse duration. A total of 64 laser shots were completed in a two-week experimental campaign, divided between the two pulse durations and among the materials. Our main purpose was to resolve wide discrepancies among reported values for Cm in the 100 ps region, where many applications exist. A secondary purpose was to compare Cm at 400 fs and 80 ps pulse duration. The 80 ps pulse was obtained by partial compression. Materials were Al, Ta, W, Au, and POM (polyoxymethylene, trade name Delrin). One application of these results is to pulsed laser ablation propulsion in space, including space debris re-entry, where narrow ranges in Cm and specific impulse Isp spell the difference between dramatic and uneconomical performance. We had difficulty measuring mass loss from single shots. Imparted momentum in single laser shots was determined using pendulum deflection and photonic Doppler velocimetry. Cm was smaller at the 400 fs pulse duration than at 80 ps. To our surprise, Cm for Al at 80 ps was at most 30 N/MW with 30 kJ/m2 incident fluence. On the other extreme, polyoxymethylene (POM, trade name Delrin) demonstrated 770 N/MW under these conditions. Together, these results offer the possibility of designing a Cm value suited to an application, by mixing the materials appropriately.

Solid-like ablation propulsion generation in nanosecond pulsed laser interaction with carbon-doped glycerol**Project supported by the Fundamental Research Funds for the Central Universities, China (Grant Nos. 53200859165 and 2562010050).

A solid-like propellant of carbon-doped glycerol ablated by a nanosecond pulsed laser is investigated. The results show that the specific impulse increases with increasing carbon content, and a maximum value of 228 s is obtained. The high specific impulse is attributed to the low ablated mass loss that occurs at high carbon content. More importantly, with increasing carbon content, the properties of the doped glycerol approach to those of a solid. These results indicate that propulsion at the required coupling coefficient and specific impulse can be realized by doping a liquid propellant with an absorber.

Thrust noise minimization in long-term laser ablation of propellant material in the nanosecond and picosecond regime

The avoidance of any moving parts in a microthruster exhibits a great potential for low-noise thrust generation in the micronewton range. This is required, e.g., for scientific missions that need attitude and orbit control systems with exquisite precision. Laser ablation propulsion offers the opportunity of permanent inertia-free, electro-optical delivery of laser energy to access the propellant entirely without moving it. New propellant is accessed by ablating the previous surface in layers, essentially damaging the surface with a laser over and over again. The resulting surface properties for different fluences and scanning patterns were investigated for multiple layers of aluminum, copper, and gold. The pulse-length-specific issues of various ablation mechanisms such as vaporization, spallation, and phase explosion are accounted for by the use of a 10-ps laser system and a 500-ps laser system. We show that the surface roughness produced with 500-ps laser pulses is approximately twice the surface roughness generated by using 10-ps laser pulses. Furthermore, with 500-ps pulses, the surface roughness shows low dependency on the fluence for carefully chosen scanning parameters. Therefore, we conclude that laser pulse duration differences in the picosecond and nanosecond regimes will not necessarily alter surface roughness properties.

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.

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.

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.

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.

An advanced optical system for laser ablation propulsion in space

We propose a novel space-based ablation driven propulsion engine concept utilizing transmitted energy in the form of a series of ultra-short optical pulses. Key differences are generating the pulses at the transmitting spacecraft and the safe delivery of that energy to the receiving spacecraft for propulsion. By expanding the beam diameter during transmission in space, the energy can propagate at relatively low intensity and then be refocused and redistributed to create an array of ablation sites at the receiver. The ablation array strategy allows greater control over flight dynamics and eases thermal management. Research efforts for this transmission and reception of ultra-short optical pulses include: (1) optical system design; (2) electrical system requirements; (3) thermal management; (4) structured energy transmission safety. Research has also been focused on developing an optical switch concept for the multiplexing of the ultra-short pulses. This optical switch strategy implements multiple reflectors polished into a rotating momentum wheel device to combine the pulses from different laser sources. The optical system design must minimize the thermal load on any one optical element. Initial specifications and modeling for the optical system are being produced using geometrical ray-tracing software to give a better understanding of the optical requirements. In regards to safety, we have advanced the retro-reflective beam locking strategy to include look-ahead capabilities for long propagation distances. Additional applications and missions utilizing multiplexed pulse transmission are also presented. Because the research is in early development, it provides an opportunity for new and valuable advances in the area of transmitted energy for propulsion as well as encourages joint international efforts. Researchers from different countries can cooperate in order to find constructive and safe uses of ordered pulse transmission for propulsion in future space-based missions.

Assessing the Potential of a Laser-Ablation-Propelled Tug to Remove Large Space Debris

Reducing the future threat of orbital debris will require active removal of the larger objects, such as old satellites and upper stages. Material ablation by intense laser radiation, which can be applied to most materials, provides a unique means of solving this problem. Such ablation will allow the tug to use the inert mass of the debris itself as propellant for the deorbit process, greatly reducing the mass launched to orbit. It will further allow the tug to zero the rotation of the debris from a distance of several meters, reducing the risk associated with docking. This paper looks at some basic performance parameters for a laser ablation tug to show that a tug could use laser ablation propulsion to circumvent the high launch mass and some of the docking risks that are problematic for more traditional tugs.

Measurement of ablative laser propulsion parameters for aluminum, Co–Ni ferrite and polyurethane polymer

Laser ablation propulsion is a form of beam-powered propulsion in which a pulsed laser ablates a target material thus producing thrust. We report in this work the measurements of various parameters related to laser-induced micropropulsion in toluene diisocyanate-based polyurethane polymer, aluminum and Co–Ni ferrite. The targets were irradiated by a Q-switched pulsed Nd–YAG laser at 1064 nm (pulse duration 5 ns) under atmospheric conditions. A contact-free optical triangulation method was used to measure the laser ablation induced thrust in the samples. The measurements and calculations depict that Co–Ni ferrite is better in terms of critical propulsion parameters C m and I sp. It has been observed that the propulsion parameters depend on the energy per pulse of the incident laser beam.

Reversed-Thrust Laser Propulsion and Astronaut Retrieval

Aspace-based laser ablation propulsion systemhas the potential to produce a paradigm shift in themanagement of space resources. This paper outlines practical considerations for in-space use of a laser ablation propulsion system for generating an attractive force between two space objects. Limitations of energy delivery to the target are determined, and mass removal and impulse generation are calculated as functions of range for a variety of laser wavelengths. A unique in-space application is proposed for a reversed-thrust system: emergency retrieval of astronauts and tools on-orbit.

Review of CO2Laser Ablation Propulsion with Polyoxymethylene

Polyoxymethylene (POM) has been widely studied as a promising laser propulsion propellant when paired to CO2 laser radiation. POM is a good test case for studying ablation properties of polymer materials, and within limits, for study of general trends in laser ablation-induced impulse. Mechanisms such as vaporization, combustion, and plasma are evaluated and a description is made of the link between the fluence of the beam and the resulting temperature of the target. For characterization of propulsion parameters, almost all previous studies of POM considered limited ranges of ambient pressure and incident fluence. As a result, despite many studies, there is no general understanding of POM ablation that takes into account pressure, spot area, fluence, and effects from confinement and combustion. This paper reviews and synthesizes CO2 laser ablation propulsion work using POM targets in order to make preliminary steps to address this deficiency. Previously published data is compared in terms of ablated mass ...

Experimental Determination of the Impulse Coupling Coefficient - Standardization Issues

In research on beamed energy propulsion, the momentum coupling coefficient cm is a central figure of merit to characterize a propulsion system. The determination of cm is based on the measurement of imparted impulse and laser pulse energy. Nevertheless, the knowledge of laser pulse length, laser spot area and ablated mass is of great importance for the comparability of experimental results in laser ablative propulsion. The use of a great variety of measurement techniques for these parameters throughout the scientific community implies the risk of misunderstandings and might impede the comparability of results. In this paper, we present critical issues concerning the measurement of the aforementioned key parameters with respect to possible standardization issues. As an example, a simple laser propulsion experiment will be presented and compared with an experimental model from a different research group.