Computer Simulations of Exothermic Propellants in a Microlaser Ablation Plasma Thruster (original) (raw)
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MACH2 Simulations of Exothermic Propellants in a Micro-laser Ablation Plasma Thruster
"An interest in the development of subkilogram forms of satellite micropropulsion has led to the design of the micro-laser plasma thruster (μLPT). Previous work succeeded in constructing a working computational model of the micro-thruster’s operation in the magnetohydrodynamic code MACH2; however, the previous work was limited to simulating only the non-energetic solid propellant ablation mode of the thruster. Recent experiments have shown that the use of an exothermic propellant might be more beneficial for higher-thrust modes of operation. This work reviews improvements made to the computational model to simulate both the sub-detonation experimental ablation and laser-supported detonation of the glycidyl azide polymer fuel used in experiments. Simulation results indiciate that the sub-detonation ablation of this fuel demonstrates an improvement in the coupling coefficient of 70% and in the specific impulse of 20% over the non-energetic solid-propellant case. The laser-supported detonation shows an increase in the coupling coefficient and specific impulse over the baseline solid-propellant case by at least two orders of magnitude. The laser-supported detonation simulation also indicates vast damage to the fuel tape, but the possibility of implementing rigid-wall boundary conditions to the fuel tape is presented. "
MACH2 Simulations of a Micro-laser Ablation Plasma Thruster with Nozzles
Recent work has investigated the micro-laser ablation plasma thruster (μLPT), a sub-kilogram form of satellite propulsion. Computational simulations that simulate the operation of the micro-thruster using the magnetohydrodynamic code MACH2 have already been established. The investigations made here have extended the capabilities of the previous computational model and have been applied to a new micro-thruster operation design incorporating a conical nozzle to demonstrate enhanced thruster performance. A methodology is presented that was developed in the MACH2 code that allows for the calculation of performance parameters characterizing the micro-thruster operation mode, such as coupling coefficient and specific impulse. The presence of a nozzle is shown to improve the coupling coefficient by as much as 36% and the specific impulse by as much as 50%, and the resulting nozzle performance enhancement follows typical nozzle trends realized in thermal rockets.
Plasma generation and plume expansion for a transmission-mode microlaser ablation plasma thruster
Journal of Applied Physics, 2004
An end-to-end model is presented of the transient plume created by a microlaser ablation plasma thruster. In this article, we describe a model of the plasma generation and expansion for a micro-laser plasma thruster operated in transmission-mode ͑T-mode͒. The laser ablation and plasma formation processes are modeled using a kinetic ablation model. This procedure provides boundary conditions at the target surface for the plume model that is based on a particle computational approach. The present study considers a 2.5-8 W diode-based laser irradiating a poly-vinyl chloride target for a pulse length of 3-10 ms. Laser beam shape full width at half maximum at the target is about 25ϫ25 m. The plume simulations reveal many details of the multicomponent plasma expansion. The results are compared with experimentally obtained plume signatures. Generally good agreement between experimental and calculated flux profiles is found.
Micropropulsion using laser ablation
Applied Physics A, 2004
The micro-laser plasma thruster (µLPT) is a new micropropulsion device that uses laser ablation to create very small thrusts (0.1-100 µN) for pointing and positioning microand nano-satellites. In this paper, we discuss the expected performance of the µLPT. For a ms-pulse device, target materials are restricted to those of low thermal conductivity, e.g. polymers. Volume ablation theory adequately describes their behavior. In a ns-pulse version, exhaust velocity can be an order of magnitude higher with correspondingly lower thrust-to-power ratio. The theory for surface absorbers describes the observed behavior.
Optimization Issues for a Micropulsed Plasma Thruster
Journal of Propulsion and Power, 2006
In this work we consider several issues related to design of a micro-Pulsed Plasma Thruster (µ µPPT). One example of such a device has been developed at the Air Force Research Laboratory for delivery of a very small impulse bit. It is concluded that the choice of the optimal energy level for a given micro-PPT geometry is very important. If discharge energy is small, the so called propellant charring would limit the operational time of the thruster. It is found that the charring phenomenon is associated with non-uniformity (in the radial direction between the electrodes) in the propellant ablation rate. On the other hand higher energy leads to discharge constriction on the positive electrode and causes azimuthal non-uniformity. Reasoning leading to such non-uniformity is considered and recommendations for optimal energy and thruster size selections are presented.
Proceedings of SPIE, 2004
The micro laser plasma thruster (tLPT) is a micropropulsion device, designed for the steering and propelling of small satellites (10 to 100 kg). A diode laser is focused on a two-layer polymer tape, where it forms a plasma. The thrust produced by this plasma is used to control the satellite motion. Three different polymers (GAP, PVN and PVC) doped with carbon and/or IR-dye were investigated for their performance as fuel polymer. The different dopants for GAP seem to have only little influence in the ablation properties. The most pronounced differences are observed in the fragment ejection detected in the shadowgraphy measurements and the crater appearance. For all carbon doped polymers, the ablation spots have a similar rough morphology. The shadowgraphy measurements of PVN reveal, that the shockwave and particle plume propagates faster as in the case of the other polymers. The particle plumes showed a very different expansion behavior for all polymers, whereas the plasma temperature and electron density measurements showed no significant difference. Only PVC displayed a slower almost liner drop of the plasma temperature over time. The thrust measurements showed the best results for GAP. *
Initial Development of the Microcavity Discharge Thruster
2009
Proof-of-concept efforts to demonstrate the propulsion capabilities of microcavity plasma discharges through design and fabrication of a Microcavity Discharge (MCD) thruster are discussed. The primary goal is to design and fabricate a MCD thruster and to demonstrate that the MCD thruster can ultimately achieve performance levels of 1 mN per cavity, a thrust efficiency exceeding 60%, and an I sp of 160 seconds. Because the MCD thruster has low specific mass and is scalable over a large number of cavities, a successful performance demonstration would ultimately result in an advanced propulsion system useful for primary (orbit transfer, maneuvering) and secondary (attitude, position and acceleration control) applications for a wide range of satellites. Research at the University of Illinois (Optical Physics and Engineering, Electric Propulsion labs) and the University of Texas at Austin (Computational Plasma Research Lab) is described. Microcavity electrode arrays with integral micronozzles on each cavity are fabricated and are driven at 20-150 kHz at a power level of up to 0.25 W per cavity. Thruster and mass flow measurements are made with cold flow to determine nozzle performance. Heating measurements are made to determine stagnation temperature and heat loss. Computational modeling provides a simulation-based understanding of the plasma physics in the microcavity and supports the experimental measurements. A detailed first-principles computational model provides time-accurate solutions of the multi-species, multi-temperature, self-consistent plasma governing equations for discharge physics, coupled to the compressible Navier-Stokes equations for the bulk fluid flow through the MCD thruster.
Polymer ablation: From fundamentals of polymer design to laser plasma thruster
Applied Surface Science, 2007
UV-Laser ablation of polymers is a well-established method to structure and deposit polymers, but the mechanisms of ablation are still controversial, i.e. photothermal or photochemical processes. An approach to probe the ablation mechanisms and to improve ablation is to incorporate photoactive groups into the polymer structure. The investigation of the ablation behavior of designed triazene polymers showed that the ablation mechanism is always a combination of both photothermal and photochemical processes, but the ratio can be changed by using different polymers and irradiation wavelengths. Also the quality of structures in the triazene polymers is superior at an irradiation wavelength of 308 nm compared to commercially available polymers. Polymers can be designed not only for UV irradiation, but also for applications in the IR range, but with different requirements. One application for designed polymers in the near-IR range is as fuel for the laser plasma thruster, which is used as propulsion system for small satellites. With commercially available polymers the necessary thrust could not be achieved. A specially designed polymer-absorber system for this application produce more energy in the form of thrust, than the laser delivered.
A Java-Based Direct Monte Carlo Simulation of a Nano-Scale Pulse Detonation Engine
2002
Recently, the Aerospace community has focused much of its effort on the development of micro-air vehicle technology. The treatment of problems at the micro-scale and nano-scale levels has traditionally been difficult, and one of the most challenging aspects of the design of these aircraft is the development of compact propulsion systems for them. Here, the pulse detonation engine is proposed as a means of propulsion for micro-air vehicles and nano-air vehicles and its performance is simulated using a DSMC flow solver. The major problem arising when attempting to implement the pulse detonation engine at such small length scales is the dominance of the wall effects inside the detonation chamber. To alleviate the loss of thrust due to wall effects, an adiabatic wall boundary condition was developed, ultimately affecting a thermodynamic environment that is more favorable for the formation of a detonation wave, while maintaining real-wall viscous effects. The chemistry and physics of the...
Diode laser-driven microthrusters - a new departure for micropropulsion
AIAA Journal, 2002
We developed an entirely new type of orientation thruster for micro-and nanosatellites. The laser plasma thruster is based on the recent commercial availability of diode lasers with sufficient brightness and 100% duty cycle to produce a repetitively pulsed or continuous vapor or plasma jet on a surface in vacuum. A low-voltage semiconductor switch can drive the laser. A lens focuses the laser diode output on the ablation target, producing a miniature jet that provides the thrust. Single-impulse dynamic range is nearly five orders of magnitude, and the minimum impulse bit is 1 nN/s in a 100-µs pulse. Even with diffraction-limited focusing optics, at least 0.5-W optical power is needed to produce thrust from selected ablator materials. Thrust-to-power ratio C m is 50 to 100 µN/W and specific impulse I sp is 200-500 s with a 1-W laser, depending partially on the illumination mode. Transmission and reflection (R) illumination modes are discussed. R mode gives about 50% better I sp and two times better C m. Improved results are anticipated from higher laser power in the reflection mode. The prototype engine we are developing is intended to provide lifetime on-orbit steering for a 5-kg satellite, as well as reentering it from low Earth orbit.