Jose Leonardo Ferreira

Controlling the Eccentricity of Polar Lunar Orbits with Low-Thrust Propulsion

It is well known that lunar satellites in polar orbits suffer a high increase on the eccentricity due to the gravitational perturbation of the Earth. The final fate of such satellites is the collision with the Moon. Therefore, the control of the orbital eccentricity leads to the control of the satellites lifetime. In the present work we study this problem and introduce an approach in order to keep the orbital eccentricity of the satellite at low values. The whole work was made considering two systems: the 3-body problem, Moon-Earth-satellite, and the 4-body problem, Moon-Earth-Sun-satellite. First, we simulated the systems considering a satellite with initial eccentricity equals to 0.0001 and a range of initial altitudes between 100 km and 5000 km. In such simulations we followed the evolution of the satellites eccentricity. We also obtained an empirical expression for the length of time needed to occur the collision with the Moon as a function of the initial altitude. The results found for the 3-body model were not significantly different from those found for the 4-body model. Secondly, using low-thrust propulsion, we introduced a correction of the eccentricity every time it reached the value 0.05.

G. stearothermophilus Spores' Inactivation by a Single Dielectric Barrier Discharge in Air at Atmospheric Pressure

In this paper, we present some results of a plasma source developed at the Plasma Laboratory of the University of Brasilia for sterilization studies at atmospheric pressure. This source was primarily conceived to produce a corona-type discharge to be used on pollutant control experiments. We used ordinary air as the precursor gas. Our apparatus consists of two coaxial cylindrical tubes with different radii connected to a high-voltage power source. We used G. stearothermophilus spores as the biological indicators. We counted the viable spores after the exposure to the plasma with the pour plate technique. Finally, we studied the biocide mechanisms of the plasma and related the inactivation of the microorganisms to plasma-induced chemical and physical processes.

Permanent magnet Hall Thrusters development and applications on future brazilian space missions

The Plasma Physics Laboratory (PPLUnB) has been developing a Permanent Magnet Hall Thruster (PHALL) for the Space Research Program for Universities (UNIESPACO), part of the Brazilian Space Activities Program (PNAE) since 2004. The PHALL project consists on a plasma source design, construction and characterization of the Hall type that will function as a plasma propulsion engine and characterized by several plasma diagnostics sensors. PHALL is based on a plasma source in which a Hall current is generated inside a cylindrical annular channel with an axial electric field produced by a ring anode and a radial magnetic field produced by permanent magnets. In this work it is shown a brief description of the plasma propulsion engine, its diagnostics instrumentation and possible applications of PHALL on orbit transfer maneuvering for future Brazilian geostationary satellite space missions.

Development of a helicon double layer thruster

This work describes the development of a Helicon Double Layer Thruster and its acquisition system at the University of Brasilia Plasma Physics Laboratory. Together with the data analysis process, we are able to measure important plasma characteristics in order to compound an Integrated Plasma Diagnostics System. Experimental results can be compared with computational simulations in order to improve parameters and optimize the performance of the thruster.

A Permanent Magnet Hall Thruster for Pulsed Orbit Control of Lunar Polar Satellites

Future Moon missions devoted to Lunar surface remote sensing, for example, will require very fine and accurate orbit control. It is well known that Lunar satellites in polar orbits will suffer a high increase on the eccentricity due to the gravitational perturbation of the Earth. Without proper orbit correction the satellite lifetime will decrease and end up in a collision with the Moon surface. It is pointed out by many authors that this effect is a natural consequence of the Lidov-Kozai resonance. We studied different arcs of active lunar satellite propulsion, centered on the orbit apoapsis or periapsis, in order to be able to introduce a correction of the eccentricity at each cycle. The proposed method is based on an approach intended to keep the orbital eccentricity of the satellite at low values.

PPPS-2013: Abstract submission performance and development of permanent magnet hall thrusters for the Brazilian space program

Summary form only given. Electric propulsion is now a successful method for primary propulsion of deep space long duration missions and for geosynchronous satellite attitude control. The Closed Drift Thruster, also called Hall Thruster or SPT (Stationary Plasma Thruster) was primarily conceived in USSR (the ancient Soviet Union) and since then, it has been developed by space agencies, space research institutes and industries in several countries such as France, USA, Israel, Russian Federation and Brazil. In this work, we present the main features of the Permanent Magnet Hall Thruster (PMHT) developed at the Plasma Laboratory of the University of Brasilia. This project is supported by the Brazilian Space Agency program for universities named UNIESPAÇO. The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magnetic field inside the plasma channel of the thruster is very significant. It allows the development of a Hall Thruster with power consumption low enough to be used in small and medium size satellites. The description of a new vacuum chamber built to test the second prototype of the PMHT (PHALL II) is given. PHALL II has an aluminum plasma chamber and is smaller with 15 cm diameter and will contain rare earth magnets. We show the plasma density and temperature space profiles inside and outside the thruster channel. Ion temperature measurements based on the Doppler broadening of spectral lines and ion energy measurements are also shown. Based on the measured plasma parameters, we construct an aptitude figure of the PMHT. It contains the specific impulse, total thrust, propellant flow rate and power consumption necessary for satellites orbit raising and attitude control. Based on previous studies of geosynchronous satellite orbit positioning, we perform numerical simulations of satellite orbit raising from an altitude of 700 km to 36000 km using a PMHT operating in the 100mN-500 mN thrust range. In order to perform these calculations integration techniques were used. The main simulation parameters were orbit raising time, fuel mass, total satellite mass, thrust and exhaust velocity. We conclude comparing our results with results obtained with known space missions performed with Hall Thrusters.