Thruster design for position/attitude control of spacecraft

The objective of this work is to design the configuration of thrusters and valves of a propulsion system which should reject external and internal perturbations to control position and attitude of a spacecraft. As has been proved in a previous paper by Pena et al. (see ibid., vol. 36, no. 3, 2000), there exist configurations of 6 thrusters which can achieve this task, even under the failure of any one of them. Nevertheless, that previous result only presents analysis conditions and furthermore its implementation would demand also 6 valves, one for each thruster. Here we propose a design method that can solve the aforementioned problem with 6 thrusters/3 valves.     

Analysis of solar panel orientation in low altitude satellites

The computation of the optimal orientation of solar panels which are fixed to the body of the satellite, from the point of view of average power, is presented. In practical cases, some of the parameters which determine the optimal orientation vary during the lifetime of the satellite. In these cases we compute a worst case optimum, which maximizes the average power in the worst case situation. Finally, an application of these procedures to an Earth observation satellite is performed     

Electrokinetic bioprocessing under microgravity in France as illustrated by space bioseparation: a programme initiated in France and in cooperation with Belgium and Spain.

The use of electrokinetic phenomena should prove to be a promising bioseparation technique especially as an application of bioprocessing under microgravity. Therefore, a bioseparation Research and Development programme involving several research teams has been under way for three years in France. Based upon the results of this fundamental research, a programme is now proposed for the development of an automated process chain making it possible to obtain biological macromolecules of high purity under microgravity. This Space Bio Separation programme received the Eureka label at the 6th Ministerial Eureka conference. The project will last six years. It will involve the cooperation of several scientific and industrial partners in France, in Spain and in Belgium. The programme includes the development and validation of three different bioseparation facilities for space.     

Synergistic approach of asteroid exploitation and planetary protection

The asteroid and cometary impact hazard has long been recognised as an important issue requiring risk assessment and contingency planning. At the same time asteroids have also been acknowledged as possible sources of raw materials for future large-scale space engineering ventures. This paper explores possible synergies between these two apparently opposed views; planetary protection and space resource exploitation. In particular, the paper assumes a 5 tonne low-thrust spacecraft as a baseline for asteroid deflection and capture (or resource transport) missions. The system is assumed to land on the asteroid and provide a continuous thrust able to modify the orbit of the asteroid according to the mission objective. The paper analyses the capability of such a near-term system to provide both planetary protection and asteroid resources to Earth. Results show that a 5 tonne spacecraft could provide a high level of protection for modest impact hazards: airburst and local damage events (caused by 15–170 m diameter objects). At the same time, the same spacecraft could also be used to transport to bound Earth orbits significant quantities of material through judicious use of orbital dynamics and passively safe aero-capture manoeuvres or low energy ballistic capture. As will be shown, a 5 tonne low-thrust spacecraft could potentially transport between 12 and 350 times its own mass of asteroid resources by means of ballistic capture or aero-capture trajectories that pose very low dynamical pressures on the object.     

On the effects of each term of the geopotential perturbation along the time I: Quasi-circular orbits

This paper provides a useful new method to determine minimum and maximum range of values for the degree and order of the geopotential coefficients required for simulations of orbits of satellites around the Earth. The method consists in a time integration of the perturbing acceleration coming from each harmonic of the geopotential during a time interval T. More precisely, this integral represents the total velocity contribution of a specific harmonic during the period T  . Therefore, for a pre-fixed minimum contribution, for instance 1×10^-8$1\times {10}^{-8}$ m/s during the period of time T, any harmonic whose contribution is below this value can, safely, be neglected. This fact includes some constraints in the degree and order of the terms which are present in the geopotential formula, saving computational efforts compared to the integration of the full model. The advantage of this method is the consideration of other perturbations in the dynamics (we consider the perturbations of the Sun, the Moon, and the direct solar radiation pressure with eclipses), since these forces affect the value of the perturbation of the geopotential, because these perturbations depend on the trajectory of the spacecraft, that is dependent on the dynamical model used. In this paper, we work with quasi-circular orbits and we present several simulations showing the bounds for the maximum degree and order (M) that should be used in the geopotential for different situations, e. g., for a satellite near 500 km of altitude (like the GRACE satellites at the beginning of their mission) we found 35?M?198$35?M?198$ for T=1$T=1$ day. We analyzed the individual contribution of the second order harmonic (_J2$J_2$) and we use its behavior as a parameter to determine the lower limit of the number of terms of the geopotential model. In order to test the accuracy of our truncated model, we calculate the mean squared error between this truncated model and the “full” model, using the CBERS (China-Brazil Earth Resources Satellite) satellite in this test.     

Gravitationally bound geoengineering dust shade at the inner Lagrange point

This paper presents a novel method of space-based geoengineering which uses the mass of a captured near Earth asteroid to gravitationally anchor a cloud of unprocessed dust in the vicinity of the _L1${\mathrm{L}}_1$ position to reduce the level of solar insolation at Earth. It has subsequently been shown that a cloud contained within the zero-velocity curve of the largest near Earth asteroid, Ganymed, can lead to an insolation reduction of 6.58% on Earth, which is significantly larger than the 1.7% required to offset a 2 °C increase in mean global temperature. The masses of the next largest near Earth asteroids are found to be too small to achieve the required level of insolation reduction, however, they are significant enough to be used as part of a portfolio of geoengineering schemes.     

The American Institute of Aeronautics and Astronautics pre-college outreach program

Many United States, school children perceive science, technology, engineering, and mathematics (STEM) as difficult, boring and often irrelevant subjects. The possible reasons for this problem are endlessly debated. However, the economic, social, and overall national importance of producing graduates who are technically literate and enthusiastic in their support of a rational scientific world is essential to our nation. This apparent STEM crisis should motivate the many scientific and engineering societies to develop STEM outreach programs aimed at students, parents, teachers and schools (grades K-12).     

Influence of buoyancy-driven convection on protein separation by free-flow electrophoresis.

In free-flow electrophoresis, the stability and reproducibility of the flow field are prerequisites for a satisfactory separation. Due to the presence of the species to be separated and due to mass- and heat-transfer phenomena, non-uniformities in density inevitably appear, both within the carrier buffer and between the carrier buffer and the sample stream. On earth they give rise to buoyancy-driven convection which interferes with the separation. These effects have been quantified by numerical modelling. Agreement has been found between the numerical results and experimental observations.