the aim of this thesis is to regard all aspects concerning mass optimization with respect to small satellite structures and deployers, specifically aimed at the DelfiPQ PocketQube mission.

When sunlight illuminates a body, a tiny pressure is exerted upon its surface due to the photons impacting on it. Such a principle forms the basis of solar sailing, in which the solar radiation pressure is used to accelerate highly reflective lightweight structures called solar sails. Similarly, a laser-enhanced solar sail is a solar sail in which also an external laser beam pointed towards the sail is exploited to generate thrust. In this way an additional laser radiation pressure is exerted onto the sail, hence conferring higher propulsive and steering capabilities, and leading to an increased maneuverability of the sailcraft. The main purpose of this thesis project is to provide a model of the laser-enhanced solar sail dynamics and to establish the advantages of laser-enhanced solar sailing as compared to "traditional" solar sailing. The analysis has been pursued focusing on interplanetary missions and considering ideal sails, i.e. sails able to perfectly reflect the impinging radiation. Normally, for low-thrust interplanetary missions the propellant consumption and time of flight required for the transfers to take place play a crucial role. However, since solar sails do not exploit any propellant, the traditional and laser-enhanced sailcraft performances have been compared by analyzing their flight-time optimal trajectories, focusing on three different mission scenarios: a Mercury orbit rendezvous, Mars orbit rendezvous and Neptune flyby. These trajectories have been computed by taking advantage of an evolutionary neurocontrol optimizer, in which newly added functionalities have been implemented with the purpose of optimizing laser-enhanced solar sail trajectories. The trajectory analysis results have shown that, if laser-enhanced sailcraft are used instead of traditional sailcraft, flight time gains in the order of 8-11% can be achieved for the missions to Mercury and Mars orbits, while a smaller 2.5% gain is achieved for the flyby mission to Neptune.

Space exploration could be significantly aided by combining the disciplines of machine learning and computer vision, but these disciplines need to be developed further for specific space-related applications to have merit. One of the applications for space exploration is the detection of certain structures designating areas of interest. This thesis demonstrates a method of structure-detecting that is applied to staircases. In addition to incorporating certain physical features, like other algorithms have done, the proposed algorithm (Step-1) also takes into account the spatial relation between these features, in order to increase its robustness. Looking at a staircase from the front, the distances between each step become warped, as they are further away from the observer. This exponential spatial distortion is known as a ’chirp’. Step-1 tries to match a chirp-waveform to every edge along a straight line randomly drawn through an image, and based on that match classify the image as containing a staircase or not. The random lines are then weighted based on their effectiveness using Adaboost, which are finally combined to obtain a final classification. The results show potential but there are still some issues to be addressed. However, once the algorithm has been upgraded it could aid space exploration by being applied to satellite images and autonomous rovers.

Plasma actuators are fully electronic devices without any moving mechanical parts. Hence they have increased reliability and lower complexity when compared to conventional actuators used for same purposes. Mobile components also contribute to increased vibrations, noise, loss of energy and they require lubrication. Non-thermal plasma actuators are highly efficient as they directly convert electrical into kinetic energy without use of any mechanical parts. Lack of mobile components in plasma actuators contribute to lower mass, meaning lower cost of spacecrafts. Another benefit related to use of these actuators is their short response time, which increases dynamical and control abilities of complete spacecraft. All the benefits just stated make this technology potentially very interesting for space-based applications. Presented thesis represents feasibility study, a first step required for application of plasma actuator on a spacecraft. This research examined two objectives. First was to study the effect of an altitude on momentum exchange between high velocity external flow and created ionic wind. Second objective was to investigate and design DBD plasma actuator able to withstand orbital thermal loads. This study consists of literature research on two most common plasma actuators; various aspects of launch, orbit and re-entry of spacecrafts; and two analytical models. First model aims in estimating the influence of an altitude on the actuator force creation, which can be used for shock stand-off distance modification, and thus steering applications. Other model aims in estimating actuator thermal loads occurring due to spacecraft orbit in Low Earth Orbit. Results show that altitude has large effect on actuator force production. Analytical model shows an average reduction of 4.51 or 4.44 times per 10 km, depending on actuator’s orientation with respect to external flow. Difficulties relating high velocity flow fields such as molecular dissociation and very high friction heat loads are presented. Results show that DBD actuator system can produced significant perturbations between spacecraft surface and natural shockwave. Made perturbations are in form of a compression wave that interacts with natural shock wave and creates a dis-balance of forces proficient for spacecraft reentry steering. Second analytical model shows that there exist actuator materials which can withstand thermal loads due to spacecraft orbital Sun exposure. This thesis shows a promising first order results needed to qualify and apply DBD actuator on spacecraft. However much research on optimization and design are still required.

Recent studies have shown the feasibility of (quasi-)pole-sitter orbits at Mars and Venus, which involves a satellite positioned along or near the polar axis of a planet in order to have a continuous, hemispherical view of the planet's polar regions. In order to further demonstrate the feasibility of this mission concept, this thesis investigates time-optimal solar sail transfers to these (quasi-)pole-sitters. In particular, (quasi-)pole-sitters which are achievable when assuming solar sail technology expected in a near- to mid-term time-frame. To reduce mission operational cost, the objective of this research is to minimize the time required for the transfer, which requires the solution to an optimal control problem. Initial guess solutions for this optimal control problem are provided through two completely different techniques, in order to compare and validate the individual performances: first, a technique derived from dynamical systems theory (a type of grid search) and second, a genetic algorithm. Subsequent optimization using a direct pseudospectral algorithm results in time-optimal transfers to the considered Mars (quasi-)pole-sitters that span 2.61 and 2.72 years, and 1.07 and 1.19 years to the considered Venus (quasi-)pole-sitters. Effects due to variations in performance of the ideal sail, non-ideal sail properties, and Earth departure orbit are investigated. In addition, this paper demonstrates that a genetic algorithm is well suited to generate initial guesses for similar interplanetary transfers in the inner solar system. It provides initial guesses that outperform the more conventional grid search technique, in terms of feasibility of the initial guess transfers, as well as in computation time and ease of implementation.

The objective of this MSc thesis was to design a miniaturised Raman spectrometer that can be used in terrestrial deep ice applications of the IceMole probe. This probe is a manoeuvrable subsurface system for clean in situ analysis and sampling, developed at FH Aachen University of Applied Sciences since 2008, that is now part of a bigger DLR collaborative initiative, called Enceladus Explorer (EnEx). It combines melting with a hollow rotating ice screw and it now presents a cross sectional area of 80mm x 80mm. A Raman spectrometer is a promising non-destructive technique that allows to identify both mineral and biological compounds with a minimum amount of sample, by measuring the inelastic scattering of light. In order to achieve an appropriate design for the instrument, the project followed a systems engineering approach. The first step was the derivation of the requirements related to the technical constraints dictated by the miniaturised design of the probe and to the performances that allow the spectrometer to detect potential biosignatures. The design process was carried out by successive choices so as to propose a final configuration, developed as a CAD model in the software CATIA™. The instrument performs its measurements through a sapphire window in the IceMole probe, looking directly into the ice. It excites the sample with a laser wavelength of 532nm transmitted via a dichroic beamsplitter. The scattered light is collected by a long-pass edge filter and a 30° off-axis parabolic mirror that focuses the light into a collimator. The light is then delivered to a CCD spectrometer via an optical fibre. The spectrometer is able to measure a spectral range of 546.9-700nm with an accuracy of at least 0.4nm, combination of the characteristics of the optical components. The final result is a Raman spectrometer design modelled by the use of off-the-shelf components, selected through systems engineering trade-offs. The final dimensions of the instrument are 65mm x 65mm x 150mm, with a mass of about 1.1kg. The outcome of this thesis will have to be verified and validated in order to ensure the correct working of the system, the compliance with the derived requirements and the validity of the use of this instrument to satisfy the customers’ needs and expectations. Therefore, a preliminary verification plan was proposed in accordance to systems engineering. Eventually, the future of such a Raman spectrometer will be space exploration and life detection missions as payload of the subsurface probe. The space targets for those missions are the ones identified as most promising for harbouring potential living micro-organisms: the polar caps of Mars, Jupiter’s moon Europa and Saturn’s moon Enceladus.

The project under analysis is about the development and qualification of a demonstrator for a miniaturized foam rheology experiment performed in microgravity environment. The thesis is part of a larger feasibility study to evaluate the possibility of implementing such experiment on the International Space Station as an internal payload of the Fluid Science Laboratory in the Columbus module. The project was developed in the Fluid Physics and Payloads department at Airbus Defence & Space in Immenstaad, in accordance with European Space Agency expectations and under the supervision of the experts of foam science from the Pierre and Marie Curie University of Paris. The study was dedicated to the development and validation of a miniaturized hardware, which will be integrated in the existent Soft Matter Dynamics Experiment Container available on the International Space Station. It was focused on the design and testing of the demonstrator hardware in a Verification Test Facility, which was as close as possible to the real target system intended for use in the future mission. The system qualification was done in close cooperation with the science team interested in the results of the space experiment. The main findings of this research are related to the possibility of the studying foam in space. The microgravity conditions experienced in that environment are extremely useful to study specific fluid phenomena in gravity absence, to investigate foam proprieties and stability, and to obtain advance knowledge useful for foam practical applications on Earth. In particular, the understanding of rheology in wet foams has proven to be difficult on Earth and a dedicated space investigation could carry out interesting unknown properties, which could affect enormously the application of foams in industrial and commercial processes. The work started with the study of the requirements and was focused on the evaluation of the design through the assembly, integration and testing of the miniaturized system. During the hardware evaluation the weaknesses of the proposed design were identified. Alternative solutions for the demonstrator were developed and recorded in order to improve the future system. Various tests were carried out to verify the design performances and functionality. Good results were obtained with the improvements applied after the first testing campaign. Eventually, a series of verification tests were performed to complete the requirements compliance analysis. The majority of the results obtained was successful, however the full compliance of the current hardware was not reached and the validation campaign was not possible due to an open issue in the membrane application. At the present time, a solution for a multi-layer membrane is under development. Once it will be available, the demonstrator will be assembled and integrated, and a new series of verification tests will be performed. The final steps of the project will be the validation campaign and the presentation to European Space Agency about the system status and suggestions for future design improvements.

In this thesis, we propose a new class of pairwise frequency, multi-domain time synchronization and ranging algorithms for anchorless mobile networks of asynchronous nodes. We apply these techniques and study network and mission level aspects of time synchronization to Orbiting Low Frequency Array for Radio astronomy (OLFAR), a proposed distributed radio interferometer. In the first step, the Frequency Pairwise Least Squares (FPLS) that estimates clock skew and relative velocity in a pairwise setup using only frequency measurements is formulated. In the second step, we extend this method to a motion model with constant acceleration. Since frequency domain methods do not estimate clock offset and pairwise range, relying purely on frequency domain estimates is not feasible for various applications. To harness the potential of frequency domain synchronization and ranging, the Combined Pairwise Least Squares (CPLS) has been proposed. The combined method reduces the number of minimum required messages from 4 to 3 compared to current methods and decreases the computational complexity. Using a generic simulation with nodes in pairwise non-linear motion, we show that frequency domain methods can outperform time domain methods in clock skew and relative velocity estimation and that the proposed multi-domain method delivers better clock offset and pairwise range estimation in low to medium SNR conditions. In the second part of our work, we apply the proposed methods to OLFAR –— a space-borne large aperture radio interferometric array platform. We address network level and mission level aspects, proposing network path planning for pairwise synchronization algorithms and determining the required resynchronization period.

The use of Taylor Series Integration (TSI) for the propagation of spacecraft trajectories and its combination with the relatively unknown Unified State Model (USM) coordinate system, resulting in the TSI-USM propagator, is known to allow fast propagation of interplanetary low-thrust trajectories. Unfortunately, the TSI-USM propagator is a problem-specific method, which is detrimental for its use in evolutionary algorithms. In this thesis, a method was developed to generalize the TSI-USM propagator. The TSI-USM was generalized to allow the propagation of a spacecraft trajectory in a central gravitational field subject to any pre-set thrust profile, without the need to adapt the internal working of the propagator. The three-dimensional thrust profile should be specified a priori, and with respect to time, by the user or by an evolutionary algorithm. The method used to generalize the TSI-USM requires the coefficients of the cubic spline interpolation of the pre-set thrust profile to compute the recurrence relations of the TSI-USM. Results show that, although the method indeed generalizes the TSI-USM, it is less accurate and requires more CPU time for a given accuracy than existing RK8(7)13M-based propagators. From this result, it can be expected that future attempts to generalize the TSI-USM propagator, without sacrificing its accuracy and computational speed, will be challenging.