In the frame of Ariane 5 performance improvement plan, several ideas have arisen. One of them affects the Cryogenic Upper Stage (ESC-A). Indeed since the Ariane 5 flight V 157, the loading level of liquid hydrogen has been raised in order to improve the performance of the launcher, enabling to increase the payload mass or the altitude of the delivery orbit. However, this change raises safety problems. Optimal safety should be guaranteed both on ground and during flight. However, this study focuses only on the flight preparation phase, that is to say the ground phase starting from tank loading until lift-off (H0).

The thesis work aims at developing a liquid monopropellant injector for a high power electrodeless plasma thruster. The feasibility of using a chemical monopropellant for electric propulsion is investigated. After a design phase, the injector is put to the test with a simulant to the real liquid monopropellant in a simulated environment. Theoretical models are created to predict the power needed to vaporize a mass flow of the monopropellant without decomposing the heavy molecules. Testing has proved that the injector is able to vaporize the simulant of the real monopropellant. The properties of the propellant are compared to that of Xenon and Argon, showing good and promising results.

This thesis deals with the determination of loads on an aircraft struc- ture during flight. The focus is on flight conditions where the loads are significantly time-dependent. Analysis of flight loads is primarily motivated to ensure that structural failure is avoided. The ability to ac- curately determine the resulting structural loads which can occur during operation allows for a reduction of the safety margins in the structural design. Consequently it is then possible to decrease the aircraft struc- tural weight. The demand for safe and fuel efficient aircraft creates a desire for efficient and accurate methods for determining the structural loads. The first paper of this thesis discusses the use of control laws for robust atmospheric turbulence load alleviation in the time domain. A numerical aircraft model including structural elasticity and unsteady aerodynamic effects is used. A limited set of longitudinal flight mechanic degrees of freedom are considered and two methods for structural load analysis are compared for evaluation of the wing root bending moment. In the second paper a method to perform time domain simulation of both motion of center of gravity and elastic deformation is described. The intention with the development of this simulation method is to enable efficient analysis of dynamic flight loads. A third study is finally included, where steady and unsteady pressure measurements have been carried out during wind tunnel testing. The motivation for performing these experiments is that knowledge about the aerodynamic force distribution which affect an aircraft structure is needed to correctly determine the structural loads. / QC 20120529

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The thesis is a preliminary mission analysis and design of a small satellite swarm. The concept of the mission is to probe altitudes between 200 km and 6000 km to study the structures and dynamics of the magnetic field aligned currents. The mission lifetime is about 3 months. Aerodynamic drag at low altitudes is used for orbit and formation control. During the perigee passage, the satellite would decelerate due to drag, therefore, reducing its apogee. In addition, the attitude control of the spacecraft during the perigee passage could be used for formation control by changing its cross-sectional area. The simulations indicated that an appropriate insertion orbit should be at the perigee of 168 km and an apogee of 6000km. Moreover, from the orbital decay simulations, it was found that by maintaining a constant ram-facing area of 0.1 m2, it is possible for the satellite to decay in 90 days. The attitude simulations show that for at least one perigee passage at a perigee altitude of 168 km, the satellite is able to maintain its attitude and not tumble throughout the trajectory. In addition, investigation of the leader-follower satellite formation yielded that the relative translation of a circular orbit oscillates in all relative directions whereas in an elliptical orbit it only oscillates in the cross-track direction. Furthermore, the simulation has also shown that the relative translation of a leader-follower formation with a elliptical reference orbit, would spiral out of the radial-cross-track plane.

Equipment planned to be part of space missions is put through a substantial series of tests inorder to ensure a very high degree of reliability. This also applies to the HPGP thrusters manufactured by ECAPS AB. While conducting live fire tests the temperature is monitored using two separate systems, one pyrometer and one Infrared camera. The two systems show a difference in temperature for the same spot on the thruster. This is believed to be due to changes in the emissivity. An experimental setup is designed in order to measure the behavior of the emissivity of this material to decrease measurement errors. The emissivity of the main construction, an aerospace alloy called TZM, is proven to change as function of temperature and surface state, thus giving rise to large inaccuracies in temperature when conducting measurements using an infrared camera.The acquired emissivity data are presented together with a suggested method to implement the results back into the system.

This paper deals with the adaptation of a flight-test tool on A350 simulators in order to support a flight profile. This adaptation has been performed by doing first, an anal- ysis of the current situation of the existing tool on old programs like the A320 or the A330. Then, several modifications on the tool have been performed in order to adapt this tool on simulators. Finally, the validation of this tool has been done by performing several tests on A350 simulators. The difficulty of this adaptation was due to the appari- tion of new state-of-the-art technologies. The main improvement concerned the signals technology that appeared from the A380. Therefore, a modification on the parameters acquisition process has been done to take into account these improvements. Finally, the implementation of this mock-up on A350 simulators consists in a feasibility study that enables simulator test engineers to automate the tests performed on simulators and to do a traceability of these tests. The realisation of this mock-up is necessary because the simulator test engineers need this tool for the end of 2012 in order to develop the A350 whereas the real evolution of this tool will be done when the real aircraft A350 will be produced in 2014.

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No description available.

The aerodynamic sub-discipline of flow control has for many years been, and still is today, a very prominent subject of research. This field encompasses devices that produce a beneficial change in wall-bounded or free shear flows that may lead to, among many possibilities, reduced drag of ground vehicles and airplanes. The end result could have a substantial improved impact on fuel economy and also introduce new possible design options. Creo Dynamics AB recently started to venture into the field of active flow control with huge interest for the technology and its possible applications. One such application includes a system that reduces drag on ground vehicles via the use of active flow control. The system is composed of three components: actuators, controller and sensors. The work carried out in this thesis deals with a study into the sensory placement and control approach related to the system on a very conceptual level. According to Creo’s vision of the project the sensor shall record the pressure distribution and characteristics up-stream of the actuators. In turn the algorithm shall be capable of translating and correlating this data to the flow state downstream and in the wake. This data is then to be relayed to a control system producing the correct actuation response to achieve desired flow characteristics. For this system to work knowledge about the coupling between wake behavior and pressure distribution on surfaces upstream of the separated flow is necessary. This thesis is an initial investigation into the possible couplings that can be found. The scope also includes investigation of the coupling during cross-winds and gusts. Simulations of a simplified car geometry were carried out using the CFD package OpenFOAM and the DDES turbulence model. The initial investigation yielded promising results, showing that a link between the wake behavior and pressure distribution up-stream exists. But further work has to be carried out, as is discussed in the last chapter, before the algorithm according to Creo’s specifications can be constructed.