Inflatable Gravity Gradient Boom
- Paper number
IAC-05-C1.P.07
- Author
Mr. Bogdan-Constantin Dumitrescu, Technical University of Delft (TUDelft), The Netherlands
- Year
2005
- Abstract
Application of inflatable space structures is a relatively new development with great perspectives and has potential to be 10 to 100 times less expensive than conventional structures. Other advantages are that inflatable structures are lighter and take less volume (in launch configuration) than their conventional counterparts. However, to make these great expectations come true, research still has to be done. Four years ago the faculty of Aerospace Engineering of the Delft University of Technology started with the design of a low-cost micro satellite called DELFI-1. The current baseline for the DELFI-1 satellite was been established in the 1999-2000 design synthesis undergraduate exercise (DEUS) and has been amplified by a number of graduate projects. The satellite will make use of an inflatable gravity gradient boom as an attitude control actuator. It is this report’s goal to investigate the modelling and control feasibility of the inflation process and to add to the knowledge of the boom’s behaviour. Next to the aspects that purely concern the boom’s pressurization process, the influences due to the hostile environment in space are also discussed. This comprises the boom’s shape control as well as the material and inflation gas selection. In order to address these issues the project team started off with a literature search. Subsequently 4 specialists in the fields of inflatable structures, material science, and space technology were consulted. This preparatory work was necessary in order to get familiar with the topic and to aid to a good understanding of the problem. Because of the complexity of the whole, the problem was subdivided into smaller problems. These sub-problems were solved by use of computer programs. The computer simulations were written in Matlab Simulink. Two computer programs were written to simulate the boom’s behaviour. The first simulates the pressurization phase. This program is also responsible for the pressure control when a steady state pressurized phase is achieved. It is designed to keep the pressure constant, regardless leaks and temperature variations. The second program aims at maintaining the shape of the boom. The boom may deflect due to temperature variations throughout the orbit. These deflections will in reality be counteracted by piezo-electric strips attached to the boom’s surface. Concerning the simulation of the inflation phase conclusions can be made. Firstly the simplistic model shows exactly the expectations of linear behaviour. When a small leak is introduced from the start, the behaviour of the inflation process changes. It will take longer to inflate; simply because gas escapes. Because the leak mass flow depends on the internal pressure, the inflation now loses its linearity. When temperature comes into play, high peaks in the pressure are observed. The emergency valve successfully counteracts these large fluctuations of the pressure. Because of the large temperature variations throughout the satellite’s orbit the gravity gradient boom will deflect. These deflections might cause inaccuracies in attitude control and must be counteracted. This is done by application of piezo-electric strips attached to the boom’s surface. When the boom deforms more then a certain critical value the electric strips are actuated. They will counteract the boom’s deflection. Based on the outcome of our computer programs it can be said that application and maintainability of such a structure in space is feasible. Bogdan-Constantin Dumitrescu
- Abstract document