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Optimized separation system for small satellites missions
No full textThe launch phase is a critical step in a spacecraft operative life and it is therefore mandatory to provide for a robust and reliable interface between the launch vehicle and the spacecraft, focusing the attention at the same time on both the mechanical aspects and the resulting mass, due to the impact on the overall launch costs.
In this paper the Separation System designed and manufactured by ALMASpace S.r.l. is described, taking into account the FM provided for the ALMASat-1 mission, as interface with the VEGA launch vehicle: concerning the mechanical aspects, the entire design and optimization workflow is presented; in the second half the qualification test campaign performed in order to verify the compliancy with the requirements imposed by the launch vehicle is described.
In particular, since the entire Separation System would like to become a future standard for microsatellite-class spacecrafts, the requirements imposed by the VEGA launch vehicle have been taken into account: the vibration, thermal vacuum and functional tests results will be reported.
The test campaign confirmed the good quality of both the numerical analysis performed on the Separation System and the manufacturing process, allowing the Separation System to achieve the full qualification for the launch
Design, Assembly and Verification of the ALMASat-1 Separation System
No full textThis paper presents the activities that led to the assembly and verification of the ALMASat-1 microsatellite separation system carried out at the Microsatellite Laboratory of the University of Bologna, Forlì Campus. ALMASat-1 adapter and separation system was designed according to the requirements imposed by the European launch vehicle VEGA, general mission requirements and additional specific requirements related to ALMASat-1 microsatellite geometry and inertial properties. The analysis of these requirements drove the whole design process. The general architecture selected for the interface is the classical cylindrical
canister adapter with a 2-clamps constraining system. This solution, common for micro- and nano- satellites, has a wide flight heritage, is typically simple and affordable and could be easily implemented for a wide range of launch vehicles. The sizing of the whole
mechanism was carried out by means of theoretical calculations while advanced dynamics simulations based on MATLAB and Nastran code were performed to deeply investigate the transient phenomena characterizing the separation dynamics in the very first tens of milliseconds.
Along with numerical simulations, experimental tests have been performed by means of a separation test-bed, specifically designed to reproduce the correct dynamics of both the separation system and the spacecraft. As part of this experimental activity, the spacecraft angular velocities arising from potential non-symmetric actions of the four DV springs or clamps asynchronous actuation were estimated. This evaluation is extremely important in order to avoid damages to the satellite, other payloads and LV upper stage due to possible collisions. Finally, the structural and topological optimization process performed on the ALMASat-1 Adapter and Separation System will be presented, focusing on the reduction of
the system overall mass which, in turns, determines the launch costs and represents one of the most critical aspects in microsatellite missions
Design and Verification of an Optimized Separation System for Microsatellites: The ALMASat-1 Case Study
No full textThe time of separation of a satellite from its launch vehicle often signs the beginning of its operational life in orbit and this is especially true for micro- and nano-satellites. To preserve the integrity and the efficiency of the spacecraft during launch and perform a correct separation capable to grant safe operations of the spacecraft in orbit, it is necessary to design and manufacture an efficient and reliable interface and separation system from the launch vehicle. The VEGA Qualification Flight has now been postponed till the end of 2010 and several payloads will be released in orbit. First, a scientific payload named LARES will be released along a circular 1450x1450 km orbit, at 71 of inclination. ESA and ASI agreed on embarking a set of secondary payloads which will be released along an elliptic de-orbiting trajectory, after the perigee of the upper stage will be lowered to about 350 km. The 10 secondary payloads include 9 Cubesats and ALMASat-1, the first microsatellite developed, manufactured and assembled by the University of Bologna, Forlì Campus. ALMASat-1 flight opportunity was granted to the University of Bologna under the obligation that the S/C adapter and separation system was part of the ALMASat-1 systems. This paper presents the activities that led to the design, manufacturing, verification and qualification of the ALMASat-1 separation system carried out at the Microsatellite Laboratory of the University of Bologna. The general architecture selected for the interface is the classical cylindrical canister adapter with a 2-clamps constraining system. This solution, common for micro- and nano-satellites, has a wide flight heritage, is typically simple and affordable and could be easily implemented for a wide range of launch vehicles. In order to reduce the power consumption and enhance the system reliability and safety, the release clamps will be retained by Non- Explosive electro-mechanical Actuators (NEA) that allow to preload two couples of springs, one pair for each clamp, until the separation signal is obtained by the LV avionics. Along with numerical simulations, experimental tests have been performed by means of a separation test-bed, specifically designed to reproduce the correct dynamics of both the separation system and the spacecraft. Finally, the structural optimization process performed on the ALMASat-1 Adapter and Separation System will be presented, focusing on the reduction of the system overall mass which, in turns, determines the launch costs and represents one of the most critical aspect in microsatellite missions
THE ADAPTER AND SEPARATION SYSTEMS SERIES FOR THE VEGA LAUNCH VEHICLE
No full textThe VEGA Maiden Flight represented an important milestones for the ALMASat-1 program. In that frame, ALMASpace has been in charge of the design, manufacturing, testing and qualification for launch of the ALMASat-1 ADapter and Separation System (AD-SS), retaining the spacecraft during the early launch phases and providing the S/C separation when the separation command was received from the on-board avionics.
The ALMASpace AD-SS has been sized and qualified for the launch according to the VEGA requirements, therefore being hitherto the real benchmark for future missions onboard the VEGA flights for satellites up to 35 kg.
In order to extend the AD-SS capabilities to larger spacecraft, ESA has undertaken an activity aimed at the development and qualification of a wider series of products, achieving the goal of supporting satellites missions up to 200 kg, thanks to an overall set of three different AD-SS models.
This paper presents the improvements and the results of the design phases, started in late 2011, aimed at the completion of the second model of ALMASpace AD-SS and its delivery to ESA for the integration on the next VERTA-1 mission, currently scheduled in early 2013
TEST DI VIBRAZIONE CONDOTTI SUL MICROSATELLITE ALMASAT-1
No full textIl presente articolo illustra e riassume l’attività di qualifica al volo spaziale dei sottosistemi del satellite ALMASat-1 svolta presso il laboratorio per prove di vibrazione della Seconda Facoltà di Ingegneria dell’Università di Bologna, sede di Forlì. Nello specifico, vengono presentati i test di vibrazione condotti sui singoli sottosistemi che compongono il microsatellite universitario, allo scopo di verificare la robustezza dei diversi componenti alle sollecitazioni previste durante il lancio, che avverrà mediante il lanciatore VEGA, a bordo del quale ALMASat-1 sarà alloggiato. Per l’esecuzione dei test sono stati utilizzati uno shaker elettrodinamico Dongling ES-2-150 e la relativa piattaforma di controllo ed acquisizione LMS Test.Lab/SCADAS III forniti da LMS Italiana, in dotazione al laboratorio
ALMASat Attitude Control Hardware-in-the-Loop simulations
No full textThe purpose of Hardware-In-The-Loop (HIL) simulations of complex dynamic systems is the validation of the control laws and intensive hardware testing. This is usually obtained through specific configurations where flight hardware and the relative on-board software are placed in a loop together with external PC-based simulations of the external environment. This paper describes the HIL tests performed to validate the attitude determination and control system (ADCS) of ALMASat, the first educational spacecraft being developed in the Forlì laboratories of the II School of Engineering of the University of Bologna
Solar Array Simulator for Microsatellites Power System Testing
No full textPower systems verification requires the stability of the environmental conditions during the entire testing period, because small variations in irradiance, temperature and solar angle incidence can compromise the test results making difficult the real device performance evaluation. For this reason a traditional photovoltaic module is not a practical power source for laboratory testing, but it is necessary to use instruments that can simulate the I-V characteristic of a solar array.
Because of the high cost of these instruments, in the framework of university satellite programs, and the requirement of several devices to simulate each solar array, the design and prototyping of a low-cost system, with the purpose of testing microsatellites power systems, was undertaken at University of Bologn
ALMASat-1 Cold Gas Micropropulsion System: Final Layout, Qualification and Functional Tests
No full textIn this paper the final layout, the qualification and functional tests of the ALMASat-1 micropropulsion system are presented. The ALMASat-1 project is a small educational microsatellite (its weight is about 12 kg) entirely designed and assembled in the aerospace laboratories of II School of Engineering of the University of Bologna, scheduled for launch onboard the VEGA Maiden Flight as part of the LARES payload, which launch is currently scheduled at the end of 2010.
The micropropulsion system on-board the microsatellite is a nitrogen cold gas system which uses MEMS (Micro Electro-Mechanical System) devices, such as the microthrusters, in order to generate the required thrust level for the whole mission, about 0.75 mN. The use of MEMS technologies for micropropulsion systems is very attractive due to the small throat nozzle size, down to 10 micron, that can be manufactured. This reduces the thrust level and, theoretically, the impulse bits achievable using MEMS-based propulsion devices. In the field of propulsion for attitude control systems, it is very important to have the smallest possible impulse bit. The goal of the micropropulsion system is to perform three different types of experiments: three axis stabilization and target attitude maintenance; momentum wheel desaturation and pitch axis fine pointing and a small orbital maneuver, aimed at raising the S/C altitude (semi major axis). The micropropulsion system is mounted inside one of the trays of the ALMASat-1 microsatellite. The final layout, has been designed to satisfy the requirements of the specific type of propulsion selected among a variety of systems, as a result of a trade-off analysis performed in the conceptual design phase. Different types of tests have been performed on the micropropulsion system: (a) microthruster thrust measurements using a high precision microbalance in vacuum chamber in order to characterize the pressure–thrust curve; (b) microvalve tests aimed at measuring the valve gas leakage at different pressure levels (from 1 bar to 6 bar); (c) isolation valve tests, in order to qualify the valve in term of working pressure, gas leakage and power consumption; (d) burst tests on the nitrogen tank; (e) vibration and thermal vacuum tests at system and subsystem level and (f) functional tests (before and after the environmental tests).
The total mass of the propulsion system, tank, isolation valve, pressure transducers, pipes, pressure regulator, twelve silicon wafer microthrusters, fourteen microthrusters control valves and thrusters pod, is less than 1.5 kg
Modal Analysis of Aeroelastic Response of a Hovering Rotor -- The Impact of the Mode Choice
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