Elsevier

Acta Astronautica

Volume 95, February–March 2014, Pages 210-217
Acta Astronautica

An innovative deployable solar panel system for Cubesats

https://doi.org/10.1016/j.actaastro.2013.11.011Get rights and content

Abstract

One of the main Cubesat bus limitations is the available on-board power. The maximum power obtained using body mounted solar panels and advanced triple junction solar cells on a triple unit Cubesat is typically less than 10 W. The Cubesat performance and the mission scenario opened to these small satellite systems could be greatly enhanced by an increase of the available power. This paper describes the design and realization of a modular deployable solar panel system for Cubesats, consisting of a modular hinge and spring system that can be potentially used on-board single (1U), double(2U), triple (3U) and six units (6U) Cubesats. The size of each solar panels is the size of a lateral Cubesat surface. The system developed is the basis for a SADA (Solar Array Drive Assembly), in which a maneuvering capability is added to the deployed solar array in order to follow the apparent motion of the sun. The system design trade-off is discussed, comparing different deployment concepts and architectures, leading to the final selection for the modular design. A prototype of the system has been realized for a 3U Cubesat, consisting of two deployable solar panel systems, made of three solar panels each, for a total of six deployed solar panels. The deployment system is based on a plastic fiber wire and thermal cutters, guaranteeing a suitable level of reliability. A test-bed for the solar panel deployment testing has been developed, supporting the solar array during deployment reproducing the dynamical situation in orbit. The results of the deployment system testing are discussed, including the design and realization of the test-bed, the mechanical stress given to the solar cells by the deployment accelerations and the overall system performance. The maximum power delivered by the system is about 50.4 W BOL, greatly enhancing the present Cubesat solar array performance.

Introduction

The development of small satellites, characterized by the involvement of small personnel teams, very short time from concept to launch and limited on-board resources, requires non-traditional design approaches [1], [2], [3], [4]. This article is the result of a cooperation established between the Laboratorio di Sistemi Aerospaziali of University of Rome “La Sapienza” and IMT Srl, Ingegneria Marketing Tecnologia, with the aim to complement the academic and industrial expertise and skills in the development of a nanosatellite subsystem. This experience follows a previous initiative undertaken in the framework of the education and outreach program Edusat [5], [6].

The diffusion of the Cubesat nanosatellite standard bus, described in [7], has made access to space affordable by lowering the launch cost through the use of specifically developed nanospacecraft dispensers allowing for multiple spacecraft launches [8], [9]. This gave impulse to on-board component miniaturization and in particular to the development of standardized components and innovative missions [10], [11], [12], [13].

The Cubesats capabilities could be greatly enhanced by increasing the available on-board power, while maintaining the compactness and volume limitations imposed by the standard. Technologies and methods for efficient power generation and storage on-board micro and nano-spacecraft have been sought, including the possibility of using commercial solar panels in space [14], [15], [16], [17], commercial Li-ion batteries [18], [19] and ways to maximize solar array power output by efficient interfacing with the load and batteries [20]. Concerning Cubesat power systems, the available surface for body mounted solar panels is so low that there are no alternatives to using high efficiency triple junction solar cells. In this case, the typical maximum delivered power is in the order of 10 W for triple Cubesats. The main advantage of body mounted solar panels is that no particular attitude pointing is required. However, the most performing Cubesats developed recently, including the 1U, 2 U and 3U size, can take advantage of current state of the art miniaturized attitude control systems [21], guaranteeing accurate pointing and maneuvering capabilities, as required by typical high performance and power demanding, missions.

Deployable solar arrays have been developed for micro and nano-spacecraft in order to improve the on-board power generation capability (e.g. [17], [22]). Some have been tested in orbit and are commercially available as a standard “building block” for newly developed Cubesat systems. These systems are based on many different deployment geometries and mechanisms and some have been developed having in mind particular satellite orbital and attitude stabilization scenarios. The simplest systems are based on single deployable solar arrays, connected to the main satellite body by one single hinge (e.g. [17]). In more complex configurations, the system is based on a number of interconnected solar panels [22], [23], [24], [25], [26].

A performance parameter expressing the solar array capabilities that can be used in general, not being related to a particular mission geometry, is the maximum delivered power, when the sun is orthogonal to the solar array in free space (AM0). The increase of on-board power generated by deployable solar panel with respect to body fixed ones is significant. Several deployable solar panel solutions for 3U Cubesat have been developed, with total delivered power ranging from 22 W to 56 W (e.g. [22], [23], [24], [25], [26]), increasing the performance with respect to body mounted solar panels from 160% to 400% [27].

A broad classification of these systems can be performed based on the deployment geometry and solar panel's orientation once deployed. Three categories have been determined based on this classification: (i) the deployment involves single solar panels, which are connected to the satellite body by one single hinge; (ii) the deployment involves a number of solar panels connected in a chain and one solar panel is connected to the satellite body by one single hinge, without the possibility of steering the solar array once deployed; (iii) the deployment involves one or more solar panels connected in a chain and one solar panel is connected to the satellite body by a system of two hinges, allowing to rotate the solar panel system relative to the satellite body once the solar panel is deployed. The system described in this paper is of type (ii), but it has been designed as a building block of a SADA (Solar Array Drive Assembly).

The deployable solar array system described in this paper has been dimensioned for the maximum obtainable solar array power, compatible with the standard Cubesat dimensions and Cubesat dispenser limitations. As far as the single solar panel size is concerned, the obvious choice is to make it as large as the Cubesat lateral face. The number of solar panels is limited by the maximum number of staked solar panels that can fit between the Cubesat structure and the dispenser in the stowed configuration during launch. The typical solar cell, wires and hinge thickness allow in practice only for three stacked solar panels in the ISISPOD dispenser [28], or two solar panels in the P-POD dispenser [8]. A study on the deployment mechanics of this system can be found in [29].

The solar panel performance strongly depends on the relative orientation of the sun and the orbit, as well as on the attitude motion, as discussed in Section 2. The solar panel deployment system mechanical and electrical designs are depicted in Section 3 and the prototype realization and test is dealt with in Section 4.

Section snippets

Geometrical configuration

The geometrical configuration has been selected based on orbit and attitude stabilization considerations and on the deployment sequence reliability and impact on the future SADA system and other satellite subsystems.

Requirements

The deployable solar panel system has been designed based on the overall geometrical configuration selected above and taking into account of the main system requirements imposed by the Cubesat structure, Cubesat dispenser, commercial advanced triple junction solar cell size and thickness, mechanical and electrical interfaces. No requirements have been fixed a-priori concerning the system mass. The goal is to have the system as light as possible, compatible with the other requirements.

An

Prototype integration and test

A prototype of the system, assembled as shown in Fig. 15, has been realized and used for the deployment sequence ground testing.

The prototype includes six solar panels assembled in two packs made of three solar panels each, as described above, and a dummy structure of a 3U Cubesat respecting all of the standard dimensions concerning the external shape. The assembled prototype ready for testing is shown in Fig. 16.

A special equipment set has been developed for the solar panel deployment sequence

Conclusions

A deployable solar panel system for Cubesats has been developed in the framework of a cooperation established between Laboratorio di Sistemi Aerospaziali of University od Rome “la Sapienza” and IMTsrl, Ingegneria Marketing Tecnologia. The system has been developed for 3U Cubesats, but it is conceived to be scalable to all Cubesat shape factors, including 6U, 2U and 1U Cubesats, respecting all of the geometrical constraints given by the Cubesat standard and by the deployment system. The system

References (32)

  • I. Nason, J. Puig-Suari, R. Twiggs, Development of a family of picosatellite deployers based on the CubeSat standard,...
  • F. Santoni et al.

    Nanosatellite cluster launch collision analysis

    J. Aerosp. Eng.

    (2013)
  • A., Toorian; K., Diaz; S., Lee, The CubeSat approach to space access, in: Proceedings of the Aerospace Conference, 2008...
  • L. Alminde; K.K. Laursen, A strategic approach to developing space capabilities using Cubesat technology, in:...
  • F. Santoni, M. Ferrante, F. Graziani, F. Ferrazza, In orbit performance of the UNISAT terrestrial technology solar...
  • F. Santoni, F. Piergentili, F. Graziani, In orbit performances of the UNISAT-3 solar arrays, in: Proc. of the 57th...
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