Architectural framework and toolflow concepts for rapidly composable wireless spacecraft

Abstract

This paper provides a glimpse of work being done in a nearly decade-long joint US/Sweden and spacecraft research collaboration exploring rapid spacecraft design based on modular components whose simplicity and composability motivate the exploitation of modern design automation approaches and concepts that have been popularized in consumer and industrial online commerce. Modular systems are engineered to minimize tight couplings between components, with an aim of permitting interchangeability of elements and free composability to form many different possible system designs. Physical wiring often contributes to the complexity, and reducing or eliminating it aids in the objectives of modularity. In this paper, we consider an approach to create modular spacecraft, with a particular emphasis on cube satellites having a 6U form factor, based on a composition of “nearly wireless” elements. Since efficient power delivery remains problematic, our scheme permits the introduction of two terminals (analogous to residential wall outlets) for the sole purpose of power access. All other functions are delivered through a wireless network self organized based on a given collection of components necessary to form a particular spacecraft design. Panel structures can be prewired for power-only distribution, eliminating the need for custom wiring harnesses. In the proposed 6U Cubesat concept, a primary flat surface (∼200mm × 300mm) substrate is the basis of a “dinner tray” convention. Modules are added to the pegboard-like “dinner tray” by plugging them in topside, forming a single unified planar interface for electrical, mechanical, and thermal integration. Electrical power blocks energize the substrate, processor modules provide wireless connection access points, and all other modules extract power from the strategically distributed contact points throughout the substrate. Once powered, these modules are networked through a “join and discovery” mechanism which provides a dynamically extensible application programming interface (API) expressed in the form of electronic data sheets. A sophisticated middleware layer (running on the same processing modules that provide the wireless “hotspots”) matches applications using a “brokerage” publish and subscribe mechanism. When the dependencies of each application is satisfied through the existence of suitable modules, the application is activated. The entire application suite is a hierarchy implemented as a direct acyclic graph (DAG) of these dependencies that when satisfied form a viable system (in this case a spacecraft) design. The implications of the method are profound in that it is possible to rapidly develop an virtually infinite variety of system designs given a sufficiently large collection of building block hardware and software applications. This paper describes a pushbutton toolflow (PBTF) motivated by concepts electronic design automation, only they are now extended to encompass satellite (or other system) designs. This pushbutton toolflow involves a configurator concept through which the user could negotiate (with relatively simple wizard like dialogs) a variety of viable spacecraft designs. The tool would access a multi-vendor “electronic store”, where prebuilt components and applications are marshaled into DAGs corresponding to buildable systems. The approach is analogous to a shopping cart metaphor, in which system cost and delivery times can be tracked based on the collection of dependencies formed by the selection of particular components need to satisfy design constraints. Documentation, including bill of materials, data sheets, and a full work breakdown structure can be produced as a byproduct. The toolflow itself could be extended to encompass automatic program generation and three-dimensional printing approaches to permit automated, customizable software and hardware generation (respectively), to complement the catalog of available components. The toolflow has other profound impacts, such as the ability to publish “recipes” (i.e., useful system representations) for use by other users, the ability to automatically coordinate communications (through a “space dialtone” concept) between orbiting platforms in ground station networks, and techniques that arrange for the construction and launch of these configurator produced spacecraft design by cooperating third-party networks.