Spaceframe: Modular Spacecraft Building Blocks for Plug And Play Spacecraft

SpaceFrame is a highly capable, reconfigurable spacecraft architecture built around a modular set of mechanical “building blocks” called SpaceFrame Blocks (SFB). This paper will discuss the technologies and design approaches involved in the implementation of SpaceFrame-based spacecraft architecture. It will detail the characteristics of this method and outline the path forward toward on-orbit servicing and rapid reconfiguration. Traditional satellite design approaches produce custom satellite buses with the exclusive goal of maximizing specific system performance. These satellites are composed of a selection of custom and semi-custom components that are integrated in a highly specific manner for that particular spacecraft. While this approach produces extremely efficient single spacecraft, it requires extensive, non-recurring engineering that results in large development costs and an inability to take advantage of development work from one system on the next system. The goal of SpaceFrame is to move away from expensive, proprietary system solutions with a single vehicle application towards less expensive, "modular" hardware solutions that support a variety of spacecraft applications. The SpaceFrame technology involves mechanical and electrical ‘plug-and-play’ interfaces that permit simple, reliable integration with other SFB modules. The SpaceFrame technology is an important first step towards on-orbit configuration, servicing, and upgrading of satellites. The standardized mechanical and electrical interfaces allow one block to be easily removed and replace with another. Ultimately, via autonomous rendezvous and docking, an existing space asset utilizing the SFB standard could be upgraded, augmented, or repaired through SFB addition or replacement. AeroAstro is currently working with the Space Vehicles Directorate at the Air Force Research Lab, with commercial funding contributions from a third party investor (ATSB) to develop the SpaceFrame technologies and transition them into a commercial Small Payload ORbit Transfer vehicle (SPORT). SPORT is an upper stage vehicle designed to deliver a payload from GTO to LEO by means of a deployed aerobrake. Jon Miller 16 Annual/ USU Conference on Small Satellites 2 Introduction Today’s aerospace industry treats every space system as if it were a specialized project, each with a solution by definition completely different from any other. This focused custom approach produces beautifully designed and integrated systems at the cost of years of effort and millions of dollars. Even though most space systems have analogues that have been developed previously, aerospace companies are constantly redesigning systems to produce a product that fits their exact requirements. Costs, that for any other industry would be considered truly non-recurring, are incurred time and time again. Furthermore, the reliability of a custom system is relative to the money spent on its design. High reliability for a custom system requires a lot of time and money invested in each specific point of design. In contrast, if every time someone wanted to purchase a personal computer they had to approach a computer designer with their exact requirements and allow them time to custom build a computer to specification, the price would increase significantly and schedules would be extended. As it is, a customer can walk into any computer store and walk out 5 minutes later with a complete system. Another 10 minutes at home is sufficient for setup and integration time. Because computer companies have anticipated their customer’s recurring needs and built a product that satisfies or exceeds them all, only 15 minutes is needed to acquire a fully functional personal computer that fulfills all common requirements at a fraction of the cost of a custom built model. The interfaces are built in so that if a new or better technology becomes available, integration of the new components is quick and simple. The SpaceFrame Solution SpaceFrame is a reconfigurable spacecraft architecture using standard structural modules and interfaces designed to be used as the basis for a commercial or production system rather than custom satellites. When used, if significantly decreases the effort and engineering needed for interface definition and design, shortens the integration and testing time, and makes space programs more affordable. A primary feature of SpaceFrame modularity is the grouping of related subsystems into standardized structural modules in a way that makes them easily integrated to each other. These modules, or SpaceFrame Blocks (SFB), are then assembled as needed through the use of standard mechanical and electrical interfaces to become a fully integrated and operational satellite. Because the blocks are all connected through standard interfaces, they can be changed or upgraded throughout the lifetime of the satellite. Technologies Involved Standard Interfaces The core concept behind SpaceFrame technology is the development of standard mechanical and electrical interfaces. A classic example of interface standardization applied to the aerospace industry is the set of interface standards imposed on spacecraft by launch vehicles. Launch vehicles provide a set of ICDs to the payloads that define the interfaces that a spacecraft is required to meet in order to be launched. The mechanical interface consists of a bolt pattern that is formed to accommodate a separation device. The electrical interface consists of an umbilical cord for pre-launch satellite care and the electrical connections needed to activate the separation system. The interfaces defined are independent of the payload to be launched. If a payload does not require the full service that these connections provide, they are still included but not utilized. Jon Miller 16 Annual/ USU Conference on Small Satellites 3 The technique of including excess capabilities in interface design is commonly used in the commercial arena. Products are equipped with the ability to accommodate more capabilities than what are necessarily needed. This is essential for any product that claims the capability to accommodate upgrades. In a small spacecraft, the limiting factors are generally cost and volume, rather than mass. Therefore, the SFB architecture will follow this technique by providing a standard set of interfaces, which are used or ignored depending on program requirements. These standard interfaces refer to both internal and external connections, and the breakdown of electrical interfaces for an SFB can be compared to those of a personal computer. Personal computers contain both external interfaces for keyboards, monitors, etc and internal interfaces to accommodate processors, memory boards, and other cards. Externally, each SFB will be equipped with standard mechanical and electrical connections that permit simple, reliable integration with other SFB modules and externally mounted components. Internally, an SFB will contain mounting locations for a variety of components, mostly VME-based. The electrical connectors and wiring harnesses will be made integral to the SpaceFrame block as possible. Internal flexibility must be allowed in an SFB to achieve the full range of modularity that is required for spacecraft development. Internal electronics will be allowed to vary as long as the standard interfaces remain intact. There are two main SFB modules: the Core SFB and the payload SFB. Core SFB The Core SFB, when populated with avionics and other critical components, constitutes the nucleus of an SFB-based spacecraft. It contains all the avionics and electronics necessary to support the spacecraft and its payload throughout the mission. These components can include, but are not limited to: