Technical Sessions

Session VII: Spacecraft Systems

Chair: John London, U.S. Army Space and Missile Defense Technical Center

Wednesday, August 11, 2010

8:15 a.m. Satellite Capabilities Mapping – Utilizing Small Satellites

David Grigsby, Jonathan Black – Air Force Institute of Technology

ABSTRACT: The cost and schedule advantages small satellites have over larger legacy systems have been studied for years, but there has been very little experimentation performed to determine whether small satellites can actually deliver any of the capabilities of a larger spacecraft. To date, a desired operational capability has not been fully realized by a scalable satellite design. Advances in sensor technology have led to significant reductions in size, weight, and power (SWaP) presenting an opportunity to exploit the evolution of space operations by using small satellites to perform specific missions. This paper describes a methodology developed to map a specific set of defined large space vehicle capabilities to a constellation of small satellites. The process includes an analysis of user needs, capability gaps, and examines the utility of advanced sensors. This leads to determining: number of satellites; orbit geometry; sensor configurations; and the satellite bus.

Space weather has been identified as an excellent mission to exploit the potential of small satellites. Advances in micro-electronics have produced sensors with reduced SWaP, making them a viable test subject. Therefore, mapping capabilities to a small satellite, or constellation of small satellites, could provide solutions and affordable options to the adverse challenges facing space operations. The methodology developed here maps the National Polar-Orbiting Environmental Satellite System (NPOESS) Space Environmental Sensor Suite (SESS) to a constellation of small satellites intended to perform this operational mission.

8:30 a.m.Eliminating the Need for Payload-Specific Coupled Loads Analysis

Tom Sarafin, Seth Kovnat – Instar Engineering and Consulting, Inc.; Arya Majed, Ed Henkel – Applied Structural Dynamics, Inc.; Gerry Murphy – Design Net Engineering LLC

ABSTRACT: Through a project recently completed for Operationally Responsive Space (ORS), we have demonstrated the feasibility of a more efficient structural verification process for small satellites. This new process eliminates the need for payload-specific coupled loads analysis (CLA) and simplifies structural testing while not increasing mission risk. The process entails

• Derivation of appropriate physical constraints for the satellite (launch-vehicle payload) or the satellite’s payload, including mass, center of gravity, envelope, and natural frequencies.
• Up-front, rapid performance of multiple cycles of CLA for one or more launch vehicles and selected combinations of the payload’s variable physical properties within the derived constraints. (We refer to this analysis as “variational CLAs.”)
• Derivation of equivalent, single-axis load cases that are at least as severe as the max/min results of the variational CLAs, for design and sine-burst testing of the payload’s primary structure.

This process can be applied to multiple launch vehicles and variable combinations of small satellites in rideshare missions to provide flexibility, enable rapid integration, and accommodate late manifest changes. The process also can be extended to provide a loads envelope for spacecraft equipment or to reduce risk for large spacecraft.

The benefits of this process are simplified structural verification and reduced programmatic risk during hardware development.

8:45 a.m.Small Satellite Capability Analysis: A Systems Approach for Defining Translational Performance in Small Satellites

Mathew Zwack, Brian Engberg, Jeff Ganley – Air Force Research Laboratory/RVSS

ABSTRACT: With recent technological advances, small satellite systems have evoked great interest from both commercial and military sectors. These systems offer reductions in both development time and mission cost, which make them attractive alternatives to the large systems in use today, especially for developing space nations. Small satellites are inherently less capable due to their resource constraints, yet as technology advances, a widening array of supportable missions may be enabled. Due to this, it is important for future Space Situational Awareness (SSA) applications to understand and analyze the capabilities and limitations of these small systems. In order to achieve this, a subsystem-by-subsystem analysis approach may be employed to define the capabilities of each sub-system that may be found in a small satellite. This study is intended to analyze the propulsion sub-system and define an upper bound for translational performance in micro-satellites. During the study, each element of the propulsion subsystem was characterized in terms of the satellite size to define the metrics that have the greatest effect on the overall performance. Both monopropellant and cold gas propulsion, which are proven and viable options for small satellites, were chosen for the analysis. From this study, conclusions can be drawn for both systems that identify the upper bounds of available Delta-V in terms of the sub-system and overall satellite size.

9:00 a.m.Optimization of Various Thermal Management Techniques for High Thermal Loads

Carl Schwendeman, Rebecca Hay, Cable Kurwitz – Texas A&M University

ABSTRACT: The increasing thermal demands for spacecraft require the development of new technologies. To efficiently allocate resources to research and development efforts, a tool was developed that can be used to investigate the impact of new thermal technologies on spacecraft mass. The thermal tool is presented here as part of a mass study of three different types of thermal management technologies. The heat pipe radiator is recommended for a thermal load below 700W if the radiator is able to radiate to space from both sides. A heat pipe radiator radiating to space from a single side should be considered for loads at or less than 100W given the linear data trend. Loop heat pipe and single phase pumped looped radiators should be considered for loads exceeding 700W as their configuration allows for deployable radiators. The results indicate that for assumptions used in the paper, technologies associated with the radiator such as alternate materials are desirable above 700W whereas improvements should focus on the pipe and face sheet materials to reduce radiator mass.

9:15 a.m.How Do We Do the Same as the Big Boys? Enabling Systems and Technologies for Advanced Small Satellite Engineering

Andrew Carrel, Andrew Cawthorne, Guy Richardson, Luis Gomes – Surrey Satellite Technology Ltd.

ABSTRACT: To date small satellites have tended not to compete directly with the capability of traditional larger, more expensive spacecraft, instead filling niches or simply offering less capability where operators’ needs (and budgets) are smaller. Recently, however, Earth Observing small satellites have been closing this performance gap and are now competing more directly with their bigger rivals. In particular this paper will discuss how a new, agile sub-metre imaging platform will be able to deliver an Earth Observation capability close to the limit of what is currently available in the commercial market. This platform is an evolution of the recently built NigeriaSat-2 spacecraft, which is due to be launched later this year.

Achieving this level of performance within the constraints of a small satellite creates new challenges in maintaining the quality of image products. The emerging technologies used to meet these challenges and the ways in which they are combined into a small satellite solution is described. These technologies vary from novel mechanical design solutions to compact, low-power high-performance attitude sensors.

What little shortfall that remains in EO small satellites' ability is primarily coverage, which can be overcome using constellations where necessary. This paper will also discuss how multiple small satellites can work together to achieve the same result as complex imaging modes of larger spacecraft. A further advantage that has been demonstrated by the Disaster Monitoring Constellation is that several agencies can pool limited resources to create a more capable shared facility. An explanation of how this experience can be translated to sub-metre Earth Observation will be given.

9:30 a.m.A Plug-and-Play Approach Based on the I2C Standard

James Lyke, Jesse Mee – Air Force Research Laboratory; Fredrik Bruhn, Gael Chosson, Robert Lindegren, Henrik Lofgren, Jan Schulte – AAC Microtec AB; Scott Cannon, Jacob Christensen – Utah State University; Bryan Hansen – Space Dynamics Laboratory; Robert Vick – SAIC; Alonzo Vera – Micro-RDC; Josette Calixte-Rosengren – Swedish Defence Materiel Administration (FMV)

ABSTRACT: Plug-and-play architectures can reduce the timeline for constructing complex systems by automating the connections between components. While plug-and-play technologies have been successfully applied to aerospace systems, the overhead of the interface circuitry is a concern affecting its widespread use, particularly in smaller satellites. In this paper, we discuss a “minimalist” plug-and-play interface based on the popular inter-integrated circuit (I2C) standard, leading to dramatic simplifications of the interface circuitry necessary to be plug-and-play compliant. This concept, referred to as “mini-plug-and-play” (the space-qualified version is called “SPA-1”), has been created as a direct product of an international cooperative program between the United States and Sweden. At the simplest level, mini-PnP/SPA-1 is a protocol layer over I2C, readily implemented with existing devices that already support this ubiquitous standard. Using gateways, networks of mini-PnP/SPA-1 devices can connect to legacy forms of plug-and-play (e.g., SPA-U and SPA-S). Like these other legacy interfaces, SPA-1 devices support key features of plug-and-play, including electronic datasheets, automatic enumeration, and are readily integrated into plug-and-play software. This paper describes the development and demonstration of COTS and rad-tolerant versions of SPA-1 interface modules along with current status of the international program.

9:45 a.m. How Can Small Satellites be Used to Support Orbital Debris Removal Goals Instead of Increasing the Problem?

Jose Guerrero, Jon Manash, Matt Russell, Doyle Towles – ATK Spacecraft, Systems and Services; Steve Stone – ATK Aerospace Structures

ABSTRACT: Orbital debris is a serious concern for the NASA, DARPA, Air Force organizations and the commercial space industry. Since 2005, the space debris environment has been unstable and began a collision cascade effect per NASA. A recent International Orbital Debris Conference focused on the need to find solutions for Orbital Debris Removal and manage any space debris increase potential. The purpose of this paper is to explore what orbital debris issues can be address by Small Satellites. The paper will discuss a technology supported by Small Satellites to resolve the Orbital Debris problem. It will concentrate on mitigation of debris sizes from 1cm to 10cm, which are unable to be tracked by current ground systems capabilities but can cause serious damage or destroy spacecraft. Requirements will be for the LEO orbit, where there are known significant numbers of debris of this size. A Method will be proposed, by which a small spacecraft can be used to sweep volumes of specific orbits to remove or collect debris.