Session
Technical Session IV: Policies, Practices, or Methods to Enhance Low-Cost Space Access
Abstract
Over the past six years, over two billion dollars worth of commercial, civil, and military satellites have been written-off as a result of launch and on-orbit failures. Many of these failures would be relatively straightforward to repair on the ground but the equivalent repair in space is thought to be costly and technically difficult. It is proposed that a Smallsat could be ideally suited to perform some of these repairs, for instance, to provide attitude sensing if a sensor has failed. In this scenario, the Smallsat servicer vehicle would remain attached to the client satellite to provide the attitude determination function. Such a Smallsat mission would be far more cost effective than scrapping an otherwise functional large satellite and purchasing its replacement. The key technical difficulty is that most current satellites are not designed for robotic servicing. Challenges include docking with an uncooperative interface and then closing the control loop between the servicer vehicle, the client satellite, and the ground. This paper provides a definition of the Smallsat servicing system concept. It discusses rendezvous techniques, docking subsystem design, and ground segment operations. Strategies to deal with communication latency are also discussed. On the basis that docking is one of the key challenges, some concepts for interfacing with existing geostationary spacecraft were investigated using multi-body dynamic simulations that included the appropriate contact dynamics of the two spacecraft interfaces. To validate the simulations, proof-of-principle testing was conducted on a tetherless air-bearing testbed to emulate zero gravity conditions in two dimensions. The results show that a Smallsat can successfully dock with current commercial spacecraft that are not equipped with special robotic interfaces and can do so under a variety of conditions.
Presentation Slides
A Small Satellite Concept for On-Orbit Servicing of Spacecraft
Over the past six years, over two billion dollars worth of commercial, civil, and military satellites have been written-off as a result of launch and on-orbit failures. Many of these failures would be relatively straightforward to repair on the ground but the equivalent repair in space is thought to be costly and technically difficult. It is proposed that a Smallsat could be ideally suited to perform some of these repairs, for instance, to provide attitude sensing if a sensor has failed. In this scenario, the Smallsat servicer vehicle would remain attached to the client satellite to provide the attitude determination function. Such a Smallsat mission would be far more cost effective than scrapping an otherwise functional large satellite and purchasing its replacement. The key technical difficulty is that most current satellites are not designed for robotic servicing. Challenges include docking with an uncooperative interface and then closing the control loop between the servicer vehicle, the client satellite, and the ground. This paper provides a definition of the Smallsat servicing system concept. It discusses rendezvous techniques, docking subsystem design, and ground segment operations. Strategies to deal with communication latency are also discussed. On the basis that docking is one of the key challenges, some concepts for interfacing with existing geostationary spacecraft were investigated using multi-body dynamic simulations that included the appropriate contact dynamics of the two spacecraft interfaces. To validate the simulations, proof-of-principle testing was conducted on a tetherless air-bearing testbed to emulate zero gravity conditions in two dimensions. The results show that a Smallsat can successfully dock with current commercial spacecraft that are not equipped with special robotic interfaces and can do so under a variety of conditions.
