A Parametric Investigation of Satellite Servicing Requirements, Revenues, and Options in Geostationary Orbit

摘要

A variety of viewpoints can be heard concerning the utility of on-orbit satellite servicing, the maturity of the robotic systems being developed to address servicing opportunities, and the viability of business cases. This paper seeks to quantify the opportunities and address the myths directly. Based on that analysis, we further refine servicing models using a variety of servicing vehicle parameters to identify promising configurations and missions. We review the past opportunities for geostationary Earth orbit (GEO) on-orbit servicing interventions both for unexpected anomalies and for lifetime extension. These opportunities are characterized in a number of ways, including AV for a servicer to rendezvous with the client satellite, the corrective up-mass required to perform the servicing task, the robotic degree of difficulty of accomplishing the task, and economic measures of the value of the service. Past work by two of the authors categorized satellite failures into serviceable and non-serviceable cases, and further parameterized the serviceable cases by the complexity of servicing required. After updating this database to include recent satellite failure histories, we add new dimensions to the study by characterizing serviceable failure histories by the logistics mass required to accomplish the repair. In some cases, no significant additional mass is required, such as in the case of a spacecraft requiring deployment of a stowed boom or other structural element. In other cases, consumables replenishment may require tens or hundreds of kilograms of station-keeping propellant. In still others, major systems such as photovoltaic arrays would have to be replaced to return the satellites to functionality. To provide an input into the revenue side of a cost-benefit trade, we present a revenue model for inspection and repair services, which complements revenue assessments in the literature for different services such as refueling. The episodic nature of revenues from inspection and repair missions is treated statistically. The cost side of the trade is modeled in terms of propellant consumed by the servicer. For most of the emerging servicing concepts, the notional servicing systems have delivery masses similar to or greater than the typical communications satellite servicing client spacecraft. Since the mission costs are as large or greater than a replacement satellite would be, economic viability requires a sizeable pool of satellites ready to pay for services, and willing to wait in line for servicing mission concepts, which may require the successful servicing of a number of client satellites to break even. Based on the required logistics mass and the potential revenues, the paper then seeks to examine the practicality of servicing systems at a variety of scales in terms of the relative numbers of potential servicing clients and differences in practical servicing architectures. Given existing and future client satellites that could be returned to operation with minimal logistics mass, there is a potential business case for servicing vehicles even at the smallsat class (less than 100 kg). The paper develops strawman designs for servicing systems at several different mass points, at a variety of fractions of the mass of the average geostationary communications satellite, and for candidate launch and delivery systems to allow GEO servicing. Finally, we examine in more detail various aspects of servicing, and how they differ across the scale of servicing systems. This includes issues such as small vehicles stabilizing much larger client vehicles during servicing operations, required reach capabilities between grapple points and servicing sites, and scaling of electrical power requirements with servicer size. We also model the costs of less elegant solutions to servicer deliveries: dedicated launches in the event that secondary launch approaches prove to be infeasible or unavailable, and how the greater transportation costs would affect overall economic viability.