Station Payload Orbiting Transport - Abstract
Station Payload Orbiting Transport

Kari Lewis, et. all

May 5, 1995

Executive Overview

With the advent of the construction on the International Space Station Alpha, a need has developed to move large propulsively-inert structures in space. At the current time, NASA is proposing to use a combination of a station-attached crane and the shuttle arm to move objects close to the space station. Space Systems and Services (S3) Corporation has designed a Station Payload Orbiting Transport (SPOT) system which is capable of moving objects beyond the limited range of the station crane and is adaptable to a wide range of missions.

The SPOT system is designed to move a 40,000 kg station element a maximum distance of 350 m within 45 or 90 minutes and allow for one astronaut to stop the element within 1 m. The SPOT system is capable of autonomously or manually attaching itself to the propulsively-inert object and then guide the object to its designated site on the Space Station. As a design philosophy, the SPOT system utilizes existing technologies, line replaceable units, and modular construction to minimize cost and reduce maintenance time.

The four main SPOT subsystems are guidance, navigation, and control, propulsion, structural, and electrical. The GNC and electrical subsystems are based upon the Clementine mission, which significantly reduced mass and power over previous designs. A simple cold gaseous nitrogen (GN2) propulsion subsystem is used for both attitude control and orbital maneuvers. The SPOT bus structure will be constructed out of aluminum and will have a three point docking mechanism for attachment to the payloads. Possible designs of the remaining subsystems have been determined, but need further analysis to optimize their performance.