A case for a robotic Martian airship

摘要

A robotic airship can provide an extremely versatile tool that has several advantages over orbiters, landers, rovers, and balloons. The airship can survey an extremely large expanse of territory, unlike landers and rovers, at a proximity allowing detailed resolution imagery, unlike orbiters, while retaining maneuverability, unlike balloons. The question then arises: Is a robotic airship feasible on Mars? An airship must be able to survive in the hostile environment as well as perform effectively within it. Furthermore, it should provide a capability commensurate with its overall cost. This project found that a robotic Martian airship would be feasible. First, a characterization of the atmosphere determined the parameters of the operational environment. Then, a suitability analysis used the atmospheric model and narrowed down the airship configuration to a superpressure type. Additionally, an experimental composite gas envelope beat out Mylar and Nylon 66 as the only practical material. Finally, an actual design of a robotic airship demonstrated sufficient capability with a respectable safety margin at a low launch mass. ACKNOWLEDGMENTS I would like to thank the following for their support: Dr. Earl Thornton, Kerry Nock of JPL, Dr. Rand of Winzen Engineering, John Krausman of TCOM L.P., Matt Hume, George Weinmann, and Mr. and Mrs. Rene A. Girerd SECTION 1: INTRODUCTION This paper seeks to prove the validity of an airship as a robotic exploration vehicle for the planet Mars. Results from an investigation of the compatibility of airship vehicles with the particular parameters of the Martian environment will lead to a preliminary design of an actual Martian airship. The paper intends to establish a starting point from which further development of its original concept may proceed. Rationale and Scone I advance that airships provide an ideal platform for the robotic exploration of Mars. In the near term, robotic Martian exploration will be affected by four different methods; orbiters, landers, rovers, and of Aeronautics and balloons. Of these, only the surface rovers can explore the Martian landscape directly in a mobile and intelligent manner. Orbiters fly far away, landers remain stationary, and balloons travel on the whims of a breeze. Yet even the surface rovers currently envisioned have severe limitations. They move excruciatingly slowly. The robotic rover scheduled to launch to Mars in late 1996 as part of the Mars Pathfinder program travels at around 1 cm per second. Such a rate does not allow widespread investigation of the planet's surface. The limiting factor lies in the difficulty in traversing the often rocky and boulder-strewn terrain. Since signals can take up to about 44 minutes to travel between Mars and Earth and back, having an Earth based controller for a robotic rover appears impractical. For example, the time between when a rover detected a boulder, and when it received the controller's command to turn either right or left, could be approaching an hour. This is due to the vast distance between the two planets. Because of the vast distance, sophisticated artificial intelligence circuits must reside in the rover to provide a degree of autonomy, which, in order to operate effectively, requires it to travel at a very slow speed. This speed limits the exploration footprint area, and virtually negates a rover's understood goal of opening up uncharted territory away from the lander. A robotic airship, on the other hand, would operate above the rough terrain, so it would require a less timedependent and complex artificial intelligence system. Between periodic course corrections from Earth, its autopilot could maintain a cruise while its sensors gathered data from a stable platform. Thus, an airship could survey much more of the Martian surface than a rover, and from a more useful vantage point. A robotic airship, aside from taking photos, video, and spectroscopic data of its surroundings from a distance, can also be use