John-Paul Clarke
Georgia Institute of Technology
Description
We propose to overcome some of the limitations of current technologies for Mars exploration and even extend current operational capabilities by introducing the concept of a vacuum airship. This concept is similar to a standard balloon, whereas a balloon uses helium or hydrogen to displace air and provide lift, a vacuum airship uses a rigid structure to maintain a vacuum to displace air and provide lift.
A vacuum airship made of a homogenous material cannot withstand the atmospheric pressure on Earth for any material humans have yet discovered, which can be proven using the critical buckling load of a sphere. However, from an initial analysis of the vacuum airship structure and relationship to atmospheric conditions, Mars appears to have an atmosphere in which the operation of a vacuum airship would not only be possible, but beneficial over a conventional balloon or dirigible. In addition, a multi-layer approach, in conjunction with a lattice, would circumvent the buckling problems of a single homogenous shell. The lattice used to support the two layers of the vacuum airship shell can be made, using modulation of the lengths of the members, to fit the curvature of the vacuum airship precisely by following an atlas approach to the modulation. The Martian atmosphere has a pressure to density ratio that is very beneficial to the operation of a vacuum airship; this is a result of the high average molecular weight of the atmosphere (relative to other planets in the solar system) and the temperature of the atmosphere, the trend for which can be observed from the ideal gas law. Through a more in-depth analysis of the vacuum airship model, it can be shown that the vacuum airship may theoretically carry more than twice as much payload as a modeled dirigible of the same size, a 40-meter radius, in the Martian atmosphere.
A vacuum airship would be a valuable design for a vehicular probe for Mars. There are far fewer obstacles for an aerial vehicle as compared to a land vehicle such as existing Mars rovers, e.g. one need not worry about the vacuum airship getting stuck in a trench or being unable to traverse terrain. The vacuum airship could be used as a communication relay for other vehicular probes on Mars thereby overcoming line of sight constraints. If the vacuum airship is damaged, it can land, be repaired, and re-evacuated to resume operation, whereas a balloon would need to have gas pumped back into the vessel. Since the vacuum airship does not use a lifting gas, it can perform a near infinite number of compensation maneuvers to adjust or stabilize its altitude in a temperature variant environment. The vacuum airship could use its structure to protect the instruments from solar radiation and high energy particles. The vacuum airship probe would be able to traverse a much greater area of the planet in a smaller amount of time because there is no need to worry about getting stuck, and the vacuum airship can also observe a greater swath of land by rising in elevation. Even though the vacuum airship would be aerially base, the vehicle would still be able to touch down and perform tasks on the ground; it is even possible the vacuum airship could be used to transport ground probes to different locations. As far as energy is concerned, the large surface area of the vacuum airship would provide plenty of area for solar cells which would allow the vehicle to gather a large amount of solar energy without any additional structure, and once the airship is evacuated, the only energy it requires is for propulsion which can be accomplished by electric motors, unlike helicopters and airplanes which require energy to be devoted to lift.
