ESMD Senior Design Project 2007
Robotic Transportation Vehicle for Mars Surface Exploration
At Old Dominion University, VSGC is supporting a student team under Dr. Robert Ash to develop designs for a Mars Airborne Rover using CO2 from the Martian atmosphere as a propellant.
Exploration of Mars from orbit has been the backbone of the overall Mars exploration program to date.
NASA Langley Research Center has proposed using a rocket-propelled airplane for an early Mars Scout mission. The proposed Aerial Regional-Scale Environmental Survey (ARES) vehicle will be designed to fly at an altitude of one- to two-kilometers above Mars’ surface, That vehicle opens up an important array of improved resolution measurements of magnetic field variations, surface spectroscopy, isotopic ratios of atmospheric constituents and in situ measurement of methane and hydrogen peroxide concentrations, along with the first direct atmospheric water vapor, and near-surface active gas concentration measurements. It will be the first 500 km-scale measurement platform employed at Mars and will demonstrate the desirability of future reusable airplanes.
In order to cover very large surface areas of the planet at close range, a rocket-propelled airplane is preferred to a hopper because airplanes are easier to control and solar cell power generators can be integrated into their wings, facilitating on-surface science and reuse. For the purposes of the present discussion, it is instructive to examine a reuseable airplane in the context of the Mars surface environment.
Compressed carbon dioxide propulsion
Local Mars resources include: solar energy, a nominal 50o to 100o C diurnal temperature swing, night-time temperatures that can dip below the frost point for carbon dioxide during Mar winter, and a carbon dioxide rich (95.32%) atmosphere. An ARES-type vehicle appears to be feasible49, operating with an inner surface temperature of 145 K and rejecting heat at 205 K. That unit would consume approximately 6100 kJe/kg of dry ice. Allowing for other losses, we will assume that the electrical energy required to form one kilogram of dry ice out of the atmosphere at night is 7000 kJ/kg. Hence, it would be possible for a 6 m2 solar array to produce enough dry ice during the Martian night to accumulate approximately 35 kg of solid carbon dioxide in two 20-liter tanks.
During the day, it should be possible to utilize the warmer temperatures, solar heating and reverse operation of the thermoelectric refrigerator to melt the stored carbon dioxide and heat it to 300 K. This warmed carbon dioxide gas would achieve a tank pressure of 500 bar at this temperature. It would then be possible to use a heated (300 K), gimbaled, Mach 2.6 nozzle for a vertical ascent, propelled flight and a thrust-assisted landing, covering distances of approximately 10 km.
Obviously, there are some rather significant questions concerning the viability of this approach, such as the weight and performance of the thermoelectric refrigerator/heater, the weight and performance of the compressed gas propulsion system and all of the necessary flight control hardware. However, the cost of integrating a solar array on the ARES upper wing surface as a means of enabling future recovery and reuse should be considered. Furthermore, the apparent ease with which pressurized carbon dioxide can be produced on the Martian surface suggests that an array of systems and tools should be considered that exploit compressed gas for propulsion and power.
It should be possible to deploy arrays of these devices, with platform suites dedicated to particular types of measurements, capable of traversing kilometer distances either individually or as “fleets”. One unit might serve as the communication hub and the remaining elements would work together forming a mobile wireless sensor network, moving over the Martian surface.
Modified Mars ARES airplane, incorporating solar arrays on upper wing surfaces.
John Companion, email@example.com