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Hot Wheels

by Perry Pezzolanella

The neatest way to explore the surface of a world is with a set of wheels. Who would pass up a chance to take a road trip across alien terrain to see what strange beauty lies beyond the next ridge? The successes of the Spirit, Opportunity, and Curiosity rovers prove that it is possible to explore Mars by wheels, so why not Venus?

Concepts have been proposed for two different types of rovers that may someday roam the blistering hot surface of Venus where temperatures approach 900ºF. Heat is the biggest challenge in operating a rover on a planet where lead, tin, and zinc melt; high-temperature electronics have not yet been perfected to operate in such intense heat. The tremendous pressure of the dense carbon dioxide atmosphere and the sulfuric acid mist can be surmounted using titanium and ceramics for the rover body and wheels. Optical instruments can operate through sapphire windows. The necessary technology being developed at NASA include high-temperature electronics and radioisotope power systems that can operate in the intense heat, Stirling-based power and cooling systems to keep the components under 600ºF, high temperature and corrosion resistant materials, and high temperature sensors, motors, actuators, and bearings. The rover must be able to withstand heat as intense as 950ºF preferably for as long as 50 days. Since daylight on Venus lasts 58.5 Earth days, it would be beneficial if the rover could last from nearly sunrise to sunset to get a better idea on how the weather works and to get the most out of exploring its surroundings during the daylight. The power and cooling system is the most critical portion of a functioning rover. For structural strength to fend off the crushing atmosphere and to minimize heat leaking into the compartment housing the electronics, a sphere is the best shape. The electronics will be enclosed in a spherical vault surrounded by a thick ceramic-based insulator and cooled using a Stirling cooler.

Another way to roam Venus is with a landsailing rover using solar panels. The technology for solar panels is so good that some power can be generated in spite of the perpetually cloudy skies. Even though the winds on the surface of Venus probably do not exceed 5 miles per hour, the atmosphere is so dense that even this slight breeze can generate a significant force to propel the rover across the surface. A landsailing rover can climb hills and over small obstacles, but will need to rove across land that is relatively flat and free of clutter and large boulders. The few images available from the Venera landers show that Venus has a rather smooth, volcanic surface free of numerous boulders, so a landsailing rover has a good chance of covering a lot of territory. A regular rover such as those on Mars would use hazard navigation to avoid dangerous obstacles including sand dunes and will be nuclear powered. Most of the energy generated would be needed to cool the rover. Both types of rovers would be equipped with science experiments, drills, tools, full color panoramic camera, and a weather station.

Venus is a world nearly as large as Earth but poorly understood with many unanswered questions in the fields of geology, geochemisty, surface-atmosphere interactions, and most importantly its climate. Venus once had an ocean but somehow it all went so wrong. How did Venus become a pressurized, toxic inferno? Can the same fate befall Earth? It is time to hit the road and ramp up the exploration of Venus so that we can better understand climate change and global warming here on Earth before it is too late.