Mohawk Valley Astronomical Society

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Probing the Inferno

by Perry Pezzolanella

A new era of Venus exploration is dawning with three approved NASA and ESA missions and several more are in the works from Russia, India, and even a fleet of Smallsats/Cubesats. Eventually it will be necessary to explore the torrid depths of the atmosphere and the forbidden surface. Designing spacecraft of any kind to withstand a raging inferno is tough, but it is becoming possible with silicon carbide chips and high temperature technology. It is not the pressure, which averages 92 times Earth’s, and the sulfuric acid, those can be defeated, but the nearly 900ºF heat that is the challenge. It is becoming easier to imagine planes, gliders, drones, rovers, and even a sample return mission.

Venus’ thick atmosphere is perfect for powered flight and the light level below the clouds is reasonable enough to use solar power. A small plane can be folded up, enclosed in a capsule, and launched to Venus. The capsule would be equipped with a heat shield to slow it down enough to deploy the plane among the clouds starting its powered flight to lower levels to begin its mission. A plane can fly anywhere it wants unlike a balloon that is at the mercy of the wind, but it is limited because the plane relies on solar power and must remain in daylight. Since Venus rotates so slowly, once every 243 days, daylight lasts 58.5 Earth days for any given location on the surface, thus a plane only needs to fly 8 miles per hour to keep up with the rotation to remain on its dayside. It can fly at higher altitudes where temperatures are under 300ºF to cool off after flying in the hotter depths observing selected targets at close range. It would be equipped with several instruments that would measure the chemistry and composition of the lower atmosphere, analyze the surface composition from aloft using spectral imaging, use infrared sensors to accurately measure the surface temperature for hot spots, and a visual imager to take high resolution images of the landscape below. A plane can study large swaths of terrain and create a comprehensive map giving a better idea how the landscape formed/evolved and can also look for active volcanoes.

A rover is also being planned which is perfect for scouting the surface and traveling to interesting sites as the Mars rovers have proven. It must work in incredible heat, up to 900ºF, and survive long enough to obtain useful observations and data. The design would not be much different than the Mars rovers. Silicon carbide chips have been tested under Venus’ conditions and have survived at least sixty days, which is sufficient to survive one daylight period on Venus. The rover would be powered by a dynamic isotope power supply, an advanced version of the radioisotope generators used on planetary spacecraft that use plutonium to heat a small mechanical generator to provide electrical power to the rover.

The ultimate goal for exploring Venus is bringing back samples for study in labs. A gas sample return mission is the easiest as the spacecraft would skim the upper atmosphere and return samples to Earth. A variation of the mission is to go into orbit around Venus and deploy a probe that would collect atmospheric samples deep down. It would then reunite with the orbiter for return to Earth. The most challenging of all is a sample return from the surface. The spacecraft must survive on the surface long enough to collect surface samples and drill deep enough to gather a sample of soil not altered by weathering. The texture of the landing site adds to the challenge as it could be too soft for a good collection or too hard to drill deep enough. In either case any sample is better than nothing. The ascent portion of the spacecraft would have to blast off in gravity similar to Earth, but through an atmosphere far thicker and hotter. A balloon could solve the problem nearer the surface and rocket propulsion could take over higher up.

There is a lot of excellent science to be done at Venus that will ultimately reveal how Venus evolved, why it the way it is today, and what it might become in the future when volcanic activity eventually ceases. Venus may be the key that unlocks the door to understanding how and why the Earth is the way it is and what is yet to come.