Mohawk Valley Astronomical Society

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Mean Machines

by Perry Pezzolanella

Lightning flashes in an acid-filled sky, air pressure soars to crushing levels, and temperatures rocket so high that lead melts as a lone spacecraft descends to the surface and to certain death within a few hours. This is not science fiction. This is one of several spacecraft sent from Earth to explore other planets and moons. This scenario is real and the planet is not far away. Welcome to Venus.

It is not easy to design a spacecraft to explore the Solar System and survive. There are extreme environments everywhere: frigid cold, extreme heat, intense atmospheric pressure, high radiation, excessive dust, and corrosive fluids. Any one, or a combination, may be encountered, provided the spacecraft endures the rigors of launch and spaceflight to reach its target world. Each destination has its challenges; the following describes how spacecraft are designed to overcome them.

Mercury: Extreme heat from being so close to the Sun can easily overheat a spacecraft and destroy its scientific instruments. MESSENGER will arrive in March 2011 to orbit Mercury for at least one Earth year. It is equipped with a giant sun shield that will shadow the sensitive instruments and cameras to help keep them cooler.

Venus: Temperatures nearly 900ºF, air pressure over 90 times Earth’s, and sulfuric acid mist may conspire to make it almost impossible to land on the surface of Venus, but landers are designed with a chilled titanium pressure vessel to withstand the crushing atmosphere and keep electronics cool for at least a few hours. Cameras and other optical windows that require glass use sapphire and industrial grade diamonds that resist the corrosive effects of the sulfuric and other acids in the atmosphere. The acid and intense pressure have pretty much been defeated by the engineers leaving heat the remaining enemy since it quickly fries electronics. Scientists would like to have a spacecraft last for more than just a few hours on the surface.

Mars: Dust and cold are the main challenges, and the next rover, Curiosity, will use nuclear power to generate power and heat. Solar panels are okay, but Spirit and Opportunity have suffered from low power from dust storms and accumulating dust on their solar panels. Opportunity’s small nuclear generator has helped keep it warm for over seven years. Dust can also affect a rover’s surface mobility, sometimes trapping them, and even with the best wheel designs, the deep, soft sand will always win if a rover makes the unfortunate mistake of driving into it.

Jupiter: A lethal radiation belt can kill a person in seconds and disable a spacecraft. Future missions to Jupiter and its moons will have spacecraft components that are radiation-hardened, which means they can withstand and accumulate larger doses of radiation than the Galileo orbiter ever could.

Saturn and beyond: Intense cold is the greatest challenge beyond Jupiter and yet the U.S. has pretty much conquered this problem with the proven successes of the Voyager and Cassini spacecraft. Nuclear power provides all the energy and heat necessary to keep a spacecraft functioning where temperatures can plummet as low as -400ºF. New Horizons is on its way to a July 14, 2015 flyby of Pluto. It uses nuclear power to keep it warm and operating with the hopes of amazing discoveries.

Space exploration is not easy, and designing spacecraft that can withstand hostile environments is costly, but once they are designed and proven, costs come down for future spacecraft and a wealth of discovery is opened for all: for awe and research.