The perhaps not-so-coincidental timing of the announcement of the discovery of salty, liquid water on the surface of Mars and the release of the critically-acclaimed – and scientifically solid – Ridley Scott flick The Martian means that, for many of us, we have the Red Planet at the forefront of our minds. You can’t blame NASA for taking advantage of this: It seems that every other day, a new piece of Martian-themed news is plastered all over the Internet. Yesterday was no exception, as NASA announced that it has completed a successful heat shield test designed for future Mars exploration vehicles.
Whenever an object falls through the atmosphere of a planet, whether that be a spacecraft or a piece of space rock, it heats up. For smaller objects, the friction of the atmospheric particles on the rapidly descending mass does heat it up somewhat, but for larger objects such as an exploratory vehicle, it is the pressure of the particles on the object that produces incredible spikes in temperature.
The faster a spacecraft is traveling through an atmosphere, the more rapidly the atmosphere becomes compressed around it. The denser the atmosphere, the greater the level of compression. This combination of an object’s extremely high entry velocity and the thickness of the atmosphere produces the dramatic heating effect that large meteors and spacecraft experience when they enter Earth’s atmosphere.
Mars has a thinner atmosphere than our own planet, but it is still thick enough to produce a dangerous heating effect on any exploratory spacecraft NASA wants to send to the surface of our neighbouring world. As you would expect, it has been working on developing a heat shield against the Martian atmosphere for some time through its Adaptive Deployable Entry and Placement Technology (ADEPT) project.
Spacecraft are complex pieces of machinery: they need a rocket for launch, smaller thruster systems to send them to their destination, a landing craft to explore the planet itself and, for future manned missions, a vehicle designed to return them to the original craft for its journey back to Earth. There isn’t much spare room to go around, so a heat shield needs to be both effective and compact.
To this end, the ADEPT program has produced a small, mechanically-deployable heat shield composed of a carbon fabric. It expands rapidly, similar to an automatic umbrella opening, and is more flexible than older designs that failed to take the heat. At a recent test at NASA’s Ames Research Center in Silicon Valley, California, this design was subjected to realistic Martian atmospheric entry conditions.
A flow of extremely hot air was blasted straight at the heat shield, causing its surface temperature to reach 1,700 degrees Celsius (3,100 degrees Fahrenheit). Extensive instrumentation on and around the heat shield confirm that it passed the test with flying colors, withstanding the bombardment of heat, bringing NASA one step closer to sending a human being to the Martian surface.
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