When Solar Orbiter launches this weekend (it's currently set to lift off on Sunday, Feb. 9), it will be protected from the sun by a very special "sandwich" heat shield.
The spacecraft, which is the result of a collaboration between NASA and the European Space Agency (ESA), will take a journey through space that will allow it to take a close look at the sun's poles. It will then move out past the orbit of Venus and back to the sun, again and again. At its most extreme, Solar Orbiter will dip just inside the orbit of Mercury; that's 26 million miles (42 million kilometers) away from the sun, NASA said in a statement.
Solar Orbiter needs to achieve this close proximity to the sun, despite the star's intense heat, in order to collect data about how the sun generates the "heliosphere." This feature of the sun blankets the entire solar system with solar particles. To stay cool, the craft has a 324-lb. (150 kilograms) heat shield, which is built to withstand searing temperatures more than twice that of a typical oven setting: 970 degrees Fahrenheit (520 degrees Celsius).
This "sandwich" heat shield is made up of layers. At the very front are extremely thin sheets of titanium foil that are designed to reflect as much heat as possible. Aluminum also covers the base, made of aluminum, to insulate the portion closest to the spacecraft. Holding the sandwich together are "toothpicks," which are star-shaped titanium brackets.
The only thing missing from this "sandwich" is something in the middle. Instead, there's a 10-inch (25 centimeters) gap that is needed to vent excess heat out to space. A smaller gap between the inner slice and the spacecraft provides additional heat ejection, NASA said.
While the shield was constructed using seriously advanced science and technology, surprisingly, part of the heat shield employs technologies found in cave paintings thousands of years ago. The calcium phosphate coated on the heat shield resembles the powder used in pigments found in ancient cave paintings, NASA said. Not only can the substance produce pretty pictures, but it can also serve as a shield against ultraviolet radiation from the sun.
"It's funny that something as technologically advanced as this is actually very old," Anne Pacros, the payload manager at ESA's European Space Research and Technology Centre in the Netherlands, said in the same statement.
In addition to the heat from the sun, Solar Orbiter must also combat heat generated from its own science activities, as its instruments create heat while doing their work. This warmth funnels out into space through panels of radiators on the spacecraft.
Overall cooling requirements will require Solar Orbiter to do a "crab walk" in space, NASA added. This means that the spacecraft will always keep its heat shield pointed at the sun, keeping the rest of the spacecraft protected in the cooler shadow cast by the shield.
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