Science & Technology

NASA Is Sending a Probe to the Sun. Here's How They Keep It From Melting

A new NASA spacecraft is about to touch the sun. The Parker Solar Probe (PSP) will launch no earlier than August 4 to probe the sun's outer atmosphere, known as the corona, where temperatures are hot enough to destroy steel. Five decades in the making, this mission is only possible because PSP has a special heat shield to stop it from melting in those extreme conditions.

A Carbon Sandwich

When PSP zooms through the sun's corona, temperatures will crescendo to almost 2,500 degrees Fahrenheit (1,370 degrees Celsius). How does the spacecraft get so hot without disintegrating?

It's all thanks to a special heat shield that can withstand those temperatures for a short while, using a very resilient element — carbon. Carbon will stay intact in heat well beyond coronal temperatures. If you imagine the heat shield as a sandwich, the "bread" (the two outer layers) is made up of a carbon composite. Inside those layers is a carbon foam core that's 4.5 inches (11.4 centimeters) thick.

Even more astounding? The heat shield has a mass of only 160 pounds (73 kilograms) — roughly the weight of a full-grown adult. NASA made it so lightweight to make sure the spacecraft could reach its top speed of 430,000 miles per hour (nearly 700,000 kilometers per hour) when zooming by the sun. That's fast enough to get from Philadelphia to Washington, D.C. in only a second, NASA says.

Dipping Into the Sun's Atmosphere

Another secret to the spacecraft's resilience is its mission design, or how PSP will execute its scientific tasks. The engineers won't keep PSP in the heat of the sun for its entire seven-year mission. Instead, it will be dipping in and out of the corona.

After PSP blasts off from Earth, it heads for Venus, where it'll do seven flybys. Each time, it will use the planet's gravity to boost it closer to the sun. Then PSP's path through space will bring it back towards Venus (and cooler realms) to prepare for another flyby targeting the sun.

This mission design gives PSP a chance to cool off in between runs. Think of it like reading a book on a warm beach. When you get too hot, you can take a break and swim in the water to bring your body back to a cooler temperature.

What's the Point?

So PSP will spend several years getting up close to the sun and demonstrating just how clever engineers are. But what's the point? Why go to the bother of spending millions of dollars and 50 years developing this spacecraft concept?

It's because we need to understand space weather, which changes in large part due to the sun. Our stellar neighbor is great because it gives us light and energy to sustain life on Earth. But the sun also belches out solar flares, along with the occasional coronal mass ejection full of hazardous, radiation-bearing particles. What if those charged particles hit the wrong part of a satellite? Zap. Or encounter an unprotected spacecraft full of humans? Possible radiation sickness, cancer, or even death.

It's also to understand the sun more fully. It turns out that the corona is 300 times hotter than the photosphere: a region of the sun below the corona where we see flares and sunspots. Scientists don't understand why that is. They would like to pinpoint how that transfer of energy occurs and better understand how charged particles emanate across the solar system. Then, we can better protect our satellites, our astronauts, and all the other space stuff we need to explore the universe.

 Get stories like this one in your inbox each morning. Sign up for our daily email here. 

To learn more about that bright orb in the sky, check out "Nearest Star: The Surprising Science of our Sun" by Leon Golub and Jay M. Pasachoff. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

60 Second Science: NASA's Parker Probe

Written by Elizabeth Howell July 20, 2018

Curiosity uses cookies to improve site performance, for analytics and for advertising. By continuing to use our site, you accept our use of cookies, our Privacy Policy and Terms of Use.