Reentry and Heat Shields

Coming back to Earth from space is one of the most dangerous parts of a space mission. When a spacecraft dives back into Earth's atmosphere, it hits the air at incredible speeds. This creates extreme heat that can reach thousands of degrees. Heat shields protect the spacecraft and its crew from burning up.

Why Reentry Is So Hot

A spacecraft returning from orbit travels at about 17,500 miles per hour. At this speed, the air in front of the spacecraft gets squeezed and heated. Temperatures on the outside of the spacecraft can reach 3,000 degrees Fahrenheit or more. That is hot enough to melt steel. Without protection, the spacecraft would be destroyed.

How Heat Shields Work

Heat shields are made of special materials that can handle extreme heat. Some heat shields work by slowly burning away, carrying the heat with them. This is called ablation. Others use special tiles that block the heat. The Space Shuttle used thousands of ceramic tiles on its belly to survive reentry.

Fun Facts

• The Space Shuttle had over 24,000 individual heat shield tiles, and each one was a different shape.
• During reentry, astronauts experience forces up to 4 times their normal weight.
• A spacecraft in reentry is surrounded by superheated gas called plasma.

Did You Know?

During reentry, there is a radio blackout period when the spacecraft cannot communicate with Earth. The hot plasma blocks all radio signals.