The term "heat shield" refers primarily to a special structure that protects a re-entry vehicle from the intense heat generated by friction with a planet's atmosphere. Less commonly, it can refer to the insulating material that surrounds the entire spacecraft, protecting the interior from the extremes in temperature encountered during the course of the mission. Heat shields are a vital part of every vehicle designed to return its crew and/or instruments safely to Earth, as the heat of re-entry would easily incinerate a spacecraft without this form of protection.

Space Capsules

The cone-shaped capsules of the early U.S. space program had heat shields attached to their base. These shields were designed to vaporize slowly during re-entry. The materials used in the heat shield, as they vaporized, would carry excess heat away from the spacecraft and its crew. For example, the Mercury and Gemini capsules...