Chemical Concepts Demonstrated: Materials science, thermal conductivity differences in solids
Demonstration:
| A small cube of the space shuttle tile material is heated until it glows red hot. It is allowed to cool for 10-30 seconds and is picked up with bare fingers. | |
Observations:
The tile, red hot only seconds ago, can be held with the naked hand.
Explanation:
During reentry, a space shuttle passes through an enormous quantity of air in a very short time. This friction produces intense heat. Naturally, protecting the ship and the crew from such heat is very important. Space shuttle tiles are made up of silica (SiO2), which has a thermal conductivity low enough to provide the necessary protection.
Some of the specifics of the material are given below:
| Density | 9 lb/ft3 |
| Specific heat | .15 BTU/lb-oF |
| Thermal conductivity | .028 BTU/ft-hr-oF at 70oF and 1 atm |
| .073 BTU/ft-hr-oF at 2000oF and 10-4 atm | |
| Maximum reuse temperature | >2300 oF |
| Maximum single use temperature | 2800 oF |
| Reusability at 2300 oF | >100 missions |