Thursday, April 14, 2011

Ceramics the Final Frontier

The Space Shuttle first flew in 1981 and is the current entering its last phase of operation. These vehicles were designed to be reusable, meaning they had to be able to enter and exit the Earth’s atmosphere multiple times. All previous space exploration vehicles were one uses devices. One of the main reasons Space Shuttles can safely exit and enter the atmosphere is the ceramic tiles that cover up most of the shuttle’s exterior surfaces.

Early space exploration utilized different means to maintain safe temperature control. During the Mercury Space Program the spacecraft used a heat sink that would safely absorb and dissipate the heat generated by reentry. The Apollo Space Program spacecrafts utilized an ablative shield place on the bottom of the spacecraft to protect the vehicle during reentry. Ablative shield is a cover made of materials that will char and vaporize off the surface of the spacecraft when placed under extreme heat and pressure, thus protecting the spacecraft. Although these materials were effective in protecting the spacecraft they were only good once meaning a whole new spacecraft had to be design for another mission.

The materials currently being used to protect the space shuttles are made up of thousands of ceramic tiles strategically placed throughout the exterior. Now you’re probably wondering how the material that makes up your tea set, fine china, and pottery could possible protect a spacecraft during reentry into Earth’s atmosphere. We have all done it before, dropped a plate and watch as it shattered into a million pieces. Not exactly what we want to happen in a material that determines whether our astronauts live or die. So, why would we use this kind of material when we have strong metals like steel, aluminum, and even titanium to build our spacecraft? The reason is heat.

When a Space Shuttle is reentering the atmosphere its surface temperature can range from 315 to 1465 degrees Celsius. The melting point of aluminum, which is the primary material that makes up a Space Shuttle’s structure, melts at 660 degrees Celsius. So making a spacecraft that melts as it enters the atmosphere is probably not what you want to do. Another property that ceramics have is their heat insulation ability. As seen in the video below a space shuttle tile can have a lit blow torch placed directly on its surface burning away and after it is removed a few seconds later can be held in your hand.

In conclusion the space shuttle exterior is comprised of thousands of ceramic tiles came from a necessity to have a reusable space exploration vehicle. The ceramic tiles give the Space Shuttle greater thermal shielding and can withstand the extremely high reentry temperatures.  I'd like to think that ceramics have served the shuttle and space exploration admirably.

1 comment:

  1. Great post--you're finding a way to explain some important properties of ceramics but in a way most of us can understand.