Ask the Astronaut: Why wasn’t the space shuttle built out of titanium?

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Atlantis over the Bahamas during the last space shuttle flight in 2011.

Q: Why was the space shuttle built out of aluminum? Why not use titanium? While expensive and difficult to work with, wouldn’t the additional costs and hassle have been worth it? Titanium has a much higher melting point than aluminum, which means that a hotter wing with less thermal insulation would have been acceptable. (David Rolfe, Dublin, Ireland)

It’s all a question of weight. Titanium is lighter than steel, but heavier than aluminum. Aluminum is a proven, strong, lightweight material for building an airframe like the shuttle orbiter. The silica-based, reusable thermal insulation invented for use on the orbiter protected the craft’s aluminum structure from reentry temperatures. The combined weight of the aluminum and thermal insulation tiles was less than a titanium airframe coated with thinner thermal tiles. That meant the orbiter could carry more payload to orbit—its reason for existence.

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