PDA

View Full Version : White vs. Rust-colored shuttle fuel tanks



Eirik
2003-Feb-04, 11:46 PM
I've become a bit curious about a quirk of the shuttle history. The early flights of the shuttle used a fuel tank that was white instead of the more current and familiar rust-color. I remember my father telling my as a kid that the change was because they were trying to save weight and they realized that the paint they used added several hundred pounds to the launch vehicle while adding no additional protection.

What I've been wondering is, was that really the full extent of the difference between the white and rust tanks, essentially cosmetic? Or was there a perceived value in the white color (or coating) for the tank at one time that fell out of favor?

Doodler
2003-Feb-04, 11:55 PM
The white ones were painted, they stopped to save weight.

JayUtah
2003-Feb-04, 11:59 PM
In the engineering world there is no such thing as a superfluous coating. Paint is as important as nuts and bolts.

The original ET coating was for two reasons: thermodynamics and drag.

White paint reduces propellant boil-off by reducing how much solar energy is absorbed by the tank. It also has a high emissivity, enabling to reject heat radiatively much better.

Look at the paint on airliners. It's very glossy. That's not just for appearance. Providing that smooth surface makes the airplane slip through the air easier, reducing operating costs.

Engineers found that the decreased drag coefficient of the tank didn't offset the fuel savings that would be gained by deleting the weight of the paint. And the cost of the paint could be spent on topping off the tanks just one more time to account for evaporation.

Eirik
2003-Feb-05, 12:56 AM
Thanks for the clarification. That generally fits with what I recall my father telling me (he has always loved the space program, even if his work for Honeywell only put him very peripherally, and rarely, into it). Nice to know that my old man wasn't just making it up as he went along. /phpBB/images/smiles/icon_smile.gif