Thanks for visiting my website! Your son has a great question — in fact I asked that very same question just a few weeks ago. I noticed that the color of the External Tank on Discovery was much lighter than I remembered the other tanks being. It turns out the answer to that question is: the sun! The UV rays from the sun makes the insulating foam on the tank darken.

The tank is sprayed with the insulating foam to help keep the liquid hydrogen and liquid oxygen in tank cold. The liquid hydrogen is -423 degrees and the liquid oxygen is -297, so its very cold!

When they spray on the foam at the factory that makes the tanks in Louisiana, the foam is a pale yellow color. The tank is put into a covered barge that takes it to Kennedy Space Center. From there it goes directly into the big Vertical Assembly Building, which is very close to where the barge drops it off, so the tank is not out in the sun very much. When I saw Discovery and the tank roll out to the launchpad on March 2, the foam still looked yellow. But last week I was back out at the launchpad (I’ll be posting those pictures soon on my website!) and the tank looked orange, like I always remember seeing it.

Your son has a keen eye for detail! Tell him to keep up the great questions and he’ll go far — maybe even to space one day!

Sincerely,
Nancy

He wants to know why the ET has changed colors? It was much darker when he saw some of the previous launches and now it’s lighter…why is that? (His words I just did the typing.) lol

So I told him I would find out for him and I knew I could find someone online that worked in or around the shuttle program.

So if you have a little free time I would love to let him read an email from you about his question. Hopefully this isn’t a time buster for you and I explained to him that working with the shuttle, people are very busy and it may take a while, so no rush.

Thanks,

Virgil Lovett
BlkCigarCzar (Twitter) or BlkAv8tor2003 (Blog)