Orange Rocket Good?
Why did Starship turn orange? Isn’t orange rocket bad?
If you watched the full stream of Starship’s 10th test flight you may have noticed something striking at the end. Just before Ship 37 touched down in the Indian Ocean a video buoy captured a striking orange color on the heatshield. It seemed to originate at a point three-quarters up the fuselage, and fanned out in a V-shape towards the bottom. This wasn’t observed on any of the previous flights. What was it?
Speculation immediately started with follow-up videos and inside chat rooms. Did the tiles fall off? Were we looking at the bare skin underneath? Was it some sort of ablative (meaning it gets blasted away) coating on the tiles for added heat protection? As the Internet wondered, a few clues started to emerge.
The Tiles in Question
Starship rusted. Wait…what? It was orange before it landed in the water! When looked at from a materials physics standpoint it does make sense: We know SpaceX conducted multiple experiments with the heatshield, one or more of those involved using metal tiles instead of ceramic. It turns out that when you use an iron-alloy, like steel, it can rust! The way rust forms is an iron molecule transfers a couple electrons to oxygen when it comes into contact with water, bonding it to the oxygen. (Fun fact this is how your red blood cells work. The molecule containing iron, called heme, bonds to the oxygen inhaled from your lungs. You’re alive because of rust in your blood cells. It’s also why it’s red). Also a fun fact, the oxidation of iron can be accelerated in the presence of heat. We know where a lot of heat was generated on Starship.
As Ship 37 plummeted through the atmosphere at supersonic speeds, the air (containing water moisture) slammed into the iron-alloy and the subsequent plasma cooked those poor tiles into gaining oxygen. The newly formed rust was then blasted around the rest of the heat shield, coating it in an orange hue.
Now it remains to be seen if SpaceX will stick with metallic tiles for Starship. I’m interested to see which direction they chose to go with the heatshield, it’s definitely the hardest problem to solve when it comes to reusability. The Shuttle program was plagued with heatshield issues, and it’s going to take a lot of effort to make it feasible with minimal refurbishment. Many experiments were carried out, and there’s lots of data to go over.
Another theory is that SpaceX is just throwing shade at Boeing. Apparently orange rocket good.
August 29th: This article has been edited to include new information as it becomes available.
