- SpaceX’s Starship rocket is predominantly silver instead of the traditional white.
- The silver color comes from corrosion-resistant stainless steel that SpaceX used to build the rocket.
- The spacecraft is also covered in black hexagonal tiles to protect it upon re-entering the atmosphere.
Nestled on the far southern tip of Texas, near the small village of Boca Chica, sits a not-so-small space rocket: SpaceX’s Starship mega rocket.
Starship is not only the largest and most powerful rocket in the world, it also looks unlike anything SpaceX has ever built. In fact, it is unlike any other rocket in the world.
As shown below, the Mega Rocket consists of two stages. The first stage rocket booster, called Super Heavy (far left), is all silver, while the second stage starship, called Starship, is half silver, half black.
This silver and black color scheme is a big change from SpaceX’s white Falcon 9 rockets or NASA’s orange and white Space Launch System.
So why the flashy specs, SpaceX?
SpaceX’s silver rocket made of steel
Starship’s mostly silver appearance comes from a type of non-corrosive alloy called 300-series stainless steel. It’s the first time anyone has built a rocket out of this material since the 1950s.
The reason most rocket manufacturers avoid steel is because it’s heavy, and the heavier your actual rocket is, the less payload you can carry into space with the same fuel tanks.
Instead, the outer frame of most rockets is made of durable but lightweight metals like aluminum and titanium. Titanium is great for keeping a rocket light, but it can cost up to 15-20 times more than steel.
That’s why SpaceX replaced the titanium mesh fins on its Falcon 9 rockets with welded steel fins in 2019. However, cost isn’t the only reason SpaceX is now favoring steel over titanium in its rockets.
According to materials science experts, steel performs better than titanium in extreme temperature conditions. That means both under extreme heat, like during launch and re-entry into the atmosphere, and under extreme cold, like in space.
And that’s important, since Starship’s mission is to eventually take humans to the Moon and Mars, exposing the spacecraft to temperatures as low as -455 degrees Fahrenheit (-270 degrees Celsius), making most rocket materials weak, brittle and susceptible to Could crack or breaks.
Stainless steel, on the other hand, actually increases in strength at these cryogenic temperatures, making it ideal for space travel.
Additionally, Mike Gruntman, a professor of astronautics at the University of Southern California, told Insider, “It’s imperative to use stainless steel to prevent corrosion of the materials, which is also important. The price also plays a role.”
The black crewed spaceship Starship from SpaceX
Starship has a black underside, similar to NASA’s space shuttles, and also for similar reasons.
The black is a series of heat-resistant silicon dioxide hexagonal tiles designed to protect the spacecraft from searing temperatures as it re-enters Earth’s atmosphere.
You can see a close-up of these tiles in action from multiple flamethrowers in this video posted to Twitter by SpaceX founder and CEO Elon Musk in March 2019:
—Elon Musk (@elonmusk) March 17, 2019
One difference between the Starship and Space Shuttle tiles is their hexagonal shape. The tiles of the shuttles were square.
When a Twitter user asked about the tile’s unusual shape, Musk said answered that hexagonal tiles “leave no straight path for hot gas to accelerate through the gaps”.
In other words, it’s an extra measure to prevent the spacecraft from overheating and exploding on re-entry.
Why are most rockets white?
The reason is simple: cost.
White absorbs the least heat of any color in the visible spectrum, which helps keep the rocket as cool as possible. And that’s important because rocket fuel typically needs to be kept at temperatures between -297 degrees Fahrenheit and -432 degrees Fahrenheit.
So if your rocket is baking in the bright sun on the launch pad for hours or days, it’s cheaper to keep it cool if it’s white. This could also be the case for silver, according to research that found silver cars had cooler cabins than black cars.
SpaceX declined to comment on whether or not this is the reason for their silver Starship rocket. But it makes sense that if they don’t have to paint the rocket white and keep their natural steel color, not only will they save money on paint, they’ll also have a lighter rocket since paint is heavy.
“Absorption and emission properties, including color, will always play a role in passive thermal control,” Gruntman said. But when it comes to thermal management, white is even better than silver.
Despite a clear explanation from SpaceX for Starship’s silver and black face, there’s a chance it keeps the rocket light and secure, and isn’t just for show.
Recently, during a conference in Washington, DC, SpaceX President and COO Gwynne Shotwell said, “The ultimate goal is not to blow up the launch pad. That is success.”