Musk’s instincts said otherwise. “Run the numbers,” he told the team. “Run the numbers.” When they did so, they determined that steel could, in fact, turn out to be lighter in the conditions that Starship would face. At very cold temperatures, the strength of stainless steel increases by 50 percent, which meant it would be stronger when holding the supercooled liquid oxygen fuel. In addition, the high melting point of stainless steel would eliminate the need for a heat shield on Starship’s space-facing side, reducing the overall weight of the rocket.
